Patent Application
20220393486
The subject matter described herein relates generally to systems, devices, and methods for control of multiple energy sources, particularly current control to achieve and maintain balanced operating characteristics of the energy sources.
Energy storage systems are becoming more prevalent due to the growing popularity of electric vehicles, the desire to buffer energy from renewable energy generation sources, and the integration of storage systems in residential, commercial, and industrial environments. These energy storage systems are typically a serial connection of identical storage elements, such as battery cells of the same electrochemistry and nominal voltage, that permit the system to store large amounts of energy for long periods of time. For discharging, electrical current output from the system as a whole can be routed through a single transformer, inverter, or other conversion device to produce the desired DC or AC output voltage. For example, in conventional electric vehicles the total DC voltage generated by the serially-connected cells within the battery pack is rapidly switched between two extremes, the positive DC voltage and the negative DC voltage, to generate the sinusoidal AC waveform that drives the motor.
While battery cells of identical type and voltage are used, these cells are not truly identical as variations in the manufacturing process introduce small variations in chemistry and structure. As the system is repeatedly discharged and charged, these variations are magnified and give rise to differing degrees of degradation of capacity and performance in each cell. This degradation imbalance is exacerbated as the cells or subjected to different thermal conditions due to cell-to-cell variations in ohmic resistance and placement within the overall system. While intricate cooling systems can be provided to mitigate thermal variation across cells, such cooling systems are complex and expensive and fail to wholly compensate for the degradation imbalance. Often the system is limited in performance to that of the weakest cell, and severe degradation imbalance rapidly ages the system, requiring premature replacement of the degraded cells or even the system as a whole.
As such, much effort is invested in tightening manufacturing tolerances for battery cells to limit variation. However the use of identical cells limits performance of the system in another respect. Battery cells of various electrochemistries have different advantages and disadvantages. A cell of a first electrochemical type might have an energy density that is relatively higher than a cell of a second electrochemical type, but a power density that is relatively lower than the cell of the second electrochemical type. Use of cells of only one electrochemical type therefore limits performance of the overall system in those respects inherent to the cell type.
For these and other reasons, needs exist for systems, devices, and methods capable of operating multiple energy sources in a balanced fashion.
Example embodiments of systems, devices, and methods are provided herein for controlling current in systems having two or more energy sources. The source current can be controlled in a manner that seeks balance in one or more operating parameters of the sources while meeting load demand. Examples of balanceable operating parameters can include charge, temperature, voltage, state of health, state of energy, state of power, current, and others. Example embodiments are described that utilize a balance factor for each parameter being balanced, where the balance factor can vary with the magnitude of the parameter being balanced. A reference current can be determined that is selected to satisfy the load demand while at the same time taking into account present offset values of the balanced operating parameters between the sources. The sources can be the same or different, and different characteristics of the sources can be utilized in the current control design. For example, embodiments are provided that detect a transient condition and the load and because relatively more current to be provided from a source having a relatively higher power density in order to meet the transient demand. The embodiments applied to the system while in either a discharge or a charge state.
Other systems, devices, methods, features and advantages of the subject matter described herein will be or will become apparent to one with skill in the art upon examination of the following figures and detailed description. It is intended that all such additional systems, methods, features and advantages be included within this description, be within the scope of the subject matter described herein, and be protected by the accompanying claims. In no way should the features of the example embodiments be construed as limiting the appended claims, absent express recitation of those features in the claims.
The details of the subject matter set forth herein, both as to its structure and operation, may be apparent by study of the accompanying figures, in which like reference numerals refer to like parts. The components in the figures are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the subject matter. Moreover, all illustrations are intended to convey concepts, where relative sizes, shapes and other detailed attributes may be illustrated schematically rather than literally or precisely.
Before the present subject matter is described in detail, it is to be understood that this disclosure is not limited to the particular embodiments described, as such may, of course, vary. The terminology used herein is for the purpose of describing particular embodiments only, and is not intended to be limiting, since the scope of the present disclosure will be limited only by the appended claims.
Before describing the example embodiments pertaining to energy source control, it is first useful to describe these underlying systems in greater detail. With reference to
Stationary applications are those in which the modular energy system is located in a fixed location during use, although it may be capable of being transported to alternative locations when not in use. The module-based energy system resides in a static location while providing electrical energy for consumption by one or more other entities, or storing or buffering energy for later consumption. Examples of stationary applications in which the embodiments disclosed herein can be used include, but are not limited to: energy systems for use by or within one or more residential structures or locales, energy systems for use by or within one or more industrial structures or locales, energy systems for use by or within one or more commercial structures or locales, energy systems for use by or within one or more governmental structures or locales (including both military and non-military uses), energy systems for charging the mobile applications described below (e.g., a charge source or a charging station), and systems that convert solar power, wind, geothermal energy, fossil fuels, or nuclear reactions into electricity for storage. Stationary applications often supply loads such as grids and microgrids, motors, and data centers. A stationary energy system can be used in either a storage or non-storage role.
Mobile applications, sometimes referred to as traction applications, are generally ones where a module-based energy system is located on or within an entity, and stores and provides electrical energy for conversion into motive force by a motor to move or assist in moving that entity. Examples of mobile entities with which the embodiments disclosed herein can be used include, but are not limited to, electric and/or hybrid entities that move over or under land, over or under sea, above and out of contact with land or sea (e.g., flying or hovering in the air), or through outer space. Examples of mobile entities with which the embodiments disclosed herein can be used include, but are not limited to, vehicles, trains, trams, ships, vessels, aircraft, and spacecraft. Examples of mobile vehicles with which the embodiments disclosed herein can be used include, but are not limited to, those having only one wheel or track, those having only two-wheels or tracks, those having only three wheels or tracks, those having only four wheels or tracks, and those having five or more wheels or tracks. Examples of mobile entities with which the embodiments disclosed herein can be used include, but are not limited to, a car, a bus, a truck, a motorcycle, a scooter, an industrial vehicle, a mining vehicle, a flying vehicle (e.g., a plane, a helicopter, a drone, etc.), a maritime vessel (e.g., commercial shipping vessels, ships, yachts, boats or other watercraft), a submarine, a locomotive or rail-based vehicle (e.g., a train, a tram, etc.), a military vehicle, a spacecraft, and a satellite.
In describing embodiments herein, reference may be made to a particular stationary application (e.g., grid, micro-grid, data centers, cloud computing environments) or mobile application (e.g., an electric car). Such references are made for ease of explanation and do not mean that a particular embodiment is limited for use to only that particular mobile or stationary application. Embodiments of systems providing power to a motor can be used in both mobile and stationary applications. While certain configurations may be more suitable to some applications over others, all example embodiments disclosed herein are capable of use in both mobile and stationary applications unless otherwise noted.
Module-Based Energy System Examples
System 100 is configured to supply power to load 101. Load 101 can be any type of load such as a motor or a grid. System 100 is also configured to store power received from a charge source.
Control system 102 can be configured as a single device (e.g.,
Control system 102 can be configured to execute control using software (instructions stored in memory that are executable by processing circuitry), hardware, or a combination thereof. The one or more devices of control system 102 can each include processing circuitry 120 and memory 122 as shown here. Example implementations of processing circuitry and memory are described further below.
Control system 102 can have a communicative interface for communicating with devices 104 external to system 100 over a communication link or path 105. For example, control system 102 (e.g., MCD 112) can output data or information about system 100 to another control device 104 (e.g., the Electronic Control Unit (ECU) or Motor Control Unit (MCU) of a vehicle in a mobile application, grid controller in a stationary application, etc.).
Communication paths or links 105, 106, 115, 116, and 118 (
Control system 102 is configured to control one or more modules 108 based on status information received from the same or different one or more of modules 108. Control can also be based on one or more other factors, such as requirements of load 101. Controllable aspects include, but are not limited to, one or more of voltage, current, phase, and/or output power of each module 108.
Status information of every module 108 in system 100 can be communicated to control system 102, from which subsystem 102 can independently control every module 108-1 . . . 108-N. Other variations are possible. For example, a particular module 108 (or subset of modules 108) can be controlled based on status information of that particular module 108 (or subset), based on status information of a different module 108 that is not that particular module 108 (or subset), based on status information of all modules 108 other than that particular module 108 (or subset based on status information of that particular module 108 (or subset) and status information of at least one other module 108 that is not that particular module 108 (or subset), or based on status information of all modules 108 in system 100.
The status information can be information about one or more aspects, characteristics, or parameters of each module 108. Types of status information include, but are not limited to, the following aspects of a module 108 or one or more components thereof (e.g., energy source, energy buffer, converter, monitor circuitry): State of Charge (SOC) (e.g., the level of available charge of an energy source relative to its capacity, such as a fraction or percent) of the one or more energy sources of the module, State of Health (SOH) (e.g., a figure of merit of the physical condition, such as age, of an energy source compared to its ideal conditions) of the one or more energy sources of the module, temperature of the one or more energy sources or other components of the module, capacity of the one or more energy sources of the module, voltage of the one or more energy sources and/or other components of the module, current of the one or more energy sources and/or other components of the module, State of Power (SOP) (e.g., the available power limitation of the energy source during discharge and/or charge), State of Energy (SOE) (e.g., the present level of available energy of an energy source relative to the maximum available energy of the source), and/or the presence of absence of a fault in any one or more of the components of the module.
LCDs 114 can be configured to receive the status information from each module 108, or determine the status information from monitored signals or data received from or within each module 108, and communicate that information to MCD 112. In some embodiments, each LCD 114 can communicate raw collected data to MCD 112, which then algorithmically determines the status information on the basis of that raw data. MCD 112 can then use the status information of modules 108 to make control determinations accordingly. The determinations may take the form of instructions, commands, or other information (such as a modulation index described herein) that can be utilized by LCDs 114 to either maintain or adjust the operation of each module 108.
For example, MCD 112 may receive status information and assess that information to determine a difference between at least one module 108 (e.g., a component thereof) and at least one or more other modules 108 (e.g., comparable components thereof). For example, MDC 112 may determine that a particular module 108 is operating with one of the following conditions as compared to one or more other modules 108: with a relatively lower or higher SOC, with a relatively lower or higher SOH, with a relatively lower or higher capacity, with a relatively lower or higher voltage, with a relatively lower or higher current, with a relatively lower or higher temperature, or with or without a fault. In such examples, MCD 112 can output control information that causes the relevant aspect (e.g., output voltage, current, power, temperature) of that particular module 108 to be reduced or increased (depending on the condition). In this manner, the utilization of an outlier module 108 (e.g., operating with a relatively lower SOC or higher temperature), can be reduced so as to cause the relevant parameter of that module 108 (e.g., SOC or temperature) to converge towards that of one or more other modules 108.
The determination of whether to adjust the operation of a particular module 108 can be made by comparison of the status information to predetermined thresholds, limits, or conditions, and not necessarily by comparison to statuses of other modules 108. The predetermined thresholds, limits, or conditions can be static thresholds, limits, or conditions, such as those set by the manufacturer that do not change during use. The predetermined thresholds, limits, or conditions can be dynamic thresholds, limits, or conditions, that are permitted to change, or that do change, during use. For example, MCD 112 can adjust the operation of a module 108 if the status information for that module 108 indicates it to be operating in violation (e.g., above or below) of a predetermined threshold or limit, or outside of a predetermined range of acceptable operating conditions. Similarly, MCD 112 can adjust the operation of a module 108 if the status information for that module 108 indicates the presence of an actual or potential fault (e.g., an alarm, or warning) or indicates the absence or removal of an actual or potential fault. Examples of a fault include, but are not limited to, an actual failure of a component, a potential failure of a component, a short circuit or other excessive current condition, an open circuit, an excessive voltage condition, a failure to receive a communication, the receipt of corrupted data, and the like. Depending on the type and severity of the fault, the faulty module's utilization can be decreased to avoid damaging the module, or the module's utilization can be ceased altogether.
MCD 112 can control modules 108 within system 100 to achieve or converge towards a desired target. The target can be, for example, operation of all modules 108 at the same or similar levels with respect to each other, or within predetermined thresholds limits, or conditions. This process is also referred to as balancing or seeking to achieve balance in the operation or operating characteristics of modules 108. The term “balance” as used herein does not require absolute equality between modules 108 or components thereof, but rather is used in a broad sense to convey that operation of system 100 can be used to actively reduce disparities in operation (or operative state) between modules 108 that would otherwise exist.
MCD 112 can communicate control information to LCD 114 for the purpose of controlling the modules 108 associated with the LCD 114. The control information can be, e.g., a modulation index and a reference signal as described herein, a modulated reference signal, or otherwise. Each LCD 114 can use (e.g., receive and process) the control information to generate switch signals that control operation of one or more components (e.g., a converter) within the associated module(s) 108. In some embodiments, MCD 112 generates the switch signals directly and outputs them to LCD 114, which relays the switch signals to the intended module component.
All or a portion of control system 102 can be combined with a system external control device 104 that controls one or more other aspects of the mobile or stationary application. When integrated in this shared or common control device (or subsystem), control of system 100 can be implemented in any desired fashion, such as one or more software applications executed by processing circuitry of the shared device, with hardware of the shared device, or a combination thereof. Non-exhaustive examples of external control devices 104 include: a vehicular ECU or MCU having control capability for one or more other vehicular functions (e.g., motor control, driver interface control, traction control, etc.); a grid or micro-grid controller having responsibility for one or more other power management functions (e.g., load interfacing, load power requirement forecasting, transmission and switching, interface with charge sources (e.g., diesel, solar, wind), charge source power forecasting, back up source monitoring, asset dispatch, etc.); and a data center control subsystem (e.g., environmental control, network control, backup control, etc.).
In
In the embodiments of
Modules within Cascaded Energy System Examples
Module 108 can include one or more energy sources and a power electronics converter and, if desired, an energy buffer.
Converter 202 can be also (or alternatively) be configured to perform AC to DC conversion (e.g., a rectifier) such as to charge a DC energy source from an AC source, DC to DC conversion, and/or AC to AC conversion (e.g., in combination with an AC-DC converter). In some embodiments, such as to perform AC-AC conversion, converter 202 can include a transformer, either alone or in combination with one or more power semiconductors (e.g., switches, diodes, thyristors, and the like). In other embodiments, such as those where weight and cost is a significant factor, converter 202 can be configured to perform the conversions with only power switches, power diodes, or other semiconductor devices and without a transformer.
Energy source 206 is preferably a robust energy storage device capable of outputting direct current and having an energy density suitable for energy storage applications for electrically powered devices. Energy source 206 can be an electrochemical battery, such as a single battery cell or multiple battery cells connected together in a battery module or array, or any combination thereof.
Energy source 206 can also be a high energy density (HED) capacitor, such as an ultracapacitor or supercapacitor. An HED capacitor can be configured as a double layer capacitor (electrostatic charge storage), pseudocapacitor (electrochemical charge storage), hybrid capacitor (electrostatic and electrochemical), or otherwise, as opposed to a solid dielectric type of a typical electrolytic capacitor. The HED capacitor can have an energy density of 10 to 100 times (or higher) that of an electrolytic capacitor, in addition to a higher capacity. For example, HED capacitors can have a specific energy greater than 1.0 watt hours per kilogram (Wh/kg), and a capacitance greater than 10-100 farads (F). As with the batteries described with respect to
Energy source 206 can also be a fuel cell. The fuel cell can be a single fuel cell, multiple fuel cells connected in series or parallel, or a fuel cell module. Examples of fuel cell types include proton-exchange membrane fuel cells (PEMFC), phosphoric acid fuel cells (PAFC), solid acid fuel cells, alkaline fuel cells, high temperature fuel cells, solid oxide fuel cells, molten electrolyte fuel cells, and others. As with the batteries described with respect to
Energy buffer 204 can dampen or filter fluctuations in current across the DC line or link (e.g., +VDCL and −VDCL as described below), to assist in maintaining stability in the DC link voltage. These fluctuations can be relatively low (e.g., kilohertz) or high (e.g., megahertz) frequency fluctuations or harmonics caused by the switching of converter 202, or other transients. These fluctuations can be absorbed by buffer 204 instead of being passed to source 206 or to ports IO3 and IO4 of converter 202.
Power connection 110 is a connection for transferring energy or power to, from and through module 108. Module 108 can output energy from energy source 206 to power connection 110, where it can be transferred to other modules of the system or to a load. Module 108 can also receive energy from other modules 108 or a charging source (DC charger, single phase charger, multi-phase charger). Signals can also be passed through module 108 bypassing energy source 206. The routing of energy or power into and out of module 108 is performed by converter 202 under the control of LCD 114 (or another entity of subsystem 102).
In the embodiment of
Module 108 can also include monitor circuitry 208 configured to monitor (e.g., collect, sense, measure, and/or determine) one or more aspects of module 108 and/or the components thereof, such as voltage, current, temperature or other operating parameters that constitute status information (or can be used to determine status information by, e.g., LCD 114). A main function of the status information is to describe the state of the one or more energy sources 206 of the module 108 to enable determinations as to how much to utilize the energy source in comparison to other sources in system 100, although status information describing the state of other components (e.g., voltage, temperature, and/or presence of a fault in buffer 204, temperature and/or presence of a fault in converter 202, presence of a fault elsewhere in module 108, etc.) can be used in the utilization determination as well. Monitor circuitry 208 can include one or more sensors, shunts, dividers, fault detectors, Coulomb counters, controllers or other hardware and/or software configured to monitor such aspects. Monitor circuitry 208 can be separate from the various components 202, 204, and 206, or can be integrated with each component 202, 204, and 206 (as shown in
LCD 114 can receive status information (or raw data) about the module components over communication paths 116, 118. LCD 114 can also transmit information to module components over paths 116, 118. Paths 116 and 118 can include diagnostics, measurement, protection, and control signal lines. The transmitted information can be control signals for one or more module components. The control signals can be switch signals for converter 202 and/or one or more signals that request the status information from module components. For example, LCD 114 can cause the status information to be transmitted over paths 116, 118 by requesting the status information directly, or by applying a stimulus (e.g., voltage) to cause the status information to be generated, in some cases in combination with switch signals that place converter 202 in a particular state.
The physical configuration or layout of module 108 can take various forms. In some embodiments, module 108 can include a common housing in which all module components, e.g., converter 202, buffer 204, and source 206, are housed, along with other optional components such as an integrated LCD 114. In other embodiments, the various components can be separated in discrete housings that are secured together.
Modules 108 of system 100 can be physically arranged with respect to each other in various configurations that depend on the needs of the application and the number of loads. For example, in a stationary application where system 100 provides power for a microgrid, modules 108 can be placed in one or more racks or other frameworks. Such configurations may be suitable for larger mobile applications as well, such as maritime vessels. Alternatively, modules 108 can be secured together and located within a common housing, referred to as a pack. A rack or a pack may have its own dedicated cooling system shared across all modules. Pack configurations are useful for smaller mobile applications such as electric cars. System 100 can be implemented with one or more racks (e.g., for parallel supply to a microgrid) or one or more packs (e.g., serving different motors of the vehicle), or combination thereof.
Examples of these and further configurations are described in Int'l. Appl. No. PCT/US20/25366, filed Mar. 27, 2020 and titled Module-Based Energy Systems Capable of Cascaded and Interconnected Configurations, and Methods Related Thereto, which is incorporated by reference herein in its entirety for all purposes.
Energy source 206 can be configured as any of the energy source classes described herein (e.g., a battery as described with respect to
Ports IO3 and IO4 of energy buffer 204 can be connected to ports IO1 and IO2, respectively, of converter 202A, which can be configured as any of the power converter types described herein.
The switches can be any suitable switch type, such as power semiconductors like the metal-oxide-semiconductor field-effect transistors (MOSFETs) shown here, insulated gate bipolar transistors (IGBTs), or gallium nitride (GaN) transistors. Semiconductor switches can operate at relatively high switching frequencies, thereby permitting converter 202 to be operated in pulse-width modulated (PWM) mode if desired, and to respond to control commands within a relatively short interval of time. This can provide a high tolerance of output voltage regulation and fast dynamic behavior in transient modes.
In this embodiment, a DC line voltage VDCL can be applied to converter 202 between ports IO1 and IO2. By connecting VDCL to ports IO3 and IO4 by different combinations of switches S3, S4, S5, S6, converter 202 can generate three different voltage outputs at ports IO3 and IO4: +VDCL, 0, and −VDCL. A switch signal provided to each switch controls whether the switch is on (closed) or off (open). To obtain +VDCL, switches S3 and S6 are turned on while S4 and S5 are turned off, whereas −VDCL can be obtained by turning on switches S4 and S5 and turning off S3 and S6. The output voltage can be set to zero (including near zero) or a reference voltage by turning on S3 and S5 with S4 and S6 off, or by turning on S4 and S6 with S3 and S5 off. These voltages can be output from module 108 over power connection 110. Ports IO3 and IO4 of converter 202 can be connected to (or form) module IO ports 1 and 2 of power connection 110, so as to generate the output voltage for use with output voltages from other modules 108.
The control or switch signals for the embodiments of converter 202 described herein can be generated in different ways depending on the control technique utilized by system 100 to generate the output voltage of converter 202. In some embodiments, the control technique is a PWM technique such as space vector pulse-width modulation (SVPWM) or sinusoidal pulse-width modulation (SPWM), or variations thereof.
Each module 108 can be configured with multiple energy sources 206 (e.g., two, three, four, or more). Each energy source 206 of module 108 can be controllable (switchable) to supply power to connection 110 (or receive power from a charge source) independent of the other sources 206 of the module. For example, all sources 206 can output power to connection 110 (or be charged) at the same time, or only one (or a subset) of sources 206 can supply power (or be charged) at any one time. In some embodiments, the sources 206 of the module can exchange energy between them, e.g., one source 206 can charge another source 206. Each of the sources 206 can be configured as any energy source described herein (e.g., battery, HED capacitor, fuel cell). Each of the sources 206 can be the same class (e.g., each can be a battery, each can be an HED capacitor, or each can be a fuel cell), or a different class (e.g., a first source can be a battery and a second source can be an HED capacitor or fuel cell, or a first source can be an HED capacitor and a second source can be a fuel cell).
In this example embodiment of module 108B, primary energy source 202A, along with the other modules 108 of system 100, supplies the average power needed by the load. Secondary source 202B can serve the function of assisting energy source 202 by providing additional power at load power peaks, or absorbing excess power, or otherwise.
As mentioned both primary source 206A and secondary source 206B can be utilized simultaneously or at separate times depending on the switch state of converter 202B. If at the same time, an electrolytic and/or a film capacitor (CEs) can be placed in parallel with source 206B as depicted in
Converter 202C differs from that of 202B as switch portion 602B includes switches S1 and S2 configured as a half bridge and coupled between ports IO5 and IO2. A coupling inductor LB is connected between port IO1 and a node1 present between switches S1 and S2 such that switch portion 602B is configured to regulate voltage.
Control system 102 or LCD 114 can independently control each switch of converters 202B and 202C via control input lines 118-3 to each gate. In these embodiments and that of
In embodiments where a module 108 includes three or more energy sources 206, converters 202B and 202C can be scaled accordingly such that each additional energy source 206B is coupled to an additional IO port leading to an additional switch circuitry portion 602A or 602B, depending on the needs of the particular source. For example a dual source converter 202 can include both switch portions 202A and 202B.
Modules 108 with multiple energy sources 206 are capable of performing additional functions such as energy sharing between sources 206, energy capture from within the application (e.g., regenerative braking), charging of the primary source by the secondary source even while the overall system is in a state of discharge, and active filtering of the module output. The active filtering function can also be performed by modules having a typical electrolytic capacitor instead of a secondary energy source. Examples of these functions are described in more detail in Int'l. Appl. No. PCT/US20/25366, filed Mar. 27, 2020 and titled Module-Based Energy Systems Capable of Cascaded and Interconnected Configurations, and Methods Related Thereto, and Int'l. Publ. No. WO 2019/183553, filed Mar. 22, 2019, and titled Systems and Methods for Power Management and Control, both of which are incorporated by reference herein in their entireties for all purposes.
Each module 108 can be configured to supply one or more auxiliary loads with its one or more energy sources 206. Auxiliary loads are loads that require lower voltages than the primary load 101. Examples of auxiliary loads can be, for example, an on-board electrical network of an electric vehicle, or an HVAC system of an electric vehicle. The load of system 100 can be, for example, one of the phases of the electric vehicle motor or electrical grid. This embodiment can allow a complete decoupling between the electrical characteristics (terminal voltage and current) of the energy source and those of the loads.
Module 108C can thus be configured to supply one or more first auxiliary loads in the manner described with respect to load 301, with the one or more first loads coupled to IO ports 3 and 4. Module 108C can also be configured to supply one or more second auxiliary loads in the manner described with respect to load 302. If multiple second auxiliary loads 302 are present, then for each additional load 302 module 108C can be scaled with additional dedicated module output ports (like 5 and 6), an additional dedicated switch portion 602, and an additional converter IO port coupled to the additional portion 602.
Energy source 206 can thus supply power for any number of auxiliary loads (e.g., 301 and 302), as well as the corresponding portion of system output power needed by primary load 101. Power flow from source 206 to the various loads can be adjusted as desired.
Module 108 can be configured as needed with two or more energy sources 206 (
Control system 102 can perform various functions with respect to the components of modules 108A, 108B, and 108C. These functions can include management of the utilization (amount of use) of each energy source 206, protection of energy buffer 204 from over-current, over-voltage and high temperature conditions, and control and protection of converter 202.
For example, to manage (e.g., adjust by increasing, decreasing, or maintaining) utilization of each energy source 206, LCD 114 can receive one or more monitored voltages, temperatures, and currents from each energy source 206 (or monitor circuitry). The monitored voltages can be at least one of, preferably all, voltages of each elementary component independent of the other components (e.g., each individual battery cell, HED capacitor, and/or fuel cell) of the source 206, or the voltages of groups of elementary components as a whole (e.g., voltage of the battery array, HED capacitor array, and/or fuel cell array). Similarly the monitored temperatures and currents can be at least one of, preferably all, temperatures and currents of each elementary component independent of the other components of the source 206, or the temperatures and currents of groups of elementary components as a whole, or any combination thereof. The monitored signals can be status information, with which LCD 114 can perform one or more of the following: calculation or determination of a real capacity, actual State of Charge (SOC) and/or State of Health (SOH) of the elementary components or groups of elementary components; set or output a warning or alarm indication based on monitored and/or calculated status information; and/or transmission of the status information to MCD 112. LCD 114 can receive control information (e.g., a modulation index, synchronization signal) from MCD 112 and use this control information to generate switch signals for converter 202 that manage the utilization of the source 206.
To protect energy buffer 204, LCD 114 can receive one or more monitored voltages, temperatures, and currents from energy buffer 204 (or monitor circuitry). The monitored voltages can be at least one of, preferably all, voltages of each elementary component of buffer 204 (e.g., of CEB, CEB1, CEB2, LEB1, LEB2, DEB) independent of the other components, or the voltages of groups of elementary components or buffer 204 as a whole (e.g., between IO1 and IO2 or between IO3 and IO4). Similarly the monitored temperatures and currents can be at least one of, preferably all, temperatures and currents of each elementary component of buffer 204 independent of the other components, or the temperatures and currents of groups of elementary components or of buffer 204 as a whole, or any combination thereof. The monitored signals can be status information, with which LCD 114 can perform one or more of the following: set or output a warning or alarm indication; communicate the status information to MCD 112; or control converter 202 to adjust (increase or decrease) the utilization of source 206 and module 108 as a whole for buffer protection.
To control and protect converter 202, LCD 114 can receive the control information from MCD 112 (e.g., a modulated reference signal, or a reference signal and a modulation index), which can be used with a PWM technique in LCD 114 to generate the control signals for each switch (e.g., S1 through S6). LCD 114 can receive a current feedback signal from a current sensor of converter 202, which can be used for overcurrent protection together with one or more fault status signals from driver circuits (not shown) of the converter switches, which can carry information about fault statuses (e.g., short circuit or open circuit failure modes) of all switches of converter 202. Based on this data, LCD 114 can make a decision on which combination of switching signals to be applied to manage utilization of module 108, and potentially bypass or disconnect converter 202 (and the entire module 108) from system 100.
If controlling a module 108C that supplies a second auxiliary load 302, LCD 114 can receive one or more monitored voltages (e.g., the voltage between 10 ports 5 and 6) and one or more monitored currents (e.g., the current in coupling inductor LB, which is a current of load 302) in module 108C. Based on these signals, LCD 114 can adjust the switching cycles (e.g., by adjustment of modulation index or reference waveform) of S1 and S2 to control (and stabilize) the voltage for load 302.
Cascaded Energy System Topology Examples
Two or more modules 108 can be coupled together in a cascaded array that outputs a voltage signal formed by a superposition of the discrete voltages generated by each module 108 within the array.
System 100 can be arranged in a broad variety of different topologies to meet varying needs of the applications. System 100 can provide multi-phase power (e.g., two-phase, three-phase, four-phase, five-phase, six-phase, etc.) to a load by use of multiple arrays 700, where each array can generate an AC output signal having a different phase angle.
The concepts described with respect to the two-phase and three-phase embodiments of
System 100 can be configured such that arrays 700 are interconnected at electrical nodes between modules 108 within each array.
In the embodiments described herein, although it is advantageous for the number of modules 108 to be the same in each array 700 within system 100, such is not required and different arrays 700 can have differing numbers of modules 108. Further, each array 700 can have modules 108 that are all of the same configuration (e.g., all modules are 108A, all modules are 108B, all modules are 108C, or others) or different configurations (e.g., one or more modules are 108A, one or more are 108B, and one or more are 108C, or otherwise). As such, the scope of topologies of system 100 covered herein is broad.
Control Methodology Examples
As mentioned, control of system 100 can be performed according to various methodologies, such as hysteresis or PWM. Several examples of PWM include space vector modulation and sine pulse width modulation, where the switching signals for converter 202 are generated with a phase shifted carrier technique that continuously rotates utilization of each module 108 to equally distribute power among them.
An alternative is to utilize both a positive and a negative reference signal with the first (N−1)/2 carriers. A nine-level example is shown in
In multi-phase system embodiments, the same carriers can be used for each phase, or the set of carriers can be shifted as a whole for each phase. For example, in a three phase system with a single reference voltage (Vref), each array 700 can use the same number of carriers with the same relative offsets as shown in
The appropriate switching signals can be provided to each module by control system 102. For example, MCD 112 can provide Vref and the appropriate carrier signals to each LCD 114 depending upon the module or modules 108 that LCD 114 controls, and the LCD 114 can then generate the switching signals. Or all LCDs 114 in an array can be provided with all carrier signals and the LCD can select the appropriate carrier signals.
The relative utilizations of each module 108 can adjusted based on status information to perform balancing or of one or more parameters as described herein. Balancing of parameters can involve adjusting utilization to minimize parameter divergence over time as compared to a system where individual module utilization adjustment is not performed. The utilization can be the relative amount of time a module 108 is discharging when system 100 is in a discharge state, or the relative amount of time a module 108 is charging when system 100 is in a charge state.
As described herein, modules 108 can be balanced with respect to other modules in an array 700, which can be referred to as intra-array or intraphase balancing, and different arrays 700 can be balanced with respect to each other, which can be referred to as interarray or interphase balancing. Arrays 700 of different subsystems can also be balanced with respect to each other. Control system 102 can simultaneously perform any combination of intraphase balancing, interphase balancing, utilization of multiple energy sources within a module, active filtering, and auxiliary load supply.
The modulation indexes and Vrn can be used to generate the switching signals for each converter 202. The modulation index can be a number between zero and one (inclusive of zero and one). For a particular module 108, the normalized reference Vrn can be modulated or scaled by Mi, and this modulated reference signal (Vrnm) can be used as Vref (or −Vref) according to the PWM technique described with respect to
Controller 906 can generate an Mi for each module 108 using any type or combination of types of status information (e.g., SOC, temperature (T), Q, SOH, voltage, current) described herein. For example, when using SOC and T, a module 108 can have a relatively high Mi if SOC is relatively high and temperature is relatively low as compared to other modules 108 in array 700. If either SOC is relatively low or T is relatively high, then that module 108 can have a realtively low Mi, resulting in less utilization than other modules 108 in array 700. Controller 906 can determine Mi such that the sum of module voltages does not exceed Vpk. For example, Vpk can be the sum of the products of the voltage of each module's source 206 and Mi for that module (e.g., Vpk=M1V1+M2V2+M3V3 . . . +MNVN, etc). A different combination of modulation indexes, and thus respective voltage contributions by the modules, may be used but the total generated voltage should remain the same.
Controller 900 can control operation, to the extent it does not prevent achieving the power output requirements of the system at any one time (e.g., such as during maximum acceleration of an EV), such that SOC of the energy source(s) in each module 108 remains balanced or converges to a balanced condition if they are unbalanced, and/or such that temperature of the energy source(s) or other component (e.g., energy buffer) in each module remains balanced or converges to a balanced condition if they are unbalanced. Power flow in and out of the modules can be regulated such that a capacity difference between sources does not cause an SOC deviation. Balancing of SOC and temperature can indirectly cause some balancing of SOH. Voltage and current can be directly balanced if desired, but in many embodiments the main goal of the system is to balance SOC and temperature, and balancing of SOC can lead to balance of voltage and current in a highly symmetric systems where modules are of similar capacity and impedance.
Since balancing all parameters may not be possible at the same time (e.g., balancing of one parameter may further unbalance another parameter), a combination of balancing any two or more parameters (SOC, T, Q, SOH, V, I) may be applied with priority given to either one depending on the requirements of the application. Priority in balancing can be given to SOC over other parameters (T, Q, SOH, V, I), with exceptions made if one of the other parameters (T, Q, SOH, V, I) reaches a severe unbalanced condition outside a threshold.
Balancing between arrays 700 of different phases (or arrays of the same phase, e.g., if parallel arrays are used) can be performed concurrently with intra-phase balancing.
Controllers 900 and 950 (as well as balance controllers 906 and 910) can be implemented in hardware, software or a combination thereof within control system 102. Controllers 900 and 950 can be implemented within MCD 112, distributed partially or fully among LCDs 114, or may be implemented as discrete controllers independent of MCD 112 and LCDs 114.
Interconnection (IC) Module Examples
Modules 108 can be connected between the modules of different arrays 700 for the purposes of exchanging energy between the arrays, acting as a source for an auxiliary load, or both. Such modules are referred to herein as interconnection (IC) modules 108IC. IC module 108IC can be implemented in any of the already described module configurations (108A, 108B, 108C) and others to be described herein. IC modules 108IC can include any number of one or more energy sources, an optional energy buffer, switch circuitry for supplying energy to one or more arrays and/or for supplying power to one or more auxiliary loads, control circuitry (e.g., a local control device), and monitor circuitry for collecting status information about the IC module itself or its various loads (e.g., SOC of an energy source, temperature of an energy source or energy buffer, capacity of an energy source, SOH of an energy source, voltage and/or current measurements pertaining to the IC module, voltage and/or current measurements pertaining to the auxiliary load(s), etc.).
Switch circuitry units 604 are coupled between positive and negative terminals of energy source 206 and have an output that is connected to an IO port of module 108IC. Units 604-PA through 604-PΩ can be controlled by control system 102 to selectively couple voltage +VIC or −VIC to the respective module I/O ports 1 through Ω. Control system 102 can control switch circuitry 603 according to any desired control technique, including the PWM and hysteresis techniques mentioned herein. Here, control circuitry 102 is implemented as LCD 114 and MCD 112 (not shown). LCD 114 can receive monitoring data or status information from monitor circuitry of module 108IC. This monitoring data and/or other status information derived from this monitoring data can be output to MCD 112 for use in system control as described herein. LCD 114 can also receive timing information (not shown) for purposes of synchronization of modules 108 of the system 100 and one or more carrier signals (not shown), such as the sawtooth signals used in PWM (
For inter-phase balancing, proportionally more energy from source 206 can be supplied to any one or more of arrays 700-PA through 700-PΩ that is relatively low on charge as compared to other arrays 700. Supply of this supplemental energy to a particular array 700 allows the energy output of those cascaded modules 108-1 thru 108-N in that array 700 to be reduced relative to the unsupplied phase array(s).
For example, in some example embodiments applying PWM, LCD 114 can be configured to receive the normalized voltage reference signal (Vrn) (from MCD 112) for each of the one or more arrays 700 that module 108IC is coupled to, e.g., VrnPA through VrnPΩ. LCD 114 can also receive modulation indexes MiPA through MiPΩ for the switch units 604-PA through 604-PQ for each array 700, respectively, from MCD 112. LCD 114 can modulate (e.g., multiply) each respective Vrn with the modulation index for the switch section coupled directly to that array (e.g., VrnA multiplied by MiA) and then utilize a carrier signal to generate the control signal(s) for each switch unit 604. In other embodiments, MCD 112 can perform the modulation and output modulated voltage reference waveforms for each unit 604 directly to LCD 114 of module 108IC. In still other embodiments, all processing and modulation can occur by a single control entity that can output the control signals directly to each unit 604.
This switching can be modulated such that power from energy source 206 is supplied to the array(s) 700 at appropriate intervals and durations. Such methodology can be implemented in various ways.
Based on the collected status information for system 100, such as the present capacity (Q) and SOC of each energy source in each array, MCD 112 can determine an aggregate charge for each array 700 (e.g., aggregate charge for an array can be determined as the sum of capacity times SOC for each module of that array). MCD 112 can determine whether a balanced or unbalanced condition exists (e.g., through the use of relative difference thresholds and other metrics described herein) and generate modulation indexes MiPA through MiPΩ accordingly for each switch unit 604-PA through 604-PΩ.
During balanced operation, Mi for each switch unit 604 can be set at a value that causes the same or similar amount of net energy over time to be supplied by energy source 206 and/or energy buffer 204 to each array 700. For example, Mi for each switch unit 604 could be the same or similar, and can be set at a level or value that causes the module 108IC to perform a net or time average discharge of energy to the one or more arrays 700-PA through 700-PQ during balanced operation, so as to drain module 108IC at the same rate as other modules 108 in system 100. In some embodiments, Mi for each unit 604 can be set at a level or value that does not cause a net or time average discharge of energy during balanced operation (causes a net energy discharge of zero). This can be useful if module 108IC has a lower aggregate charge than other modules in the system.
When an unbalanced condition occurs between arrays 700, then the modulation indexes of system 100 can be adjusted to cause convergence towards a balanced condition or to minimize further divergence. For example, control system 102 can cause module 108IC to discharge more to the array 700 with low charge than the others, and can also cause modules 108-1 through 108-N of that low array 700 to discharge relatively less (e.g., on a time average basis). The relative net energy contributed by module 108IC increases as compared to the modules 108-1 through 108-N of the array 700 being assisted, and also as compared to the amount of net energy module 108IC contributes to the other arrays. This can be accomplished by increasing Mi for the switch unit 604 supplying that low array 700, and by decreasing the modulation indexes of modules 108-1 through 108-N of the low array 700 in a manner that maintains Vout for that low array at the appropriate or required levels, and maintaining the modulation indexes for other switch units 604 supplying the other higher arrays relatively unchanged (or decreasing them).
The configuration of module 108IC in
Furthermore, IC modules can be configured to exchange energy between two or more subsystems of system 100.
In this embodiment each module 1081C is coupled with a first array of subsystem 1000-1 (via IO port 1) and a first array of subsystem 1000-2 (via IO port 2), and each module 1081C can be electrically connected with each other module 1081C by way of I/O ports 3 and 4, which are coupled with the energy source 206 of each module 1081C as described with respect to module 108C of
Each module 1081C has a switch unit 604-1 coupled with IO port 1 and a switch unit 604-2 coupled with I/O port 2, as described with respect to
In systems with IC modules between phases, interphase balancing can also be performed by neutral point shifting (or common mode injection) as described above. Such a combination allows for more robust and flexible balancing under a wider range of operating conditions. System 100 can determine the appropriate circumstances under which to perform interphase balancing with neutral point shifting alone, inter-phase energy injection alone, or a combination of both simultaneously.
IC modules can also be configured to supply power to one or more auxiliary loads 301 (at the same voltage as source 206) and/or one or more auxiliary loads 302 (at voltages stepped down from source 302).
The energy source 206 of each IC module can be at the same voltage and capacity as the sources 206 of the other modules 108-1 through 108-N of the system, although such is not required. For example, a relatively higher capacity can be desirable in an embodiment where one module 1081C applies energy to multiple arrays 700 (
Topology Examples for Applications with Intermittent Charging
Example embodiments pertaining to modular energy systems 100 used in applications with intermittently available charge sources are described with reference to
The example embodiments can be implemented in a variety of configurations to store and deliver energy while the electric tram is moving through sections of rail where no charge source is available.
Tram 1100 can be configured with one or more iterations of system 100, each with its own control system 102, and each iteration of system 100 can supply one or more loads, such as motor loads and auxiliary loads. The tram can have a single iteration of system 100 with one or more subsystems 1000 that supplies power for all loads of all cars. The one or more subsystems 1000 can share one control system 102 (e.g., a single MCD 112 for all subsystems 1000) or can have independent control systems 102. The cars can each have one or more subsystems 1000 of system 100 for supplying the loads within that car, or the cars can rely wholly on power supplied by a subsystem 1000 in another car. A combination of approaches can be used where a particular car has a subsystem 1000 for supplying certain loads of that particular car and that particular car can also have other loads that receive power from another subsystem 1000 in a different car.
System 100 can also be configured to supply multiple voltages for auxiliary loads having different power requirements, including multiphase power, single phase power, and DC power at one or more voltages each. Examples of auxiliary loads can include compressors for HVAC systems, a battery thermal management system (BTMS), onboard electrical networks for powering all automated aspects of tram 1100, and others. Here, system 100 is configured to supply three-phase power (PD, PE, PF) to three-phase auxiliary load 1112-1 over lines 1113, single phase (SP) power (line (L), neutral (N)) to single phase auxiliary load 1114-1 over lines 1115, DC voltage at a first level to auxiliary load 301-1 over lines 1117, and DC voltage at a second level to auxiliary load 302-1 over lines 1119 (see, e.g., power supply for loads 301 and 302 as described with respect to
One or more motors 1110 (e.g., one, two, three, four, or more) can be secured to or associated with a bogie, and the rail-based vehicle can have multiple (e.g., two or more) such bogies for every car. Placement of system 100 and its subsystems 1000 can be in close proximity to motors 1110 or elsewhere as described herein.
Each subsystem 1000 can be connected to sets of shared lines for sharing DC power, and these lines can cross between cars 1101 and 1102 through interconnection 1103. Lines 1130 can carry high-voltage positive and negative DC signals, DC_CS+ and DC_CS−, respectively, from charge source 150, for supplying charge voltage to all of the modules 108 of each system 100 when tram 1100 is connected to a charge source 150. The shared lines can also exchange lower DC voltages for supply to auxiliary loads 301 and 302. Lines 1131 can carry positive and negative DC signals, DC1+ and DC1−, respectively, for supplying a lower DC voltage to auxiliary loads 301. For example, these lines can be similar to the lines interconnecting ports 3 and 4 of IC modules 1081C (and 108C) as described with respect to
The embodiments of
The embodiments of
Modules 108A-C and 108IC described herein can be used within tram 1100. Additional example embodiments of module configurations are also described.
Module 108D includes converter 202B or 202C coupled with energy sources 206A and 206B in a manner similar to that described with respect to module 108B of
Transformer and rectifier section 1204 can include a high-frequency transformer and one phase diode rectifier. The DC voltage on ports 7 and 8 may be a voltage that is lower than the total voltage supplied by the charge source as subsystem 1000 may include many such modules 108 receiving charge simultaneously. Transformer and rectifier section 1204 can modify the voltage of the AC signal from converter 1202, if necessary, and convert the AC signal back into DC form to charge sources 206A and 206B. Section 1204 also provides high-voltage isolation to the other components 202, 204, 206 and 114 of module 108D.
Unidirectionality is provided by virtue of the diode rectifier which permits current to be received from charge source 150 and passed to buffer 204 but does not permit outputting current in the opposite manner. For example, upon braking if the vehicle has an energy recovery system then the current from braking can be transferred back to each module 108 through power connection 110 and routed to either of sources 206A and 206B by way of converter 202B,C. Presence of unidirectional DC-DC isolated converter 1200 (diode rectifier) will prevent that recovered energy from passing through module 108D back to the charge source via lines 1130.
LCD 114 can monitor the status of converter 1200, particularly converter 1202 and section 1204, over data connections 118-5 and 118-6, respectively. As with the other components of module 108E, monitor circuitry for converter 1202 and section 1204 can be included to measure currents, voltages, temperatures, faults, and the like. These connections 118-5 and 118-6 can also supply control signals to control switching of converter 1202 and to control any active elements within section 1204. Isolation of LCD 114 can be maintained by isolation circuitry present on lines 118-5 and 118-6 (e.g., isolated gate drivers and isolated sensors).
Bidirectional converter 1210 is connected between I/O ports 7 and 8 and buffer 204 includes DC-AC converter 1202, connected to transformer 1206, which in turn is connected to AC-DC converter 1208. Converter 1202 can convert the DC voltage at ports 7 and 8 into a high-frequency AC voltage, which transformer 1206 can modify to a lower voltage if needed, and output that modified AC voltage to AC-DC converter 1208, which can convert the AC signal back into DC form for provision to sources 206A, 206B, or module ports 1 and 2. Transformer 1206 can also isolate module components 202, 204, 206, 1208, and 114 from the high voltage at ports 7 and 8. As with the other components of module 108E, monitor circuitry for converter 1202, transformer 1206, and converter 1208 can be included to measure currents, voltages, temperatures, faults, and the like. LCD 114 can monitor the status of converter 1210, particularly converter 1202, transformer 1206 (e.g., monitor circuitry or an active component associated therewith), and converter 1208, over data connections 118-5, 118-7, and 118-8, respectively. These connections 118-5 and 118-6 can also supply control signals to control switching of converter 1202 and to control any controllable elements associated with transformer 1206. Isolation of LCD 114 can be maintained by isolation circuitry present on lines 118-5 and 118-6 (e.g., isolated gate drivers and isolated sensors).
Furthermore, for electrochemical battery sources 206, the length of the charge pulses applied to sources 206 by AC-DC converter 1208 can be maintained to have a certain length, e.g., less than 5 milliseconds, to promote the occurrence of the electrochemical storage reaction in the cells without the occurrence of significant side reactions that can lead to degradation. The charge methodology can incorporate active feedback from each energy source to ensure that battery degradation, if detected, is mitigated by lowering voltage or pausing the charge routine for that module, or otherwise. Such pulses can be applied at high C rates (e.g., 5C-15C and greater) to enable fast charging of the sources 206. The duration and frequency of the charge pulses can be controlled by control system 102. Examples of such techniques that can be used with all embodiments described herein are described in Int'l Appl. No. PCT/US20/35437, titled Advanced Battery Charging on Modular Levels of Energy Storage Systems, which is incorporated by reference herein for all purposes.
Each array 700 can also include a module 1081C having interconnected sources 206 for energy sharing and interphase balancing. Modules 1081C-1 through 1081C-3 can be configured like the embodiments described with respect to
In some embodiments, a separate subsystem 1000 may not be needed to generate the requisite three-phase and single phase voltages for auxiliary loads. In such embodiments, subsystem 1000-5 can be omitted and an auxiliary power converter can be used to instead generate the three-phase in single phase auxiliary load voltages. This auxiliary converter can be connected to DC charge source lines 1130 and can receive power either from charge source 150 or the other subsystems 1000 when charge source 150 is not connected.
The use of bidirectional converters 1210 in the modules of subsystems 1000-1 through 1000-5 allows those subsystems to supply relatively higher DC voltages across lines 1130, for example in a configuration where a large auxiliary load, such as a battery thermal management system (BTMS), is powered directly from lines 1130. In such an instance the auxiliary load connected across lines 1130 can be powered directly by the charge source when connected to tram 1100 and then can be powered by one or more subsystems 1000 outputting power from sources 206 through bidirectional converters 1210 of each module 108.
The embodiments disclosed herein are not limited to operation with any particular voltage, current, or power. By way of example and for purposes of context, in one sample implementation charge source 150 may provide a voltage of 600-1000V on lines 1130. Each of subsystems 1000-1 through 1000-4 may provide multiphase voltages that are regulated and stabilized by voltage and frequency if required, in those voltages may be 300-1000V depending on the needs of the motors. An example three-phase auxiliary voltage for load 1112 can be 300-500V, regulated and stabilized as needed. An example single phase auxiliary voltage for load 1114 can be 120-240V, regulated and stabilized as needed. Example auxiliary voltages for load 301 can be 48-60V and example auxiliary voltages for load 302 can be 24-30V. Again these are examples only for purposes of context and the voltages that system 100 can provide will vary depending on the needs of the application.
To maintain a balanced overall system, the energy of sources 206 of auxiliary subsystem 1000-5 can be transferred to any of the (non-auxiliary) subsystems 1000-1 through 1000-4 by way of lines 1131 and the shared interconnection module connections, and this energy can be used either for charging those subsystems 1000-1 through 1000-4 or supply to the motors. Thus energy from auxiliary subsystem 1000-5 can be used to power one or more motors even though not directly connected to those motors, but rather indirectly connected to those motors by way of one or more other subsystems 1000-1 through 1000-4. Similarly, energy recovered through braking can be shared between subsystems 1000-1 through 1000-5 by way of lines 1131 and the shared interconnection module connections.
Example Embodiments of Current Control for Multiple Sources
Example embodiments pertaining to the control of systems having multiple discretely controllable energy sources are now described with reference to
The present embodiments can be implemented in systems having two or more energy sources, regardless of whether they are in a cascaded arrangement, provided the sources are discretely controllable such that the power supplied by one source can be controlled (e.g., varied) with respect to the power supplied by at least one other source.
Several example embodiments of different control configurations are described with respect to
In each of the examples of
The inclusion of multiple energy sources in a system can provide numerous benefits. Having multiple energy sources of the same class, type and electrical characteristics increases the energy and power capacity of the system or module. Mixing multiple energy sources of different classes (e.g., battery, HED capacitor, fuel cell), different types within each class (e.g., different chemistries, different structural designs), and/or different electrical operating characteristics (e.g., different nominal voltages, capacities, capacitances, maximum power outputs, etc.) also increases the energy and power capacity of the system, subsystem, or module, but in a manner that can provide improvements in other respects where the sources differ. Such differences can be in terms of energy density, power density, cost, lifespan or cyclability, safety, operating range (e.g., voltage, temperature), capacity, and/or charge time, to name a few examples. Thus, source classes, types, and/or electrical characteristics can be mixed in a wide variety of different combinations to achieve superior performance over those aspects in which the sources differ, with such differences being selected to tailor the system for a particular application.
For example, a system or module may have a first energy source of a first class (e.g., an HED capacitor) and a second energy source of a second class (e.g., a battery). By way of another example the system or module may have a first battery source of a first type (e.g., LTO) and a second battery source of a second type (e.g., NMC). In both examples the first source may have a relatively higher power density and a relatively lower energy density, thus making it desirable to utilize the first source more than the second source during operation times requiring high power, while the second source may have a relatively lower power density and relatively higher energy density, thus making utilization of the second source preferred over the first source during operation at lower power levels for prolonged periods of time.
In other embodiments, the system or module can have a renewable energy source, such as a photovoltaic (PV) device (e.g., a solar panel) or a wind-harnessing energy device, as a first source instead of using a stored energy source. The second energy source can be a stored energy source such as a battery (e.g., LTO or NMC). The system or module can utilize the first source to a relatively higher degree during times when the renewable energy is available and power requirements are higher, and the second source for meeting relatively lower power requirements but for longer periods of operation (e.g., higher energy density).
Although not limited to such, the following current control embodiments will be described in the context of a cascaded system 100 where one or more modules 108 have multiple discretely controllable energy sources 206.
Example embodiments of modules 108 having multiple sources 206 are described with respect to module 108B of
The current output by source 206A is equivalent to IA, the current output by source 206B is equivalent to IB, and the current output by switch circuitry 602A to switch circuitry 601 is equivalent to IOUT, as described with respect to
PMC 1800 can be provided with information assessing the present or recent state of module 108 and its sources 206, and the load requirements, and on this basis generate control information that can be used to generate control signals for switch circuitry 602A to discretely control the current (IB) output by source 206B when system 100 is in a discharge state. In this embodiment, PMC 1800 includes a current controller loop section 1802 and a reference current control section 1804. Reference current control section 1804 can generate a reference current IB* based on at least one measured or estimated operating parameter of each source 206 and based on a measured or estimated current or power requirement of the load. Determination of reference current IB* can also be based on whether the load power requirements are relatively constant (e.g., steady-state) or changing (e.g., transient). The generated reference current IB* can be used by current controller loop section 1802, along with information about the present state of module 108, to generate duty cycle information for switch circuitry 602A. This duty cycle information can then be used to generate control signals that drive the individual switches S1 and S2 into on-off states (e.g., S1 is on while S2 is off, and S1 is off while S2 is on) at a rate that sets the actual time average current IB consistent with IB*.
The reference current IB* can be generated such that the at least one measured or estimated operating parameter of each source 206 converges towards a balanced condition if unbalanced, or is maintained in a balanced condition if already balanced, provided that balancing does not prevent achievement of the power output requirements of module 108 at any one time. This operating parameter can be, e.g., one of SOC, temperature, capacity, SOH, voltage, or current of the sources 206A and 206B. Many aspects of balancing are already described herein and likewise apply to these embodiments.
Since balancing all parameters may not be possible at the same time (e.g., balancing of one parameter may further unbalance another parameter), a combination of balancing any two or more parameters (SOC, T, Q, SOH, V, I) may be applied with priority given to either one depending on the requirements of the application. For example, priority in balancing can be given to SOC over other parameters (T, Q, SOH, V, I), with exceptions made if one of the other parameters (T, Q, SOH, V, I) reaches a severe unbalanced condition outside a threshold.
Example Embodiments Balancing SOC and Temperature
Example embodiments are now described where PMC 1800 controls the source currents while balancing SOC and temperature of the two sources 206A and 206B. The aspects of these examples can be applied to other embodiments seeking to balance one, two, three, or more different operating parameters of two or more sources 206.
Current controller loop section 1802 can be configured according to various control architectures. In this embodiment, section 1802 is configured with a model predictive control (MPC) architecture that exhibits a fast response and can compensate for errors in the measured parameters. In another embodiment section 1802 can be implemented as a proportional-integral (PI) or proportional-integral-derivative (PID) controller.
The voltage of source 206B (VB), the current from source 206B (IB), and the DC link voltage (VDCL) are measured at each sampling instant j and this information is provided to PMC 1800. Taking of this measurement can be coordinated by PMC 1800 (controlling monitor circuitry 208) or another element of control system 102.
The variations of VB and VDCL typically occur slower in time than variations in IB. In the time domain, VB [j+1] and VDCL [j+1] are assumed to be equal to their measured values at the jth sampling instant. Using the Euler approximation, the variables can be expressed as (2), where TS=1/fSF, with fSF being the sampling frequency which can be equal to the switching frequency of switch circuitry 601 of converter 202:
Using these equations to satisfy IB[j+1]=IB*, DB can be expressed as (3):
The reference current IB* can be calculated by reference current control section 1804 and provided to section 1802 as described below. Determination of DB[j] can be performed by current controller loop section 1802 and this information can be used to produce the drive signals for switching circuitry 602A, which in turn will set the actual current IB.
The power of source 206B (PB) in an environment (e.g., module) with two sources can be expressed as shown in (4), where balancing of N parameters concurrently is desired:
P
B=[0.5+KR1(R1B−R1AVE)+KR2(R2B−R2AVE) . . . +KRN(RNB−RNAVE)]*PL (4)
where R1 is a first parameter being balanced, KR1 is a balance factor for the first parameter, R1B is the value of the first parameter for source 206B, R1AVE is the average value of R1 for the two sources, R2 is a second parameter being balanced, KR2 is a balance factor for the second parameter, R2B is the value of the second parameter for source 206B, R2AVE is the average value of R2 for the two sources, and so forth for the N parameters, where RN is an Nth parameter being balanced, KRN is a balance factor for the Nth parameter, RNB is the value of the Nth parameter for source 206B, and RNAVE is the average value of RN for the two sources. The sign (+/−) of each balancing term (e.g., KR1(R1B−R1AVE)) can be selected based on whether that balancing term should tend to increase or decrease current of source 206B to rectify a particular imbalance.
Equation (4) can be tailored specifically for the example where SOC and temperature are concurrently balanced, as shown in (5):
P
B=[0.5+KSOC(SOCB−SOCAVE)−KTemp(TB−TAVE)]*PL (5)
where PL is the power demanded or supplied by the load 2002, SOCB is the state of charge of source 206B, SOCAVE is the average state of charge of sources 206A and 206B, TB is the temperature of source 206B, TAVE is the average temperature of sources 206A and 206B, KSOC is a balancing factor for SOC, and KTemp is a balancing factor for temperature. The value of PL can be provided to PMC 1800 by control system 102 or an external control device 104 (e.g., a motor or demand controller). SOC and temperature values can be measured via one or more sensors or measurement circuits, or estimated using an estimation function or algorithm (e.g., SOC can be determined through use of Coulomb counting). The balance factors (KSOC and KTemp) can be determined in a number of different ways as will be described.
Reference current control section 1804 can utilize (5) to determine the desired reference power PB of source 206B, and from this the desired reference current IB*, which can be used in turn by section 1802 to determine the duty cycle DB. For this example, function (5) can be used to select a desired current of source 206B that, along with the current of source 206A according to IA=IOUT−IB, will meet the present requirements of the load 2002, while concurrently considering the present SOC and temperature of each of sources 206A and 206B, and adjusting the relative current of each source to: cause the sources to maintain balance in SOC and temperature, to cause the sources to converge towards a balanced target value for SOC and/or temperature, or to minimize divergence of the sources away from a balanced target value for SOC and/or temperature.
There may be conditions or limitations that render it undesirable to seek balance while controlling the current. PMC 1800 may detect or consider such conditions or limitations and, in response, control current without applying balancing rules. For example, PMC 1800 can control the current without violation of maximum charge or discharge current thresholds for each of sources 206. One of the sources may reach its maximum current requiring the difference to be made up by the other source even though that source is lower in SOC or higher in temperature. Other examples may be specific to the specific operating configuration of system 100. For example, in an embodiment where source 206B has a relatively higher power density than source 206A, it may be desirable to utilize source 206B primarily or exclusively to meet the load demands in times of transient or higher than normal current, which may cause the sources to diverge from a balanced condition. When the transient condition concludes, continued operation of PMC 1800 will cause the sources to converge towards a balanced condition.
The balance factors KSOC and KTemp control how aggressively an imbalance in SOC and temperature are addressed, e.g., a relatively higher balance factor corresponds to a relatively higher disparity between source output currents. PMC 1800 can reference the SOC value of both sources, identify which has the lower SOC value, and utilize this SOC value to select or determine KSOC. Similarly, PMC 1800 can reference the temperature of both sources, identify which has the lower temperature, and utilize this temperature value to select or determine KTemp.
While a single constant value can be used as a balance factor for a range of SOC and temperature values, the use of variable balance factors enables the system to compensate for imbalances differently depending on the source conditions (e.g., SOC and temperature) or conditions of other elements of the module or system (e.g., cooling system load). For example, as states of charge decrease, it can be desirable to likewise decrease the SOC balance factor KSOC in order to maintain operating margins in available energy. Similarly, as battery temperatures increase, it can be desirable to likewise increase the temperature balance factor KTemp in order to stay within the battery's operating range.
Referring back to (5), a positive value for the term (+KSOC(SOCB−SOCAVE)) indicates an unbalanced condition with source 206B having a higher SOC than source 206A, and will tend to increase current from source 206B to balance the SOC values. A negative value for the subsequent term (−KTemp(TB−TAVE)) indicates an unbalanced condition with source 206B having a higher temperature than source 206A, and will tend to decrease current from source 206B. The relative values of the terms depend on the value of the balance factor and the magnitude of the difference between source 206B's value and the average. Thus the variable balance factor linked to the actual SOC and temperature of one or both sources allows PMC 1800 to prioritize balancing of one parameter over the other. For example, if sources 206A and 206B have comparable differences in SOC and temperature, with SOC in a moderate range and temperatures in a relatively high range, then PMC 1800 will prioritize balancing of temperature over SOC through execution of equation (5).
The balance factors can be one or more discrete values stored in memory in the form of a data structure (e.g., one or more arrays or lookup tables) expressed in or accessible by the program instructions of control system 102 (e.g., PMC 1800). The balance factors can also, or alternatively, be represented as one or more algorithmic functions expressed in the program instructions of control system 102 (e.g., PMC 1800). For certain values of SOC or temperature, it may be desirable to use a discrete value for the balance factor whereas for different values of SOC or temperature it may be desirable to use in algorithmic function, thus both approaches can be used in a single embodiment. The balance factors can alternatively be implemented in hardware or combination of software and hardware.
The balance factors can be predetermined, such as through experimentation or modeling, prior to use in a real-world setting. The balance factors, once determined or set, can be adjusted or iterated for purposes of enhancement. For example, control system 102 can utilize a machine learning algorithm to identify more efficient or effective balance factors as system 100 is used, and can adjust the stored balance factors, whether in discrete-value form or algorithmic form, to achieve superior performance during the next iterative use of system 100.
In many embodiments different balance factors can be used depending on whether the system is presently in a state of charging or discharging. For discharge scenarios, in some embodiments the SOC balance factor magnitudes can increase with increasing SOC percentage and the temperature balance factor magnitudes can increase with increasing temperature. For charge scenarios, in some embodiments the SOC balance factor magnitudes can decrease with increasing SOC percentage and the temperature balance factor magnitudes can decrease with increasing temperature.
Several examples of balance factors are described with respect to Tables 1A, 1B, 2A, and 2B. These examples are appropriate for either or both charge and discharge scenarios. Table 1A presents an embodiment where each SOC value (e.g., 0-99%) has a discrete balance factor numeric value (e.g., x1, x2, x3, . . . x99) associated with it. In this embodiment there is also a minimum SOC (e.g., 4%) and maximum SOC (e.g., 96%) that represent optional thresholds below and above which no balancing occurs, and do not have corresponding balance factors. Table 1B presents an embodiment where temperature values within the combined thermal operating range of the sources (e.g., −20 C to 60 C) have discrete balance factor values (e.g., y1, y2, y3, . . . y60) associated with them. In this example, no balancing is performed for operating temperatures of 0 C and below and thus balancing factors are not necessary. Different and more or less granular ranges of SOC and temperature can be used. The actual numeric values used for the balancing factors can be selected based on the needs of the particular system configuration and application.
In another embodiment, all or part of the range of states of charge can have balance factors expressed as or correlating to a mathematical function, e.g., a linear or nonlinear function. The same is true for all or part of the range of temperatures. Tables 2A and 2B show examples where different ranges of SOC and temperature, respectively, are expressed as different mathematical functions FS1-FS5 and FT1-FT3, respectively. For example the differing functions may have different slopes such that the balance factors increase with SOC and temperature. In this example the SOC values are separated into five ranges between SOCmin and SOCmax and the temperature values are separated into three ranges.
In some embodiments a relatively small variation exists from one balance factor to the next so as to minimize the possibility of current spikes. For example, the balance factor values or functions can be set such that a balance factor (e.g., x1) for a first SOC or temperature measurement (or estimation) (e.g., 25% SOC or 35 degrees C.) does not vary by more than a threshold from a balance factor (e.g., x1+/−threshold) of an adjacent SOC or temperature measurement (e.g., 24% and 26% for SOC, 34C and 36C for temperature). The threshold can be determined based on the needs of the application. In some embodiments, the threshold is 5% or less, and in other embodiments the threshold is 2% or less, and in still other embodiments the threshold is 1% or less.
As described above, these embodiments can be executed within control system 102 by, e.g., reference to the balance factors stored as one or more discrete values, mathematical functions, or combinations thereof.
Further Control Embodiments
Example embodiments of methods related to the control of current and multiple source applications are described with respect to
At 2204, a reference current (I*) is determined for at least one of the multiple sources depending on controller design and the number of sources being balanced, as described with respect to
At 2206, switching signals for the current regulation circuitry (e.g., portion 602A) are generated to set the output current of the one or more sources being discretely controlled based on the reference current I* and the current state of the sources (e.g., source voltages). The reference current can be used to determine a desired duty cycle of the switching circuitry, such as by reference to equation (3), which can then be translated to the switching signals and output to the switch circuitry.
At 2304, PMC 1800 can evaluate whether a net discharge or a net charge scenario exists for example by evaluating the polarity of the load current or by receiving an indication of a discharge or charge scenario from control system 102 or an external control device. Operation in a discharge scenario may require the use of different thresholds (step 2304) or balance factors (2308) as compared to those selected for a charge scenario. Step 2303 can be performed at this or different times in the sequence of this and other embodiments.
At 2306, it is determined whether the assessed operating parameter is within a threshold or permissible range for balancing. For example, an SOC level of 1-3% may be too low for SOC balancing, or a temperature of 60 C may be too high for temperature balancing. PMC 1800 can make this determination for each of the relevant operating parameters and exit the balance factor selection routine if one such parameter is outside of the threshold or permissible range for balancing. If within the permissible range(s), then PMC 1800 can proceed to the next step. In some embodiments, the determination at step 2306 is omitted and the balance factors are set such that when the assessed parameter is in a range where balancing is less desirable, or not desirable, then the balance factor in that range will be a constant, e.g., with a value that is relatively low (or zero), thus minimizing the impact of imbalance in that parameter in the overall balancing scheme performed by PMC 1800.
At 2308, the extreme (e.g., greatest or lowest) value for each assessed operating parameter is identified for use in selecting the balance factor for that operating parameter. For example with respect to SOC, the lowest SOC level of the assessed SOC levels of the multiple sources can be used in identifying the SOC balance factor KSOC to be used. An example with respect to temperature, the highest temperature level of the assessed temperature levels of the multiple sources can be used in identifying the temperature balance factor KTemp to be used. At 2310, the balance factor is identified (e.g., selected or calculated) for each operating parameter being balanced. This can be performed in accordance with any of the examples described herein. The identified one or more balance factors can then be passed or output to the function and/or hardware responsible for determining the reference current.
At 2404 the target value is compared to the present value of that operating parameter. The present value can be directly measured, determined based on measurements of other values (e.g., determination of SOC based on measured voltages or charge counting), or otherwise estimated or calculated. The difference between the target value and the present value is an indication of the amount of offset that the source presently has from the operating goal.
At 2406 the reference current I* can be determined based on the power or current requirements of the load, as well as the offset amount and balance factor for each operating parameter being balanced (see, e.g., equations (4) and (5)). The balance factor can vary based on the magnitude of the operating parameter, e.g., the balance factor can scale with the operating parameter. As stated, the power or current requirements of the load can be reported to PMC 1800 by control system 102 or an external control source, can be predicted or estimated by control system 102, can be measured by system 100, and/or any combination thereof. Steps 2404 and 2406 need not be executed separately and can be combined such as through execution of equation (4) or (5).
In some embodiments where sources of different power densities are utilized, it may be desirable to increase current supplied by the source with relatively greater power density to meet rapidly changing, or transient, discharge demands by the load. The embodiments described herein can be modified to detect a transient condition and adjust current control based thereon.
If a transient condition is detected, then at 2504 PMC 1800 can determine an adjustment to the reference current to cause the higher power density source to contribute relatively more current to meet the load requirements. PMC 1800 can utilize a gain factor that sets the proportion of transient current to be applied by the higher power density source. The gain factor can set such that, for example in a two source module, the higher power density source supplies between 51% and 100% of the transient current above the steady-state current supplied by both sources. This adjustment can be applied as part of the reference current determination step 2204 of method 2200 or step 2406 of method 2400, such that the reference current I* determined by the system and utilized for generating the switching signals accounts for the transient condition.
In many embodiments, it is desirable to evaluate the processed output (or input) currents of each source to ensure that PMC 1800 does not exceed a maximum current output (or input) to each source. The embodiments described herein can be modified to monitor for maximum current violations and adjust the reference current accordingly.
In embodiments where current is adjusted on the basis of a transient condition (e.g., method 2500) and/or the basis of a maximum current violation (e.g., method 2600), such adjustments may prevent the sources from converging towards a balanced condition, or may prevent the sources from maintaining a balanced condition. In these embodiments, control system 102 is configured to override or ignore the balancing target temporarily, and to revert to balancing as soon as possible conditions permit, such as a return to steady-state conditions or operation within maximum current thresholds.
The embodiments described herein can be used in a cascaded system 100 having one or more different arrays 700 each having two or more modules 108. System 100 can be arranged in a manner that permits inter-array balancing with IC modules 1081C (e.g.,
Control system 102 can perform balancing for the same one or more operating parameters for all sources, or can balance a first one or more operating parameters for a first subset of sources while balancing a second one or more operating parameters for a second subset of sources. For example, control system 102 can balance SOC and temperature for all sources 206 of an array 700, and can balance SOC for all arrays 700 but not temperature. Thus numerous different balancing combinations can be configured in accordance with the present subject matter.
At 2704, control system 102 can balance one or more operating parameters of the sources of each module 108 of a particular array 700 corresponding to a particular phase. This intraphase balancing of step 2704 can be performed by adjustment of modulation indexes like that described with respect to array controller 900 of
If system 100 is configured to perform interphase balancing, then at 2706, control system 102 can balance one or more operating parameters of the sources of different arrays 700. This interphase balancing of step 2706 can be performed by injecting common mode to the phases (e.g., neutral point shifting) or through the use of interconnection modules or through both, as described herein. The one or more operating parameters balanced in step 2706 can be the same or different than those balanced in steps 2704 and 2702. If the same one or more operating parameters are balanced, then control system 102 will manage the power of all modules (or the balanced subset of modules) of all arrays 700 to seek balance in those parameters.
Simulation Results
As can be seen the temperature of both sources remains relatively balanced over the entire 100 seconds, as does the SOC of both sources. The maximum temperature variation between sources is less than 2° C., and the maximum variation in SOC is less than 2%. While the SOC and temperature values remain close, it is not required that the SOC values converge towards each other at the same time as the temperature values are converging towards each other in order for the system to maintain a balanced state. As noted in regions 2822 (
Various aspects of the present subject matter are set forth below, in review of, and/or in supplementation to, the embodiments described thus far, with the emphasis here being on the interrelation and interchangeability of the following embodiments. In other words, an emphasis is on the fact that each feature of the embodiments can be combined with each and every other feature unless explicitly stated or taught otherwise.
In many embodiments, a method of controlling current of a first energy source and a second energy source is provided, the method comprising: determining reference currents for the first energy source based on demand values of a load; and generating switching signals for switch circuitry coupled to the first energy source based on the reference currents, wherein the reference currents are determined such that a state of charge (SOC) of the first energy source is balanced with a SOC of the second energy source and such that a temperature of the first energy source is balanced with a temperature of the second energy source.
In some embodiments, the method further comprises: assessing a present SOC of the first energy source and a present SOC of the second energy source; assessing a present temperature of the first energy source and a present temperature of the second energy source; identifying an SOC balance factor and a temperature balance factor; and determining a first reference current for the first energy source based on the SOC balance factor and the temperature balance factor. Identifying the SOC balance factor can include referencing a data structure comprising a plurality of SOC balance factors. The data structure can be a lookup table. The data structure can include a first plurality of SOC balance factors cross-referenced with SOC values such that the first plurality of SOC balance factors increase with increasing SOC values. The first plurality of SOC balance factors can be used when the first and second energy sources are discharging. The data structure can include a second plurality of SOC balance factors cross-referenced with SOC values such that the first plurality of SOC balance factors decrease with increasing SOC values. The second plurality of SOC balance factors can be used when the first and second energy sources are charging.
In some embodiments, identifying the SOC balance factor can include executing an SOC balance factor algorithm.
In some embodiments, the method further includes determining whether to balance SOC of the first and second energy sources based on the present SOC of the first energy source and the present SOC of the second energy source.
In some embodiments, the method further includes determining the SOC balance factor based on the present SOC of the first energy source or the present SOC of the second energy source.
In some embodiments, the method further includes determining the SOC balance factor based on whether the first and second energy sources are in a discharge state or a charge state.
In some embodiments, identifying the temperature balance factor can include referencing a data structure comprising a plurality of temperature balance factors. The data structure can be a lookup table. The data structure can include a first plurality of temperature balance factors cross-referenced with temperature values such that the first plurality of temperature balance factors increase with increasing temperature values. The first plurality of temperature balance factors can be used when the first and second energy sources are discharging. The data structure can include a second plurality of temperature balance factors cross-referenced with temperature values such that the first plurality of temperature balance factors decrease with increasing temperature values. The second plurality of temperature balance factors can be used when the first and second energy sources are charging.
In some embodiments, identifying the temperature balance factor includes executing a temperature balance factor algorithm.
In some embodiments, the method further includes determining whether to balance temperature of the first and second energy sources based on the present temperature of the first energy source and the present temperature of the second energy source.
In some embodiments, the method further includes determining the temperature balance factor based on the present temperature of the first energy source or the present temperature of the second energy source.
In some embodiments, the method further includes determining the temperature balance factor based on whether the first and second energy sources are in a discharge state or a charge state.
In some embodiments, the method further includes determining duty cycles for the switch circuitry based on the reference currents.
In some embodiments, the switching signals are generated based on the duty cycles. The duty cycles can be determined using a model predictive control (MPC) technique.
In some embodiments, determining the reference currents for the first energy source includes determining a first reference current by: determining a target SOC for the first energy source; and determining the first reference current in part based on an offset between the target SOC and a present SOC of the first energy source. The target SOC can be an average of the present SOC of the first energy source and a present SOC of the second energy source.
In some embodiments, one of the first and second energy sources can have a relatively higher power density than the other, and determining the reference currents for the first energy source can include: identifying a transient increase in demand values; and determining or adjusting the reference currents such that the energy source with the relatively higher power density outputs at least a majority of current to meet the transient increase. The method can further include determining or adjusting the reference currents such that the energy source with the relatively higher power density outputs more current than the energy source with the relatively lower power density.
In some embodiments, determining the reference currents for the first energy source includes determining or adjusting the reference currents such that a maximum current threshold for either the first energy source or the second energy source is not exceeded.
In some embodiments, the reference currents are determined such that the SOC of the first energy source converges towards the SOC of the second energy source at a first time, and such that the temperature of the first energy source converges towards the temperature of the second energy source at a second time.
In many embodiments, a method of controlling current in a system having a plurality of energy sources is provided, the method including: assessing a first operating parameter for each of the plurality of sources and a second operating parameter for each of the plurality of sources; identifying a first balance factor for the assessed first operating parameters and a second balance factor for the assessed second operating parameters; and controlling current based on the first and second balance factors.
In some embodiments, the first operating parameter is one of: state of charge, temperature, voltage, current, state of health, state of energy, and state of power. The second operating parameter can be different from the first operating parameter, and the second operating parameter can be one of: state of charge, temperature, voltage, current, state of health, state of energy, and state of power.
In some embodiments, identifying the first and second balance factors is performed with reference to whether the plurality of sources are discharging or charging.
In some embodiments, the method further includes identifying an extreme value of the first operating parameters. Identifying the first balance factor can include referencing the extreme value.
In some embodiments, the method further includes identifying a first extreme value of the first operating parameters and a second extreme value of the second operating parameters, and identifying the first balance factor and the second balance factor can include referencing the first and second extreme values. The first operating parameter can be state of charge, the first extreme value can be a minimum state of charge of the plurality of energy sources, the second operating parameter can be temperature, and the second extreme value can be a maximum temperature of the plurality of energy sources.
In some embodiments, identifying a first balance factor for the assessed first operating parameters and a second balance factor for the assessed second operating parameters includes referencing at least data structure.
In some embodiments, identifying a first balance factor for the assessed first operating parameters and a second balance factor for the assessed second operating parameters includes algorithmically determining the first and second balance factors.
In many embodiments, a method is provided for controlling currents in an energy storage system having a first module and a second module connected in a first array, wherein each of the first and second modules as a first and a second energy source, the method including: controlling, for each module, energy outputs from the first and second energy sources such that the first energy source is balanced with the second energy source for a first operating parameter; and controlling energy outputs, for each module, such that the first and second modules are balanced for the first operating parameter.
In some embodiments, controlling, for each module, energy outputs from the first and second energy sources includes controlling a duty cycle of switch circuitry within each module.
In some embodiments, controlling, for each module, energy outputs from the first and second energy sources includes: determining reference currents for the first energy source based on demand values of a load; and generating switching signals for switch circuitry coupled to the first energy source based on the reference currents.
In some embodiments, controlling energy outputs such that the first and second modules are balanced for the first operating parameter includes controlling converter circuitry of each of the first and second modules according to a pulse width modulation technique. The method can further include adjusting modulation indexes for the first and second modules.
In some embodiments, the energy storage system includes a third module and a fourth module connected in a second array, and the method includes controlling energy outputs within the system such that the first and second arrays are balanced for the first operating parameter. Controlling energy outputs within the system such that the first and second arrays are balanced for the first operating parameter can include using common mode injection. The energy storage system can include an interconnection module coupled between the first and second arrays, and controlling energy outputs within the system such that the first and second arrays are balanced for the first operating parameter can include controlling an energy output of the interconnection module.
The first operating parameter can be one of: state of charge, temperature, voltage, current, state of health, state of energy, and state of power.
In many embodiments, a method is provided for controlling currents in an energy storage system having a first module and a second module connected in a first array, wherein each of the first and second modules has a first and a second energy source, the method including: controlling, for each module, energy outputs from the first and second energy sources such that the first energy source is balanced with the second energy source for a first operating parameter and a second operating parameter; and controlling energy outputs, for each module, such that the first and second modules are balanced for the first operating parameter and the second operating parameter.
In some embodiments, controlling, for each module, energy outputs from the first and second energy sources includes controlling a duty cycle of switch circuitry within each module. Controlling, for each module, energy outputs from the first and second energy sources can include: determining reference currents for the first energy source based on demand values of a load; and generating switching signals for switch circuitry coupled to the first energy source based on the reference currents.
In some embodiments, controlling energy outputs such that the first and second modules are balanced for the first operating parameter and the second operating parameter includes controlling converter circuitry of each of the first and second modules according to a pulse width modulation technique. The method can further include adjusting modulation indexes for the first and second modules.
In some embodiments, the energy storage system includes a third module and a fourth module connected in a second array, and the method includes controlling energy outputs within the system such that the first and second arrays are balanced for the first operating parameter and the second operating parameter. Controlling energy outputs within the system such that the first and second arrays are balanced for the first operating parameter and the second operating parameter can include using common mode injection. The energy storage system can include an interconnection module coupled between the first and second arrays, and controlling energy outputs within the system such that the first and second arrays are balanced for the first operating parameter and the second operating parameter can include controlling an energy output of the interconnection module.
The first operating parameter can be state of charge and the second operating parameter can be temperature.
In many embodiments, an energy storage system is provided, the energy stored system having a control system configured to: determine reference currents for a first energy source of the energy storage system based on demand values of a load; and generate switching signals for switch circuitry coupled to the first energy source based on the reference currents, wherein the reference currents are determined such that a state of charge (SOC) of the first energy source is balanced with an SOC of a second energy source of the energy storage system, and such that a temperature of the first energy source is balanced with a temperature of the second energy source.
In some embodiments, the control system is further configured to: assess a present SOC of the first energy source and a present SOC of the second energy source; assess a present temperature of the first energy source and a present temperature of the second energy source; identify an SOC balance factor and a temperature balance factor; and determine a first reference current for the first energy source based on the SOC balance factor and the temperature balance factor. The control system can be configured to identify the SOC balance factor by reference to a data structure comprising a plurality of SOC balance factors. The data structure can be a lookup table. The data structure can include a first plurality of SOC balance factors cross-referenced with SOC values such that the first plurality of SOC balance factors increase with increasing SOC values. The data structure can include a second plurality of SOC balance factors cross-referenced with SOC values such that the first plurality of SOC balance factors decrease with increasing SOC values.
In some embodiments, the control system can be further configured to identify the SOC balance factor by execution of an SOC balance factor algorithm.
In some embodiments, the control system can be further configured to determine whether to balance SOC of the first and second energy sources based on the present SOC of the first energy source and the present SOC of the second energy source.
In some embodiments, the control system can be further configured to determine the SOC balance factor based on the present SOC of the first energy source or the present SOC of the second energy source.
In some embodiments, the control system can be further configured to determine the SOC balance factor based on whether the first and second energy sources are in a discharge state or a charge state.
In some embodiments, the control system can be further configured to identify the temperature balance factor by reference to a data structure comprising a plurality of temperature balance factors. The data structure can be a lookup table. The data structure can include a first plurality of temperature balance factors cross-referenced with temperature values such that the first plurality of temperature balance factors increase with increasing temperature values. The data structure can include a second plurality of temperature balance factors cross-referenced with temperature values such that the first plurality of temperature balance factors decrease with increasing temperature values.
In some embodiments, the control system can be further configured to identify the temperature balance factor by execution of a temperature balance factor algorithm.
In some embodiments, the control system can be further configured to determine whether to balance temperature of the first and second energy sources based on the present temperature of the first energy source and the present temperature of the second energy source.
In some embodiments, the control system can be further configured to determine the temperature balance factor based on whether the first and second energy sources are in a discharge state or a charge state.
In some embodiments, the control system can be further configured to determine duty cycles for the switch circuitry based on the reference currents. The control system can be configured to determine the duty cycles with a model predictive control (MPC) technique.
In some embodiments, the control system can be further configured to: determine a target SOC for the first energy source; and determine a first reference current in part based on an offset between the target SOC and a present SOC of the first energy source.
In some embodiments, one of the first and second energy sources can have a relatively higher power density than the other, and the control system can be further configured to: identify a transient increase in demand values; and determine or adjust the reference currents such that the energy source with the relatively higher power density outputs at least a majority of current to meet the transient increase.
In some embodiments, the control system can be further configured to determine or adjust the reference currents such that a maximum current threshold for either the first energy source or the second energy source is not exceeded.
In some embodiments, the control system can be further configured to determine the reference currents such that the SOC of the first energy source converges towards the SOC of the second energy source at a first time, and such that the temperature of the first energy source converges towards the temperature of the second energy source at a second time.
In some embodiments, the control system includes a master control device and a local control device, wherein the local control device is associated with a module of the energy stored system, the module including the first and second energy sources and the switch circuitry.
In many embodiments, an energy storage system is provided that includes a plurality of energy sources and a control system configured to: assess a first operating parameter for each of the plurality of sources and a second operating parameter for each of the plurality of sources; identify a first balance factor for the assessed first operating parameters and a second balance factor for the assessed second operating parameters; and control current of the plurality of energy sources based on the first and second balance factors.
In some embodiments, the first operating parameter can be one of: state of charge, temperature, voltage, current, state of health, state of energy, and state of power. The second operating parameter can be different from the first operating parameter, and the second operating parameter can be one of: state of charge, temperature, voltage, current, state of health, state of energy, and state of power.
In some embodiments, the control system can be further configured to identify the first and second balance factors by reference to whether the plurality of sources are discharging or charging.
In some embodiments, the control system can be further configured to identify an extreme value of the first operating parameters. The control system can be further configured to identify the first balance factor by reference to the extreme value.
In some embodiments, the control system can be further configured to: identify a first extreme value of the first operating parameters and a second extreme value of the second operating parameters; and identify the first balance factor and the second balance factor by reference to the first and second extreme values. The first operating parameter can be state of charge, the first extreme value can be a minimum state of charge of the plurality of energy sources, the second operating parameter can be temperature, and the second extreme value can be a maximum temperature of the plurality of energy sources.
In many embodiments, an energy system is provided that includes a first module and a second module connected in a first array, wherein each of the first and second modules as a first and a second energy source, wherein the energy system further includes a control system configured to: control, for each module, energy outputs from the first and second energy sources such that the first energy source is balanced with the second energy source for a first operating parameter; and control energy outputs, for each module, such that the first and second modules are balanced for the first operating parameter.
In some embodiments, the control system can be further configured to control a duty cycle of switch circuitry within each module to control energy outputs from the first and second energy sources.
In some embodiments, the control system can be further configured to: determine reference currents for the first energy source based on demand values of a load; and generate switching signals for switch circuitry coupled to the first energy source based on the reference currents.
In some embodiments, the control system can be further configured to control energy outputs such that the first and second modules are balanced for the first operating parameter by control of converter circuitry of each of the first and second modules according to a pulse width modulation technique. The control system can be further configured to adjust modulation indexes for the first and second modules.
In some embodiments, the energy system further includes a third module and a fourth module connected in a second array, wherein the control system is further configured to: control energy outputs within the system such that the first and second arrays are balanced for the first operating parameter. The control system can be further configured to determine a common mode injection to control energy outputs within the system such that the first and second arrays are balanced for the first operating parameter.
In some embodiments, the energy system further includes an interconnection module coupled between the first and second arrays, wherein the control system is further configured to control and energy output of the interconnection module to balance the first and second arrays for the first operating parameter.
In some embodiments, the first operating parameter can be one of: state of charge, temperature, voltage, current, state of health, state of energy, and state of power.
In many embodiments, an energy system is provided that includes a first module and a second module connected in a first array, wherein each of the first and second modules has a first and a second energy source, wherein the energy system further includes a control system configured to: control, for each module, energy outputs from the first and second energy sources such that the first energy source is balanced with the second energy source for a first operating parameter and a second operating parameter; and control energy outputs, for each module, such that the first and second modules are balanced for the first operating parameter and the second operating parameter.
In some embodiments, the control system can be further configured to control a duty cycle of switch circuitry within each module to control energy outputs from the first and second energy sources.
In some embodiments, the control system can be further configured to: determine reference currents for the first energy source based on demand values of a load; and generate switching signals for switch circuitry coupled to the first energy source based on the reference currents.
In some embodiments, the control system can be further configured to control energy outputs such that the first and second modules are balanced for the first operating parameter and the second operating parameter by control of converter circuitry of each of the first and second modules according to a pulse width modulation technique. The control system can be further configured to adjust modulation indexes for the first and second modules.
In some embodiments, the energy system can further include a third module and a fourth module connected in a second array, wherein the control system is further configured to: control energy outputs within the system such that the first and second arrays are balanced for the first operating parameter and the second operating parameter. The control system can be further configured to determine a common mode injection to control energy outputs within the system such that the first and second arrays are balanced for the first operating parameter and the second operating parameter.
In some embodiments, the energy system can further include an interconnection module coupled between the first and second arrays, wherein the control system is further configured to control and energy output of the interconnection module to balance the first and second arrays for the first operating parameter and the second operating parameter.
In some embodiments, the first operating parameter can be state of charge and the second operating parameter can be temperature.
In the aforementioned embodiments, the control system can include processing circuitry and non-transitory memory on which is stored a plurality of instructions that, when executed by the processing circuitry, cause the control system to perform its functions.
The term “module” as used herein refers to one of two or more devices or sub-systems within a larger system. The module can be configured to work in conjunction with other modules of similar size, function, and physical arrangement (e.g., location of electrical terminals, connectors, etc.). Modules having the same function and energy source(s) can be configured identical (e.g., size and physical arrangement) to all other modules within the same system (e.g., rack or pack), while modules having different functions or energy source(s) may vary in size and physical arrangement. While each module may be physically removable and replaceable with respect to the other modules of the system (e.g., like wheels on a car, or blades in an information technology (IT) blade server), such is not required. For example, a system may be packaged in a common housing that does not permit removal and replacement any one module, without disassembly of the system as a whole. However, any and all embodiments herein can be configured such that each module is removable and replaceable with respect to the other modules in a convenient fashion, such as without disassembly of the system.
The term “master control device” is used herein in a broad sense and does not require implementation of any specific protocol such as a master and slave relationship with any other device, such as the local control device.
The term “output” is used herein in a broad sense, and does not preclude functioning in a bidirectional manner as both an output and an input. Similarly, the term “input” is used herein in a broad sense, and does not preclude functioning in a bidirectional manner as both an input and an output.
The terms “terminal” and “port” are used herein in a broad sense, can be either unidirectional or bidirectional, can be an input or an output, and do not require a specific physical or mechanical structure, such as a female or male configuration.
The term “nominal voltage” is a commonly used metric to describe a battery cell, and is provided by the manufacturer (e.g., by marking on the cell or in a datasheet). Nominal voltage often refers to the average voltage a battery cell outputs when charged, and can be used to describe the voltage of entities incorporating battery cells, such as battery modules and subsystems and systems of the present subject matter.
The term “C rate” is a commonly used metric to describe the discharge current divided by the theoretical current draw under which the battery would deliver its nominal rated capacity in one hour.
Different reference number notations are used herein. These notations are used to facilitate the description of the present subject matter and do not limit the scope of that subject matter. Some figures show multiple instances of the same or similar elements. Those elements may be appended with a number or a letter in a “−X” format, e.g., 123-1, 123-2, or 123-PA. This −X format does not imply that the elements must be configured identically in each instance, but is rather used to facilitate differentiation when referencing the elements in the figures. Reference to a genus number without the −X appendix (e.g., 123) broadly refers to all instances of the element within the genus.
Various aspects of the present subject matter are set forth below, in review of, and/or in supplementation to, the embodiments described thus far, with the emphasis here being on the interrelation and interchangeability of the following embodiments. In other words, an emphasis is on the fact that each feature of the embodiments can be combined with each and every other feature unless explicitly stated otherwise or logically implausible.
Processing circuitry can include one or more processors, microprocessors, controllers, and/or microcontrollers, each of which can be or can be part of a discrete or stand-alone chip or distributed amongst (and a portion of) a number of different chips. Any type of processing circuitry can be implemented, such as, but not limited to, personal computing architectures (e.g., such as used in desktop PC's, laptops, tablets, etc.), field programmable gate array (FPGA) architectures, proprietary architectures, custom architectures, and others. Processing circuitry can be an application specific integrated circuit (ASIC), an application specific standard part (ASSP), or all or a part of a system-on-ship (SoC). Processing circuitry can include a digital signal processor, which can be implemented in hardware and/or software. Processing circuitry can execute software instructions stored on memory that cause processing circuitry to take a host of different actions and control other components.
Processing circuitry can also perform other software and/or hardware routines. For example, processing circuitry can interface with communication circuitry and perform analog-to-digital conversions, encoding and decoding, other digital signal processing, multimedia functions, conversion of data into a format (e.g., in-phase and quadrature) suitable for provision to communication circuitry, and/or can cause communication circuitry to transmit the data (wired or wirelessly).
Any and all communication signals described herein can be communicated wirelessly except where noted or logically implausible. Communication circuitry can be included for wireless communication. The communication circuitry can be implemented as one or more chips and/or components (e.g., transmitter, receiver, transceiver, and/or other communication circuitry) that perform wireless communications over links under the appropriate protocol (e.g., Wi-Fi, Bluetooth, Bluetooth Low Energy, Near Field Communication (NFC), Radio Frequency Identification (RFID), proprietary protocols, and others). One or more other antennas can be included with communication circuitry as needed to operate with the various protocols and circuits. In some embodiments, communication circuitry can share antenna for transmission over links. RF communication circuitry can include a transmitter and a receiver (e.g., integrated as a transceiver) and associated encoder logic.
Processing circuitry can also be adapted to execute the operating system and any software applications, and perform those other functions not related to the processing of communications transmitted and received.
Computer program instructions for carrying out operations in accordance with the described subject matter may be written in any combination of one or more languages, including computer and programming languages. A non-exhaustive list of examples includes hardware description languages (HDLs), SystemC, C, C++, C#, Objective-C, Matlab, Simulink, SystemVerilog, SystemVHDL, Handel-C, Python, Java, JavaScript, Ruby, HTML, Smalltalk, Transact-SQL, XML, PHP, Golang (Go), “R” language, and Swift, to name a few.
Memory, storage, and/or computer readable media can be shared by one or more of the various functional units present, or can be distributed amongst two or more of them (e.g., as separate memories present within different chips). Memory can also reside in a separate chip of its own.
To the extent the embodiments disclosed herein include or operate in association with memory, storage, and/or computer readable media, then that memory, storage, and/or computer readable media are non-transitory. Accordingly, to the extent that memory, storage, and/or computer readable media are covered by one or more claims, then that memory, storage, and/or computer readable media is only non-transitory. The terms “non-transitory” and “tangible” as used herein, are intended to describe memory, storage, and/or computer readable media excluding propagating electromagnetic signals, but are not intended to limit the type of memory, storage, and/or computer readable media in terms of the persistency of storage or otherwise. For example, “non-transitory” and/or “tangible” memory, storage, and/or computer readable media encompasses volatile and non-volatile media such as random access media (e.g., RAM, SRAM, DRAM, FRAM, etc.), read-only media (e.g., ROM, PROM, EPROM, EEPROM, flash, etc.) and combinations thereof (e.g., hybrid RAM and ROM, NVRAM, etc.) and variants thereof.
It should be noted that all features, elements, components, functions, and steps described with respect to any embodiment provided herein are intended to be freely combinable and substitutable with those from any other embodiment. If a certain feature, element, component, function, or step is described with respect to only one embodiment, then it should be understood that that feature, element, component, function, or step can be used with every other embodiment described herein unless explicitly stated otherwise. This paragraph therefore serves as antecedent basis and written support for the introduction of claims, at any time, that combine features, elements, components, functions, and steps from different embodiments, or that substitute features, elements, components, functions, and steps from one embodiment with those of another, even if the following description does not explicitly state, in a particular instance, that such combinations or substitutions are possible. It is explicitly acknowledged that express recitation of every possible combination and substitution is overly burdensome, especially given that the permissibility of each and every such combination and substitution will be readily recognized by those of ordinary skill in the art.
As used herein and in the appended claims, the singular forms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise.
While the embodiments are susceptible to various modifications and alternative forms, specific examples thereof have been shown in the drawings and are herein described in detail. It should be understood, however, that these embodiments are not to be limited to the particular form disclosed, but to the contrary, these embodiments are to cover all modifications, equivalents, and alternatives falling within the spirit of the disclosure. Furthermore, any features, functions, steps, or elements of the embodiments may be recited in or added to the claims, as well as negative limitations that define the inventive scope of the claims by features, functions, steps, or elements that are not within that scope.
This application claims priority under 35 U.S.C. 119 to Provisional Application No. 63/197,292, filed Jun. 4, 2021, which is incorporated by reference.
| Number | Date | Country | |
|---|---|---|---|
| 63197292 | Jun 2021 | US |
