Patent Application
20200119571
The present invention relates to battery sourced power conversion system. The battery sourced power conversion system may be able to deliver power exceeding 10 Kilowatts (KW) (e.g., 50 Kilowatts).
The following presents a simplified summary of one or more embodiments of the invention in order to provide a basic understanding of such embodiments. This summary is not an extensive overview of all contemplated embodiments, and is intended to neither identify key or critical elements of all embodiments, nor delineate the scope of any or all embodiments. Its sole purpose is to present some concepts of one or more embodiments in a simplified form as a prelude to the more detailed description that is presented later.
In one embodiment, the present invention is directed to a battery sourced power conversion system connected to a load and a source. The battery sourced power conversion system includes a plurality of battery units connected in series and plurality of switches. Each of the plurality of switches is connected to one of the plurality of battery units. The battery sourced power conversion system also includes at least one controller connected to the plurality of battery units. The at least one controller is configured to control the plurality of switches to generate a voltage (in the form of a square wave) output from one or more of the battery units of the plurality of battery units, wherein the step up voltage outputs of the battery units of the plurality of battery units in combination form an output. In some embodiments, the output is a modified sinusoidal wave formed of a plurality of steps. In some embodiments, the output has a resolution of at least 50. In some embodiments, the output has a resolution of greater than 100. In some embodiments, the output has a resolution of greater than 500.
In some embodiments, the plurality of battery units comprises a first plurality of battery units, a second first plurality of battery units, and a third plurality of battery units and the plurality of switches comprises a first plurality of switches, a second plurality of switches, and a third plurality of switches. In such an embodiment, the at least one controller is configured to control the first plurality of switches, the second plurality of switches, and the plurality of switches to cause the first plurality of battery units, the second plurality of battery units, and the third plurality of battery units respectively to generate a first modified sinusoidal wave, a second modified sinusoidal wave, and a third modified sinusoidal wave respectively, where the first modified sinusoidal wave, the second modified sinusoidal wave, and the third modified sinusoidal wave in combination form a three-phase modified sinusoidal output that is the output of the battery sourced power conversion system.
In some embodiments, the at least one controller is configured to generate, using the plurality of battery units, the system output, the system output being substantially equal to a difference between an output of the source and a desired input of the load.
In some embodiments, the system output when combined with the source current forms the desired input current.
In some embodiments, the at least one controller is configured to control the plurality of switches to cause the plurality of battery units to provide the desired input current based on absorbing current.
In some embodiments, the at least one controller is configured to control the plurality of switches to cause the plurality of battery units to provide the desired input current based on discharging current.
In some embodiments, the at least one controller is configured to control the plurality of switches to cause the plurality of battery units to compensate for lower generation of the output of the source by discharging charged battery units of the plurality of battery units.
In some embodiments, the at least one controller is configured to control the plurality of switches to cause the plurality of battery units to compensate for higher generation of the output of the source by charging discharged battery units of the plurality of battery units.
In some embodiments, the at least one controller is configured to control the plurality of switches to maintain substantially the same overall duty cycle for each of the plurality of battery units.
In some embodiments, at least some battery units of the plurality of battery units are configured to supply positive voltage associated with the system output and at least some other battery units of the plurality of battery units are configured to supply negative voltage associated with the system output, the at least some other battery units having reverse polarity compared to the at least some battery units.
In some embodiments, the at least one controller is configured to control the plurality of switches to achieve a gradual rise and gradual fall of voltage associated with the system output.
In some embodiments, the system comprises a bypass mechanism for the plurality of battery units.
In some embodiments, the at least one controller is configured to control the plurality of battery units based on a transfer function.
The features, functions, and advantages that have been discussed may be achieved independently in various embodiments of the present invention or may be combined with yet other embodiments, further details of which can be seen with reference to the following description and drawings.
The features and functions of the invention, and the manner in which the same are accomplished, will become more readily apparent upon consideration of the following detailed description of the invention taken in conjunction with the accompanying drawings, which illustrate preferred and exemplary embodiments and which are not necessarily drawn to scale, wherein:
and
The present invention now will be described more fully hereinafter with reference to the accompanying drawings, in which some, but not all embodiments of the invention are shown. This invention may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Like numbers refer to like elements throughout.
The term “battery unit” as used herein may include any unit which stores energy. A battery unit may itself include multiple battery units. In one embodiment, a “battery unit” may include one or more individual cells. In one embodiment, a “battery unit” may include one or more modules. Each such modules may include a plurality of cells. In one embodiment, a “battery unit” may include one or more trays. Each such tray may include a plurality of modules, and each module may include one or more cells. In one embodiment, the term “battery unit” may include one or more racks. Each such rack may include a plurality of trays, each of the plurality of trays may include a plurality of modules, and each of the plurality of modules may include one or more cells. In one embodiment the term “battery unit” may include one or more containers, where each of the one or more containers includes a plurality of racks as, where each of the plurality of racks includes a plurality of modules, where each of the plurality of modules includes a plurality of cells.
Electricity is generated at power plants using various forms of energy and is transmitted and distributed through complex systems. Electric power is typically converted at various stages of such complex systems to facilitate such transmission and distribution.
In this regard, power plants may generate AC power or DC power depending on the type of energy and the type of generation method used in the power plants. However, transmission and distribution of AC power is more advantageous as it is typically easier to step-up or step-down the voltage of AC power as compared to DC power. Accordingly, if DC power is generated at a power station, such DC power is typically converted to AC power using power conversion systems. Additionally, generated power is typically stepped-up to higher voltages before transmission as transmitting higher voltage is more efficient for transmitting power over long distances because doing so helps to minimize losses. Following transmission, the voltage of electric power is then stepped down for distribution.
Energy storage systems may be used within electric power generation, transmission and distribution systems (e.g., at substations) for storing energy for later usage during periods of peak demand and/or low supply of power. Power conversion systems are typically utilized to make the generated energy or the energy stored within such energy storage systems usable within electric power transmission and distribution systems. For example, power rectifiers are employed to convert AC power generated by electric power generation systems to DC power for storing the excess energy in energy storage systems and power inverters are employed to convert DC power from such energy storage systems into AC power for transmission and distribution. As such, separate systems are typically used for converting energy for transmission of generated energy to the load or storage, storing the converted energy, and converting the stored energy.
Moreover, additional power factor correction equipment may be used in the power systems to maintain power quality. A contributing element to power quality is power factor. The power factor is typically a measure of how effectively input power is used in the power system. When the power factor is low (e.g., less than 0.9), it can contribute to equipment instability and failure and increases energy costs. As such, power factor correction equipment is often used in the power systems to maintain power quality. An example of such power factor correction equipment is a bank of capacitors to offset an inductive load in order to improve the power factor and hence the power quality. Another example of power factor correction equipment is a reactor bank when the load is capacitive.
Conventional power conversion systems can induce significant harmonics into the power system, which can cause heating, losses, and equipment failures. In order to filter out such harmonics, such power conversion systems typically include large harmonic filters which are very expensive and add to the cost of the already existing power conversion systems. Furthermore, the large harmonic filters may contribute to overall power losses in the electrical power systems, thus decreasing the overall efficiency of such power conversion systems.
In one aspect, the present invention is directed to a battery sourced power conversion system that addresses the above mentioned problems existing in the space of grid-scale energy storage systems by integrating energy storage equipment and power conversion equipment. In this regard, the integrated energy storage and power conversion system typically includes a plurality of battery units and a plurality of switches connected to the battery units. A controller is configured to control the operation of switches to charge or discharge the battery units for generating an output. The output of the system typically provides power conversion and/or compensation. Such power conversion and/or compensation may: provide power factor correction between a source and a load, change the form of power from the source (e.g., from AC to DC or DC to AC), change the voltage or frequency of power from the source, compensate for noise from the source, store excess power from the source, and/or provide previously stored energy when power demands of the load exceed the power being provided by the source. In an embodiment where the battery sourced power conversion system is connected to an AC source and an AC load, the battery sourced power conversion system may act as a compensation system connected in parallel to the source and the load to regulate the power delivered from the source to the load. In such an embodiment, the system may provide an output that provides power factor correction. In particular, the system output in combination with the source output form a load input having an improved power factor (e.g., a power factor close to unity), namely as compared to what the power factor of the load input would be without the corrective output of the system. In an embodiment where the battery sourced power conversion system is connected to a DC source and an AC load or to an AC source and a DC load, the battery sourced power conversion acts as a gateway in between the source and the load to deliver power which meets the requirements of the load. In such embodiment, the system may change the form of power from the source when delivering an output to the load (e.g., by converting AC power to DC power or converting DC power to AC power). Regardless of whether the battery sourced power conversion system is positioned as a gateway between the source and load or in parallel to the source/load, the battery sourced power conversion system may be configured to compensate for differences between power delivered by the source and power demanded by the load, such as by storing excess power from the source and/or provide previously stored energy when power demands of the load exceed the power being provided by the source. In some embodiments, the battery sourced power conversion system may compensate for noise in the output of the source. For example, the load may be a DC load and the source may be a noisy DC source. The system may generate an output that compensates (e.g., mirrors) the noise of the output of the DC source, thereby providing a less noisy input to the DC load.
The system is typically configured to generate a high-resolution output (e.g., an output having a resolution of 50 or more). In order to generate a high-resolution output, the system typically includes a plurality of individually controllable battery units. Typically, the number of battery units is at least as great as the resolution of the system output, although the number of battery units may exceed the resolution of the system output, such as to compensate for potentially faulty battery units and/or to allow the system to concurrently generate multiple outputs (e.g., a three-phase AC output). To achieve the system output, the controller is configured to control the operation of the switches so that each battery unit generates a square wave output. The square wave outputs of the battery units are combined to form the system output. The controller is further configured to control the timing of the switches so that the square wave outputs, when combined, form the desired system output. In an exemplary embodiment, where the output of the battery sourced power conversion system is connected to an AC load, the system output may be a substantially sinusoidal AC output. In order to generate such a substantially sinusoidal AC output, the controller is further configured to control the timing of the switches so that the square wave outputs, when combined, form a modified sinusoidal wave that substantially resembles a smooth sine wave, such as by forming a modified sinusoidal wave having a resolution of at least 50 (e.g., 200 or more).
By individually switching battery units in this manner to achieve a desired output (e.g., sinusoidal AC output, noise-correcting output, power factor correcting output, DC output, etc.), the harmonics introduced into the system are very small as compared to the harmonics induced by the conventional power conversion equipment. Accordingly, the power conversion system eliminates the need to use large, expensive harmonic filters. In addition, the battery sourced power conversion system as described herein is able to convert DC power to AC power, AC power to DC power, AC power to AC power, DC power to DC power (e.g., changing voltage levels) without the use of expensive power inverters and/or power converters and regulate the power factor without the use of additional power factor correction equipment. Accordingly, the battery sourced power conversion system described herein is able to provide less expensive energy storage and/or power conversion that can be integrated within power generation, transmission, and/or distribution systems than can be achieved through existing energy storage and power conversion systems.
In some embodiments, the system 100 acts as a gateway between the source 105 and the load 150. When the system 100 acts as a gateway, power from the source 105 does not directly flow from the source 105 to the load 150, but instead power from the source 105 is delivered to the system 100 and the system 100 may then deliver an output to the load 150. In this regard, the system 100 may absorb power from the source 105 (e.g., by charging battery units of the system 100) and then generate an output (e.g., by discharging battery units) that meets the requirements of the load. In such embodiments, the battery sourced power conversion system 100 may perform power conversion, such as by converting a DC input to an AC output, or vice versa, or creating an output with a different voltage or frequency than the input. For example, DC power from the source 105 may be used to charge battery units of the system 100, and the system 100 may generate an AC output by controlling the discharge of the battery units to generate an AC waveform.
In other embodiments, the system 100 is connected in parallel to the source 105 and the load 150, such that the source 105 may directly delivery power to the load 150, but the system 100 may also deliver an output to the source/load. When the energy generation at the source 105 is greater than the requirements of the load 150, the excess energy from the source 105 may be used to charge battery units within the battery sourced power conversion system 100 and thereby store the excess energy. When the energy generation at the source 105 is less than the requirements of the load 150, the energy stored in the battery sourced power conversion system 100 may be discharged to the load 150 to meet the load requirements. In some embodiments, the battery sourced power conversion system 100 may (alternatively or additionally) deliver an output that provides power factor correction.
The battery sourced power conversion system 100 includes a plurality of battery units. In an exemplary embodiment, the battery sourced power conversion system 100 comprises at least one container 110, such container 110 comprising one or more racks. Each of the one or more racks may comprise one or more trays connected in series. In an embodiment, where the battery sourced power conversion system is connected to a three phase power system, one rack may be a single leg of a three phase battery sourced power conversion system. A first rack 120 comprising a first set of trays 124 and a second rack 130 comprising a second set of trays 134 are shown for illustrative purposes only.
The system 100 typically includes a plurality of switches to control the charging and discharging of individual battery units. By way of example,
In one embodiment, a single switch may be connected to each cell (or other battery unit). In another embodiment, a plurality of switches may be connected to each cell in the battery sourced power conversion system to reduce the thermal effect on the switch corresponding to each cell. In another embodiment, a plurality of cells may be connected to a single switch. In yet another embodiment, a plurality of cells connected in series may be connected to a plurality of switches connected in parallel. In some embodiments, the switches used in the battery sourced power conversion system 100 may be solid state switches. In some other embodiments, the switches used in the battery sourced power conversion system 100 are mechanical switches. In some embodiments, the switches used in the battery sourced power conversion system may be a combination of both solid state switches and mechanical switches. In some embodiments, the battery sourced power conversion system 100 may include switches at the rack, module, and/or other battery unit level.
The cells may be any type of cell usable for high power applications. For example, the cells used in the battery sourced power conversion system 100 may be high-drain cells. In some embodiments, the cells used in the battery sourced power conversion system 100 have small voltage range (e.g., up to 5 volts). Typically, the voltage of a cell is determined based on cell chemistry. The number of racks, modules, and cells may vary based on the desired voltage output of the battery sourced power conversion system 100, as well as other considerations such as cost and availability. For example, if a cell with a voltage of 3 volts is the most economical, then ten cells may be stacked together to achieve 30 volts, whereas if a cell with a voltage range of 5 volts is alternatively the most economical, then six cells may be stacked together to achieve 30 volts.
The battery sourced power conversion system 100 also comprises a controller 140 to perform switching of the switches (e.g., the switches 127 and 137). The controller may be any controller such as a programmable logic controller, microcontroller, or the like. In some embodiments, the battery sourced power conversion system 100 may include a single controller for all containers. In some embodiments, the battery sourced power conversion system 100 may include one controller for each of the containers, wherein the controllers in each of the containers work cohesively to perform the switching operation. In some embodiments, the battery sourced power conversion system 100 may include controllers at the rack, tray, or module level and/or cell level. For example, the battery sourced power conversion system may include a controller for each cell. In another example, the battery sourced power conversion system may include one controller for each tray comprising a bundle of cells. In another example, the battery sourced power conversion system may include one controller for each rack comprising a bundle of trays. In some embodiments, the battery sourced power conversion system 100 may include a centralized controller at the system level and one or more controllers at battery unit level (e.g., cell level, module level, tray level, rack level, and/or container level) which work together to control the switching operation in order to achieve a desired output. With respect to
The controller 140 may control the switching operation of battery units to provide power conversion and/or power matching which are explained in detail below. In one embodiment, the controller 140 may perform the switching operation based on the source output sensed by a source sensing system 106 and load requirements or load input provided by a sensing and feedback system 156 to provide a desired output from the system 100. The number of cells to be operated, the time interval of switching, and the number of steps in the output of the battery sourced power conversion system 100 is typically determined by the controller 140 based on the source output and load input. In some embodiments, the battery units may have the same number of sub-units. For example, all trays in the battery sourced power conversion system may have same number of modules and the modules may have same number of cells. In some embodiments, the battery units may have different number of subunits. For example, a first tray may have ten modules and a second tray may have 2 modules. In such an embodiment where the number of subunits in different battery units may vary, the battery units and subunits the controller may turn ON and OFF may depend upon at least the time interval and the desired output. For example, a tray having large number of cells may be used by the controller to generate a desired output at one time interval and a tray having small number of cells may be used by the controller to generate a desired output at a different time interval.
The controller 140 may control switching operation at a cell level (and/or at a module and/or rack level) to achieve a desired output by switching ON and OFF the switches corresponding to each of the cells and causing the cells to charge and discharge. When the controller switches ON a cell at a particular time, such cells produce a square wave output. These outputs of the plurality of cells when combined form the desired output with a resolution that is typically based on the number of cells employed. In order to achieve a desired output, various cells (or other battery units) may be charged and/or discharged for different lengths of time. In order to ensure that all cells have similar longevity and performance characteristics, the controller rotates the short-term duty cycle of the cells while charging and discharging so that the overall duty cycle of all the cells remains substantially the same. Maintaining the same overall duty cycle helps to prevent overcharging or undercharging of cells. By way of a simple example, if there are 3 cells (A, B, and C) in the battery sourced power conversion system and during time period t1, if cell A is turned ON for time T seconds, cell B is turned ON for time T/2 seconds, and cell C is turned ON for T/4 seconds, then during time period t2, cell A may be turned ON for T/4 seconds, cell B may be turned ON for T seconds, and cell C may be turned ON for T/2 seconds, and during time period t3, cell A may be turned ON for T/2 seconds, cell B may be turned ON for T/4 seconds, and cell C may be turned ON for T seconds. As such, the overall duty cycle of all cells within the battery sourced power conversion system remains substantially the same, even though the short term duty cycles of the cells may vary. In some embodiments, the concept of rotation may be implemented at module level, tray level, rack level, and/or container level. For example, if there are six trays in the battery sourced power conversion system, the controller may rotate the charging and/or discharging period of six trays, so that all six trays have the same overall duty cycle.
In one embodiment, the load connected to the battery sourced power conversion system may be a DC load and the source may be an AC source. In such an embodiment, the battery sourced power conversion system may act as a gateway and the controller 140 performs the switching operation to convert the input from the AC source to match the load requirements. In this regard, the controller 140 typically controls switching operation at a cell level (and/or at a module and/or rack level) so that the combined output of the cells is a substantially constant (e.g., constant other than low-level noise) DC waveform.
In another embodiment, the load connected to the battery sourced power conversion system may be an AC load and the source may be a DC source. Accordingly, the cells may be switched ON and OFF by the controller 140 so that the combined output of the cells is a sinusoidal output that substantially resembles a smooth sine wave. A simplified, exemplary output of such an embodiment is illustrated in
The battery sourced power conversion system is typically able to achieve an output with a resolution of greater than 50, such as resolution of at least 100 (e.g., 500 or more). As used herein, “resolution” refers to the number of possible voltage levels that can be achieved by the system. Where the output of the system is a modified sinusoidal output, the resolution is equal to the number of steps in the modified sinusoidal output within one period. By way of illustration, if
In an exemplary embodiment, wherein the battery sourced power conversion system is connected to a 3 kV AC load operating at 60 Hz, and the battery sourced power conversion system comprises cells with a voltage of 3 volts, the number of steps in the sinusoidal output would be 1414. Continuing with the previous example, if the number of steps is 1414, the time between each switch is 0.005 ms. The cells in the battery sourced power conversion system 100 are switched ON and OFF at a different time during a cycle to obtain the desired output. Where the desired output is an AC sinusoidal waveform, the controller typically uses a set of cells configured in the opposite polarity in the battery sourced power conversion system 100 to handle the negative output of the sinusoidal output waveform. The controller may employ similar kind of switching method which is gradual in order to achieve a DC or other (e.g., noise correcting) output wave.
Similarly, the controller 140 operates switches to perform power conversion and/or compensation when both the source and the load connected to the battery sourced power conversion system 100 are AC systems. Typically, the load 150 may include resistive, inductive, and/or capacitive loads. Capacitive and inductive loads store energy which can cause the current to move out of phase with the voltage in an AC system and in turn result in a poor power factor. When a load is inductive (e.g., an electric motor), current typically lags voltage, thereby increasing the reactive power in the power system. The increase in the reactive power causes the total apparent power in the power system to increase, thereby resulting in a low power factor which can have detrimental effects on the power system. The battery sourced power conversion system compensates for the lag induced by inductive loads by causing the cells or battery units to absorb or discharge current in order to produce a resulting current waveform which is in-phase with the voltage, thereby improving or correcting the power factor of the power system without using any additional equipment.
An illustration of power factor correction performed by the battery sourced power conversion is shown in
The battery sourced power conversion system 100 may also compensate for low or high power generation at the source and/or high or low power consumption at the load irrespective of whether the source and the load are AC or DC. In one example, when the power generation at the source is low and the power consumption is high at the load, the controller 140 may control the switching at cell level (and/or module level, tray level, and/or rack level) to discharge previously charged cells in order to compensate for the low supply of power.
In order to achieve a desired output waveform, a transfer function may be used by the controller 140 to control the switching operation of the cells (and/or other battery units). In other words, software of the controller 140 employs the transfer function to control the switches in order turn battery units ON and OFF to thereby obtain a desired output. Such transfer function may be determined based on multiple variables and the coefficients of the developed transfer function are fed into the controller 140 to achieve the desired switching operation for a resulting waveform. Such variables may include power throughput, cell configuration (cell chemistry, number of cells, architecture of cells, or the like), selection of components, allowed system voltage and current limits, and the like. In some embodiments, the process of determining the transfer function may be performed by a processor and the coefficients of the developed transfer function may be fed to the controller 140. The processor may automatically calculate the transfer function based on the inputs received from the source sensing system 106 and the sensing and feedback system 156. The transfer function may vary for different type of sources and loads. For example, when the source is an AC source and the load is an AC load, the transfer function associated with such a power system may be different when compared with the transfer function of a power system comprising a DC source and a DC load. In other words, transfer functions may vary based on the different types of conversion that is being performed by the battery sourced power conversion system.
Additional components (such as sensors at the battery unit level, mechanical bypass switches at the individual, filters) may be present in the battery sourced power conversion system along with the elements shown in
Although the battery sourced power conversion system described herein is typically for delivering power exceeding 10 kilowatts (kW), the battery sourced power conversion system may be used to deliver power below 10 kilowatts (kW).
Many modifications and other embodiments of the inventions set forth herein will come to mind to one skilled in the art to which these inventions pertain having the benefit of the teachings presented in the foregoing descriptions and the associated drawings. Therefore, it is to be understood that the inventions are not to be limited to the specific embodiments disclosed and that modifications and other embodiments are intended to be included within the scope of the appended claims. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation. In addition, where possible, any terms expressed in the singular form herein are meant to also include the plural form and/or vice versa. As used herein, “at least one” shall mean “one or more” and these phrases are intended to be interchangeable. Accordingly, the terms “a” and/or “an” shall mean “at least one” or “one or more,” even though the phrase “one or more” or “at least one” is also used herein.
This application claims priority to U.S. Provisional Patent Application Ser. No. 62/746,154, filed Oct. 16, 2018, entitled “Battery Sourced Power Conversion,” the entirety of which is incorporated herein by reference.
| Number | Date | Country | |
|---|---|---|---|
| 62746154 | Oct 2018 | US |
