Patent Application
20220321016
The present disclosure relates generally to power conversion, and more particularly, to power converters having at least two output ports, for example, multi-active-bridge (MAB) power converters.
With increased electrical integration and demand for multiple voltage- and power levels, multi-port power electronic converters provide an effective method of realizing compact and efficient power conversion. Historically, power conversion from one voltage level to multiple voltage levels was performed using discrete AC-DC and/or DC-DC converters that meet the isolation requirements associated with each voltage level. Due to a very low level of integration and cascading of power electronic stages, such solutions suffer from large volume/weight and low efficiencies. Nevertheless, such multiple input/output power electronic architectures are extensively used in a wide range of applications. For example, in electric vehicles (EVs), there is a need for power conversion between the AC wall input, the high-voltage (HV) battery, and one or more low-voltage (LV) batteries and/or supercapacitors. Many of these interfaces must be designed as bidirectional, to meet the functionality demands associated with the next generation of EVs. While multi-port converters with isolation have been developed, such converter architectures typically only provide DC-DC conversion. Furthermore, there are varying degrees of integration in existing designs, such as cascaded power electronic stages, multi-winding transformers, etc. For example, in designs where multi-winding transformers are used for the electrical- and magnetic integration, the coupling inductance is limited to an inductor, which greatly limits the operation range and possibility for zero-voltage switching (ZVS) and zero-current switching (ZCS) over wide voltage and load ranges.
Embodiments of the disclosed subject matter may address one or more of the above-noted problems and disadvantages, among other things.
Embodiments of the disclosed subject matter provide power conversion systems employing multi-directional multi-port power converters. In some embodiments, power conversion is provided by a multi-active bridge (MAB) power converter having at least three ports, among which at least one port is an input and at least one port is an output. Some embodiments employ an electrically- and magnetically-integrated multidirectional isolated multi-port conversion architecture that is universally applicable to AC-DC, DC-DC, DC-AC, and AC-AC conversion applications. In some embodiments, a unified power management strategy for multi-port converter systems is provided, based on optimal closed-loop multi-phase-shift, multi-duty ratio, variable switching frequency operation.
In one or more embodiments, a multi-port power conversion can comprise a multi-winding transformer and at least three ports. The at least three ports can be coupled to the multi-winding transformer. Each port can have a semiconductor bridge and a coupling network. The semiconductor bridge of each port can have two or more levels and can comprise at least two switches. The coupling network for each port can comprise at least one inductor. The semiconductor bridge can be coupled to the multi-winding transformer via the respective coupling network.
Any of the various innovations of this disclosure can be used in combination or separately. This summary is provided to introduce a selection of concepts in a simplified form that are further described below in the detailed description. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter. The foregoing and other objects, features, and advantages of the disclosed technology will become more apparent from the following detailed description, which proceeds with reference to the accompanying figures.
Embodiments will hereinafter be described with reference to the accompanying drawings, which have not necessarily been drawn to scale. Where applicable, some elements may be simplified or otherwise not illustrated in order to assist in the illustration and description of underlying features. Throughout the figures, like reference numerals denote like elements.
For purposes of this description, certain aspects, advantages, and novel features of the embodiments of this disclosure are described herein. The disclosed methods and systems should not be construed as being limiting in any way. Instead, the present disclosure is directed toward all novel and nonobvious features and aspects of the various disclosed embodiments, alone and in various combinations and sub-combinations with one another. The methods and systems are not limited to any specific aspect or feature or combination thereof, nor do the disclosed embodiments require that any one or more specific advantages be present, or problems be solved. The technologies from any embodiment or example can be combined with the technologies described in any one or more of the other embodiments or examples. In view of the many possible embodiments to which the principles of the disclosed technology may be applied, it should be recognized that the illustrated embodiments are exemplary only and should not be taken as limiting the scope of the disclosed technology.
Although the operations of some of the disclosed methods are described in a particular, sequential order for convenient presentation, it should be understood that this manner of description encompasses rearrangement, unless a particular ordering is required by specific language set forth below. For example, operations described sequentially may in some cases be rearranged or performed concurrently. Moreover, for the sake of simplicity, the attached figures may not show the various ways in which the disclosed methods can be used in conjunction with other methods. Additionally, the description sometimes uses terms like “provide” or “achieve” to describe the disclosed methods. These terms are high-level abstractions of the actual operations that are performed. The actual operations that correspond to these terms may vary depending on the particular implementation and are readily discernible by one skilled in the art.
The disclosure of numerical ranges should be understood as referring to each discrete point within the range, inclusive of endpoints, unless otherwise noted. Unless otherwise indicated, all numbers expressing quantities of components, molecular weights, percentages, temperatures, times, and so forth, as used in the specification or claims are to be understood as being modified by the term “about.” Accordingly, unless otherwise implicitly or explicitly indicated, or unless the context is properly understood by a person skilled in the art to have a more definitive construction, the numerical parameters set forth are approximations that may depend on the desired properties sought and/or limits of detection under standard test conditions/methods, as known to those skilled in the art. When directly and explicitly distinguishing embodiments from discussed prior art, the embodiment numbers are not approximates unless the word “about” is recited. Whenever “substantially,” “approximately,” “about,” or similar language is explicitly used in combination with a specific value, variations up to and including 10% of that value are intended, unless explicitly stated otherwise.
Directions and other relative references may be used to facilitate discussion of the drawings and principles herein but are not intended to be limiting. For example, certain terms may be used such as “inner,” “outer,”, “upper,” “lower,” “top,” “bottom,” “interior,” “exterior,” “left,” right,” “front,” “back,” “rear,” and the like. Such terms are used, where applicable, to provide some clarity of description when dealing with relative relationships, particularly with respect to the illustrated embodiments. Such terms are not, however, intended to imply absolute relationships, positions, and/or orientations. For example, with respect to an object, an “upper” part can become a “lower” part simply by turning the object over. Nevertheless, it is still the same part, and the object remains the same.
As used herein, “comprising” means “including,” and the singular forms “a” or “an” or “the” include plural references unless the context clearly dictates otherwise. The term “or” refers to a single element of stated alternative elements or a combination of two or more elements, unless the context clearly indicates otherwise.
Although there are alternatives for various components, parameters, operating conditions, etc. set forth herein, that does not mean that those alternatives are necessarily equivalent and/or perform equally well. Nor does it mean that the alternatives are listed in a preferred order, unless stated otherwise. Unless stated otherwise, any of the groups defined below can be substituted or unsubstituted.
Unless explained otherwise, all technical and scientific terms used herein have the same meaning as commonly understood to one skilled in the art to which this disclosure belongs. Although methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present disclosure, suitable methods and materials are described below. The materials, methods, and examples are illustrative only and not intended to be limiting. Features of the presently disclosed subject matter will be apparent from the following detailed description and the appended claims.
Prior power systems employ discrete AC-to-DC (or AC-DC) and DC-to-DC (or DC-DC) converters. Such prior architectures use at least two conversion stages and at least two discrete converters. In contrast, embodiments of the disclosed subject matter allow for interfacing of all ports using a single integrated multi-port converter, in particular, by integrating all power electronics into a single-stage multi-port energy router with multi-directional (multiple-input multiple-output, or MIMO) power transfer capability. In some embodiments, substantial improvements in power density and efficiency can be achieved using a circuit architecture that offers electrical and magnetic integration, and direct DC-link-capacitor-less AC-DC conversion and DC-DC conversion circuit topologies. In some embodiments, the use of resonant coupling networks (RCNs) with a multi-active bridge (MAB) converter enhances efficiency and electromagnetic interference (EMI) performance over conventional converters. As further used herein below, the terms “multi-port converter,” “multi-port architecture,” and “multi-active bridge (MAB) converter” have been used interchangeably to refer to an isolated power electronics converter with two or more ports according to one or more embodiments of the disclosed subject matter.
In some embodiments, the multi-port converter can be adapted for multiple voltage levels associated with electric vehicle (EV) charging systems. For example, typical voltage levels in EV charging systems can include 800V, 400 V, 48 V, 24 V, 12 V, etc. Alternatively or additionally, in some embodiments, the multi-port converter can be adapted for energy routing in next-generation smart DC homes. For example, in such smart home DC distribution systems, power converters interface the AC grid to various DC voltage buses having voltage levels such as, but not limited to, 1200V, 800V, 400 V, 48 V, 24 V, and 12 V. Alternatively or additionally, in some embodiments, the multi-port converter can be adapted for power distribution in a data center, for example, to interface AC input to battery storage and/or to various DC voltage buses for server applications. For example, the DC voltages buses can have voltage levels such as, but not limited to, 400 V, 230 V, 48 V, 12 V, and 1 V. Alternatively or additionally, in some embodiments, the multi-port converter can be adapted for power distribution in person computing, for example, to generate various voltage levels for different computing loads such as, but not limited to, 12 V, 5 V, 3.3 V, 1.8 V, and 1.1 V. Other applications beyond those specifically discussed above are also possible according to one or more contemplated embodiments. Indeed, based on the teachings of the present disclosure, a multi-port converter can be developed for use in any application having multiple voltage ports and/or power flow directions, such as, but not limited to, renewable energy generation and storage, and electric aircrafts.
In some embodiments, a power management control strategy for the MAB converter can be employed, for example, to provide for optimal RMS currents and zero-voltage switching (ZVS) of all MOSFET devices over an entire load range. In some embodiments, the proposed control can achieve independent decoupled control of the voltages and currents at each port. In some embodiments, the MAB converter can be modeled using an analytical modeling approach, for example, using a superposed-harmonics method in the frequency domain that is subsequently deployed in a numerical optimization algorithm. In some embodiments, the optimization algorithm obtains optimal modulation parameters for a given operating condition using numerical optimization, and also finds the optimal converter parameters (e.g., converter inductances, capacitances, and transformer turns ratios). In some embodiments, the multi-port converter employs an alternative circuit topology with a two-stage configuration, which may be able to achieve specific targets in certain applications.
In some embodiments, the MAB converter employs at least three ports, for example, four or more ports. Although many of the examples presented herein illustrate three or four ports, it should be noted that embodiments of the disclosed subject matter are not limited thereto. Rather, the MAB converter can have any number of ports according to one or more contemplated embodiments, and one of skill in the art will readily understand that the teachings presented herein can be readily extended to two-port converters (e.g., dual-active bridge), three-port converters (e.g., triple-active bridge), and/or n-port converters (e.g., n-tuple active bridge). For example,
In the illustrated example of
In some embodiments, each port 102, 112 may have a semiconductor bridge configuration 104, 108, 114 (e.g., selected from the options in Table 1) that is the same or different from the other ports and/or a resonant coupling network (RCN) 106, 116 configuration (e.g., selected from the options in Table 3 Error! Reference source not found.) that is the same or different from the other ports. For example, selection of unique arrangements for each port may be used to optimize operation of the MAB converter 100. Alternatively, in some embodiments, the MAB converter 100 may have a transformer 120, the structure of which is selected, for example, from the configurations listed in Table 2.
In some embodiments, one or more of the semiconductor bridge configurations for each port, such as semiconductor bridge 104, 108 of any of AC ports 102-1 through 102-k and semiconductor bridge 114 of any of DC ports 112-1 through 112-p, can be selected from any of the topological variations summarized in Table 1 below and illustrated in
The bridge configurations can be broadly classified as 2-level and multi-level (m-level), based on the number of voltage levels generated from each half-bridge leg. Furthermore, single-phase or three-phase version of the semiconductor bridges can be deployed in the MAB converter. In some embodiments, the bridges can be configured in parallel when connected to a matrix transformer. In some embodiments, a current-source bridge with a DC inductor can couple the semiconductor bridge to the voltage source or load at a given port. In some embodiments, for each configuration of
Referring to
Referring to
In
The bridge configurations described above can be applicable to single-phase transformers. However, in some embodiments, the bridge configurations can be used with three-phase transformer structures. For example,
In some embodiments, the flexibility in the operation of the MAB converter can allow for magnetic integration through several different transformer configurations. The transformer can form the main coupling element between various ports. In some embodiments, the transformer can also be the largest passive component in the MAB converter circuit. Proper selection of the transformer configuration can assist in achieving high efficiency and power density. In some embodiments, the transformer configuration coupling together the ports, such as transformer 120 in
Referring to
Referring to
Referring to
In some embodiments, some of the windings in a matrix transformer structure 332 can be inversely coupled to other windings. This can be used, for example, to reduce the effective turns ratios for high step-down applications, and thus result in lower conduction losses in the transformer windings.
While the illustrated examples of
In some embodiments, one or more of the RCN configurations for each port, such as RCN 106 of any of AC ports 102-1 through 102-k and RCN 116 of any of DC ports 112-1 through 112-p, can be selected from any of the topological variations summarized in Table 3 below and illustrated in
In some embodiments, the resonant networks 106, 116 in an MAB converter 100 can be used to effectively modulate the power transfer impedances in the MAB converter, and/or to achieve certain desirable operating characteristics, for example, zero voltage switching (ZVS) and/or zero current switching (ZCS). In some embodiments, the resonant networks for each port can be constructed independently (e.g., such that the resonant network for one port is different than at least one, at least some, or all other ports in the converter with respect to structure and/or component (e.g., L/C) values). In some embodiments, the optimal configuration and L/C values of the resonant network can be determined, for example, using a generalized modeling and universal multi-objective optimization algorithm as described hereinbelow. In some embodiments, the overall resonant networks can be highly asymmetric in nature, based on efficiency, ZVS/ZCS, and/or volume considerations. In some embodiments, any of the disclosed resonant network structures can be transformed into equivalent three-phase structures (e.g., arranged in star or delta fashion).
Based on the generalized configuration of the MAB converter 100 of
Referring to
The configurations of
Starting at an input/output end of the AC voltage port 502 in
In some embodiments, one or more of the RCNs can be configured to be purely inductive, thus yielding a non-resonant MAB operation. Such a topology would not include any resonant capacitors (labeled as Cr1, Cr2, Cr3, Cr4 in
In some embodiments, if a three-phase AC port is to be interfaced to an MAB converter, the indirect single-stage AC front-end (e.g., as illustrated for port 502 in
The semiconductor bridge of subsystem 808 can be coupled to transformer 620 (e.g., Type i, a single-phase multi-port transformer) via RCN 506 (e.g., Type a). Each of the DC ports 512a-512c can be defined by and/or comprise a respective semiconductor bridge 514a-514c (e.g., Type 1, full bridge). Each semiconductor bridge 514a-514c can in turn be coupled to the transformer 620 by respective RCNs 516a-516c (e.g., Type a). In the illustrated example, RCNs 506, 516a-516c have the same configuration (e.g., Type a), although the respective L/C values may be different between the different RCNs. Alternatively, in some embodiments, one, some or all of the RCNs can have different configurations from the others. Similarly, in the illustrated example, bridges 514a-514c have the same configuration (e.g., Type 1). Alternatively, in some embodiments, one, some, or all of the bridges can have different configurations from the others.
In addition to or in place of the three-phase direct single-stage AC port configurations illustrated in
In addition to the single-stage multi-port converters discussed above, in some embodiments, a separate power factor correction (PFC) rectifier stage can be connected to the AC port, for example, before interfacing to the MAB converter. For example,
In addition to or in place of the single-stage AC conversion port of
In some embodiments, the MAB converter can have asymmetric resonant networks, e.g., where one, some, or all of RCNs interfacing the semiconductor bridge of a port to the transformer have a different configuration than others of the RCNs. For example, based on a voltage variation range and power levels of various ports, the RCNs can be individually tuned to obtain more optimal performance over an entirety (or at least part of) of an operating range. For example,
The AC port 1402 can be defined by and/or comprise a single stage AC subsystem 510, which in turn can be defined by and/or comprise a line frequency synchronous rectifier 508 (e.g., Type 1, full bridge) coupled to semiconductor bridge 504 (e.g., Type 1, full bridge). EMI filter 118 can be coupled to the rectifier 508 (e.g., between an AC input/output and the single stage AC subsystem 510), and semiconductor bridge 504 can be coupled to transformer 620 (e.g., Type i, a single-phase multi-port transformer) via RCN 1406 (e.g., Type b). Each of the DC ports 1412a-1412c can be defined by and/or comprise a respective semiconductor bridge 514a-514c (e.g., Type 1, full bridge). Each semiconductor bridge 514a-514c can in turn be coupled to the transformer 620 by RCN 1416a (e.g., Type a), RCN 1416b (e.g., Type c), and RCN 1416c (e.g., Type g), respectively. Thus, each of the RCNs 1406, 1416a-1416c has a different configuration, thereby yielding a fully asymmetric resonant configuration. However, in some embodiments, the asymmetry may be applied to less than all of the ports, with the other ports remaining symmetric (e.g., DC ports having the same RCN type while AC ports having a different RCN type from the DC ports).
In some embodiments, an MAB converter can form a self-sufficient unit (e.g., providing power conversion between multiple ports for single-phase AC, three-phase AC, and/or DC applications). Alternatively or additionally, in some embodiments, multiple MAB converters can be connected together (e.g., in series or in parallel) to form a modular architecture. In some embodiments, such modular architectures can offer certain advantages such as, but not limited to, increased failure tolerance and redundancy, higher power handling capability with improved efficiency, easier maintenance with easily swappable modules, and automatic cancellation of a pulsating power ripple in three-phase systems.
In some embodiments, one or more MAB converters (e.g., modules) can be coupled together in any of the modular architecture configurations summarized in Table 4 below and illustrated in
Referring to
Referring to
An exemplary configuration 1600 for Modular Architecture 3 is shown in
While the above-discussed configurations of Modular Architectures 1-4 illustrate parallel connection of MAB converter modules to the DC ports, in some embodiments, the MAB converter modules can instead be connected in series. For example,
Referring to
In some embodiments, instead of modular MAB converters with single-phase AC input, each MAB converter module can be configured to directly connect to the three-phase AC port. Such three-phase inputs can result in automatic pulsating power ripple cancellation within each MAB module, thus leading to improved transformer and switch utilizations. However, the three-phase AC input port MABs may have a higher device count and/or cost compared to single-phase AC input port MAB converters. For example,
Referring to
In some embodiments, instead of all of the modular MAB converters having either single-phase AC input or three-phase AC input, one or some of the MAB converter modules can be configured for three-phase AC input, and one or some of the MAB converter modules can be configured for single-phase AC input. For example,
Although the examples of Modular Architectures 1-9 employ a 3-phase AC input, embodiments of the disclosed subject matter are not limited thereto. Rather, in some embodiments, a single-phase AC input can be employed according to one or more contemplated embodiments. For example,
The Modular Architectures 10 and 11 represent single-phase AC input configurations with symmetrical and asymmetrical loadings, respectively. While the pulsating power ripple cancellation benefits may not be automatically available in systems employing Modular Architectures 10 or 11, the modular connection may still offer improved failure tolerance, serviceability, and/or efficiency, in some embodiments. Alternatively or additionally, in some embodiments, in order to cancel the pulsating power ripple in a MAB configuration with single-phase input, a high-voltage (HV) power pulsation buffer (PPB) can be used. The PPB can comprise an HV capacitor with a large voltage swing and can be directly interfaced to one of the ports of the MAB converter. By controlling the ripple and power flow from the PPB port, the pulsating power AC ripple can be actively canceled. There is negligible net power flow to the PPB port; rather, only a power flow sufficient to supply the parasitic losses in the PPB capacitor is provided. Modulation and control strategies for such an architecture can be similar to those described elsewhere herein.
In some embodiments, instead of a parallel connection, the MAB converter modules can be connected in series on the AC port. For example,
In some embodiments, the series connections on the AC port are possible for both single-phase and three-phase input systems. In some embodiments, these connections can be combined with series/parallel connections on the DC ports, resulting in a truly modular architecture. For example, by appropriately selecting series/parallel connections, the voltage/current/power ratings for the modules can be selected more optimally, resulting in lower cost, lower volume, and/or higher efficiency.
In some embodiments, any of the disclosed Modular Architectures can be compatible with single-stage conversion as well as two-stage conversion at the AC ports. Additionally or alternatively, in some embodiments, two-stage conversion can be adopted on one or more of the DC ports. For example,
Referring to
Although the second stage converter is associated with a single low-voltage DC port in the illustrated examples of
The switching operation of an MAB converter according to any of the disclosed examples can be effected in any number of ways. Presented herein below are exemplary operation methods for a four-port converter; however, the teachings of the present disclosure can be readily generalized to operation of any n-port converter. For example,
In another exemplary operating configuration, phase-width modulation (PWM) can also be applied, in addition to or in place of PSM and/or PFM. For example, a combination of PWM, PSM, and PFM may be beneficial for circuit topologies comprising half-bridge configurations for certain ports, such as MAB configuration 2600 illustrated in
In some embodiments, the half bridge port configurations (e.g., as shown in
Alternatively or additionally, in some embodiments, the PWM, PSM, and/or PFM schemes can be applied to paralleled bridges connected to a matrix transformer, for example as illustrated in
In operation, the MOSFETs Q1:1 and Q1:3 of line-frequency synchronous rectifier 508 can turn on when the AC voltage is greater than zero, and the MOSFETs Q1:2 and Q1:4 of rectifier 508 can turn on when the AC voltage is less than zero. This rectifier subsystem 508 does not contain any line-frequency energy storage elements (e.g., inductors or capacitors) and only serves to rectify the AC voltage with a low-frequency switching action. The rectified AC voltage is then fed to the high-frequency bridge 3004 on the first port 3002 of the MAB converter. The process of discretization of the AC line-cycle to extract DC operating points for each switching cycle is illustrated in
In some embodiments, the above-noted strategies for operation and control of an MAB converter can be applied to MAB converters with three-phase AC ports. Alternatively or additionally, in some embodiments, the modulation strategies disclosed herein can be applied to configurations where one port acts like a power pulsation buffer (PPB), thus neither sinking nor sourcing power in an average sense.
For example,
In some embodiments, any of the disclosed examples of MAB converters, or variations thereof according to the teachings of the present disclosure, can be subjected to analysis and/or modeling (e.g., using numerical optimization techniques), for example, to select configurations and component values thereof for a particular application. For example, for a four-port MAB converter, an equivalent network 3300 as shown in
Using a voltage Fourier series coefficient at each port, the current components can be computed using the following equation:
i
bn
k=[Zk]−vbn
k,
where Zk represents the equivalent n-port impedance matrix for the network 3300. The computation of Zk can be carried out with the knowledge of the n-port transformer impedance matrix Zt,k and each of the 2-port resonant network impedance matrices Zr,n,k. As an example, the equivalent impedance matrix for a four-port series-resonant MAB converter shown in
Here, Mij refers to the mutual inductance between ith and jth ports of the multi-port transformer; Ri refers to the parasitic resistance present in ith port due to non-idealities in the corresponding transformer port, resonant capacitor, resonant inductor and interconnects (which are not explicitly shown in the figures). Once the voltage and current Fourier series coefficients are known, the real power at the nth port for the kth harmonic component can be directly computed by:
P
n,k
=
v
bn
k
i
bn
k*.
Based on the above analysis, quantities of the MAB converter can be conveniently determined and can be used for modeling, closed-loop control, and/or optimization as detailed below. In addition, the above analysis method is valid for and can be readily extended to all bridge configurations (e.g., as shown in
Referring to
The method 3400 can proceed to process block 3406, wherein an iterative procedure can begin with the selection of transformer parameters and RCN parameters such as the number of turns and impedance of RCN circuits. The method 3400 can proceed to process block 3408, where another inner iterative process can initiate. For example, with the selected parameters from process block 3406, duty ratios and phase shifts for the active bridges in various ports of the converter system can be selected. At process block 3408, Fourier coefficients of port voltages and currents can be determined using superposed harmonic analysis and a full-order admittance matrix. At process block 3410, time domain reconstruction of port voltages and currents can be performed, and at process block 3412, an objective function F(x) can be minimized. If no further iteration is desired, the method 3400 can proceed to process block 3414 for post-processing before proceeding to process block 3416 where a pareto curve is generated and an optimal solution is determined. If the determined solution fails to meet predetermined specifications (e.g., physical dimensions and/or efficiency) at decision block 3418, the method 3400 can return to process block 3406 for iteration. Otherwise, the method 3400 can proceed from decision block 3418 to terminal block 3420.
For example, based on the selected parameters, the constrained numerical optimization can minimize the objective function F(x) Pcond (x) by selecting the optimal modulation parameters (duty ratio and phase shifts). Furthermore, F(x) can be formulated to include other converter loss mechanisms including transformer core-losses and semiconductor switching losses, in addition to conduction losses in the converter. The constraints can be the reference power and the zero-voltage switching (ZVS condition) of each port. The objective function for minimizing the conduction losses can be expressed as:
minimize F(x)=Pcond(x)
x={δ
1,δ2, . . . δn,φ2,φ3, . . . Φn,fsw}
where, Pcond(x)=(Σj=1nIj2Rac,j) and j=1, 2, . . . n (number of ports).
The power and ZVS constraints can be expressed as:
P
j(x)=Pj,ref; j=1,2, . . . n (number of ports); x={δ1,δ2, . . . δn,φ2,φ3, . . . Φn,fsw}
½LjIj(a)2>Csw(Vj(a))Vj(a)2; j=1,2, . . . n (number of ports), a=switching instant,
where Csw(V) is the non-linear output capacitance of the switches with respect to the voltage. The optimal modulation parameters and volume of the transformer, which otherwise meet the efficiency and size constraints, can be selected.
In practical embodiments, the multi-port converters may not always operate at their full power rating. Therefore, targeting only a high full-load efficiency could perform poorly in terms of total energy loss. Therefore, a weighted efficiency (ηw) can be obtained by computing a weighted sum of efficiencies at different power levels:
ηw=w1η20%+w2η40%+w3η60%+w4η80%+w5η100%
The weights and corresponding power levels can be determined with the objective of minimizing total energy loss in the converter for a given load profile. In some embodiments, the loading percentages and number of weights can be extended to any number of points depending on the application. In addition, power density (ρ) computation can be parameterized by using component physical dimensions based on their specifications, which can allow another expression to be obtained for the converter volume. The obtained expressions for weighted efficiency (ηw) and the converter volume can be used by the optimization algorithm of choice as objective functions to evaluate different combinations of circuit parameters to generate a pareto front for ηw−ρ. The final design can be selected from the set of pareto-optimal designs by evaluating the performance in terms of weighted efficiency (ηw), power density (ρ), and/or design feasibility.
Although some of blocks 3402-3420 of
In some embodiments, an n-port converter system can have n number of subsystems, which can be arranged as active full bridges. The voltages at each port V1, V2 . . . Vn can be maintained at their nominal values by controlling the duty ratios δ1, δ2, . . . δn of the subsystem output voltage and the phase shift φ2, φ3 . . . φn1 between the voltage of the subsystems, where φj indicates the phase difference between the jth and the 1st port. Referring to
In either configuration, a closed loop control system can comprise a control loop subsystem (e.g., voltage control loop subsystem 3502 or current control loop subsystem 3552) and optimal trajectory subsystem 3554, which can determine the phase angle difference and duty ratios to control the port voltages and currents at its reference value. In the output voltage control scheme 3500, the voltage control loop subsystem 3502 can comprise and/or be defined by a controller block 3506, a decoupler block 3508, and a PWM/PSM block 3510. Similarly, in the output current control scheme 3550, the current control loop subsystem 3552 can comprise and/or be defined by a controller block 3556, a decoupler block 3558, and a PWM/PSM block 3560. Each controller block 3506, 3556 can comprise and/or be defined by a set of proportional and integral control (e.g., G(s)), which takes sampled port voltages 3512 and/or currents 3514 (measured using voltage and current sensors) as feedback and makes the error between the sampled feedback and reference as zero. Each decoupler block 3508, 3558 can be used to compensate for the cross-coupling between the two different ports, such that changes in one port will not affect the other ports.
The optimal trajectory subsystem 3504 or 3554 can generate steady-state duty ratios 3516 and phase shifts 3518 based on the generalized harmonic analysis. The steady-state duty ratios 3516 and phase angle differences 3518 can act as feedforward terms and can be added to the respective control loop subsystem output that is fed to the PWM/PSM block 3510 or 3560. The PWM/PSM block 3510 or 3560 in the control loop subsystem 3502 or 3552 can then be used to generate gate pulses 3520 or 3570 with appropriate deadtimes for the switches in the active bridges of various ports.
The control scheme is generic and can be implemented using any type of computer or processor, such as real-time DSP microcontrollers and/or FPGA controllers. In some embodiments, the power transfer for a port can be interrupted, or a port can be excluded from the system by hardware methods and/or software methods. For example, exemplary hardware methods can be implemented by adding a series back-to-back switch and operating it appropriately. Alternatively or additionally, exemplary software methods can be implemented by making the duty ratio for the respective port to zero (δj=π/2).
Another significant challenge that differentiates multi-port converters from conventional two-port converters is the cross-coupling of the matrix power flow in the multi-winding transformer, wherein the modification of one phase-shift (φ,δ) perturbs the power processed by all other ports. The coupled nonlinear relationship of phase-shifts with port powers can make it important to develop a phase-shift decoupling strategy to enable the use of conventional controllers for power flow regulation. In some embodiments, the designed controller can optimally modulate the inner phase-shifts (δ) and/or the switching frequency (fsw) to minimize the converter losses while ensuring soft-switching.
To achieve such goals, in some embodiments, a feed-forward multi-dimensional lookup-table (LUT) based approach can be used. The use of LUTs to store the trajectories of modulation variables can ensure that the converter operates optimally over its entire operating range (or at least a predetermined portion thereof). In some embodiments, the frequency domain generalized harmonic approximation (GHA) based optimal modulation strategy disclosed herein can be used to generate accurate look-up table values offline for all operating conditions. Next, to decouple the power flow with the LUT-based control, a closed loop control method can be used. For example,
From the small-signal modelling of the resonant QAB converter, the output voltage variations (ΔV2, ΔV3, ΔV4) are the product of the outer phase-shift angle variations (Δφ2, Δφ3, Δφ4) and the converter's transfer matrix G, expressed by below where £ is the scaling coefficient.
There are cross-coupling characteristics between the output voltage and the outer phase-shift angle variations. One approach to eliminate the cross-coupling effects and realize independent output voltage control for each individual port is to introduce a decoupling matrix H as given by:
When H=G−1, the output voltage variations and the outer phase-shift angle variations meet for a linear matrix equation, which indicates they are successfully decoupled. The precision of G affects the decoupling performance of the power flow control. Existing methods compute matrix G based on the Fundamental Harmonic Approximation (FHA) of port voltages. While these methods may offer good decoupling performance when the port high-frequency voltages and currents are close to sinusoidal, such as at the resonant operating point, such FHA-based methods cannot guarantee high accuracy at other operating points since the high-order harmonic components are non-negligible. In some embodiments, to address this issue, the converter's transfer matrix G can be derived using GHA based on the Taylor series of the port voltages. Since higher-order harmonic components besides the fundamental component are considered, the modeling accuracy can improve prediction of converter dynamic characteristics and estimation of stability margins. The proposed decoupled power flow control method together with the hybrid PI and feed-forward control can more tightly regulate the output voltage during all relevant load transients.
The computing environment 231 includes one or more processing units 235, 237 and memory 239, 241. In
A computing system may have additional features. For example, the computing environment 231 includes storage 261, one or more input devices 271, one or more output devices 281, and one or more communication connections 291. An interconnection mechanism (not shown) such as a bus, controller, or network interconnects the components of the computing environment 231. Typically, operating system software (not shown) provides an operating environment for other software executing in the computing environment 231, and coordinates activities of the components of the computing environment 231.
The tangible storage 261 may be removable or non-removable, and includes magnetic disks, magnetic tapes or cassettes, CD-ROMs, DVDs, or any other medium which can be used to store information in a non-transitory way, and which can be accessed within the computing environment 231. The storage 261 can store instructions for the software 233 implementing one or more innovations described herein.
The input device(s) 271 may be a touch input device such as a keyboard, mouse, pen, or trackball, a voice input device, a scanning device, or another device that provides input to the computing environment 231. The output device(s) 271 may be a display, printer, speaker, CD-writer, or another device that provides output from computing environment 231.
The communication connection(s) 291 enable communication over a communication medium to another computing entity. The communication medium conveys information such as computer-executable instructions, audio or video input or output, or other data in a modulated data signal. A modulated data signal is a signal that has one or more of its characteristics set or changed in such a manner as to encode information in the signal. By way of example, and not limitation, communication media can use an electrical, optical, radio-frequency (RF), or another carrier.
Any of the disclosed methods can be implemented as computer-executable instructions stored on one or more computer-readable storage media (e.g., one or more optical media discs, volatile memory components (such as DRAM or SRAM), or non-volatile memory components (such as flash memory or hard drives)) and executed on a computer (e.g., any commercially available computer, including smart-phones or other mobile devices that include computing hardware). The term computer-readable storage media does not include communication connections, such as signals and carrier waves. Any of the computer-executable instructions for implementing the disclosed techniques as well as any data created and used during implementation of the disclosed embodiments can be stored on one or more computer-readable storage media. The computer-executable instructions can be part of, for example, a dedicated software application or a software application that is accessed or downloaded via a web browser or other software application (such as a remote computing application). Such software can be executed, for example, on a single local computer (e.g., any suitable commercially available computer) or in a network environment (e.g., via the Internet, a wide-area network, a local-area network, a client-server network (such as a cloud computing network), or other such network) using one or more network computers.
For clarity, only certain selected aspects of the software-based implementations are described. Other details that are well known in the art are omitted. For example, it should be understood that the disclosed technology is not limited to any specific computer language or program. For instance, aspects of the disclosed technology can be implemented by software written in C++, Java, Perl, any other suitable programming language. Likewise, the disclosed technology is not limited to any particular computer or type of hardware. Certain details of suitable computers and hardware are well known and need not be set forth in detail in this disclosure.
It should also be well understood that any functionality described herein can be performed, at least in part, by one or more hardware logic components, instead of software. For example, and without limitation, illustrative types of hardware logic components that can be used include Field-programmable Gate Arrays (FPGAs), Program-specific Integrated Circuits (ASICs), Program-specific Standard Products (ASSPs), System-on-a-chip systems (SOCs), Complex Programmable Logic Devices (CPLDs), etc.
Furthermore, any of the software-based embodiments (comprising, for example, computer-executable instructions for causing a computer to perform any of the disclosed methods) can be uploaded, downloaded, or remotely accessed through a suitable communication means. Such suitable communication means include, for example, the Internet, the World Wide Web, an intranet, software applications, cable (including fiber optic cable), magnetic communications, electromagnetic communications (including RF, microwave, and infrared communications), electronic communications, or other such communication means. In any of the above-described examples and embodiments, provision of a request (e.g., data request), indication (e.g., data signal), instruction (e.g., control signal), or any other communication between systems, components, devices, etc. can be by generation and transmission of an appropriate electrical signal by wired or wireless connections.
In view of the above-described implementations of the disclosed subject matter, this application discloses the additional examples in the clauses enumerated below. It should be noted that one feature of a clause in isolation, or more than one feature of the clause taken in combination, and, optionally, in combination with one or more features of one or more further clauses are further examples also falling within the disclosure of this application.
Clause 1. A power conversion system comprising multiple ports coupled together via a transformer, the system employing an electrically- and magnetically-integrated isolated multi-port power conversion architecture for any of AC-to-DC, DC-to-DC, DC-to-AC, and AC-to-AC conversion and supporting multi-directional power flow.
Clause 2. The power conversion system of any clause or example herein, in particular, Clause 1, wherein the multiple ports comprise at least three ports with different voltage levels (e.g., four or more ports), each port being one of single-phase AC, three-phase AC, or DC, the multiple ports being connected in series, parallel, or stacked configurations.
Clause 3. The power conversion system of any clause or example herein, in particular, any one of Clauses 1-2, wherein the multi-directional power flow is such that an arbitrary number of ports act as sources to the system while remaining ports act as sinks to the system.
Clause 4. The power conversion system of any clause or example herein, in particular, any one of Clauses 1-3, wherein one or some of the ports act as an active pulsating power buffer (PPB) (e.g., acting as neither a power source nor a power sink).
Clause 5. The power conversion system of any clause or example herein, in particular, any one of Clauses 1-4, wherein at least one first port interfaces a single-phase or three-phase AC voltage, and the first port comprises a single-stage or two-stage topology.
Clause 6. The power conversion system of any clause or example herein, in particular, any one of Clauses 1-5, wherein the transformer is a high-frequency transformer, and each port is connected to the high-frequency transformer through a resonant coupling network (RCN).
Clause 7. The power conversion system of any clause or example herein, in particular, any one of Clauses 1-6, wherein a high-frequency circuit topology of each port is configured as a full-bridge, a half-bridge, a multilevel bridge, a three-phase bridge, bridges connected in a matrix configuration, or any combination of the foregoing.
Clause 8. The power conversion system of any clause or example herein, in particular, any one of Clauses 1-7, wherein the transformer is a multi-winding high-frequency isolation transformer, and the transformer has a single-phase, three-phase, or matrix-based configuration.
Clause 9. The power conversion system of any clause or example herein, in particular, any one of Clauses 1-8, wherein each port comprises a resonant or non-resonant coupling network, and the system comprises a symmetric or asymmetric arrangement of coupling networks on the ports.
Clause 10. The power conversion system of any clause or example herein, in particular, any one of Clauses 1-9, wherein the architecture employs a modular arrangement of multi-port converters or components thereof connected in series, in parallel, or in a stacked configuration.
Clause 11. A method for operation of the power conversion system of any clause or example herein, in particular, any one of Clauses 1-10, comprising closed-loop, multi-phase-shift, multi-duty ratio, variable switching frequency operation.
Clause 12. The method of any clause or example herein, in particular, Clause 11, wherein the power conversion system comprises a DC-to-DC multi-port resonant converter with at least three ports (e.g., each port having a configuration as listed in Table 1), and one or more modulation degrees of freedom are fixed in a trade-off between optimal performance and computation complexity.
Clause 13. The method of any clause or example herein, in particular, any one of Clauses 11-12, wherein for a half-bridge port without a DC-blocking capacitor, the phase-shift of the switching leg is independently varied, and the switching frequency of all switches is varied in conjunction with all other switches in the converter.
Clause 14. The method of any clause or example herein, in particular, any one of Clauses 11-13, wherein for a half-bridge port without a DC-blocking capacitor, the phase-shift and duty ratio of the switching leg are independently varied, and the switching frequency of all switches is varied in conjunction with all other switches in the converter.
Clause 15. The method of any clause or example herein, in particular, any one of Clauses 11-14, wherein for a full-bridge port, the phase shifts of both legs and duty ratios of both legs are independently varied, and the switching frequency of all switches is varied in conjunction with all other switches in the converter.
Clause 16. The method of any clause or example herein, in particular, any one of Clauses 11-15, wherein for a multi-level bridge, and active neutral point clamped (ANPC) or flying capacitor (FC) is employed, all of the phase shifts between the legs and duty ratios of both legs are independently varied, and the switching frequency of all switches is varied in conjunction with all other switches in the converter.
Clause 17. The method of any clause or example herein, in particular, any one of Clauses 11-16, wherein for bridge connections with matrix transformer configuration, the multiple bridges are effectively connected in parallel on a given port, and a set of phase shifts, duty ratios, and frequency for parallel bridges on the same port is kept identical except for the variations of Clauses 12-16.
Clause 18. The method of any clause or example herein, in particular, any one of Clauses 11-17, wherein one or more of the ports comprises a single-phase AC port without intermediate energy storage (e.g., single-stage operation), and one or some of the switches are commutated at an AC line frequency (e.g., ˜60 Hz) or at multiples of an AC line frequency.
Clause 19. The method of any clause or example herein, in particular, any one of Clauses 11-18, wherein one or more of the ports comprises a three-phase AC port without intermediate energy storage (e.g., single-stage operation), and one or some of the switches are commutated at an AC line frequency (e.g., ˜60 Hz) or at multiples of an AC line frequency.
Clause 20. The method of any clause or example herein, in particular, any one of Clauses 11-19, wherein one or more of the ports comprises a power pulsation buffer (PPB) operated a switching frequency that is the same as the rest of the multi-port converter, such that the PPB stores intermediate energy over an AC line cycle but does not supply or sink any average power.
Clause 21. A method for modeling operation of the power conversion system of any clause or example herein, in particular, any one of Clauses 1-10, comprising a frequency-domain modeling approach including generalized modeling of “m−1” phase shifts, “m” duty ratios, and switching frequency for a multi-port converter that has “m” independent two-level bridge legs or an equivalent combination of two-level and multi-level bridge legs.
Clause 22. The method of any clause or example herein, in particular, any one of Clauses 11-21, wherein the modeling approach comprises a generalized matrix-based modeling approach that includes translation of phase shifts, duty ratios, and switching frequency selection to an “n×n” matrix for an n-port converter, and allows for any arbitrary resonant coupling network and turns ratios for each port connected to the high-frequency transformer.
Clause 23. The method of any clause or example herein, in particular, any one of Clause 11-22, wherein the modeling approach is applicable to a DC-to-DC operating point comprising fixed DC voltages and powers on each port, and/or is applicable to single-stage AC-to-DC or DC-to-AC multi-port converters by discretization of the AC line cycle into a finite number of DC-to-DC operating points so as to preserve sufficient accuracy.
Clause 24. A method for design optimization of the power conversion system of any clause or example herein, in particular, any one of Clauses 1-10, comprising using the modulation and/or modeling frameworks of any of Clauses 11-23.
Clause 25. The method of any clause or example herein, in particular, Clause 24, wherein one or more loss objectives for a multiport converter are modeled and optimized by finding one or more corresponding optimal design parameters.
Clause 26. The method of any clause or example herein, in particular, Clause 25, wherein the one or more loss objectives comprises conduction losses, core losses, switching losses, or any combination of the foregoing, and/or the one or more optimal design parameters comprises turns ratios, resonant coupling network structure, resonant coupling network values, or any combination of the foregoing.
Clause 27. The method of any clause or example herein, in particular, any one of Clauses 24-26, further comprising constraints on achieving soft switching at all relevant operating points.
Clause 28. The method of any clause or example herein, in particular, any one of Clauses 24-27, wherein optimization objective functions are weighted by different operating points of the multi-port converters (e.g., combinations of different voltage and/or power levels at each port).
Clause 29. A method for control of the power conversion system of any clause or example herein, in particular, any one of Clauses 1-10, comprising a closed-loop optimal control scheme that enables multi-directional power flow with any number of input ports and any number of output ports.
Clause 30. The method of any clause or example herein, in particular, Clause 29, wherein the control scheme employs a hybrid approach comprising predetermined (e.g., computed offline) feedforward parameters for optimal operation and closed-loop feedback controllers for tracking and disturbance rejection due to parameter changes or other operating factors.
Clause 31. The method of any clause or example herein, in particular, any one of Clauses 29-30, wherein the control scheme comprises independent control of voltages and currents at each port (thus regulation power flow), tracking of an optimal root-mean-squared (RMS) currents, and maximizing ZVS/ZCS for all MOSFET devices over an entire load range.
Clause 32. The method of any clause or example herein, in particular, any one of Clauses 29-31, comprising a power decoupling approach, wherein the power flows among various ports are decoupled so as to realize superior transient performance and wherein the load or voltage changes on one port are decoupled from other ports.
Clause 33. The method of any clause or example herein, in particular, any one of Clauses 29-32, wherein the method is configured to be performed by firmware without any added hardware so as to realize zero power flow on any port.
Clause 34. The method of any clause or example herein, in particular, any one of Clauses 29-33, wherein the feedback controller operates in a voltage-mode control regime or average current-mode control regime.
Clause 35. The method of any clause or example herein, in particular, any one of Clauses 11-34, wherein the method is configured to be performed by a processor or microcontroller, with stored lookup tables (e.g., offline computation) for optimal operation along with closed-loop feedback controllers.
Any of the features illustrated or described herein, for example, with respect to
In view of the many possible embodiments to which the principles of the disclosed technology may be applied, it should be recognized that the illustrated embodiments are only examples and should not be taken as limiting the scope of the disclosed technology. Rather, the scope is defined by the following claims. We therefore claim all that comes within the scope and spirit of these claims.
The present application claims the benefit of U.S. Provisional Application No. 63/167,616, filed Mar. 29, 2021, entitled “Multi-port Power Converter System,” which is incorporated by reference herein in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| 63167616 | Mar 2021 | US |
