Multi-port isolated ev fast charging system using universal minimal converters

Abstract

An example multi-port DC / DC converter includes a primary bridge circuit comprising: an input, a primary winding of a transformer, and a primary H-bridge, where the primary H-bridge is coupled between the primary winding and the input; and at least one secondary bridge circuit comprising: an output, a secondary winding of the transformer, a secondary H-bridge comprising a primary side and a secondary side, and a bidirectional secondary switch, wherein the secondary winding of the transformer and the bidirectional secondary switch are coupled to the secondary side of the secondary H-bridge, and where the output is coupled to the primary side of the secondary H-bridge, where the at least one secondary bridge circuit is isolated by both the transformer and the bidirectional secondary switch.

Description

MULTI-PORT ISOLATED EV FAST CHARGING SYSTEM USING UNIVERSAL MINIMAL CONVERTERSCross-Reference to Related Applications

[0001] This application claims priority to, and the benefit of, U.S. Provisional Patent Application No. 63 / 639,377, filed April 26, 2024, entitled “MULTI-PORT ISOLATED EV FAST CHARGING SYSTEM USING UNIVERSAL MINIMAL CONVERTERS” which is incorporated by reference herein in its entirety.Technical Field

[0002] This application is directed to a power converter system and its controls.Background

[0003] Power converters change one form of electrical power into another form of electrical power. Example power converters include DC / DC converters, DC / AC converters, and AC / DC converters. Power converters allow for power generators, power consumers, and power storage systems to have different voltages and current inputs / outputs from one another. As an example, power is often transmitted in high voltage AC systems, but electric cars, battery energy storage, and industrial systems may require lower voltage DC power. Power sources for electric vehicles like fast chargers and residential chargers can include different types of AC and / or DC current at different voltage levels, current levels, and frequencies. Power converters can be used to solve this and other problems.

[0004] There are benefits to improving power converters, including power converters for electric vehicles.Summary

[0005] An example embodiment includes power converters configured to improve electric vehicle (EV) fast charging. Broad access to EV fast charging presents a major constraint on the rapid transformation of the automotive sector. The charging rates for each EV can vary widely from 100 kW to 350 kW across a wide voltage range, including bidirectional power flow when a battery is involved. An example embodiment includes an isolated bidirectional multi-port DC / DC converter for EV fast charging systems across a wide range of operations. The example system retains the benefits of multimode control of universal minimal converters (UMC) to achieve online performance optimization over a widerange of voltages. Compared with the traditional approach using multiple converters, the example embodiment realizes a smaller footprint, reduced component count, buck-boost operation, and improved performance. The example embodiment can optionally include DC / DC fast charging for multiple electric vehicles and / or local energy storage integration.

[0006] The example embodiment can include a smaller size footprint, reduced component count, buck-boost operation, and / or improved performance over conventional approaches. An example conventional approach is the use of multiple converters (each including a separate primary bridge, secondary bridge, and transformer) in parallel or series to power a single load, which can be simplified to one converter or fewer converters in embodiments of the present disclosure.

[0007] Implementations of the present disclosure include multi-port configurations of isolated universal converters, where each port of the universal converters is isolated using a bidirectional switch and control scheme, as described herein.

[0008] The term “universal” refers to the capability of the example unit cell converter in providing, via its control, controls for AC / AC, DC / AC, AC / DC, and DC / DC power conversion. The term “universal” also refers to the unit cell being mappable to any number of physical power converters having different topologies and configurations. To this end, the universal, minimal unit cell converter and its associated controls may be used ubiquitously in new standalone installation as well as retrofit systems for new or existing power converter infrastructure. The exemplary disclosure may be employed in a vehicle, hybrid vehicle, or electric vehicle, or in a structure (e.g., residence, commercial, industrial, etc.) to provide power connectivity to virtually any other power structure, e.g., to connect to the DC battery on the vehicle, connect to a DC fast charger, AC fast charger, connect to the grid, three-phase grid. It can also flexibly form a micro grid, support load, among other functions described herein, as a low-cost power electronic package that leverages available energy storage in a vehicle or building structure. In some embodiments, the system is configured for standalone installation, retrofit system, e.g., after market install in the garage. In either scenario, the exemplary systems can provide additional functionality noted herein as a universal minimal converter. In some embodiments, multiple vehicles (e.g., military, emergency systems) can be tethered through the system, as a universal power system cell, to form a microgrid for temporary, portable, or emergency power grid. In some embodiments, the system can be used in buses or large vehicles to provide power resilience for a building (e.g., school building, storm shelters, community centers, and the like).

[0009] In some aspects, implementations of the present disclosure include a multiport DC / DC converter, including: a primary bridge circuit including: an input, a primary winding of a transformer, and a primary H-bridge, wherein the primary H-bridge is coupled between the primary winding and the input; and at least one secondary bridge circuit including: an output, a secondary winding of the transformer, a secondary H-bridge including a primary side and a secondary side, and a bidirectional secondary switch, wherein the secondary winding of the transformer and the bidirectional secondary switch are coupled to the secondary side of the secondary H-bridge, and wherein the output is coupled to the primary side of the secondary H-bridge, wherein the at least one secondary bridge circuit is isolated by both the transformer and the bidirectional secondary switch.

[0010] In some aspects, implementations of the present disclosure include a multiport DC / DC converter, wherein the at least one secondary bridge circuit includes a plurality of secondary bridge circuits each including a respective bidirectional secondary switch, a respective secondary H-bridge, and a respective output.

[0011] In some aspects, implementations of the present disclosure include a multiport DC / DC converter, wherein each respective bidirectional secondary switch of the plurality of secondary bridge circuits is configured to isolate each secondary bridge circuit of the plurality of secondary bridge circuits from other secondary bridge circuits.

[0012] In some aspects, implementations of the present disclosure include a multiport DC / DC converter, wherein each secondary bridge circuit of the plurality of secondary bridge circuits is galvanically isolated from the other secondary bridge circuits.

[0013] In some aspects, implementations of the present disclosure include a multiport DC / DC converter, wherein each secondary bridge circuit of the plurality of secondary bridge circuits is configured for independent control.

[0014] In some aspects, implementations of the present disclosure include a multiport DC / DC converter, wherein the plurality of secondary H-bridge circuits are coupled in series.

[0015] In some aspects, implementations of the present disclosure include a multiport DC / DC converter, wherein the plurality of secondary H-bridge circuits are coupled in parallel.

[0016] In some aspects, implementations of the present disclosure include a multiport DC / DC converter, wherein the transformer includes a coaxial winding structure.

[0017] In some aspects, implementations of the present disclosure include a multiport DC / DC converter, wherein the primary bridge circuit and at least one secondary bridge circuit are galvanically isolated from each other.

[0018] In some aspects, implementations of the present disclosure include a multiport DC / DC converter, wherein the primary bridge circuit includes a capacitive filter.

[0019] In some aspects, implementations of the present disclosure include a multiport DC / DC converter, wherein the secondary bridge circuit includes a capacitive filter.

[0020] In some aspects, implementations of the present disclosure include a multiport DC / DC converter, wherein the primary H-bridge includes four power MOSFETS.

[0021] In some aspects, implementations of the present disclosure include a multiport DC / DC converter, wherein the secondary H-bridge includes four power MOSFETS.

[0022] In some aspects, implementations of the present disclosure include a method including: determining an operating state of a multi-port DC / DC converter; selecting, by a multimode control system, a mode corresponding to the operating state; and operating the multi-port DC / DC converter, according to the operating mode, wherein the operating mode is configured to cause soft-switching of at least one switch of the multi-port DC / DC converter, and wherein the operating mode operates a bidirectional secondary switch of the multi-port DC / DC converter to isolate a secondary bridge circuit of the multi-port DC / DC converter.

[0023] In some aspects, implementations of the present disclosure include a method, wherein the mode is at least partially based on a desired voltage transfer ratio and an average output current.

[0024] In some aspects, implementations of the present disclosure include a method, wherein the mode is configured to reduce residual DC flux in a transformer of the multi-port DC / DC converter.

[0025] In some aspects, implementations of the present disclosure include a method, wherein the multi-port DC / DC converter includes a plurality of secondary bridges, and the method further includes operating at least two secondary bridges of the plurality of secondary bridges at different voltages.

[0026] In some aspects, implementations of the present disclosure include a method, wherein the multi-port DC / DC converter includes a plurality of secondary bridges, and the method further includes operating at least two secondary bridges of the plurality of secondary bridges at different power levels.

[0027] In some aspects, implementations of the present disclosure include a system including: the multi-port DC / DC converter; a controller operably coupled to the primary bridge circuit and the secondary bridge circuit, wherein the controller is configured to determine an operating state, select, by a multimode control system, a mode corresponding to the operating state; operate the multi-port DC / DC converter according to the operating mode, wherein the operating mode is configured cause soft-switching of at least one switch of the multi-port DC / DC converter, and wherein the operating mode operates the bidirectional secondary switch to isolate the secondary bridge circuit of the multi-port DC / DC converter.

[0028] In some aspects, implementations of the present disclosure include a system, further including an AC / DC rectifier or solid-state transformer coupled to the primary bridge of the multi-port DC / DC converter.Brief Description of the Drawings

[0029] The skilled person in the art will understand that the drawings described below are for illustration purposes only.

[0030] FIG. 1 A shows an example DC / DC universal minimal converter (UMC) with four ports, in accordance with illustrative embodiments.

[0031] FIG. IB shows an example DC / DC UMC with four ports and a neutral point clamped (NPC) architecture on a primary bridge, in accordance with illustrative embodiments.

[0032] FIG. 2 illustrates a schematic of a single cell of the multi-port DC / DC converter shown in FIG. 1A and IB.

[0033] FIG. 3 illustrates example modes of operation of the multi-port DC / DC converter shown in FIG. 1A and IB.

[0034] FIG. 4 illustrates an example method of operating multi-port DC / DC universal minimal converters, in accordance with illustrative embodiments.

[0035] FIG. 5 illustrates an electric vehicle (EV) charging system with integrated storage using a DC / DC UMC, according to implementations of the present disclosure.

[0036] FIG. 6A illustrates a simulation of primary-side currents for a four-port UMC, according to a study of an example implementation of the present disclosure.

[0037] FIG. 6B illustrates a simulation of secondary-side currents for a four-port UMC, according to a study of an example implementation of the present disclosure.

[0038] FIG. 6C illustrates simulations of steady-state voltage, current, and power waveforms for a UMC, according to a study of an example implementation of the present disclosure.

[0039] FIG. 7 illustrates a hardware prototype used in an example implementation of the present disclosure.

[0040] FIG. 8 illustrates multimode operation at reduced power for a UMC, according to a study of an example implementation of the present disclosure.Detailed Description

[0041] Some references, which may include various patents, patent applications, and publications, are cited in a reference list and discussed in the disclosure provided herein. The citation and / or discussion of such references is provided merely to clarify the description of the disclosed technology and is not an admission that any such reference is “prior art” to any aspects of the disclosed technology described herein. In terms of notation, “[n]” corresponds to the nth reference in the list. For example, [1] refers to the first reference in the list. All references cited and discussed in this specification are incorporated herein by reference in their entireties and to the same extent as if each reference was individually incorporated by reference.

[0042] Example Multi-Port Universal Minimal Converter

[0043] FIG. 1 A shows an example embodiment of a multi-port DC / DC converter 100. The example embodiment of FIG. 1 A is configured as an isolated bidirectional multi-port DC / DC universal minimal converter (UMC) that can be used to support multiple EV charging functions and battery interconnection simultaneously. The multi-port DC / DC converters described herein can include voltage transfer ratios of unity, greater than 1, and less than 1.

[0044] The example embodiment of FIG. 1 A includes a primary bridge 102 and a secondary bridge 104. The secondary bridge includes four secondary bridge circuits 106a, 106b, 106c, 106d. It should be understood that embodiments of the present disclosure can include any number of secondary bridge circuits 106a, 106b, 106c, 106d in the secondary bridge 104 (e.g., more or less than four), where each secondary bridge circuit can optionally correspond to an output port of the multi-port DC / DC converter 100.

[0045] In some implementations, the number of ports can be greater than or less than the number of secondary bridge circuits 106a, 106b, 106c, 106d. The outputs of more thanone of the secondary bridge circuits 106a, 106b, 106c, 106d can be optionally coupled in series and / or in parallel to deliver greater voltage and / or power output to a single port. As a non- limiting example, two of the secondary bridge circuits 106a, 106b could be configured as: (1) two separate ports at 400 VDC and 150 kW; (2) in series as an 800 VDC and 300 kW port; and / or (3) in parallel as a single 400 VDC and 300 kW port.

[0046] The primary bridge 102 and secondary bridge 104 are coupled by a transformer 108, where the primary winding of the transformer is part of the primary bridge 102 and the secondary winding of the transformer is part of the secondary bridge 104. The transformer 108 provides galvanic isolation between the primary bridge 102 and the secondary bridge 104. Optionally, the transformer 108 can be configured with low-leakage between the windings of the transformer. For example, the transformer 108 can be a transformer with a coaxial winding structure.

[0047] An example transformer structure can include a single or split copper tube as a primary winding (e.g., with one or two turns) and secondary windings formed from Litz wires. An example turns ratio that can be used is 1 :1 or 2: 1.

[0048] The primary bridge 102 includes a primary H-bridge circuit formed by switches S 1-S4 112a, 112b, 112c, 112d between the input 101 and the primary winding of the transformer 108. Switches S 1-S4 112a, 112b, 112c, 112d can be configured to supply the primary winding of the transformer 108 with a square wave or quasi-square wave. Four secondary windings are coupled to the primary winding. The energy transfer inductances Liki - Lik4 114a, 114b, 114c, 114d connect the four secondary windings with the four secondary bridges. Optionally, the energy transfer inductances Liki - Lik4 114a, 114b, 114c, 114d can be implemented by any combination of discrete inductors and / or leakage inductance of the transformer 108 itself.

[0049] The secondary bridge 104 includes multiple secondary bridge circuits 106a, 106b, 106c, 106d that each operate as a port of the multi-port DC / DC converter 100. Each secondary bridge circuit 106a, 106b, 106c, 106d includes switches 116a, 116b, 116c, 116d configured as H-bridges. Output capacitors can optionally be coupled between the secondary switches and the output of each secondary bridge circuit 106a, 106b, 106c, 106d.

[0050] Additionally, the secondary bridge circuits 106a, 106b, 106c, 106d can each include a bidirectional switches (Ssi-SS4) 110a, 110b, 110c, 1 lOd coupled in series between the secondary winding of the transformer 108 and the switches 116a, 116b, 1 16c, 116d. The bidirectional switches (Ssi -Ss4) 110a, 110b, 110c, 1 lOd can be individually controlled, forexample to decouple the interaction of the secondary bridge circuits 106a, 106b, 106c, 106d, according to the methods described herein. The bidirectional switches 110a, 110b, 110c, HOd can optionally be implemented using four-quadrant AC switches.

[0051] In some embodiments, the primary bridge 102 can include a neutral point clamped (NPC) architecture. FIG. IB shows an example DC / DC UMC with four ports and a neutral point clamped (NPC) architecture on a primary bridge 102. The NPC architecture can be implemented using capacitors 118a, 118b. The NPC architecture uses capacitors to form a midpoint voltage at the bridge, reducing the voltage input to the switches. Additionally, the input capacitors can be used to filter the input signal.

[0052] In the example four-port system, each secondary bridge circuit 106a, 106b, 106c, 106d operates independently with specified terminal voltage Voi-Vo4 at their respective power levels. The transformer can also provide galvanic isolation between any / all of the secondary bridge circuits 106a, 106b, 106c, 106d.

[0053] Each of the secondary bridge circuits 106a, 106b, 106c, 106d can operate in buck or boost mode, with minimized overall losses. The operating point of each secondary bridge circuit 106a, 106b, 106c, 106d determines the switching losses in the secondary bridge circuit, while the aggregated current, which is a superposition of the secondary-side currents, determines losses in the primary bridge 102. The primary bridge 102 can be switched by a square wave (optionally including deadtime as needed). Optionally, the switching frequency of the primary bridge 102 is at a frequency of tens of kHz, (e.g., 20 kHz). Each secondary bridge circuit 106a, 106b, 106c, 106d synchronizes its operation with this square wave, selecting an optimum switching pattern at the desired dispatch of current and port voltage. Multiple patterns are evaluated, and the optimum is chosen. This topology has the advantage of realizing low leakage inductance between the primary and each secondary winding. The control systems described herein can manage DC flux injection into the transformer from both primary bridge 102 and secondary bridge 104.

[0054] The switches described herein can be any switching device. A non-limiting example of a switching device that can be used in implementations of the present disclosure is a reverse conducting device, for example a power MOSFET transistor. Any of the switching devices described herein can be configured as either square-wave switching devices or quasi square-wave switching devices.

[0055] Implementations of the present disclosure can replace conventional systems that would ordinarily include a primary bridge, secondary bridge, and transformer for eachport of a system. As shown in FIG. 1 A and FIG. IB, the example implementation only requires a single primary bridge 102 and transformer 108 for any number of secondary bridge circuits 106a, 106b, 106c, 106d, enabling significant system-level benefits (e.g., including reduced system cost, size, total VA rating of the devices, and fewer capacitors used). The example four-port converter described herein reduces the transformer count from 4 to 1 , device count (e.g., switches) from 32 to 28, and realizes a 30% reduction in the capacitance on the common primary bridge - representing significant savings in footprint and cost. Alternatively or additionally, embodiments of the present disclosure can realize low switching losses for all the devices in the secondary bridges under certain operating conditions and / or can realize zero voltage switching for devices under other conditions, allowing for high operating efficiencies.

[0056] FIG. 2 illustrates a schematic of a single cell of the multi-port DC / DC converter and a controller 200. The controller 200 can be implemented using any number and / or combination of computing devices. Additional description of an example computing device is described herein.

[0057] The controller 200 includes any number of sensor inputs 202 configured to measure the state of the primary bridge 102 and / or secondary bridge 104. For example, as shown in FIG. 2, the sensor inputs 202 can be configured to measure output voltage Vo and input voltage Vs. It should be understood that the sensor inputs 202 can alternatively or additionally include current and / or power measurements in implementations of the present disclosure. The sensor inputs 202 can be measured by any combination of sensors, including current and / or voltage sensors. For example, current sensors can be used to switch the switches of the converter when the current is at or near zero, referred to herein as a “soft switch.”

[0058] Embodiments of the present disclosure include methods of operations including operating patterns and switching sequences (referred to herein as “modes”). The modes can include the timing and order of switch closings and openings during a cycle of the multi-port DC / DC converter. The controller 200 can further include a multimodal control module 204. The multimodal control module 204 can select an operating mode for the multiport DC / DC converter. In some embodiments, the multimodal control module can be configured to select an operating mode in real time based on calculations performed during the switching cycle. Alternatively or additionally, the multimodal control module 204 can include a lookup table based on precalculated operating modes for different sensor inputs 202, and the multimodal control module 204 can select a mode of operation for the multi-portDC / DC converter by comparing the sensor inputs 202 to the lookup table. The Example herein provides an example configuration of a multi-port DC / DC converter controlled by a lookup table. Based on the mode selected by the multimodal control module 204, a PWM (pulse- width modulation) module 206 can be configured to output a square wave or quasisquare wave to control any or all of the switches of the multi-port DC / DC converter according to the selected mode.

[0059] Optionally, the hardware can be modeled and controlled as a Dual Active Bridge (DAB) converter with phase shift control. However, the use of phase shift control can result in very high currents and losses, particularly when the DC voltages are not very close to each other. Embodiments of the present disclosure can overcome the limitations of Dual Active Bridge converters by using the multimodal control systems and methods described herein. Multimodal control systems and methods can provide operation over a wide range of voltages with soft-switching capability and / or performance optimization (e.g., peak current stress and losses). [2], [3]. Alternatively or additionally, the multimodal control systems and methods described herein can be configured to reduce or eliminate residual DC flux in the transformer core. For example, one current level can be used on the primary side of the transformer and another current level can be used on the secondary side of the transformer.

[0060] FIG. 3 illustrates example modes 300a, 300b, 300c that perform buck and boost operation with a common square voltage wave from the primary side of the HF transformer. In FIG. 3, the leakage current waveform 302 for the positive half-cycle is shown, along with the voltage sequence 304 applied across the leakage inductor. The charge transfer Q can be derived using the terminal voltages Vsand VoLik, and switching period Tsw. For example, for 300a in Fig. 3(a):

[0061] where the expressions for Q in modes 300b and 300c can be derived similarly.Additionally, as shown in FIGS. 1A and IB, series bidirectional switches (Ssi-Ss4) are used, which can turn off during the zero states in FIG. 3 to decouple the interaction between secondary bridges.

[0062] It should be understood that the single cell of FIG. 2 can be implemented using the multi-port DC / DC converters of FIGS. 1A and IB, and that the single cell is illustrated for clarity. For example, the control techniques described herein with respect to FIG. 2 can beapplied to each secondary bridge circuit 106a, 106b, 106c, 106d shown in FIGS. 1A and IB, allowing for independent control of the secondary bridge circuits 106a, 106b, 106c, 106d.

[0063] FIG. 4 illustrates an example method of operating the multi-port DC / DC universal minimal converters described with reference to FIGS. 1 A-2. At step 410, the method includes determining an operating state of the multi-port DC / DC converter, for example using the sensors described with reference to FIG. 2.

[0064] At step 420, the method includes selecting, by a multimode control system, a mode corresponding to the operating state. Optionally, the mode can be selected based on a desired voltage transfer ratio and an average output current. Alternatively or additionally, the mode can be selected based to soft switch one or more switches of the secondary bridge circuit and thereby increase the efficiency of the multi-port DC / DC converter.

[0065] At step 430, the method includes operating the multi-port DC / DC converter according to the operating mode. Optionally, the operating mode can further include controlling the bidirectional secondary switch to isolate the secondary bridge circuit of the multi-port DC / DC converter from one or more of the other secondary bridge circuits of the multi-port DC / DC converter.

[0066] As described with reference to FIGS. 1A-2, each port of the multi-port DC / DC converters described herein can be configured for different voltage and / or current outputs. For example, the method shown in FIG. 4 can be optionally used to control each bridge circuit of a secondary bridge and thereby output different voltages from any / all of the bridge circuits of the secondary bridge.

[0067] Example System

[0068] As shown in FIG. 5, implementations of the present disclosure further include systems for using multi-port converters as multi-port charging systems. A multi-port DC / DC converter 504 according to any of the embodiments described herein is coupled between a DC electricity source 502 and a set of electrical vehicle charging bays 508a, 508b, 508n. The electricity source 502 can optionally be a transformer, an AC / DC rectifier and / or solid-state transformer. Optionally, energy storage 506 (e.g., battery storage) can also be coupled to the secondary side of the multi-port DC / DC converter 504.

[0069] Each of the electrical vehicle charging bays 508a, 508b, 508n are powered by a port of the multi-port DC / DC converter 504. While three electrical vehicle charging bays 508a, 508b, 508n are shown, it should be understood that any number of electrical vehicle charging bays can be present in various embodiments of the present disclosure. As described herein, themulti-port DC / DC converters described herein include isolation between each port and between the ports and the DC electricity source. Thus, multi-port DC / DC converter 504 can replace a DC bus with many separate converters, with a single converter. This reduces the number of components required, the size of the system, the cost of the system, and the complexity of the system.

[0070] Additionally, because the multi-port DC / DC converter 504 can include different outputs at each port, the multi-port DC / DC converter 504 can be used to charge vehicles with different charging requirements simultaneously at each of the electrical vehicle charging bays 508a, 508b, 508n. Alternatively or additionally, the multi-port DC / DC converter 504 can control the power output to each electrical vehicle charging bay 508a, 508b, 508n to optimize the efficiency of each output (e.g., by allowing for soft-switching of each bridge circuit of the multi-port DC / DC converter 504).

[0071] Experimental Results and Additional Examples

[0072] A study was performed of example implementations of the present disclosure. An example embodiment including a representative four-port converter rated at 175 kW operating from an 800 VDC bus and feeding three electrical vehicles (EVs), modeled as 400 V loads, and a battery rated at 800 V, were modeled and simulated with parameters shown in Table 1. The operating points of the example EV ports include the buck (port 3) and boost (port 2) operations as well as low power (port 2) and rated power (port 1) conditions, which are in line with the DCFC systems. Additionally, a battery was connected to provide additional power of 100 kW where the total demand exceeds the rated power of the primary bridge. This demonstrates the bidirectional power flow capability of the example embodiment of a four- port UMC, allowing peak demand management on the grid. The transformer currents on each bridge are shown in FIG. 6A. The inductor voltage sequence indicating various modes, and the terminal voltages on each bridge are shown in FIG. 6B. The steady-state voltage, current, andTABLE I. SIMULATION PARAMETERS.power waveforms of each port is shown in FIG. 6C, where the power is supplied by the DC source 602 and battery 604, and flows into EV ports 1-3 606, 608, 610.

[0073] The operation of the UMC and the mode selection strategy of the basic structure of UMC (with one secondary bridge) were verified experimentally in the study, with ahardware prototype illustrated in FIG. 7. The multimode operation at reduced power is demonstrated in FIG. 8 as the operating point changes.

[0074] Discussion:

[0075] As EV deployments increase, the challenges of providing sufficient fastcharging infrastructure will become significant. The footprint and cost of conventional multiport charging systems can be prohibitive, especially in urban areas.

[0076] Embodiments of the multi-port isolated universal minimal converter described herein can be used to overcome limitations of conventional technologies, for example in the automotive sector. Broad access to EV fast charging presents a major constraint on the rapid transformation of the automotive sector. Compared with the conventional multi-converter approach, the devices, systems, and methods described herein achieve a compact footprint and reduced device, transformer, and capacitor count. The proposed system adopts a multimode control, which has been proposed and retains benefits in operating voltage range and performance characteristics such as device stress and loss. Simulation and experimental validation are presented to validate the operating principles.

[0077] Deployment of electric vehicles is increasing rapidly, with an estimated volume of 100 million by 2040. The ability to charge these vehicles poses a big challenge. Given that it is prohibitively expensive or not feasible for many homeowners and apartment dwellers to install Level-2 charging at home, it is likely that a large part of the EV base will use DC fast charging. In many urban areas where EV populations are increasing, long wait times are seen at DCFC (DC Fast Charging) stations. DCFC stations are often designed to charge many EVs at the same time. For instance, with a peak of 350 kW, a 16 EV charging station has a peak rating of 5.6 MW. The challenge with this approach is the charging profile of typical EVs. [1] While the rate may hit a peak of 350 kW, that rate is not sustained for a long time and may only be needed for 10 minutes. The EV will dictate the charging profile, with much lower rates for a more extended time. The charging rates for each EV can vary widely from 100 kW to 350 kW across a wide voltage range, including bidirectional power flow when a battery is involved. Finally, the EV owner may be unwilling to stand by the EV and immediately stop charging once it is completed.

[0078] The example embodiment incorporates the benefits of multimode control of universal minimal converters to achieve online performance optimization over a wide range of voltages. The embodiments described herein include an isolated bidirectional multi-port DC / DC converter that can be configured for EV fast charging systems across a wide range ofoperations. Embodiments of the present disclosure overcome the limitations of a single DC bus with multiple independent converters by providing an integrated solution with a multiport converter. Embodiments of the present disclosure therefore improve the size, cost, and footprint of multi-port systems by providing an integrated converter that can replace multiple independent converters. Additionally, because embodiments of the present disclosure can be configured for bidirectional operation, implementations of the present disclosure allow for battery power to be input to one port or more ports of a converter, and that power to be used in charging (or any other output) of any other port(s) of the converter.

[0079] Compared with conventional approaches using multiple converters, the systems and methods described herein can achieve a smaller footprint, reduced component count, buck-boost operation, and / or improved performance.

[0080] Example Computing Device

[0081] The methods described herein can be implemented using a computing device. It should be understood that the example computing device described herein is only one example of a suitable computing environment upon which the methods described herein may be implemented. Optionally, the computing device can be a well-known computing system including, but not limited to, personal computers, servers, handheld or laptop devices, multiprocessor systems, microprocessor-based systems, network personal computers (PCs), minicomputers, mainframe computers, embedded systems, and / or distributed computing environments including a plurality of any of the above systems or devices. Distributed computing environments enable remote computing devices, which are connected to a communication network or other data transmission medium, to perform various tasks. In the distributed computing environment, the program modules, applications, and other data may be stored on local and / or remote computer storage media.

[0082] In its most basic configuration, computing device typically includes at least one processing unit and system memory. Depending on the exact configuration and type of computing device, system memory may be volatile (such as random access memory (RAM), non-volatile (such as read-only memory (ROM), flash memory, etc.), or some combination of the two. The processing unit may be a standard programmable processor that performs arithmetic and logic operations necessary for the operation of the computing device. The computing device may also include a communication bus or other communication mechanism for communicating information among various components of the computing device.

[0083] Computing device may have additional features / functionality. For example, computing device may include additional storage such as removable storage and nonremovable storage, including, but not limited to, magnetic or optical disks or tapes. Computing device may also contain network connection(s) that allow the device to communicate with other devices. Computing device may also have input and output means such as a keyboard, mouse, touch screen, a display, speakers, printer, etc. The additional devices may be connected to the communication bus in order to facilitate the communication of data among the components of the computing device. All these devices are well-known in the art and need not be discussed at length here.

[0084] The processing unit may be configured to execute program code encoded in tangible, computer-readable media. Tangible, computer-readable media refers to any media that is capable of providing data that causes the computing device (i.e., a machine) to operate in a particular fashion. Various computer-readable media may be utilized to provide instructions to the processing unit for execution. Example of tangible, computer-readable media may include, but is not limited to, volatile media, non-volatile media, removable media, and non-removable media implemented in any method or technology for storage of information such as computer-readable instructions, data structures, program modules or other data. System memory, removable storage, and non-removable storage are all examples of tangible, computer storage media. Examples of tangible, computer-readable recording media include, but are not limited to, an integrated circuit (e.g., field-programmable gate array or application- specific IC), a hard disk, an optical disk, a magneto-optical disk, a floppy disk, a magnetic tape, a holographic storage medium, a solid-state device, RAM, ROM, electrically erasable program read-only memory (EEPROM), flash memory or other memory technology, CD-ROM, digital versatile disks (DVD) or other optical storage, magnetic cassettes, magnetic tape, magnetic disk storage or other magnetic storage devices.

[0085] In an example implementation, the processing unit may execute program code stored in the system memory. For example, the communication bus may carry data to the system memory, from which the processing unit receives and executes instructions. The data received by the system memory may optionally be stored on the removable storage or the non-removable storage before or after execution by the processing unit.

[0086] It should be understood that the various techniques described herein may be implemented in connection with hardware or software or, where appropriate, with a combination thereof. Thus, the methods and apparatuses of the presently disclosed subjectmatter, or certain aspects or portions thereof, may take the form of program code (i.e., instructions) embodied in tangible media, such as floppy diskettes, CD-ROMs, hard drives, or any other machine-readable storage medium where, when the program code is loaded into and executed by a machine, such as a computing device, the machine becomes an apparatus for practicing the presently disclosed subject matter. In the case of program code execution on programmable computers, the computing device generally includes a processor, a storage medium readable by the processor (including volatile and non-volatile memory and / or storage elements), at least one input device, and at least one output device. One or more programs may implement or utilize the processes described in connection with the presently disclosed subject matter, e.g., through the use of an application programming interface (API), reusable controls, or the like. Such programs may be implemented in a high-level procedural or object-oriented programming language to communicate with a computer system. However, the program(s) can be implemented in assembly or machine language, if desired. In any case, the language may be a compiled or interpreted language, and it may be combined with hardware implementations.

[0087] It should be appreciated that the logical operations described above and, in the appendix, can be implemented (1) as a sequence of computer-implemented acts or program modules running on a computing system and / or (2) as interconnected machine logic circuits or circuit modules within the computing system. The implementation is a matter of choice dependent on the performance and other requirements of the computing system. Accordingly, the logical operations described herein are referred to variously as state operations, acts, or modules. These operations, acts and / or modules can be implemented in software, in firmware, in special purpose digital logic, in hardware, and any combination thereof. It should also be appreciated that more or fewer operations can be performed than shown in the figures and described herein. These operations can also be performed in a different order than those described herein.

[0088] Other examples

[0089] Although example embodiments of the present disclosure are explained in some instances in detail herein, it is to be understood that other embodiments are contemplated. Accordingly, it is not intended that the present disclosure be limited in its scope to the details of construction and arrangement of components set forth in the following description or illustrated in the drawings. The present disclosure is capable of other embodiments and of being practiced or carried out in various ways.

[0090] It must also be noted that, as used in the specification and the appended claims, the singular forms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise. Ranges may be expressed herein as from “about” or “ 5 approximately” one particular value and / or to “about” or “approximately” another particular value. When such a range is expressed, other exemplary embodiments include from the one particular value and / or to the other particular value.

[0091] By “comprising” or “containing” or “including” is meant that at least the name compound, element, particle, or method step is present in the composition or article or method, but does not exclude the presence of other compounds, materials, particles, method steps, even if the other such compounds, material, particles, method steps have the same function as what is named.

[0092] In describing example embodiments, terminology will be resorted to for the sake of clarity. It is intended that each term contemplates its broadest meaning as understood by those skilled in the art and includes all technical equivalents that operate in a similar manner to accomplish a similar purpose. It is also to be understood that the mention of one or more steps of a method does not preclude the presence of additional method steps or intervening method steps between those steps expressly identified. Steps of a method may be performed in a different order than those described herein without departing from the scope of the present disclosure. Similarly, it is also to be understood that the mention of one or more components in a device or system does not preclude the presence of additional components or intervening components between those components expressly identified.

[0093] The term “about,” as used herein, means approximately, in the region of, roughly, or around. When the term “about” is used in conjunction with a numerical range, it modifies that range by extending the boundaries above and below the numerical values set forth. In general, the term “about” is used herein to modify a numerical value above and below the stated value by a variance of 10%. In one aspect, the term “about” means plus or minus 10% of the numerical value of the number with which it is being used. Therefore, about 50% means in the range of 45%-55%. Numerical ranges recited herein by endpoints include all numbers and fractions subsumed within that range (e.g., 1 to 5 includes 1, 1.5, 2, 2.75, 3, 3.90, 4, 4.24, and 5).

[0094] Similarly, numerical ranges recited herein by endpoints include subranges subsumed within that range (e.g., 1 to 5 includes 1-1.5, 1.5-2, 2-2.75, 2.75-3, 3-3.90, 3.90-4,4-4.24, 4.24-5, 2-5, 3-5, 1-4, and 2-4). It is also to be understood that all numbers and fractions thereof are presumed to be modified by the term “about.”

[0095] The following patents, applications, and publications, as listed below and throughout this document, are hereby incorporated by reference in their entirety herein. Reference List #1[1] M. A. H. Rafi and J. Bauman, “A comprehensive review of DC Fast-Charging stations with energy storage: architectures, power converters, and analysis,” IEEE Trans, on Transport. Electrific., vol. 7, no. 2, pp. 345-368, June 2021.[2] F. Krismer, S. Round and J. W. Kolar, "Performance optimization of a high current dual active bridge with a wide operating voltage range," in Proc. 37th IEEE Power Electronics Specialists Conference, Jeju, Korea (South), 2006, pp. 1-7.[3] R. Hao, S. Belkhode, J. Benzaquen, and D. Divan, “Multimode control of HF link universal minimal converters Part II: multiphase AC systems,” in Proc. IEEE Energy Corners. Congr. Expo., Nashville, USA, 2023, pp. 3634-3640.[4] R. Hao, S. Belkhode, J. Benzaquen, and D. Divan, “A novel soft-switching scheme for three-phase DC / AC universal minimal converters (UMC),” in Proc. IEEE Energy Convers. Congr. Expo., 2024 (submitted).

Claims

What is claimed:

1. A multi-port DC / DC converter, comprising: a primary bridge circuit comprising: an input, a primary winding of a transformer, and a primary H-bridge, wherein the primary H-bridge is coupled between the primary winding and the input; and at least one secondary bridge circuit comprising: an output, a secondary winding of the transformer, a secondary H-bridge comprising a primary side and a secondary side, and a bidirectional secondary switch, wherein the secondary winding of the transformer and the bidirectional secondary switch are coupled to the secondary side of the secondary H-bridge, and wherein the output is coupled to the primary side of the secondary H-bridge, wherein the at least one secondary bridge circuit is isolated by both the transformer and the bidirectional secondary switch.

2. The multi-port DC / DC converter of claim 1, wherein the at least one secondary bridge circuit comprises a plurality of secondary bridge circuits each comprising a respective bidirectional secondary switch, a respective secondary H-bridge, and a respective output.

3. The multi-port DC / DC converter of claim 2, wherein each respective bidirectional secondary switch of the plurality of secondary bridge circuits is configured to isolate each secondary bridge circuit of the plurality of secondary bridge circuits from other secondary bridge circuits.

4. The multi-port DC / DC converter of claim 2, wherein each secondary bridge circuit of the plurality of secondary bridge circuits is galvanically isolated from other secondary bridge circuits of the plurality of secondary bridge circuits..

5. The multi-port DC / DC converter of claim 2, wherein each secondary bridge circuit of the plurality of secondary bridge circuits is configured for independent control.

6. The multi-port DC / DC converter of claim 2, wherein the plurality of secondary H-bridge circuits are coupled in series.

7. The multi-port DC / DC converter of claim 2, wherein the plurality of secondary H-bridge circuits are coupled in parallel.

8. The multi-port DC / DC converter of claim 1, wherein the transformer comprises a coaxial winding structure.

9. The multi-port DC / DC converter of claim 1 , wherein the primary bridge circuit and at least one secondary bridge circuit are galvanically isolated from each other.

10. The multi-port DC / DC converter of claim 1 , wherein the primary bridge circuit comprises a capacitive filter.

11. The multi-port DC / DC converter of claim 1 , wherein the secondary bridge circuit comprises a capacitive filter.

12. The multi-port DC / DC converter of claim 1, wherein the primary H-bridge comprises four power MOSFETS.

13. The multi-port DC / DC converter of claim 1, wherein the secondary H-bridge comprises four power MOSFETS.

14. A method comprising: determining an operating state of a multi-port DC / DC converter; selecting, by a multimode control system, a mode corresponding to the operating state; and operating the multi-port DC / DC converter, according to the operating mode, wherein the operating mode is configured to cause soft-switching of at least one switch of the multi-port DC / DC converter, and wherein the operating mode operates a bidirectional secondary switch of the multi-port DC / DC converter to isolate a secondary bridge circuit of the multi-port DC / DC converter.

15. The method of claim 14, wherein the mode is at least partially based on a desired voltage transfer ratio and an average output current.

16. The method of claim 14, wherein the mode is configured to reduce residual DC flux in a transformer of the multi-port DC / DC converter.

17. The method of claim 14, wherein the multi-port DC / DC converter comprises a plurality of secondary bridges, and the method further comprises operating at least two secondary bridges of the plurality of secondary bridges at different voltages.

18. The method of claim 14, wherein the multi-port DC / DC converter comprises a plurality of secondary bridges, and the method further comprises operating at least two secondary bridges of the plurality of secondary bridges at different power levels.

19. A system comprising: the multi-port DC / DC converter of any one of claims 1-13; a controller operably coupled to the primary bridge circuit and the secondary bridge circuit, wherein the controller is configured to: determine an operating state of a multi-port DC / DC converter of any one of claims 1-13; select, by a multimode control system, a mode corresponding to the operating state; operate the multi-port DC / DC converter according to the operating mode, wherein the operating mode is configured cause soft-switching of at least one switch of the multi-port DC / DC converter, and wherein the operating mode operates the bidirectional secondary switch to isolate the secondary bridge circuit of the multi-port DC / DC converter.

20. The system of claim 19, further comprising an AC / DC rectifier or solid-state transformer coupled to the primary bridge of the multi-port DC / DC converter.

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