Flexible static and dynamic expansion multi-active bridge system, control method and device

Abstract

The invention provides a flexible static and dynamic expansion multi-active bridge system and a control method and device, and relates to the technical field of power electronics, and the system architecture comprises a main power module which is connected with a constant-voltage DC bus and a high-frequency AC bus; the plurality of expansion sub-modules are connected with the high-frequency alternating current bus through respective isolation transformers, and a dual-active bridge converter is formed between every two expansion sub-modules in the plurality of expansion sub-modules; and the plurality of isolation switches are respectively arranged on connection points between the plurality of expansion sub-modules and the high-frequency alternating current bus, and the plurality of isolation switches are respectively used for connecting or pulling out the corresponding expansion sub-modules. According to the invention, flexible static and dynamic expansion of the multi-active bridge system can be realized.

Description

Technical Field

[0001] The present application relates to the field of power electronics technology, and in particular to a multi-active bridge system with flexible static and dynamic expansion, a control method and a device. Background Art

[0002] Multiple-Active-Bridge (MAB) converters (also called multiple-active-bridge transformers or multiple-active-bridge DC transformers, etc.) have been receiving more and more attention in research and application due to their advantages such as electrical isolation, wide voltage conversion range, high power density, control flexibility, and easy soft switching. Multiple-active-bridge converters are mostly hot-swappable control based on DC bus voltage, that is, all state variables or control references are obtained based on DC bus voltage, avoiding information interaction with the main circuit system, so that they can work as an independent dual-terminal module to achieve plug-and-play function. However, in the related art, hot-swappable control based on DC bus voltage is relatively complicated, which makes it difficult to flexibly expand the multiple-active-bridge converter system. Summary of the invention

[0003] The main purpose of the embodiments of the present application is to propose a multi-active bridge system, control method and device with flexible static and dynamic expansion, aiming to achieve flexible static and dynamic expansion of the multi-active bridge system.

[0004] To achieve the above-mentioned purpose, a first aspect of an embodiment of the present application proposes a multi-active bridge system with flexible static and dynamic expansion, and the multi-active bridge system includes:

[0005] A main power supply module, wherein the main power supply module is connected to the constant voltage DC bus and the high frequency AC bus respectively;

[0006] A plurality of expansion submodules, wherein the plurality of expansion submodules are connected to the high-frequency AC busbar through respective isolation transformers, and a dual active bridge converter is formed between every two expansion submodules in the plurality of expansion submodules;

[0007] A plurality of isolating switches are respectively arranged at connection points between each of the plurality of expansion sub-modules and the high-frequency AC bus, and the plurality of isolating switches are respectively used to connect or unplug the corresponding expansion sub-modules.

[0008] In some embodiments, the main power supply module includes a first H-bridge converter; the DC side of the first H-bridge converter is connected to a constant voltage DC bus, and the AC side of the first H-bridge converter is connected to a high-frequency AC bus;

[0009] The isolation transformer of any target submodule among the multiple expansion submodules includes a high-frequency transformer, and the target submodule also includes a second H-bridge converter, which is cascaded with the high-frequency transformer; the target submodule is connected to the high-frequency AC bus through the high-frequency transformer.

[0010] In some embodiments, the target submodule is connected to a constant voltage power supply through the second H-bridge converter, or the target submodule is connected to a DC load through the second H-bridge converter.

[0011] In some of these embodiments, each of the plurality of expansion submodules further includes a bridge controller;

[0012] The bridge controller of any target submodule among the multiple expansion submodules is used to control the disconnector between the target submodule and the high-frequency AC bus to close or open, so that the target submodule is connected to the multi-active bridge system when the disconnector is closed, and the target submodule is unplugged from the multi-active bridge system when the disconnector is opened.

[0013] To achieve the above-mentioned purpose, a second aspect of an embodiment of the present application proposes a control method for a multi-active bridge system with flexible static and dynamic expansion, and the control method is applied to the multi-active bridge system with flexible static and dynamic expansion proposed in the first aspect above, and the control method includes:

[0014] When the multi-active bridge system is in a preset state, the isolating switch corresponding to the first target submodule of the system to be unplugged among the multiple expansion submodules in the control system is turned on to unplug the first target submodule from the system; wherein the preset state includes a system stop state and a system running state; the isolating switch corresponding to the first target submodule is an isolating switch provided at a connection point between the high-frequency AC bus connected to the main power module in the system and the first target submodule;

[0015] When the multi-active bridge system is in the preset state, the isolating switch corresponding to the second target submodule to be connected to the system is controlled to be closed so as to connect the second target submodule to the system; wherein the isolating switch corresponding to the second target submodule is an isolating switch arranged at the connection point between the high-frequency AC bus and the second target submodule.

[0016] In some of these embodiments, the first target submodule includes a fault submodule;

[0017] The isolating switch corresponding to the first target submodule of the system to be unplugged among the multiple expansion submodules in the control system is turned on, including:

[0018] Controlling non-fault submodules among the plurality of extended submodules except the fault submodule to perform frequency integral compensation;

[0019] When line frequency integral compensation is performed based on the non-faulty submodule so that the port frequencies of the non-faulty submodule and the faulty submodule of the system to be removed are consistent, the isolating switch provided at the connection point between the faulty submodule and the high-frequency AC bus is controlled to be turned on.

[0020] In some embodiments, controlling the non-faulty submodules of the plurality of extended submodules except the faulty submodule to perform frequency integral compensation includes:

[0021] Sending a control signal to a bridge controller of a non-faulty submodule among the plurality of extended submodules except the faulty submodule, so as to control the bridge controller to control the non-faulty submodule to perform frequency integral compensation based on a preset frequency integral compensation value;

[0022] The frequency integral compensation value is calculated by the bridge controller based on the state data of the high-frequency AC bus.

[0023] In some embodiments, the control method further includes at least one of the following:

[0024] Performing power droop control on a submodule connected to a constant voltage power supply among the plurality of expansion submodules;

[0025] Performing voltage proportional integral control on a submodule connected to a DC load among the multiple extended submodules;

[0026] When the third target submodule among the multiple extended submodules is switched from being connected to a constant voltage power supply to being connected to a DC load, the power droop control of the third target submodule is switched to voltage proportional integral control of the third target submodule, and the third target submodule is controlled to perform high-frequency synchronization processing.

[0027] To achieve the above-mentioned purpose, the third aspect of an embodiment of the present application proposes a control device for a multi-active bridge system with flexible static and dynamic expansion. During operation, the control device controls the multi-active bridge system proposed in the first aspect above to implement the various steps of the control method provided in the second aspect above.

[0028] To achieve the above-mentioned purpose, the fourth aspect of an embodiment of the present application proposes a computer device, which includes a memory and a processor, the memory stores a computer program, and the processor implements the steps of the control method provided in the second aspect above when executing the computer program.

[0029] To achieve the above objectives, the fifth aspect of an embodiment of the present application proposes a computer-readable storage medium, which stores a computer program. When the computer program is executed by a processor, it implements the steps of the control method provided in the second aspect above.

[0030] To achieve the above objectives, the sixth aspect of an embodiment of the present application proposes a computer program product, wherein the computer program product includes a computer program, and when the computer program is executed by a processor, the steps of the control method provided in the second aspect above are implemented.

[0031] In the embodiment of the present application, the multi-active bridge system with flexible static and dynamic expansion includes a main power module and several expansion sub-modules, the main power module is respectively connected to the constant voltage DC bus and the high-frequency AC bus, and the multiple expansion sub-modules are connected to the high-frequency AC bus through their own isolation transformers, and an isolation switch is provided at the connection point. When the isolation switch is closed, the expansion sub-module can be connected to the system, and when the isolation switch is opened, the expansion sub-module is unplugged from the system. In this way, the multi-active bridge system proposed in the embodiment of the present application has dynamic and static expandability, and can flexibly adapt to different operating conditions and demand changes.

[0032] In addition, each expansion submodule in the multi-active bridge system provided by the embodiment of the present application adopts a connection method of a common high-frequency bus. If the capacity allows, expansion submodules of different voltage levels can be connected to the DC system through a high-frequency transformer that is converted to the AC bus voltage. Moreover, each expansion submodule can realize hot-swap function through precise high-frequency synchronous control. In addition to being able to be statically connected or unplugged when the system is shut down, it can also be dynamically connected or unplugged when the system is running without affecting the continuous operation of the system, which is conducive to expanding more ports, system maintenance and troubleshooting, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 This is a schematic diagram of the architecture of a multi-port modular power electronic transformer with a common DC bus according to an embodiment of the present application;

[0034] Figure 2 Schematic diagram of the structure of the star-type multi-active bridge transformer involved in the embodiment of the present application;

[0035] Figure 3 A schematic diagram of a scalable multi-active bridge DC transformer topology structure involved in some embodiments of the multi-active bridge system provided in the embodiments of the present application;

[0036] Figure 4 for Figure 3 Schematic diagram of the structure of the H-bridge converter (HB);

[0037] Figure 5A schematic diagram of the structure of a four-module multi-active bridge DC transformer based on distributed control involved in some embodiments of the multi-active bridge system provided in the embodiments of the present application;

[0038] Figure 6 A schematic diagram of the steps of the control method provided in some embodiments of the present application;

[0039] Figure 7 A control block diagram of power droop control of a multi-active bridge transformer power supply port involved in the control method provided in some embodiments of the present application;

[0040] Figure 8 A control block diagram of a load port of a multi-active bridge transformer involved in some embodiments of the control method provided in the embodiments of the present application;

[0041] Fig. 9 Voltage and current waveform diagrams when a 400V port involved in the control method provided in some embodiments of the present application switches between a power port and a load port;

[0042] Fig.10 A load port hot plug control flow chart involved in some embodiments of the control method provided in the embodiments of the present application;

[0043] Fig.11 A schematic diagram of voltage waveforms of various ports connected to the hot-swap control operation control port 4 involved in some embodiments of the control method provided in the embodiments of the present application;

[0044] Fig.12 A schematic diagram of a power transient waveform of a hot-swap control operation control port 4 involved in some embodiments of the control method provided in the embodiments of the present application;

[0045] Fig.13 A schematic diagram of voltage and current waveforms of port 1 when port 4 is connected under non-hot-swap control in some embodiments of the control method provided in the embodiments of the present application;

[0046] Fig.14 A schematic diagram of voltage and current waveforms of port 1 when port 4 is connected under hot-swap control in some embodiments of the control method provided in the embodiments of the present application;

[0047] Fig.15 A schematic diagram of voltage and current waveforms of port 3 when port 4 is connected under non-hot-swap control in some embodiments of the control method provided in the embodiments of the present application;

[0048] Fig.16 A schematic diagram of voltage and current waveforms of port 3 when port 4 is connected under hot-swap control in some embodiments of the control method provided in the embodiments of the present application;

[0049] Fig.17 A schematic diagram of voltage and current waveforms of port 2 when port 4 is connected under non-hot-swap control in some embodiments of the control method provided in the embodiments of the present application;

[0050] Fig.18 A schematic diagram of voltage and current waveforms of port 2 when port 4 is connected under hot-swap control in some embodiments of the control method provided in the embodiment of the present application;

[0051] Fig.19 A schematic diagram of voltage and current waveforms of port 4 when port 4 is connected under non-hot-swap control in some embodiments of the control method provided in the embodiments of the present application;

[0052] Fig. 20 A schematic diagram of voltage and current waveforms of port 4 when port 4 is connected under hot-swap control in some embodiments of the control method provided in the embodiments of the present application;

[0053] Fig.21 A power port hot plug control flow chart involved in some embodiments of the control method provided in the embodiments of the present application;

[0054] Fig. 22 A schematic diagram of voltage and current transient waveforms of port 1 during the access process of port 3 involved in some embodiments of the control method provided in the embodiments of the present application;

[0055] Fig.23 A schematic diagram of voltage and current transient waveforms of port 2 during the access process of port 3 involved in some embodiments of the control method provided in the embodiments of the present application;

[0056] Fig.24 A schematic diagram of voltage and current transient waveforms of port 3 during the access process of port 3 involved in some embodiments of the control method provided in the embodiments of the present application;

[0057] Fig.25 A schematic diagram of voltage and current transient waveforms of port 4 during the access process of port 3 involved in some embodiments of the control method provided in the embodiments of the present application;

[0058] Fig.26 A flow chart of hot-plug control of ports involved in some embodiments of the control method provided in the embodiments of the present application;

[0059] Fig. 27 A schematic diagram comparing transient waveforms of port 4 with and without hot-swap control in some embodiments of the control method provided in the embodiment of the present application;

[0060] Fig.28A schematic diagram of power transient waveforms of each port under hot-plug control involved in some embodiments of the control method provided in the embodiments of the present application;

[0061] Fig.29 A schematic diagram of a power waveform of a power port unplugged under non-hot-plug control involved in some embodiments of the control method provided in the embodiments of the present application;

[0062] Fig.30 A schematic diagram of a power waveform of a power port unplugged under hot-plug control involved in some embodiments of the control method provided in the embodiments of the present application;

[0063] Fig.31 A schematic diagram of transient waveforms of voltage and current at a load port under hot-swap control in some embodiments of the control method provided in the embodiments of the present application;

[0064] Fig.32 A schematic diagram of transient waveforms of AC voltage and inductor voltage and current after a switch device fails in some embodiments of the control method provided in the embodiments of the present application;

[0065] Fig.33 A schematic diagram of an H-bridge current path after a switch device fails in some embodiments of the control method provided in the embodiments of the present application;

[0066] Fig.34 A schematic diagram of a DC bias phenomenon of a submodule inductor current after a switch device failure in some embodiments of the control method provided in the embodiments of the present application;

[0067] Fig.35 A schematic diagram of a fault-tolerant architecture of a load port switch device involved in some embodiments of the control method provided in the embodiments of the present application;

[0068] Fig.36 A schematic diagram of a fault-tolerant inductor current of a load port switch device involved in some embodiments of the control method provided in the embodiments of the present application;

[0069] Fig.37 A schematic diagram of a fault-tolerant architecture of a power port switch device involved in some embodiments of the control method provided in the embodiments of the present application;

[0070] Fig.38 A schematic diagram of a fault-tolerant inductor current of a power port switch device involved in some embodiments of the control method provided in the embodiments of the present application;

[0071] Fig.39 A schematic diagram of a DC port fault short-circuit protection architecture involved in some embodiments of the control method provided in the embodiments of the present application;

[0072] Fig.40A schematic diagram of the internal structure of a computer device provided in an embodiment of the present application. DETAILED DESCRIPTION

[0073] In order to make the purpose, technical solution and advantages of the present application more clearly understood, the present application is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0074] It should be noted that, although the functional modules are divided in the device schematic diagram and the logical order is shown in the flowchart, in some cases, the steps shown or described may be performed in a different order than the module division in the device or the order in the flowchart. The terms "first", "second", etc. in the specification, claims and the above drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence.

[0075] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which this application belongs. The terms used herein are only for the purpose of describing the embodiments of this application and are not intended to limit this application.

[0076] Before introducing the embodiments of the present application, a brief introduction to the related technologies involved in the embodiments of the present application is first given here.

[0077] With the large-scale application of DC power distribution and the rapid development of power electronics technology, close access of DC users at multiple voltage levels has become a typical application scenario. This places higher requirements on the converters and systems for AC and DC power distribution. In the typical structure of a DC distribution network, DC-DC-based transformers are the core equipment for energy allocation and conversion. They connect DC buses of different voltage levels and enable various distributed energy sources and DC loads to be connected to the DC buses of corresponding levels through DC-DC converters. Multi-active bridge transformers are receiving more and more attention in research and application due to their advantages such as electrical isolation, wide voltage conversion range, high power density, control flexibility, and easy soft switching.

[0078] At the multi-active bridge transformer topology level, in order to ensure that faults between ports do not affect each other, the low-voltage DC bus is usually used as the internal energy collection link between the ports to form a star-shaped common DC bus multi-port modular power electronic transformer (such as Figure 1As shown in Figure 1). As the busbar inside the device, the common low-voltage DC busbar can reduce the risk of short-circuit faults from the structural design. In the common DC busbar star-type multi-port power electronic transformer, energy can be directly transferred between any two ports, and the closure of a port due to a fault will not affect the normal operation of other ports. However, the common DC busbar star-type multi-port converter also has obvious disadvantages: due to the use of a large number of intermediate power conversion links, the ports need to undergo two conversions, which will undoubtedly increase costs and reduce efficiency.

[0079] In order to reduce the large number of power modules and components used in multi-port power electronic transformers and avoid redundant intermediate power conversion links, a four-port power electronic transformer based on a multi-active bridge transformer can be used (such as Figure 2 As shown in Figure 1). Each port is connected through a multi-winding high-frequency transformer. Compared with the common DC bus structure, this topology significantly reduces the power conversion link and is more efficient. However, compared with the previous topology, the integrated design of the multi-winding high-frequency transformer in this structure will lead to limited scalability. Adding additional ports or capacity often requires redesigning the entire system.

[0080] In terms of control, most of the existing control strategies for multi-active bridge transformers belong to centralized control. The computational burden of the main controller and the scalability of the modules become the main problems. This control strategy is also not conducive to hot-swap and high-reliability fault-travel operation. The decentralized control strategy for multi-active bridge transformers can effectively improve the modularity and flexibility of the control system, but the technical difficulty lies in the control coordination and synchronization between multiple modules. The existing decentralized control strategy uses communication methods such as RS485 to achieve the synchronization of the pulse width modulation (PWM) circuits of each module, but this increases the consumption of additional communication resources. Therefore, a decentralized control strategy without communication is essential for multi-active bridge transformers that can be flexibly expanded statically and dynamically.

[0081] Cross-coupling is a unique challenge in multi-port DC / DC converters. There is no cross-coupling in DC / DC converters. The research on plug-and-play control strategies for active power decoupling circuits has gradually attracted the attention of researchers in recent years. At present, the plug-and-play control methods of active power decoupling circuits can be mainly classified into virtual impedance-based control methods and other control methods. The virtual impedance-based control method realizes power decoupling by shaping the impedance characteristics of both ends of the decoupling circuit to be the same as those of passive devices (large capacitors or large inductors). Since the decoupling circuit can be directly connected to the main circuit system through the busbar under this method, there is no need to invade the sensors of the main circuit and the central controller of the coordinated main circuit control, so it is easy to realize plug-and-play operation. The above methods are mostly hot-swap control methods based on DC bus voltage. All state variables or control references are obtained based on the DC bus voltage, avoiding information interaction with the main circuit system. It can work as an independent dual-terminal module to realize plug-and-play function. At this stage, research on hot-swap of multiple active bridges on the AC side is still needed.

[0082] Next, the overall concept of the embodiments of the present application will be further described.

[0083] In view of the problem that the hot-swap control based on the DC bus voltage in the related art is relatively complicated, which makes it difficult to flexibly expand the multi-active bridge converter system, the embodiment of the present application provides a multi-active bridge system, control method and device with flexible static and dynamic expansion. The multi-active bridge system includes a main power module and a plurality of expansion sub-modules. The main power module is respectively connected to the constant voltage DC bus and the high-frequency AC bus. The plurality of expansion sub-modules are connected to the high-frequency AC bus through their own isolation transformers, and an isolation switch is provided at the connection point. When the isolation switch is closed, the expansion sub-module can be connected to the system. When the isolation switch is opened, the expansion sub-module is unplugged from the system. In this way, the multi-active bridge system proposed in the embodiment of the present application has dynamic and static expandability, and can flexibly adapt to different operating conditions and demand changes.

[0084] In addition, each expansion submodule in the multi-active bridge system provided by the embodiment of the present application adopts a connection method of a common high-frequency bus. If the capacity allows, expansion submodules of different voltage levels can be connected to the DC system through a high-frequency transformer that is converted to the AC bus voltage. Moreover, each expansion submodule can realize hot-swap function through precise high-frequency synchronous control. In addition to being able to be statically connected or unplugged when the system is shut down, it can also be dynamically connected or unplugged when the system is running without affecting the continuous operation of the system, which is conducive to expanding more ports, system maintenance and troubleshooting, etc.

[0085] Based on the overall concept of the above-mentioned embodiments of the present application, various embodiments of the multi-active bridge system with flexible static and dynamic expansion provided by the embodiments of the present application are further proposed.

[0086] Please refer to Figure 3 and Figure 4 , Figure 3 A schematic diagram of a scalable multi-active bridge DC transformer topology structure involved in some embodiments of the multi-active bridge system provided in the embodiments of the present application, Figure 4 for Figure 3 Schematic diagram of the H-bridge converter.

[0087] like Figure 3 As shown, in some embodiments, the multi-active bridge system provided by the embodiments of the present application includes:

[0088] A main power supply module, wherein the main power supply module is connected to the constant voltage DC bus and the high frequency AC bus respectively;

[0089] A plurality of expansion submodules, wherein the plurality of expansion submodules are connected to the high-frequency AC busbar through respective isolation transformers, and a dual active bridge converter is formed between every two expansion submodules in the plurality of expansion submodules;

[0090] A plurality of isolating switches are respectively arranged at connection points between each of the plurality of expansion sub-modules and the high-frequency AC bus, and the plurality of isolating switches are respectively used to connect or unplug the corresponding expansion sub-modules.

[0091] The multi-active bridge system provided in the embodiment of the present application includes a main power module, several expansion sub-modules, corresponding control devices, DC port external devices and a high-frequency AC bus. The expansion sub-modules are connected to the high-frequency AC bus through their respective isolation transformers, and an isolating switch is provided at the connection point. When the isolating switch is closed, the expansion sub-module can be connected to the system; when the isolating switch is opened, the sub-module is unplugged from the system. When the expansion sub-module is connected or unplugged in the system shutdown state, it is only necessary to operate the isolating switch connected to the high-frequency AC bus to achieve static access or unplugging. When the expansion sub-module is connected in the system running state, voltage charging and high-frequency synchronization control must be performed first. After the operating frequency of the expansion sub-module is consistent with the frequency of the high-frequency AC bus and the phase meets the requirements, it can be dynamically connected to the system to realize the hot insertion operation of the sub-module. When the expansion sub-module needs to be repaired or parts are replaced and needs to be shut down separately, the system will send a shutdown signal to other expansion sub-modules and the main power module through the communication mechanism. After receiving the signal, other expansion sub-modules will perform pre-frequency compensation to ensure that when the expansion sub-module is dynamically unplugged, the impact on the operating characteristics of the rest of the system is minimized, thereby realizing the hot unplug operation of the expansion sub-module.

[0092] In some embodiments, the main power supply module includes a first H-bridge converter; the DC side of the first H-bridge converter is connected to a constant voltage DC bus, and the AC side of the first H-bridge converter is connected to a high-frequency AC bus;

[0093] The isolation transformer of any target submodule among the multiple expansion submodules includes a high-frequency transformer, and the target submodule also includes a second H-bridge converter, which is cascaded with the high-frequency transformer; the target submodule is connected to the high-frequency AC bus through the high-frequency transformer.

[0094] like Figure 3 As shown, in the multi-active bridge system provided by the embodiment of the present application, the main power module is an H-bridge converter (first H-bridge converter) without a high-frequency transformer, the DC side of the first H-bridge converter is connected to a constant-voltage DC bus, and the AC side is connected to a high-frequency AC bus. The expansion sub-modules except the main power module are all composed of an H-bridge converter (second H-bridge converter) and a high-frequency transformer (High frequency transformer, HFT) cascaded, and the expansion sub-modules are interconnected on the high-voltage side of the HFT through the high-frequency AC bus, forming a DC port on the DC side of the HB.

[0095] In some embodiments, the target submodule is connected to a constant voltage power supply through the second H-bridge converter, or the target submodule is connected to a DC load through the second H-bridge converter.

[0096] In the multi-active bridge system provided in the embodiment of the present application, the expansion submodule can be divided into a power port and a load port according to the properties of the DC terminal. When the expansion submodule is used as a power port, it is connected to the constant voltage power supply through the second H-bridge converter; and when the expansion submodule is used as a load port, it is connected to the DC load through the second H-bridge converter.

[0097] It should be noted that the DC end of the above-mentioned power port is powered by a constant voltage power supply, such as an energy storage system, a DC microgrid, and a PWM rectifier with DC voltage control. Therefore, the expansion submodule as the power port does not need to adjust the DC end voltage, and it mainly forms a high-frequency AC bus grid of the DC transformer together with the main power module. In addition, the DC end of the load port is connected to the DC load, and the DC load includes renewable energy (such as solar photovoltaic, wind turbine), active, passive load, etc. As an expansion submodule of the load port, its DC end will inject or absorb a certain amount of active power into the inside, so the load port needs to be able to maintain the DC end voltage.

[0098] like Figure 3 As shown, taking a four-port device including a main power module and three expansion sub-modules as an example, the main power module is externally connected to a constant voltage DC power supply, expansion sub-modules 2 and 4 are load ports, expansion sub-module 3 is a power port, C1, C2, C3, and C4 are capacitors of the four DC ports, respectively, and L1, L2, L3, and L4 are leakage inductances equivalent to the high-voltage side of the HFT, respectively, for realizing power transmission.

[0099] In some embodiments, each of the multiple expansion sub-modules also includes a bridge controller; the bridge controller of any target sub-module among the multiple expansion sub-modules is used to control the disconnector between the target sub-module and the high-frequency AC bus to close or open, so that the target sub-module is connected to the multi-active bridge system when the disconnector is closed, and the target sub-module is unplugged from the multi-active bridge system when the disconnector is opened.

[0100] In the multi-active bridge system provided by the embodiment of the present application, each expansion submodule has its own bridge controller HCi without the need for additional communication, and the phase shift angle of each expansion submodule can be adaptively adjusted according to the power, voltage and other information of the H bridge. Under normal operation, each expansion submodule adopts decentralized control (the decentralized control strategy adopts a variable switching frequency). Among them, the power port adopts power droop control, and the load port adopts constant voltage PI control. Whether the expansion submodule belongs to the nature of the power port or the nature of the load port is determined by its DC port, the constant voltage source type is power droop control, and the load type is constant voltage PI control. When the capacity allows, the nature of the expansion submodule can be flexibly switched by switching the control mode and the frequency pre-synchronization method. In addition to performing power droop / constant voltage control according to local information, each expansion submodule controller is also equipped with corresponding fault tolerance, hot plug and play, and high-frequency synchronization control methods.

[0101] Please refer to Figure 5 , Figure 5 A schematic diagram of the structure of a four-module multi-active bridge DC transformer based on distributed control involved in some embodiments of the multi-active bridge system provided in the embodiments of the present application.

[0102] In some embodiments, Figure 5 The four-module multi-active bridge DC transformer main circuit topology equivalent circuit is shown in the figure. The power flow between each expansion sub-module in the multi-active bridge DC transformer is directly determined by the phase angle difference between the expansion sub-modules. Therefore, every two expansion sub-modules can be regarded as a dual active bridge converter (DAB). The transmission power expression of DAB can be obtained as follows:

[0103]

[0104] Among them, i, j represent the port numbers, ni and nj are the turns ratios of the AC bus side and the DC port side of the high-frequency transformer in the submodule of the i-th and j-th ports, respectively. If it is the main power module, ni=1, f is the switching frequency, dij is the voltage shift ratio between the port i and the j-th submodule, Lij is the equivalent inductance between the ports, and Li is the leakage inductance of each submodule converted to the high-voltage side. According to the star-delta transformation, it can be known that:

[0105]

[0106] Where M is the leakage inductance conversion factor. At this time, the transmission power of each port is:

[0107]

[0108] It should be noted that in the above Figure 2 In the example of the star-type multi-active bridge transformer shown in the figure, according to GB / T35727-2017 "Guidelines for Medium and Low Voltage DC Distribution Voltages", the four DC port voltages Vd1, Vd2, Vd3, and Vd4 are set to 750V, 220V, 400V, and 48V respectively, and the rated voltage of the high-frequency AC bus is 750V. For the convenience of design, the transformation ratio of the HFT is approximately selected as the ratio of the high-frequency AC bus voltage to the voltage of each DC port. Therefore, it is assumed that the transformer turns ratio of submodule 2 is 26:8, the transformer turns ratio of submodule 3 is 26:14, and the transformer turns ratio of submodule 4 is 26:2. In addition, the rated power of ports 1, 2, and 3 is set to 10kW, and the rated power of port 4 is set to 5kW. In order to realize the modular design of miniaturized and high-power-density DC transformers, the operating frequency range of the high-frequency bus is 10-100kHz.

[0109] The multi-active bridge system provided by the embodiment of the present application has dynamic and static scalability, and can flexibly adapt to different operating conditions and demand changes. In the multi-active bridge system, each module (including the main power module and several expansion submodules) adopts a connection method of a common high-frequency bus. When the capacity permits, the expansion submodules of different voltage levels are connected to the DC system through a high-frequency transformer that is converted to the AC bus voltage. In this way, the expansion method of the system is simplified, and the expansion submodule can be mass-produced, with fewer power devices and lower costs. In addition, since each expansion submodule is equipped with an independent controller and has a hot-swap function controlled by precise high-frequency synchronization, the expansion submodule can be statically connected or unplugged when the system is shut down, and can also be dynamically connected or unplugged when the system is running, without affecting the continuous operation of the system, which is conducive to expanding more ports, system maintenance and troubleshooting.

[0110] In addition, since each expansion submodule is equipped with an independent controller, even if a module or controller fails, other expansion submodules can still operate independently without affecting the stability of the entire system. Compared with centralized control, the risk of a single point failure causing a complete system breakdown can be reduced. In addition to power droop / constant voltage control based on local information, each expansion submodule controller is also equipped with corresponding fault tolerance, hot plug, and high-frequency synchronization control methods, which can achieve a certain degree of fault immunity and static and dynamic hot plug functions. The integration of these control strategies and methods improves the system's adaptability and response speed to faults, and further enhances the reliability of the system.

[0111] In the multi-active bridge system provided by the embodiment of the present application, each module (including the main power module and several expansion submodules) uses decentralized control, which is highly targeted, has high information transmission efficiency, and has strong system adaptability. Each expansion submodule is allowed to be controlled according to local information, without communication delay, thereby improving the response speed and adaptability of the system. At the same time, in terms of topology, by reducing the use of isolation transformers and series inductors in the main power module, the total loss of the system is reduced and the overall efficiency is improved.

[0112] The multi-active bridge system provided in the embodiment of the present application realizes the deterministic design of the high-frequency AC bus voltage. The AC side of the main power module is directly connected to the AC bus, and there is no isolation transformer and series inductance, so the value of its port inductance is close to zero or much smaller than the inductance values ​​of other ports. This characteristic makes the voltage of the high-frequency AC bus basically directly determined by the main power module. Since the DC port of the main power module is externally connected to a constant-voltage DC bus, in the absence of shutdown and fault, the voltage of the AC bus appears as a highly stable 50% duty cycle square wave. If the main power module has an inductor or an isolation transformer, the voltage of the AC bus will be converted into a step wave synthesized by the AC side voltages of each expansion sub-module, and as the number of expansion sub-modules increases, the voltage waveform of the AC bus will become more complex.

[0113] Since the AC bus voltage is a highly stable 50% duty cycle square wave, the expansion module can more accurately detect the frequency and phase of the AC bus voltage, and can better implement control strategies such as high-frequency synchronization and phase compensation, which is conducive to the implementation of hot plug and fault ride-through control. At the same time, when the expansion module is connected or unplugged from the high-frequency AC bus, or when a disturbance or fault occurs, it will only affect the frequency of the bus without affecting its voltage shape, thus ensuring the stability and reliability of the system.

[0114] In the multi-active bridge system provided in the embodiment of the present application, the type of expansion submodule can be freely switched according to the DC port. In the multi-active bridge transformer topology, each expansion submodule adopts decentralized control, the power port adopts power droop control, and the load port adopts constant voltage PI control. The power supply or load properties of the expansion submodule are determined by the properties of its DC port. The constant voltage source type is power droop control, and the load type is constant voltage PI control. If the DC port needs to switch the power supply / load properties, the control of the expansion submodule only needs to switch the control method and prepare high-frequency pre-synchronization to achieve smooth static and dynamic switching.

[0115] Next, based on the embodiment of the multi-active bridge system with flexible static and dynamic expansion provided by the above-mentioned embodiment of the present application, an embodiment of a control method of the multi-active bridge system with flexible static and dynamic expansion provided by the embodiment of the application is further proposed.

[0116] It should be understood that the control method of the flexible static and dynamic expansion multi-active bridge system provided in the embodiment of the present application can be applied to the terminal, can also be applied to the server side, and can also be software running in the terminal or the server side. In some embodiments, the terminal can be a smart phone, a tablet computer, a laptop computer, a desktop computer, etc.; the server side can be configured as an independent physical server, or a server cluster or distributed system composed of multiple physical servers, and can also be configured as a cloud server that provides basic cloud computing services such as cloud services, cloud databases, cloud computing, cloud functions, cloud storage, network services, cloud communications, middleware services, domain name services, security services, CDN, and big data and artificial intelligence platforms; the software can be an application of the control method of the flexible static and dynamic expansion multi-active bridge system, etc., but is not limited to the above forms.

[0117] Alternatively, the present application may also be used in numerous general or special computer system environments or configurations. For example: personal computers, server computers, handheld or portable devices, tablet devices, multiprocessor systems, microprocessor-based systems, set-top boxes, programmable consumer computer devices, network PCs, minicomputers, mainframe computers, distributed computing environments including any of the above systems or devices, and the like. The present application may be described in the general context of computer executable instructions executed by a computer, such as program modules. Generally, program modules include routines, programs, objects, components, data structures, and the like that perform specific tasks or implement specific abstract data types.

[0118] For ease of understanding and explanation, the following text will take the multi-active bridge system as an example to describe the control method provided by the embodiment of the present application in detail. The implementation of the control method provided by the embodiment of the present application in any of the above-mentioned forms of the subject application can refer to the implementation process of the control method described below.

[0119] Please refer to Figure 6 , Figure 6 The control method provided in the present application is a flowchart of the steps in some embodiments. It should be understood that although Figure 6 The execution order of some method steps is shown in the figure, but based on different design requirements of actual applications, the control method provided in the embodiment of the present application can certainly adopt an execution order different from the method steps shown in the figure. That is, Figure 6 The order of the steps of the method shown does not constitute a limitation on the execution logic order of the control method provided in the embodiment of the present application. Figure 6 Reasonable changes in the sequence of steps of the method shown should be included in the protection scope of the control method provided in the embodiments of the present application.

[0120] like Figure 6 As shown, in some embodiments, the control method provided in the embodiments of the present application may include step S601 and step S602.

[0121] Step S601: When the multi-active bridge system is in a preset state, the isolating switch corresponding to the first target submodule of the system to be unplugged among multiple expansion submodules in the control system is turned on to unplug the first target submodule from the system; wherein the preset state includes a system stop state and a system running state; the isolating switch corresponding to the first target submodule is an isolating switch arranged at the connection point between the high-frequency AC bus connected to the main power module in the system and the first target submodule.

[0122] When the multi-active bridge system is in a system stop state, static unplugging can be achieved by controlling the disconnector of the first target submodule connected to the high-frequency AC busbar that needs to be unplugged from the multiple expansion submodules to open. When the system is in operation, if the first target submodule needs to be unplugged from multiple expansion submodules, voltage charging and high-frequency synchronization control are first performed to make the operating frequency of the first target submodule consistent with the frequency of the high-frequency AC busbar, and then after the phase meets the requirements, the disconnector of the first target submodule connected to the high-frequency AC busbar is controlled to open, thereby realizing the hot unplugging operation of the first target submodule.

[0123] Step S602: When the multi-active bridge system is in the preset state, the isolating switch corresponding to the second target submodule to be connected to the system is controlled to be closed so as to connect the second target submodule to the system; wherein the isolating switch corresponding to the second target submodule is an isolating switch arranged at the connection point between the high-frequency AC bus and the second target submodule.

[0124] When the multi-active bridge system is in a system stop state, if it is necessary to expand and connect the second target submodule in the system, it is only necessary to control the disconnector of the second target submodule connected to the high-frequency AC bus to close, and static access can be achieved. If it is necessary to connect the second target submodule when the system is running, it is also necessary to first perform voltage charging and high-frequency synchronization control to make the operating frequency of the second target submodule consistent with the frequency of the high-frequency AC bus, and then control the disconnector of the second target submodule connected to the high-frequency AC bus to close after the phase meets the requirements, so as to achieve the hot unplug operation of the second target submodule.

[0125] It should be noted that the system architecture of the multi-active bridge system includes a main power module, several expansion sub-modules, corresponding control devices, DC port external devices, and a high-frequency AC bus. The expansion sub-modules are connected to the high-frequency AC bus through their own isolation transformers, and an isolation switch is provided at the connection point. When the isolation switch is closed, the expansion sub-module can be connected to the system; when the isolation switch is opened, the sub-module is unplugged from the system.

[0126] In some embodiments, in a multi-active bridge system, the first target submodule to be unplugged from the multiple expansion submodules may include a faulty submodule. In this case, the above step S601 of "controlling the opening of the isolation switch corresponding to the first target submodule of the system to be unplugged from the multiple expansion submodules in the control system" may include:

[0127] Control non-faulty submodules among the multiple extended submodules except the faulty submodule to perform frequency integral compensation; when performing frequency integral compensation based on the non-faulty submodule so that the port frequencies of the non-faulty submodule and the faulty submodule of the system to be unplugged are consistent, control the isolating switch provided at the connection point between the faulty submodule and the high-frequency AC bus to be turned on.

[0128] In the case where there is a faulty submodule in the multiple extended submodules, the multi-active bridge system first controls the non-faulty submodules except the faulty submodule in the multiple extended submodules to perform frequency integral compensation, so that the port frequencies of the non-faulty submodules and the faulty submodule of the system to be unplugged are consistent. Then, when the port frequencies are consistent, the multi-active bridge system controls the isolating switch set at the connection point between the barrier submodule and the high-frequency AC bus to open, thereby realizing the hot unplugging operation of the faulty submodule from the system.

[0129] It should be noted that when a certain expansion submodule needs to be repaired or replaced and needs to be shut down separately, the system will send a shutdown signal to other submodules and the main power module through the communication mechanism. After receiving the signal, other expansion submodules will perform pre-frequency compensation to ensure that when the expansion submodule that needs to be shut down separately is dynamically unplugged, the impact on the operating characteristics of the rest of the system is minimized, and the hot unplug operation of the submodule is realized.

[0130] In some embodiments, when the plurality of expansion submodules each include a bridge controller, the step of “controlling the non-faulty submodules of the plurality of expansion submodules except the faulty submodule to perform frequency integral compensation” may include:

[0131] A control signal is sent to the bridge controller of the non-faulty submodules among the plurality of extended submodules except the faulty submodule, so as to control the bridge controller to control the non-faulty submodules to perform frequency integral compensation based on a preset frequency integral compensation value.

[0132] It should be noted that the frequency integral compensation value is calculated by the bridge controller based on the state data of the high-frequency AC bus. The state data includes state data obtained by collecting electrical quantities of the high-frequency AC bus.

[0133] In the case that there is a faulty submodule among the multiple extended submodules, the multi-active bridge system sends control signals to the bridge controllers of the other non-faulty submodules except the faulty submodule among the multiple extended submodules through the communication mechanism. After receiving the control signal, the bridge controllers of the other non-faulty submodules respond to the control signal to control the respective non-faulty submodules to perform frequency integral compensation based on the preset frequency integral compensation value.

[0134] In some embodiments, the control method provided in the embodiments of the present application further includes at least one of the following:

[0135] Performing power droop control on a submodule connected to a constant voltage power supply among the plurality of expansion submodules;

[0136] Performing voltage proportional integral control on a submodule connected to a DC load among the multiple extended submodules;

[0137] When the third target submodule among the multiple extended submodules is switched from being connected to a constant voltage power supply to being connected to a DC load, the power droop control of the third target submodule is switched to voltage proportional integral control of the third target submodule, and the third target submodule is controlled to perform high-frequency synchronization processing.

[0138] Under normal operation of the multi-active bridge system, each expansion submodule adopts decentralized control. Among them, the submodule belonging to the power port type connected to the constant voltage power supply adopts power droop control, while the submodule belonging to the load port type connected to the DC load adopts constant voltage proportional integral (PI) control. In addition, if the capacity allows, the properties of the expansion submodule can be flexibly switched by switching the control mode and the frequency pre-synchronization method. That is, for the third target submodule in multiple expansion submodules, when the third target submodule is connected to the constant voltage power supply as a power port and switched to being connected to the DC load as a load port, the bridge controller of the third target submodule needs to perform power droop control on the third target submodule, switch to voltage proportional integral control on the third target submodule, and control the third target submodule to perform high-frequency synchronization processing.

[0139] It should be noted that, according to the load type of the DC port of the multi-active bridge transformer, its port can be divided into two categories: power port and load port. The power port is powered by a power source that can provide a constant DC voltage, such as an energy storage system, a DC microgrid, etc. The load port is connected to a load that can absorb or inject active power, and the port voltage needs to be relatively constant. Figure 2 It can be seen that DC ports 1 and 2 are power ports, and ports 3 and 4 are load ports. To ensure the active power balance of the system, the power of each submodule satisfies:

[0140] (P1+P3)+(P2+P4)=0 (4)

[0141] Please refer to Figure 7 , Figure 7 A control block diagram of power droop control of a multi-active bridge transformer power port involved in some embodiments of the control method of the multi-active bridge system provided in the embodiments of the present application.

[0142] like Figure 7 As shown, in some embodiments, each power port determines the power sharing ratio of the power port through the maximum switching frequency deviation and the power sharing, and adaptively adjusts the switching frequency according to the power droop control.

[0143] The module switching frequency fsi is a variable value. According to the control block diagram, its calculation is shown in formula (5):

[0144]

[0145] Where i is the number of the submodule, Pi is the DC side power of the power port, fsref is the nominal switching frequency, τ is the time constant of the low-pass filter, which is used to reduce the high-frequency ripple of the measured Pi. mi is the proportional gain inversely proportional to the power output of each power port, and Δf is the compensation frequency calculated by the hot plug of the load port. After the frequency control output signal fsi is calculated by (5), it is input into the variable PWM modulation module with a duty cycle of 50% to obtain the pulse signals g1~g4 of the four switch tubes of the submodule, thereby realizing the dynamic adjustment of the high-frequency AC voltage phase angle. When the multi-active bridge transformer is in a stable state, the switching frequencies of all submodules will be synchronized.

[0146] In this embodiment, thanks to the power droop control, power distribution between power supplies can be achieved without a communication system between power supply ports. Droop control simulates the steady-state droop characteristics of the synchronous generator. Droop control changes the frequency of the output voltage according to the size of the port output active power to achieve the distribution of load power between ports; and without considering insufficient capacity, unless all power supplies fail, the failure of a single port will not affect the normal operation of the system. In addition, when the system power fluctuates and the operating mode changes, the droop control can reasonably distribute the unbalanced power by adaptively adjusting the droop coefficient.

[0147] Please refer to Figure 8 , Figure 8 A control block diagram of a multi-active bridge transformer load port involved in the control method provided in some embodiments of the present application.

[0148] like Figure 8 As shown, in some embodiments, because the DC terminal voltage of the load port is affected by the external circuit, the load port must measure and control the port DC voltage. The load port controller of the multi-active bridge system can be a traditional PI control, or it can further use first-order linear anti-disturbance control and auto-disturbance control based on cascade linear-nonlinear extended state observer to improve the transient response characteristics and load sudden disturbance resistance of the load port of the decentralized control type multi-active bridge transformer. The control of the load port can reduce the steady-state error of the system, and the response speed is fast, which makes up for the problem of unsatisfactory dynamic response of traditional droop control to a certain extent.

[0149] Taking the PI controller as an example, the switching frequency of the load port is calculated as shown in formula (6):

[0150]

[0151] Wherein, kp, ki are the proportional and integral gains of the PI controller, Vdc is the port voltage of the load port, Vref is the voltage reference value of the port, fref is the nominal switching frequency, fsi is the switching frequency of the load port, and Δf is the compensation frequency calculated by the hot plug of the load port.

[0152] In some embodiments, each expansion submodule in the multi-active bridge system provided in the embodiment of the present application adopts decentralized control. Among them, the power port adopts power droop control, and the load port adopts constant voltage PI control. If the DC port needs to switch between power supplies / loads of different natures, the control of the expansion module only needs to switch the control method and prepare for high-frequency pre-synchronization to achieve smooth static and dynamic switching. Taking the switching of the power port to the load port as an example, specifically: the bridge controller where the port that needs to be switched is located receives the instruction, and then switches the power droop control to PI control, the nominal switching frequency of the PI control is set to the frequency at the current moment, and gradually increases the frequency until it stabilizes to reduce the impact on the remaining ports. Fig. 9 The voltage and current waveforms of each sub-module port are shown when the 400V port switches from the power port to the load port at 0.2 seconds, and switches from the load port back to the power port at 0.6 seconds.

[0153] It should be noted that in the multi-active bridge system provided in the embodiment of the present application, the bridge controller of each expansion sub-module not only performs power droop / constant voltage PI control according to local information, but is also equipped with corresponding fault tolerance, hot plug and play, and high-frequency synchronization control methods.

[0154] Please refer to Fig.10 , Fig.10 A load port hot plug control flow chart involved in some embodiments of the control method provided in the embodiments of the present application.

[0155] like Fig.10 As shown, when the multi-active bridge system controls the second target submodule to access the system, if the second target submodule is a load port, the multi-active bridge system controls the second target submodule to access the system in three steps when the system is running: capacitor charging, control access, and load access. When controlling access, multiple links are required to eliminate the output error of PI control, and at the same time, it is necessary to ensure that the phase difference is small enough during access to ensure smooth hot access and reduce the impact on each port. Fig.11 It can be seen that under the hot-swap control operation scheme, the directly connected port 4 will not cause voltage and current impact on the other three ports. Fig.12 As shown, the voltage control and power distribution process of the connected port 4 is also relatively smooth.

[0156] like Fig.13 and Fig.14 As shown, Fig.13 and Fig.14 It is the voltage and current transient waveform of power port 1 with or without hot-swap control when port 4 is hot-swapped. The measured waveform is the DC port voltage and the current before capacitor filtering. Due to the voltage stabilizing effect of the port 1 voltage source, the voltage waveform is almost unaffected by the hot-swap of port 4. Fig.13 The transient current in the hot-swap control can reach 40A, and the current transient can be almost ignored after adding hot-swap control (such as Fig.14 ).

[0157] like Fig.15 and Fig.16 As shown, Fig.15 and Fig.16 What is shown is the voltage and current transient waveform of port 3 with and without hot-swap control when port 4 is hot-swapped. Similar to port 1, the voltage waveform is almost unaffected by the hot-swap operation of port 4. Fig.15 The transient current in the hot-swap control is as high as 77A, and the current transient can be almost ignored after adding hot-swap control (such as Fig.16 ).

[0158] like Fig.17 and Fig.18 As shown, Fig.17 and Fig.18 The figure shows the voltage and current transient waveforms of load port 2 with and without hot-swap control when port 4 is hot-swapped. Fig.17 and Fig.18 It can be clearly seen that the voltage and current disturbances caused by the access to port 4 are basically smoothed out after adding hot-swap control.

[0159] In addition, as an access port, it is very necessary to quickly pass the transient state without causing a big impact on other ports. Fig.19 and Fig. 20 As shown, Fig.19 and Fig. 20 What is shown is the voltage and current transient waveform of load port 2 with and without hot-swap control when port 4 is hot-swapped. It can be clearly seen that although direct access to port 4 is possible without hot-swap control, the excessive voltage and current shock is likely to damage the device of port 4 and affect the safety of the operator. Therefore, it is necessary to study the hot-swap control method. Fig. 20 It can be seen that after adding hot-swap control, the voltage fluctuation is significantly reduced and the current has almost no impact.

[0160] Please refer to Fig.21 , Fig.21 A power port hot plug control flow chart involved in some embodiments of the control method provided in the embodiments of the present application.

[0161] like Fig.21 As shown, when the multi-active bridge system controls the second target submodule to access the system, if the second target submodule is of the nature of a power port, the multi-active bridge system controls the access of the second target submodule in the system operation state, which is mainly divided into three steps: droop coefficient adjustment, frequency compensation and power allocation. Due to the existence of the power supply and the droop control facilitates the power allocation between ports, the access of the port is relatively simple, but it still needs to be adjusted in many aspects to smooth the impact of hot plugging on each port. It is necessary to ensure that the phase difference is small enough during access so that each port can smoothly transition to a new steady state.

[0162] like Figure 22 to Figure 25 As shown, Figure 22 to Figure 25 The figure shows the voltage and current transient waveforms of each port during the access process of port 3, where: Fig. 22 is port 1; Fig.23 For port 2; Fig.24 for port 3; Fig.25 It is port 4. It can be seen that the power port (port 3) is connected at about 0.08s, and the droop coefficient is adjusted at about 0.11s. The voltage and current of the main power port 1 basically smoothly transition to a new steady state. Due to the existence of the voltage source, the voltage of the connected port 3 is stable, and the current has a small overshoot in the power distribution process. The voltage fluctuations of the load port are all around 2V, and the current can smoothly transition.

[0163] Please refer to Fig.26 , Fig.26 A flow chart of hot-plug control of ports involved in some embodiments of the control method provided in the embodiments of the present application.

[0164] like Fig.26 As shown in the figure, when the multi-active bridge system controls the first target submodule in multiple expansion submodules to be pulled out of the system, the key step to be implemented is frequency integral compensation. The control is divided into two parts, one is normal closed-loop control, and the other is open-loop control with frequency integral compensation for non-fault port transition transient state. It is necessary to switch the control when the port frequency is consistent so that each port can smoothly transition to a new steady state.

[0165] like Fig. 27 and 28 As shown, Fig. 27 The figure shows the transient waveform comparison of port 4 with and without hot-swap control (load port 2 is unplugged). Fig.28 The figure shows the power transient waveform of each port under hot-swap control (load port 2 is unplugged). Fig. 27 and Fig.28It can be seen that when the load port (port 2) is unplugged at 0.3s, the power of port 2 quickly drops to 0, and the power between the power ports is also adjusted from an average of 10kW to an average of 2kW. The transient impact of port 4 can be stably passed under the control of frequency integral compensation.

[0166] In some embodiments, the multi-active bridge system is also based on Fig.26 When the power port is unplugged while the system is running, the result is as follows: Fig.29 and Fig.30 As shown in the figure, the power port can be unplugged smoothly and has almost no impact on other ports. Fig.29 The display shows the power waveform of the power port unplugged without hot-swap control (power port 3 is unplugged). Fig.30 The figure shows the power waveform when the power port is unplugged under hot-swap control (power port 3 is unplugged).

[0167] In addition, if Fig.31 As shown, Fig.31 The figure shows the voltage and current transient waveforms of the load port under hot-swap control (power port 3 is unplugged). The hot-swap control scheme can basically eliminate the voltage and current impact of each port, and the power of each port smoothly transitions to a new steady state. The transient time of high-frequency synchronization is short and the power distribution accuracy is high. The proposed multi-active bridge under distributed control has a natural advantage in the implementation of hot-swap. Even without hot-swap control, dynamic access of ports can still be achieved in simulation. However, since the impact on each port is too large and the access port has a great impact, it is easy to damage the equipment, so it is still necessary to design a hot-swap control scheme.

[0168] In some embodiments, if the multi-active bridge system is a multi-active bridge with full-bridge devices at all ports, when an open-circuit fault occurs in the full-bridge device, the mode of the forward current conducted by the device changes during normal operation. Take the open-circuit fault of the full-bridge switch tube Sb1 at the load port of module 2 as an example for analysis. The AC voltage and inductor current waveforms after the open-circuit fault are as follows: Fig.32 and Fig.33 As shown. Among them, Fig.32 The figure shows the transient waveforms of AC voltage and inductor voltage and current after the switching device fails. Fig.33 Shown is the H-bridge current path after a switching device fails.

[0169] In addition, if Fig.34 As shown in the figure, the open circuit of the switch device will cause the asymmetric duty cycle of the AC side square wave to be missing, and the slope of the inductor current change will be different from the normal working condition, causing the DC bias of the transformer. The DC bias will cause the transformer core to saturate, causing the transformer to heat up and damage the transformer.

[0170] like Fig.35 and Fig.36 As shown in the figure, the fundamental reason for the generation of DC components is the asymmetry of the circuit after an open-circuit fault. For an open-circuit fault of the H-bridge switch device at the load port, the driving signal of the bridge arm where the faulty switch tube is located can be locked during the open-circuit fault to form a symmetrical circuit structure and eliminate the DC component. The system can continue to transmit power during the fault-tolerant period, avoiding immediate power outages caused by faults. When the load demand is not high and the power supply can be suspended, the system can repair the fault without affecting the operation of the overall power grid. After the fault is repaired, the hot plug function can be used to dynamically access the system or statically access the system when it is shut down.

[0171] In addition, if Fig.37 and Fig.38 As shown in the figure, for the failure of the H-bridge switch device at the power port, since the whole bridge cannot release energy after the bridge arm drive is locked, it is necessary to adopt a fault-tolerant method of locking the module and opening the isolation switch to cut off the path of the faulty module. After the fault is repaired, the hot plug function can be used to dynamically access the system or statically access the system when it is shut down.

[0172] In some embodiments, please refer to Fig.39 , Fig.39 A schematic diagram of a DC port fault short-circuit protection architecture involved in some embodiments of the control method provided in the embodiments of the present application.

[0173] like Fig.39 As shown in the figure, the short circuit of the module DC port can be divided into load short circuit and power supply short circuit according to the port type. When the load side is short-circuited, the equivalent resistance of the load becomes smaller, and the energy stored in the capacitor is released quickly. If the short-circuit impedance characteristic is underdamped, the fault port will have an inductor freewheeling stage, which may cause the diode inside the converter to overcurrent. The overcurrent often exceeds the diode's current withstand value by several times or even dozens of times. For short-circuit faults, it is necessary to add a DC circuit breaker to the DC port according to actual requirements. When overcurrent is detected, the circuit breaker is locked and actuated to prevent the fault current from flowing into the fault port H bridge. At the same time, the isolation switch at the module connection is opened, the faulty module is removed from the DC system, and the path of the submodule is closed to prevent the non-faulty submodule from being affected. After the fault is repaired, the hot plug function is used to dynamically access the system or statically access the system in shutdown.

[0174] When a voltage source is short-circuited, the short-circuit impedance is very small, which will cause the short-circuit current to increase sharply. In order to protect the circuit and equipment, a DC power supply equipped with short-circuit protection measures should be used. When the current exceeds the preset threshold, the power supply quickly starts protection and cuts off the power supply path to prevent equipment damage and avoid risks such as electrical fires. At the same time, the faulty power supply module performs H-bridge pulse blocking, opens the DC circuit breaker and the AC side disconnector, cuts off the short-circuit current path, and removes the faulty module from the system. After the fault is repaired, the hot plug function can be used to dynamically connect to the system or statically connect to the system when it is shut down.

[0175] Based on the same inventive concept, the embodiment of the present application also provides a control device for a multi-active bridge system for realizing the flexible static and dynamic expansion of the above control method. The implementation scheme for solving the problem provided by the device is similar to the implementation scheme recorded in the above method, so the specific limitations in the control device embodiment provided in the embodiment of the present application can refer to the limitations of the control method for a multi-active bridge system with flexible static and dynamic expansion in the above text, and will not be repeated here.

[0176] Each module in the control device provided in the embodiment of the present application can be implemented in whole or in part by software, hardware, or a combination thereof. The above modules can be embedded in or independent of the processor in the computer device in the form of hardware, or can be stored in the memory in the computer device in the form of software, so that the processor can call and execute the operations corresponding to the above modules.

[0177] In some embodiments, the present application provides a computer device, which may be a server, and its internal structure diagram may be as follows: Fig.40 As shown. The computer device includes a processor, a memory, an input / output interface (Input / Output, referred to as I / O) and a communication interface. Among them, the processor, the memory and the input / output interface are connected through a system bus, and the communication interface is connected to the system bus through the input / output interface. Among them, the processor of the computer device is used to provide computing and control capabilities. The memory of the computer device includes a non-volatile storage medium and an internal memory. The non-volatile storage medium stores an operating system, a computer program and a database. The internal memory provides an environment for the operation of the operating system and the computer program in the non-volatile storage medium. The database of the computer device is used to store model parameters related to the liquid metal reactor. The input / output interface of the computer device is used to exchange information between the processor and an external device. The communication interface of the computer device is used to communicate with an external terminal through a network connection. When the computer program is executed by the processor, the steps of each embodiment of the control method provided in the above-mentioned embodiment of the present application are implemented.

[0178] Those skilled in the art will understand that Fig.40 The structure shown in the figure is only a block diagram of a part of the structure related to the solution of the present application, and does not constitute a limitation on the computer device to which the solution of the present application is applied. The specific computer device may include more or fewer components than those shown in the figure, or combine certain components, or have a different arrangement of components.

[0179] In some embodiments, a computer device is provided, including a memory and a processor, wherein a computer program is stored in the memory, and when the processor executes the computer program, the steps of each embodiment of the control method provided in the above-mentioned embodiments of the present application are implemented.

[0180] In some embodiments, a computer-readable storage medium is provided on which a computer program is stored. The steps implemented when the computer program is executed by a processor are the same as the steps implemented when the processor in the above-mentioned computer device executes the computer program, and the same content will not be repeated here.

[0181] In one embodiment, a computer program product is provided, including a computer program. The steps implemented when the computer program is executed by a processor are the same as the steps implemented when the processor in the above-mentioned computer device executes the computer program, and the same contents will not be repeated here.

[0182] Those skilled in the art can understand that all or part of the processes in the above-mentioned embodiment methods can be completed by instructing the relevant hardware through a computer program, and the computer program can be stored in a non-volatile computer-readable storage medium. When the computer program is executed, it can include the processes of the embodiments of the above-mentioned methods. Among them, any reference to the memory, database or other medium used in the embodiments provided in the present application can include at least one of non-volatile and volatile memory. Non-volatile memory can include read-only memory (ROM), magnetic tape, floppy disk, flash memory, optical memory, high-density embedded non-volatile memory, resistive random access memory (ReRAM), magnetoresistive random access memory (MRAM), ferroelectric random access memory (FRAM), phase change memory (PCM), graphene memory, etc. Volatile memory can include random access memory (RAM) or external cache memory, etc. As an illustration and not limitation, RAM can be in various forms, such as static random access memory (SRAM) or dynamic random access memory (DRAM). The database involved in each embodiment provided in this application may include at least one of a relational database and a non-relational database. Non-relational databases may include distributed databases based on blockchains, etc., but are not limited to this. The processor involved in each embodiment provided in this application may be a general-purpose processor, a central processing unit, a graphics processor, a digital signal processor, a programmable logic device, a data processing logic device based on quantum computing, etc., but are not limited to this.

[0183] The technical features of the above embodiments may be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0184] The above-described embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be construed as limiting the scope of the present application. It should be noted that, for a person of ordinary skill in the art, several modifications and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the present application shall be subject to the attached claims.

Claims

1. A multi-active bridge system with flexible static and dynamic expansion, characterized in that: The multi-active bridge system comprises: A main power supply module, wherein the main power supply module is connected to the constant voltage DC bus and the high frequency AC bus respectively; A plurality of expansion submodules, wherein the plurality of expansion submodules are connected to the high-frequency AC busbar through respective isolation transformers, and a dual active bridge converter is formed between every two expansion submodules in the plurality of expansion submodules; A plurality of isolating switches are respectively arranged at connection points between each of the plurality of expansion sub-modules and the high-frequency AC bus, and the plurality of isolating switches are respectively used to connect or unplug the corresponding expansion sub-modules.

2. The multi-active bridge system according to claim 1, characterized in that: The main power supply module includes a first H-bridge converter; the DC side of the first H-bridge converter is connected to a constant voltage DC bus, and the AC side of the first H-bridge converter is connected to a high-frequency AC bus; The isolation transformer of any target submodule among the multiple expansion submodules includes a high-frequency transformer, and the target submodule also includes a second H-bridge converter, which is cascaded with the high-frequency transformer; the target submodule is connected to the high-frequency AC bus through the high-frequency transformer.

3. The multi-active bridge system according to claim 2, characterized in that: The target submodule is connected to a constant voltage power supply through the second H-bridge converter, or the target submodule is connected to a DC load through the second H-bridge converter.

4. The multi-active bridge system according to any one of claims 1 to 3, characterized in that: Each of the plurality of expansion submodules further includes a bridge controller; The bridge controller of any target submodule among the multiple expansion submodules is used to control the disconnector between the target submodule and the high-frequency AC bus to close or open, so that the target submodule is connected to the multi-active bridge system when the disconnector is closed, and the target submodule is unplugged from the multi-active bridge system when the disconnector is opened.

5. A control method for a multi-active bridge system with flexible static and dynamic expansion, characterized in that: The control method is applied to the multi-active bridge system according to any one of claims 1 to 4, and the control method comprises: When the multi-active bridge system is in a preset state, the isolating switch corresponding to the first target submodule of the system to be unplugged among the multiple expansion submodules in the control system is turned on to unplug the first target submodule from the system; wherein the preset state includes a system stop state and a system running state; the isolating switch corresponding to the first target submodule is an isolating switch provided at a connection point between the high-frequency AC bus connected to the main power module in the system and the first target submodule; When the multi-active bridge system is in the preset state, the isolating switch corresponding to the second target submodule to be connected to the system is controlled to be closed so as to connect the second target submodule to the system; wherein the isolating switch corresponding to the second target submodule is an isolating switch arranged at the connection point between the high-frequency AC bus and the second target submodule.

6. The control method according to claim 5, characterized in that: The first target submodule includes a fault submodule; The isolating switch corresponding to the first target submodule of the system to be unplugged among the multiple expansion submodules in the control system is turned on, including: Controlling non-fault submodules among the plurality of extended submodules except the fault submodule to perform frequency integral compensation; When line frequency integral compensation is performed based on the non-faulty submodule so that the port frequencies of the non-faulty submodule and the faulty submodule of the system to be removed are consistent, the isolating switch provided at the connection point between the faulty submodule and the high-frequency AC bus is controlled to be turned on.

7. The control method according to claim 6, characterized in that: The controlling the non-fault submodules of the plurality of extended submodules except the fault submodule to perform frequency integral compensation includes: Sending a control signal to a bridge controller of a non-faulty submodule among the plurality of extended submodules except the faulty submodule, so as to control the bridge controller to control the non-faulty submodule to perform frequency integral compensation based on a preset frequency integral compensation value; The frequency integral compensation value is calculated by the bridge controller based on the state data of the high-frequency AC bus.

8. The control method according to any one of claims 5 to 7, characterized in that: The control method further includes at least one of the following: Performing power droop control on a submodule connected to a constant voltage power supply among the plurality of expansion submodules; Performing voltage proportional integral control on a submodule connected to a DC load among the multiple extended submodules; When the third target submodule among the multiple extended submodules is switched from being connected to a constant voltage power supply to being connected to a DC load, the power droop control of the third target submodule is switched to voltage proportional integral control of the third target submodule, and the third target submodule is controlled to perform high-frequency synchronization processing.

9. A control device for a multi-active bridge system with flexible static and dynamic expansion, characterized in that: When the control device is in operation, the steps of the method according to any one of claims 5 to 8 are implemented.

10. A computer program product, comprising a computer program, characterized in that When the computer program is executed by a processor, the steps of the method according to any one of claims 5 to 8 are implemented.

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