Method and device for open circuit fault ride through of co-high frequency bus multi-active bridge converter

Abstract

The application discloses a kind of open-circuit fault ride-through method and device of common high-frequency bus multi-active bridge converter, it is related to direct current distribution network protection field.The method comprises: when detecting that the open-circuit fault of submodule occurs in common high-frequency bus multi-active bridge converter, the updated active bridge topology is obtained by cutting off fault port;Compensation value is calculated based on circuit parameter information to obtain frequency integral compensation value;Integral compensation is calculated to obtain target compensation frequency for frequency integral compensation value;The preset reference frequency is added to target compensation frequency to obtain the fault ride-through frequency after compensation;The first control frequency of non-fault port is switched to fault ride-through frequency, after preset compensation time, make the updated active bridge topology enter stable state;When detecting that the real-time second control frequency of non-fault port is consistent with the preset voltage source submodule control frequency, switch back to closed-loop control to realize fault ride-through.It can reduce the interference between direct current ports and the current impact caused by adaptive adjustment.

Description

Technical Field

[0001] This application relates to the field of DC distribution network protection, and in particular to an open-circuit fault ride-through method and apparatus for a multi-active bridge converter with a common high-frequency bus. Background Technology

[0002] With the large-scale application of DC distribution networks and the rapid development of power electronics technology, multi-port power electronic converters have received increasing attention in recent years. The main circuit topologies of multi-voltage-level DC power electronic converters are mostly based on a common DC bus topology of multiple independent dual active bridges (DABs) or a high-frequency chain AC-coupled multi-active bridge (MAB) topology. Among these, the high-frequency chain AC-coupled MAB topology is a common high-frequency bus DC converter based on a modular multi-active bridge (MMAB) structure. It offers advantages such as good modular scalability and port independence, while having a relatively small number of power conversion stages and components, resulting in low cost and high power density. However, due to high-frequency chain energy aggregation, lack of energy buffer storage, and strong coupling between ports, this topology requires in-depth research into its control strategy optimization and fault impact. Regarding control strategies, existing multi-port DC power electronic converter control strategies include centralized control and distributed control strategies. Centralized control strategies are more commonly used. Under a centralized control strategy, all measurements, digital control execution, and drive signal generation are concentrated in a single processor. While centralized control architectures offer greater order, computational burden, modularity, and scalability become major challenges. Decentralized control strategies, on the other hand, distribute the computational burden of a central controller across several local controllers, effectively improving the modularity, flexibility, and cost-effectiveness of the control system.

[0003] Currently, research on fault analysis and fault ride-through methods for multi-active bridge converters with common high-frequency buses is relatively limited. Current research mainly focuses on fault analysis and fault isolation based on centralized control, such as the circuit breaker-based fault isolation technology used in the power electronic converters of the Zhangbei AC / DC hybrid distribution demonstration project. Regarding fault ride-through, overall research is scarce, and the proposed methods are relatively simple, failing to meet the diverse fault protection and fault ride-through requirements of different ports. Summary of the Invention

[0004] This application aims to address at least one of the technical problems existing in the prior art. To this end, this application proposes an open-circuit fault ride-through method and apparatus for a multi-active bridge converter with a common high-frequency bus, which can reduce the impact on non-faulty ports when a submodule is disconnected due to an open-circuit fault, and reduce interference between DC ports and current surges caused by adaptive adjustment.

[0005] In a first aspect, embodiments of this application provide an open-circuit fault ride-through method for a common high-frequency bus multi-active bridge converter. The common high-frequency bus multi-active bridge converter includes: a high-frequency AC bus, a voltage source module and a current source module connected to the high-frequency AC bus; the voltage source module further includes: a first voltage source sub-module and a second voltage source sub-module connected to the same side of the high-frequency AC bus; the current source module further includes: a first current source sub-module and a second current source module connected to the other side of the high-frequency AC bus on the same side.

[0006] The method includes:

[0007] When a submodule open-circuit fault is detected in the common high-frequency bus multi-active bridge converter, the fault location of the submodule open-circuit fault is determined;

[0008] Based on the fault location, the submodule fault disconnection process is performed, the faulty port is cut off, and an updated active bridge topology is obtained.

[0009] Based on the fault location, a frequency integral compensation value is obtained by calculating the compensation value using the acquired circuit parameter information.

[0010] Based on the fault location and the preset offset coefficient, the frequency integral compensation value is calculated by integral compensation to obtain the target compensation frequency.

[0011] The preset reference frequency is added to the target compensation frequency to obtain the compensated fault ride-through frequency;

[0012] The first control frequency of the non-faulty port in the current source module is switched to the fault ride-through frequency, and after a preset compensation time, the updated active bridge topology enters a stable state.

[0013] In the updated active bridge topology, when the real-time second control frequency of the non-faulty port is detected to be consistent with the preset voltage source submodule control frequency, the system switches back to closed-loop control to achieve fault ride-through.

[0014] Secondly, embodiments of this application provide an open-circuit fault ride-through device for a common high-frequency bus multi-active bridge converter. The common high-frequency bus multi-active bridge converter includes: a high-frequency AC bus, a voltage source module and a current source module connected to the high-frequency AC bus; the voltage source module further includes: a first voltage source sub-module and a second voltage source sub-module connected to the same side of the high-frequency AC bus; the current source module further includes: a first current source sub-module and a second current source module connected to the other side of the high-frequency AC bus on the same side.

[0015] The device includes:

[0016] An open-circuit fault detection module is used to determine the fault location of a submodule open-circuit fault when an open-circuit fault is detected in a common high-frequency bus multi-active bridge converter.

[0017] The first calculation and processing module is used to perform sub-module fault disconnection processing according to the fault location, disconnect the fault port, and obtain an updated active bridge topology.

[0018] The second calculation and processing module is used to calculate and process the compensation value based on the obtained circuit parameter information according to the fault location to obtain the frequency integral compensation value.

[0019] The third calculation and processing module is used to perform integral compensation calculation on the frequency integral compensation value according to the fault location and the preset offset coefficient to obtain the target compensation frequency.

[0020] The fault ride-through frequency calculation module is used to add the preset reference frequency to the target compensation frequency to obtain the compensated fault ride-through frequency.

[0021] The frequency switching module is used to switch the first control frequency of the non-faulty port in the current source module to the fault ride-through frequency, and after a preset compensation time, so that the updated active bridge topology enters a stable state.

[0022] The closed-loop control switching module is used to switch back to closed-loop control in the updated active bridge topology when the real-time second control frequency of the non-faulty port is detected to be consistent with the preset voltage source submodule control frequency, thereby achieving fault ride-through.

[0023] Thirdly, embodiments of this application provide an electronic device, including at least one processor and a memory for communicatively connecting to the at least one processor; the memory stores instructions executable by the at least one processor, the instructions being executed by the at least one processor to enable the at least one processor to perform the open-circuit fault-crossing method as described in any of the embodiments of the first aspect.

[0024] This application embodiment includes: a common high-frequency bus multi-active bridge converter comprising: a high-frequency AC bus, a voltage source module and a current source module connected to the high-frequency AC bus; the voltage source module further includes: a first voltage source sub-module and a second voltage source sub-module connected to the same side of the high-frequency AC bus; the current source module further includes: a first current source sub-module and a second current source sub-module connected to the other side of the high-frequency AC bus; during the operation of the common high-frequency bus multi-active bridge converter, when a sub-module open-circuit fault is detected in the common high-frequency bus multi-active bridge converter, the fault location of the sub-module open-circuit fault is determined; based on the fault location, sub-module fault disconnection processing is performed, the fault port is cut off, and an updated active bridge topology is obtained; based on the fault location and the acquired circuit parameter information, compensation value calculation processing is performed to obtain the frequency integral. The compensation value is calculated by integral compensation based on the fault location and preset offset coefficient to obtain the target compensation frequency. The preset reference frequency is added to the target compensation frequency to obtain the compensated fault ride-through frequency. The first control frequency of the non-faulty port in the current source module is switched to the fault ride-through frequency. After a preset compensation time, the updated active bridge topology enters a stable state. In the updated active bridge topology, when the real-time second control frequency of the non-faulty port is detected to be consistent with the preset voltage source submodule control frequency, the closed-loop control is switched back to achieve fault ride-through. This reduces current surge. In other words, the embodiments of this application can reduce the impact on non-faulty ports when the submodule is disconnected due to an open-circuit fault, and reduce interference between DC ports and current surge caused by adaptive adjustment. Attached Figure Description

[0025] Figure 1A This is a schematic diagram of the topology of a multi-active bridge DC-DC converter provided in one embodiment of this application;

[0026] Figure 1B This is a schematic diagram of the topology of a multi-active bridge converter with a common low-voltage high-frequency bus provided in one embodiment of this application;

[0027] Figure 2A This is a schematic diagram of the specific topology of a voltage source submodule provided in one embodiment of this application;

[0028] Figure 2B This is a control block diagram of a voltage source submodule provided in one embodiment of this application;

[0029] Figure 3A This is a schematic diagram of the specific topology of a current source submodule provided in one embodiment of this application;

[0030] Figure 3B This is a schematic diagram of the specific topology of a current source submodule provided in one embodiment of this application;

[0031] Figure 4 This is a flowchart illustrating the open-circuit fault ride-through method for a common high-frequency bus multi-active bridge converter provided in some embodiments of this application;

[0032] Figure 5 This is a schematic diagram of an open-circuit submodule provided in one embodiment of this application;

[0033] Figure 6 This is a schematic diagram of the capacitor voltage change of the first current source submodule when an open-circuit fault occurs in the first current source submodule;

[0034] Figure 7 This is a schematic diagram showing the change in capacitor voltage of the non-faulty second current source submodule when the first current source submodule experiences an open-circuit fault.

[0035] Figure 8 This is a schematic diagram showing the waveform changes of the port power of each submodule when the first current source submodule experiences an open-circuit fault.

[0036] Figure 9 This is a schematic diagram showing the changes in capacitor voltage between the first current source module and the second current source module when the second voltage source module experiences an open-circuit fault.

[0037] Figure 10 This is a schematic diagram showing the waveform changes of the port power of each submodule when an open-circuit fault occurs in the second voltage source submodule;

[0038] Figure 11 This is a schematic diagram of the frequency integration compensation process of the second current source submodule;

[0039] Figure 12 This is a schematic diagram of the port power waveform changes of each submodule when the first current source submodule has an open circuit fault and no operation.

[0040] Figure 13 This is a schematic diagram showing the changes in the port power waveforms of each submodule during fault crossing when an open-circuit fault occurs in the first current source submodule.

[0041] Figure 14 This is a schematic diagram showing the changes in the port power waveforms of each submodule when the second voltage source submodule has an open-circuit fault and no operation.

[0042] Figure 15 This is a schematic diagram showing the changes in port power waveforms of each submodule during fault crossing when an open-circuit fault occurs in the second voltage source submodule. Detailed Implementation

[0043] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be noted that although a logical order is shown in the flowcharts in this application, in some cases, the steps shown or described may be performed in a different order than that shown in the flowcharts. In the description of this application, "several" means one or more, and "more" means two or more. The terms "first" and "second" are used only to distinguish technical features and should not be construed as indicating or implying relative importance, or implicitly indicating the number of indicated technical features, or implicitly indicating the sequential relationship of the indicated technical features. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains. The terminology used herein is for the purpose of describing embodiments of this application only and is not intended to limit this application.

[0044] With the large-scale application of DC distribution networks and the rapid development of power electronics technology, multi-port power electronic converters have received increasing attention in recent years. The main circuit topologies of multi-voltage-level DC power electronic converters are mostly based on a common DC bus topology of multiple independent dual active bridges (DABs) or a high-frequency chain AC-coupled multi-active bridge (MAB) topology. Among these, the high-frequency chain AC-coupled MAB topology is a common high-frequency bus DC converter based on a modular multi-active bridge (MMAB) structure. It offers advantages such as good modular scalability and port independence, while having a relatively small number of power conversion stages and components, resulting in low cost and high power density. However, due to high-frequency chain energy aggregation, lack of energy buffer storage, and strong coupling between ports, this topology requires in-depth research into its control strategy optimization and fault impact. Regarding control strategies, existing multi-port DC power electronic converter control strategies include centralized control and distributed control strategies. Centralized control strategies are more commonly used. Under a centralized control strategy, all measurements, digital control execution, and drive signal generation are concentrated in a single processor. While centralized control architectures offer greater order, computational burden, modularity, and scalability become major challenges. Decentralized control strategies, on the other hand, distribute the computational burden of a central controller across several local controllers, effectively improving the modularity, flexibility, and cost-effectiveness of the control system.

[0045] Currently, research on fault analysis and fault ride-through methods for multi-port power electronic converters with common high-frequency bus is relatively limited. Among related technologies, one paper, based on a four-port power electronic transformer with MMAB isolation, analyzes the instability mechanism of voltage dips at high-voltage AC ports from an energy perspective and proposes a low-voltage ride-through control scheme. This scheme achieves low-voltage ride-through by switching the power balance port and port control strategy during a fault. Another paper, based on a demonstration project of a common high-frequency bus power router, proposes a master-slave switching control for AC port modes based on duty cycle synchronization, achieving a smooth transition when the master and slave inverter control structures differ significantly. Furthermore, a major challenge of high-frequency coupled multi-port power electronic converters is that all modules are connected to a common high-frequency link or multi-winding transformer. Fault-locked modules can still maintain capacitor voltage through uncontrolled rectification. Based on this, a high-frequency oscillation model of the locked-out module under a common high-frequency bus structure is established. This model analyzes the system oscillation characteristics and module power transmission behavior after partial module lockout and proposes measures to install disconnect switches on the AC side of the modules to disconnect the locked-out H-bridge from the system and prevent power transmission, ensuring safe system operation. However, for multi-port DC-DC converters, the exit of submodules under fault conditions can significantly impact the continuous operation of the system, and transient coupling between ports can easily cause a fault to escalate from a single port to multiple ports. Furthermore, current research primarily focuses on fault analysis and isolation based on centralized control, such as the circuit breaker-based fault isolation technology used in the power electronic converters of the Zhangbei AC / DC hybrid distribution demonstration project. Regarding fault ride-through, overall research is limited, and the proposed methods are relatively simple, failing to meet the diverse fault protection and fault ride-through requirements of different ports.

[0046] Based on this, this application provides an open-circuit fault ride-through method, device, and electronic equipment for a common high-frequency bus multi-active bridge converter. The method includes: when an open-circuit fault is detected in a submodule of the common high-frequency bus multi-active bridge converter, the faulty port is disconnected to obtain an updated active bridge topology; a frequency integral compensation value is calculated based on circuit parameter information; a target compensation frequency is obtained by integral compensation calculation of the frequency integral compensation value; a preset reference frequency is added to the target compensation frequency to obtain the compensated fault ride-through frequency; the first control frequency of the non-faulty port is switched to the fault ride-through frequency, and after a preset compensation time, the updated active bridge topology enters a stable state; when the real-time second control frequency of the non-faulty port is detected to be consistent with the preset voltage source submodule control frequency, the closed-loop control is switched back to achieve fault ride-through. This can reduce interference between DC ports and current surges caused by adaptive adjustment.

[0047] The embodiments of this application will be further described below with reference to the accompanying drawings.

[0048] like Figure 1AAs shown, the multi-active bridge DC-DC converter topology includes: a first voltage source submodule 1, a second voltage source submodule 2, a first current source submodule 3, a second current source submodule 4, and a multi-winding high-frequency transformer. By... Figure 1A The multi-winding high-frequency transformer in the multi-active bridge DC-DC converter topology is split into multiple interconnected two-winding high-frequency transformers, which can be obtained as follows: Figure 1B The topology of a multi-active bridge converter with common low voltage and high frequency is shown.

[0049] Figure 1B The design and fabrication of the multi-active bridge converter with a common high-frequency bus (i.e., the common high-frequency bus multi-active bridge converter) shown is simplified, and it is easy to interconnect any number of high-frequency transformers. Specifically, the topology of the common high-frequency bus multi-active bridge converter includes: a high-frequency AC bus, voltage source modules and current source modules connected to the high-frequency AC bus; the voltage source modules further include: a first voltage source sub-module 1 and a second voltage source sub-module 2 connected to the same side of the high-frequency AC bus; the current source modules further include: a first current source sub-module 3 and a second current source sub-module 4 connected to the other side of the high-frequency AC bus; the common high-frequency bus multi-active bridge converter also includes: four two-winding high-frequency transformers; a two-winding high-frequency transformer is connected between the high-frequency AC bus and the bus input terminal of each sub-module.

[0050] It should be noted that in each submodule, the full-bridge converter achieves bidirectional interconnection between the DC and AC ports, enabling bidirectional energy conversion and high-frequency voltage switching. The high-frequency transformer interconnects the AC ports and the AC bus, achieving high-frequency AC voltage matching and high-voltage gain conversion. The DC capacitor provides necessary voltage support and ripple filtering for the DC bus. The common-high-frequency-bus multi-active-bridge converter is also a type of multi-port power electronic transformer. Its topology is well-suited for expansion to multiple modules and ports, and the blocking of a faulty module has minimal impact on the normal operation of other modules within the power electronic transformer, ensuring that faults between ports are independent. However, the energy collection link between the ports of the common-high-frequency-bus multi-active-bridge converter is a high-frequency chain, lacking energy storage capacitors as energy buffers, resulting in strong coupling between modules and ports. Therefore, in-depth research is needed on the integrated design and control of this multi-port power electronic transformer, as well as the coupling and impact under fault conditions.

[0051] Furthermore, combined Figure 1AThis section explains the distributed control principle of a multi-bridge DC-DC converter (MMAB). Specifically, in a traditional centralized control strategy, the global electrical variables of the MMAB converter are measured and transmitted to a central controller, which then determines the phase shift of each submodule. In contrast, the distributed control strategy employs a variable PWM switching frequency, allowing the phase angle of the MMAB converter's submodules to be adaptively adjusted based on local information (such as power and voltage).

[0052] Understandably, in combination Figure 1B To ensure system active power balance, in a multi-active bridge converter with a common high-frequency bus, the power of each sub-module must satisfy the following:

[0053] (1).

[0054] in, The first power of the first voltage source submodule 1, For the second power of the second voltage source submodule 2, The third power source of the first current source submodule 3 The sum of the fourth power of the second current source submodule 4 is zero.

[0055] Furthermore, combined Figure 2A and Figure 2B This section describes the control strategy for the voltage source submodule in a common high-frequency bus active power converter. The voltage source submodule includes: an input voltage source and a capacitor. The system consists of a full-bridge converter with four switching transistors and a two-winding transformer. The control strategy for the voltage source submodules is as follows: each voltage source submodule determines its power sharing ratio based on the maximum switching frequency deviation and power sharing, and adaptively adjusts its switching frequency according to power droop control. This means the module switching frequency of the voltage source submodules... It is a variable value, according to, for example Figure 2B The control block diagram shown indicates the module switching frequency. The formula for calculation is:

[0056] (2).

[0057] Where i is the number of the voltage source submodule, i.e., i=1 represents the first voltage source submodule 1, and i=2 represents the second voltage source submodule 2. For the DC-side power of the voltage source submodule, It is the nominal switching frequency. The time constant of the low-pass filter is used to reduce the measured value. High-frequency ripples. It is a proportional gain that is inversely proportional to the output power of each voltage source submodule. This yields the module switching frequency. Then, it is input into a variable PWM modulation module with a duty cycle of 50% to achieve dynamic adjustment of the phase angle of the high-frequency AC voltage. When in a stable state, the switching frequencies of each submodule will reach a consensus.

[0058] Furthermore, when all voltage source submodules are synchronized with each other, the active power of the voltage source submodules is... Inversely proportional, that is:

[0059] (3);

[0060] Therefore, according to equations (1) and (3), we can obtain:

[0061] (4);

[0062] Substituting equation (4) into equation (2), we can solve for the steady-state switching frequency of the module:

[0063] (5);

[0064] Equation (5) shows that the switching frequency of the voltage source submodule is related to both the sum of the power of the current source submodule and the voltage source submodule. It relates to the sum of the reciprocals. To find the maximum value of the molecule, we can consider the most extreme case, where all current source submodules simultaneously absorb or deliver power. Furthermore, Increasing this ratio will lead to a larger frequency variation. To prevent variations in the module switching frequency from affecting the design of the multi-active bridge converter, the proportional gain should be adjusted appropriately. At this point, the maximum value of the switching frequency change is shown in equation (6): (6).

[0065] The phase shift angle between voltage source submodule i and voltage source submodule j is shown in equation (7):

[0066] (7).

[0067] The switching frequency of voltage source submodule i is disturbed and becomes lower than the switching frequency of other submodules. Over time, The phase angle will gradually lag behind, and more active power will flow to submodule i, which will lead to... Decreasing the power consumption of one module increases the power consumption of the other. This is because there is a negative correlation between submodule power and switching frequency. The frequency of submodule i will increase, while the frequency of other submodules will decrease, and the phase angle of submodule i will automatically catch up with the other submodules. This process continues until the frequencies of all submodules are synchronized.

[0068] Furthermore, combined Figure 3A and Figure 3BExplain the control strategy of the current source submodule in the common high-frequency bus multi-active converter.

[0069] like Figure 3A As shown, the external circuit is modeled as a current source. . The value can be positive (equivalent to generating power) or negative (equivalent to absorbing power). Unlike the voltage source submodule, the DC terminal voltage of the current source submodule is affected by the external circuit. Therefore, the current source submodule must measure and control the DC voltage at the port. The switching frequency of the current source submodule is calculated as shown in equation (8):

[0070] (8).

[0071] in, The proportional gain of the PI controller. This is the integral gain of the PI controller. Assume the DC terminal voltage of submodule i is... Initially smaller than At this time, the submodule switching frequency The voltage will continue to decrease, causing this submodule's voltage phase to lag behind other submodules, resulting in power loss. Reduce external power input Greater than The difference between the two will charge the DC-side capacitor, and this process will continue until... equal .

[0072] Those skilled in the art will understand that the system structure shown in the figures does not constitute a limitation on the embodiments of this application, and may include more or fewer components than shown, or combine certain components, or have different component arrangements.

[0073] The system embodiments described above are merely illustrative. The units described as separate components may or may not be physically separate; that is, they may be located in one place or distributed across multiple network units. Some or all of the modules can be selected to achieve the purpose of this embodiment according to actual needs.

[0074] It will be understood by those skilled in the art that the system architecture and application scenarios described in the embodiments of this application are for the purpose of more clearly illustrating the technical solutions of the embodiments of this application, and do not constitute a limitation on the technical solutions provided in the embodiments of this application. It is known by those skilled in the art that with the evolution of system architecture and the emergence of new application scenarios, the technical solutions provided in the embodiments of this application are also applicable to similar technical problems.

[0075] Based on the structure of the above-mentioned common high-frequency bus multi-active bridge converter, various embodiments of the open-circuit fault ride-through method of this application are proposed below.

[0076] Firstly, such as Figure 4 As shown, this open-circuit fault ride-through method can be applied to, for example... Figure 1B The common high-frequency bus active bridge converter shown includes: a high-frequency AC bus, a voltage source module and a current source module connected to the high-frequency AC bus; the voltage source module further includes: a first voltage source sub-module 1 and a second voltage source sub-module 2 connected to the same side of the high-frequency AC bus; the current source module further includes: a first current source sub-module 3 and a second current source module 4 connected to the other side of the high-frequency AC bus; the open-circuit fault ride-through method may include, but is not limited to, steps S110 to S170.

[0077] Step S110: When a submodule open-circuit fault is detected in the common high-frequency bus multi-active bridge converter, determine the fault location of the submodule open-circuit fault.

[0078] Step S120: Perform submodule fault disconnection processing according to the fault location, disconnect the faulty port, and obtain the updated active bridge topology.

[0079] Step S130: Based on the fault location and the acquired circuit parameter information, calculate the compensation value to obtain the frequency integral compensation value.

[0080] Step S140: Perform integral compensation calculation on the frequency integral compensation value according to the fault location and preset offset coefficient to obtain the target compensation frequency.

[0081] Step S150: Add the preset reference frequency to the target compensation frequency to obtain the compensated fault ride-through frequency.

[0082] Step S160: Switch the first control frequency of the non-faulty port in the current source module to the fault ride-through frequency, and after a preset compensation time, so that the updated active bridge topology enters a stable state.

[0083] Step S170: In the updated active bridge topology, when the real-time second control frequency of the non-faulty port is detected to be consistent with the preset voltage source submodule control frequency, switch back to closed-loop control to achieve fault ride-through.

[0084] According to some embodiments of this application, the method further includes: in the updated active bridge topology, when it is detected that the real-time second control frequency of the non-faulty current source module is inconsistent with the preset voltage source sub-module control frequency, no closed-loop control switching is performed; and the real-time second control frequency of the non-faulty port is continued to be detected.

[0085] It should be noted that the preset reference frequency in step S150 is the control frequency of the port of the first voltage source submodule 1.

[0086] Through steps S110 to S170, during the operation of the common high-frequency bus multi-active bridge converter, when a submodule open-circuit fault is detected in the common high-frequency bus multi-active bridge converter, the fault location of the submodule open-circuit fault is determined; based on the fault location, submodule fault disconnection processing is performed, the fault port is cut off, and an updated active bridge topology is obtained; based on the fault location and the acquired circuit parameter information, a compensation value is calculated to obtain a frequency integral compensation value; based on the fault location and a preset offset coefficient, the frequency integral compensation value is integrally compensated to obtain the target compensation frequency; the preset reference frequency and the target compensation frequency are then compared. The frequencies are summed to obtain the compensated fault ride-through frequency. The first control frequency of the non-faulty port in the current source module is switched to the fault ride-through frequency. After a preset compensation time, the updated active bridge topology enters a stable state. In the updated active bridge topology, when the real-time second control frequency of the non-faulty port is detected to be consistent with the preset control frequency of the voltage source submodule, the closed-loop control is switched back to achieve fault ride-through, thereby reducing current surges. Therefore, the embodiments of this application can reduce the impact on non-faulty ports when a submodule is disconnected due to an open-circuit fault, and reduce interference between DC ports and current surges caused by adaptive adjustment.

[0087] According to some embodiments of this application, the voltage source module includes: a first busbar access terminal connected to a high-frequency AC busbar, and a power supply terminal for connecting to a power source; the first busbar access terminals of both the first voltage source submodule 1 and the second voltage source submodule 2 are connected to the high-frequency AC busbar. Further explanation of step S120: The submodule fault disconnection process is performed according to the fault location, including but not limited to steps S121 to S122.

[0088] Step S121: When the fault location is the power supply terminal of the first voltage source submodule, control the path between the first voltage source submodule and the high-frequency AC bus to be closed, and disconnect the first voltage source submodule from the common high-frequency bus multi-active bridge converter.

[0089] Step S122: When the fault location is the power supply terminal of the second voltage source submodule, control the path between the second voltage source submodule and the high-frequency AC bus to close, and disconnect the second voltage source submodule from the common high-frequency bus multi-active bridge converter.

[0090] Understandably, when the fault location is at the first bus connection terminal of the first voltage source submodule 1 or the second voltage source submodule 2, the first voltage source submodule 1 or the second voltage source submodule 2 has already been directly disconnected from the common high-frequency bus active bridge converter. Therefore, when the fault location is at the first bus connection terminal of the first voltage source submodule 1 or the second voltage source submodule 2, no additional operation is required to disconnect the fault. However, when the fault location is at the power supply terminal of the first voltage source submodule 1 or the second voltage source submodule 2, the faulty first voltage source submodule 1 or the second voltage source submodule 2 still exists in parallel with the high-frequency AC bus, generating a current surge to the non-faulty submodules in the common high-frequency bus active bridge converter. Therefore, in this case, additional operation is required to disconnect the faulty submodule.

[0091] Through steps S121 to S122, in the event of an open-circuit fault at the power supply terminal of the first voltage source submodule 1 or the second voltage source submodule 2, the fault is promptly cleared to protect other non-faulty submodules in the common high-frequency bus active bridge converter.

[0092] According to some embodiments of this application, the current source module includes: a second busbar access terminal connected to a high-frequency AC busbar and a load access terminal for connecting a load; the second busbar access terminals of the first current source submodule 3 and the second current source submodule 4 are both connected to the high-frequency AC busbar. Further explanation of step S120: Submodule fault disconnection processing is performed according to the fault location, including but not limited to step S120.

[0093] Step S123: When the fault location is the load access terminal of the first current source submodule, control the path between the first current source submodule and the high-frequency AC bus to be closed, and disconnect the first current source submodule from the common high-frequency bus multi-active bridge converter.

[0094] Step S124: When the fault location is the load connection terminal of the second current source submodule, control the path between the second current source submodule and the high-frequency AC bus to close, and disconnect the second current source submodule from the common high-frequency bus multi-active bridge converter.

[0095] Understandably, when the fault location is at the second bus connection terminal of the first current source submodule 3 or the second current source submodule 4, the first current source submodule 3 or the second current source submodule 4 has already been directly disconnected from the common high-frequency bus active bridge converter. Therefore, when the fault location is at the second bus connection terminal of the first current source submodule 3 or the second current source submodule 4, no additional operation is required to disconnect the fault. However, when the fault location is at the load connection terminal of the first current source submodule 3 or the second current source submodule 4, the faulty first current source submodule 3 or the second current source submodule 4 still exists in parallel with the high-frequency AC bus, generating current surges to the non-faulty submodules in the common high-frequency bus active bridge converter. Therefore, in this case, additional operation is required to disconnect the faulty submodule.

[0096] In steps S123 to S124, in the case of an open-circuit fault at the load access terminal of the first current source submodule 3 or the second current source submodule 4, the fault is promptly cleared to protect other non-faulty submodules in the common high-frequency bus active bridge converter.

[0097] Furthermore, a principle-based fault characteristic analysis is performed on the common high-frequency bus multi-active bridge converter of this application embodiment to further understand steps S121 to S124.

[0098] Considering the operating characteristics of the common high-frequency bus multi-active bridge converter and the fault ride-through strategy of this application, the following assumptions are made in this application:

[0099] First, port 1 is defined as the first voltage source submodule 1, which itself will not malfunction, and its frequency data, as the main power supply frequency signal, can be obtained from various submodules through communication. It can be understood that port 2 is defined as the second voltage source submodule 2, port 3 as the first current source submodule 3, and port 4 as the second current source submodule 4.

[0100] Secondly, the multi-active bridge converter with common high-frequency bus is stable during normal operation, and information such as operating voltage and power can be obtained through communication, and this data can be analyzed to identify open circuit faults.

[0101] Third, after an open-circuit fault occurs in one port, the remaining non-faulty ports can recover to their previous stable operating state after a transient impact.

[0102] like Figure 5 As shown, this application classifies possible open-circuit faults into four types: first, open circuit at the high-frequency AC bus input terminal of the current source submodule; second, open circuit at the load terminal of the current source submodule; third, open circuit at the high-frequency AC bus input terminal of the voltage source submodule; and fourth, open circuit at the power supply terminal of the voltage source submodule.

[0103] It should be noted that the fault ride-through method is the same when the first current source submodule 3 experiences an open-circuit fault as it is when the second current source submodule 4 experiences an open-circuit fault, and the fault ride-through method is the same when the first voltage source submodule 1 experiences an open-circuit fault as it is when the second voltage source submodule 2 experiences an open-circuit fault. This application will specifically discuss the cases where the first current source submodule 3 and the second voltage source submodule 2 experience open-circuit faults. The fault ride-through methods for the other two fault scenarios have the same technical principles and the same technical effects, and will not be described further to avoid repetition.

[0104] Specifically, such as Figure 5 As shown, an open circuit fault occurs at the second bus input terminal of the first current source submodule 3, and the location of this fault is recorded as case1; an open circuit fault occurs at the load input terminal of the first current source submodule 3, and the location of this fault is recorded as case2; an open circuit fault occurs at the first bus input terminal of the second voltage source submodule 2, and the location of this fault is recorded as case3; an open circuit fault occurs at the power supply terminal of the second voltage source submodule 2, and the location of this fault is recorded as case4.

[0105] It should be noted that in both cases 1 and 2, the power of the first current source submodule 3 abruptly drops to 0, and the non-faulty submodules are subjected to transient impacts, particularly affecting the voltage of the non-faulty second current source submodule 4. The difference lies in that in case 1, the entire first current source submodule 3 is essentially disconnected from the system, while in case 2, the faulty first current source submodule 3 remains connected in parallel with the high-frequency AC bus. It is understandable that even with no load absorbing power under full-bridge blocking after the fault in case 2, the resonant impedance network composed of the leakage inductance of the high-frequency transformer and the stray capacitances of various components still exhibits high-frequency oscillations of hundreds of kHz. This would cause power transmission to continue at the faulty port in case 2, affecting the non-faulty second current source submodule 4. Therefore, to protect the non-faulty second current source submodule 4, after detecting an open circuit in the current source submodule load, the first current submodule is temporarily disconnected from the high-frequency transformer side, closing its path. It is then reconnected to the system after the fault is cleared. Therefore, case 2 can be considered equivalent to case 1. Thus, it can be understood that for the entire common high-frequency bus multi-active bridge converter, it is equivalent to cutting off a current source that absorbs power, reducing the power of the P3 part of the system, and the remaining first voltage source submodule 1, second voltage source submodule 2, and second current source submodule 4 form a three-active bridge topology (i.e. the updated active bridge topology obtained in step S120).

[0106] Similarly, a similar fault clearing method can be used to protect the common high-frequency bus multi-active bridge converter in case 4. Therefore, if the faulty second voltage source submodule 2 is cleared in time, case 4 is equivalent to case 3. It can be understood that after the second voltage source submodule 2 is cleared, for the entire common high-frequency bus multi-active bridge converter, it is equivalent to clearing a voltage source of output power. The system reduces the power of P2. The remaining first voltage source submodule 1, first current source submodule 3, and second current source submodule 4 form a three-active bridge topology (i.e., the updated active bridge topology obtained in step S120).

[0107] Furthermore, the open-circuit fault characteristics of the current source submodule in the embodiments of this application will be further explained.

[0108] Taking the open-circuit fault of the first current source submodule 3 as case 1 as an example, for the faulty port (i.e., the second bus input terminal of the first current source submodule 3), since the inductor circuit of the first current source submodule 3 is cut off at the instant the open-circuit fault occurs, the inductor current drops to 0 instantaneously. The port output capacitor of the first current source submodule 3 releases the stored charge, causing the port voltage to drop to 0 after approximately τ = 5RCs. Figure 6 As shown. This process mainly manifests as the first current source submodule 3 losing its power transmission path and shutting down, without causing damage to itself.

[0109] Understandably, after the first current source submodule 3 experiences an open-circuit fault, the power at its port drops to zero instantaneously. Therefore, for the non-faulty ports, the total power output by the voltage source module is greater than the power absorbed by the non-faulty second current source submodule 4. Consequently, the voltage of the non-faulty second current source submodule 4 will be as follows: Figure 7 The diagram shows a transient process that exceeds the original operating value.

[0110] When the secondary side of the transformer in the first current source submodule 3 is open-circuited, for the entire DC / DC isolation converter (i.e., the common high-frequency bus multi-active bridge converter), it is equivalent to cutting off a current source that absorbs power. The power of P3 in the common high-frequency bus multi-active bridge converter is reduced. The remaining submodules form a three-active bridge topology. Therefore, the output frequency of each controller and the phase shift angle between each port need to be readjusted. After a brief transient, the non-faulty submodules (including: the first voltage source submodule 1, the second voltage source submodule 2, and the second current source submodule 4) re-enter a new steady state.

[0111] like Figure 8As shown, the port power of the first current source submodule 3 changes from its original rated power to 0 after an open-circuit fault occurs. For the non-faulty first voltage source submodule 1, second voltage source submodule 2, and second current source submodule 4, after a certain transient period, the port power of the first voltage source submodule 1 changes from its original rated power to 0. Fall to The port power of the second voltage source submodule 2 is provided by Fall to After a fault, the steady-state power values ​​of the first voltage source submodule 1 and the second voltage source submodule 2 can be obtained by formula (4). Formula (4) is:

[0112] .

[0113] Furthermore, the port power of the second current source submodule 4 remains stable after the disturbance. Non-faulty ports can continue to operate normally after the fault transient ends.

[0114] Furthermore, the open-circuit fault characteristics of the voltage source submodule in the embodiments of this application will be further explained.

[0115] Taking case 3 (open-circuit fault in second voltage source submodule 2) as an example, if the faulty port (i.e., the first bus access terminal of second voltage source submodule 2) is promptly locked after an open-circuit fault, second voltage source submodule 2 will lose its power transmission path and shut down. This process is similar to the aforementioned process of an open-circuit fault in first current source submodule 3. It is understandable that after the open-circuit fault in second voltage source submodule 2 is cleared, the multi-active bridge converter on the common high-frequency bus loses one voltage source submodule. For the non-faulty submodules, at the moment of the fault, the output power of first voltage source submodule 1 is less than the sum of the absorbed power of first current source submodule 3 and second current source submodule 4. Therefore, first current source submodule 3 and second current source submodule 4 will experience a transient process lower than their original operating values. After the transient, they will stabilize back at their original operating values. Figure 9 As shown.

[0116] like Figure 10 As shown in the power waveform, when the second voltage source submodule 2 experiences an open-circuit fault, the system changes from the original shared power output of the first voltage source submodule 1 and the second voltage source submodule 2 to power output solely by the first voltage source submodule 1. To restore normal operation after the fault, the power output of the first voltage source submodule 1 will decrease from its original value. Rise to During the transient process, the power of the first current source submodule 3 and the second current source submodule 4 returns to their original operating values ​​after the transient ends.

[0117] According to some embodiments of this application, the circuit parameter information includes first parameter information before the fault and second parameter information after the fault; further, step S130 is described as follows: based on the fault location, the frequency integral compensation value is calculated and processed based on the acquired circuit parameter information, including but not limited to steps S131 to S135.

[0118] Step S131: If the open circuit fault is determined to occur in the first current source submodule based on the fault location, then the first current source submodule is disconnected.

[0119] Step S132: Perform phase shift angle calculation based on the first parameter information before the fault and the preset inter-port transmission power expression to obtain the first phase shift angle before the fault.

[0120] Step S133: Perform phase shift angle calculation based on the second parameter information after the fault and the preset inter-port transmission power expression to obtain the second phase shift angle after the fault.

[0121] Step S134: Subtract the first phase shift angle from the second phase shift angle to obtain the compensated phase shift angle.

[0122] Step S135: Divide the compensation phase shift angle by the preset compensation time to obtain the frequency integral compensation value.

[0123] According to some embodiments of this application, the expression for inter-port transmission power is as follows:

[0124] ; ;

[0125] in, It is the voltage referred from port i to the first voltage source submodule 1. It is the voltage referred from port j to the first voltage source submodule 1. For equivalent inductance, It is the phase shift angle; It is the output power of voltage source submodule i;

[0126] Equivalent Inductance The expression is: .

[0127] Through steps S131 to S135, the frequency integral compensation value is calculated, laying the data foundation for calculating the target compensation frequency and the fault ride-through frequency.

[0128] According to some embodiments of this application, step S140 is further described. Step S140: Perform integral compensation calculation on the frequency integral compensation value according to the fault location and the preset offset coefficient to obtain the target compensation frequency, including: when it is determined that the open circuit fault occurs in the first current source submodule 3 or the second current source submodule 4 according to the fault location, determine the first offset coefficient; multiply the first offset coefficient with the frequency integral compensation value to obtain the target compensation frequency.

[0129] Understandably, when an open-circuit fault occurs in the first current source submodule 3 or the second current source submodule 4, the new steady-state frequency will be higher than the steady-state frequency before the fault after reaching a new steady state. Therefore, it is necessary to set the fault ride-through voltage higher than a given value, and by setting a first offset coefficient, make the control frequency of the non-faulty port larger, thereby achieving a smooth switchback to closed-loop control after the fault ride-through ends. Specifically, the first offset coefficient is 1.05.

[0130] According to some embodiments of this application, step S140 is further described. Step S140: Perform integral compensation calculation on the frequency integral compensation value according to the fault location and the preset offset coefficient to obtain the target compensation frequency, including: when it is determined that the open circuit fault occurs in the first voltage source submodule 1 or the second voltage source submodule 2 according to the fault location, determine the second offset coefficient; multiply the second offset coefficient with the frequency integral compensation value to obtain the target compensation frequency; wherein, the second offset coefficient is less than the first offset coefficient.

[0131] Understandably, when an open-circuit fault occurs in either the first voltage source submodule 1 or the second voltage source submodule 2, the new steady-state frequency will be lower than the steady-state frequency before the fault. Therefore, it is necessary to set the voltage of the non-faulty first current source submodule 3 and the second current source submodule 4 to be lower than a given value during the fault ride-through process, so that the control frequency of the non-faulty ports is lower, thereby achieving a smooth switchback to closed-loop control after the fault ride-through ends. Specifically, the second offset coefficient is 0.95.

[0132] Furthermore, the fault ride-through mechanism involved in the embodiments of this application is as follows: As analyzed above, during the fault persistence phase after capacitor discharge, the current flowing through the faulty port device is usually within the rated current range; however, for non-faulty ports, adjustments should be made promptly after a fault occurs to reduce power transient impacts and maintain stable output. The transient impact of non-faulty ports is mainly caused by the adjustment of the phase shift angle of the non-faulty submodule after the open circuit occurs, and the phase shift angle of each submodule is determined by the frequency in the distributed control strategy. Therefore, by taking corresponding measures to compensate the phase shift angle of the current source submodule after a fault occurs, the adaptive adjustment process of its phase shift angle can be artificially controlled to suppress voltage transient impacts.

[0133] Furthermore, the compensation value calculation process provided in the embodiments of this application will be further explained.

[0134] Taking Case 1 as an example, the time immediately before the open-circuit fault occurs is defined as... The time to reach a new steady state after the fault occurs is For the first voltage source submodule 1 and the second voltage source submodule 2, according to formula (5), the change in the controller frequency output of the voltage source submodule before and after the fault is:

[0135] (9).

[0136] For the first voltage source submodule 1, its steady-state frequency after the failure of case 1 is:

[0137] (10).

[0138] in, It is the steady-state frequency before the cas1 failure; It is the change in the controller frequency output of the first voltage source submodule 1; The nominal switching frequency; It is the DC-side power of the second current source submodule 4; It is a proportional gain that is inversely proportional to the power output of each voltage source submodule; It is the DC-side power of the first current source submodule 3.

[0139] When case 1 experiences an open-circuit fault, and the second current source submodule 4 returns to its pre-fault operating value, comparing equations (5) and (10) reveals that the system frequency after the fault will differ from the pre-fault frequency. Since the distributed control system requires all submodules to maintain consistent frequencies under normal operating conditions when it reaches a stable state, this means the controller of the non-faulty second current source submodule 4 will undergo a transient adjustment process, changing from its original control frequency to a new control frequency. According to the definition of distributed control, the control frequency of the first voltage source submodule 1 during this transient process... Control frequency of the second current source submodule 4 Integrating the difference in the changes yields the change in phase angle of the non-faulty submodule during the transient process. The phase angle of the steady-state submodule after the fault is:

[0140] (11).

[0141] in, The control frequency for the first voltage source submodule 1, The control frequency for the second current source submodule 4. The phase shift angle before the failure of the second current source submodule 4.

[0142] During this transient process, the voltage of the second current submodule 4 will be disturbed due to the regulation of the controller, and then it will return to a steady state.

[0143] From the perspective of power change, the expression for the power transmitted between port i and port j is:

[0144] (12);

[0145] (13);

[0146] in, It is the DC side voltage of submodule i's port. It is the DC-side voltage of port j referred to submodule i. The equivalent inductance between submodule i and submodule j It is the phase shift angle between submodule i and submodule j; It is the output power of submodule i, that is The calculation method is shown in Equation (13), which is the sum of the transmission power of submodule i and the other n-1 submodules, where n is the total number of submodules; The control frequency for submodule i;

[0147] Specifically, the equivalent inductance calculation expression in formula (12) is as follows:

[0148] (14).

[0149] in, Let n be the equivalent inductance between submodule i and submodule j, and n be the total number of submodules. For the inductance of submodule i, For the inductance of submodule j, If we calculate the equivalent inductance from submodule n to submodule i, then it can be understood that... These are the equivalent inductances of submodules 1 to n referred to as submodule i.

[0150] From formulas (12) and (14), it can be seen that after an open circuit fault occurs in case 1, the power of each port will also change due to the loss of the inductance of the first current source submodule 3 that is faulty.

[0151] Since the steady-state power of the first current source submodule 3 remains the same after the fault as before the fault, the system frequency and voltage source submodule power are both determined by the current source module power and the power sharing ratio. Therefore, by solving equations (12) to (14), the phase shift angle of the port of the second current source submodule 4 before and after the fault can be calculated. and ,in It is both the phase shift angle of port 4 of the second current source submodule 4 after adjustment, and the phase shift angle of port 4 finally obtained by the adaptive adjustment of the system under closed-loop control.

[0152] In practical systems, converters often require a certain amount of time to reach steady state after a fault occurs. When the voltage at the faulty port drops to the non-faulty port, a transient impact occurs. Due to the slow response of the magnetic components, phase-shift compensation can be applied to port 4 of the second current source submodule 4 after the first current source submodule 3 is open-circuited, achieving a smooth transition of port power. The compensation value is calculated as follows:

[0153] (15).

[0154] In distributed control, the phase shift angle between submodules is adaptively obtained by the control frequency of each submodule, as shown in equation (11). Therefore, the phase shift angle cannot be directly compensated in distributed control, but the same purpose can be achieved by integrating the frequency. From the relationship between the phase shift angle and the frequency, the compensation expression can be obtained as follows:

[0155] (16).

[0156] Since both current source submodules in the distributed control adopt PI constant voltage control and both voltage source submodules adopt power droop control, there will inevitably be a difference in frequency output between the two controls during the transient process of port open circuit fault, which will affect the integral compensation effect. However, since all controllers have the same frequency output before the fault, according to the assumed conditions, the control frequency of the first voltage source submodule 1 can be selected as the reference frequency of the transient process, and the compensation frequency is compensated in this reference frequency, which is then used as the control frequency input to the non-fault current value submodule for control. Taking the first current source submodule 3 open circuit as an example, and the port 4 of the non-fault second current source submodule 4 is compensated with the port 1 of the first voltage source submodule 1 as the frequency reference, equation (16) is converted to:

[0157] (17).

[0158] Therefore, when the compensation angle is known, the compensation frequency can be calculated simply by setting the compensation time Δt. Size.

[0159] Furthermore, the integral compensation calculation process provided in the embodiments of this application will be further explained.

[0160] For the non-faulty second current source submodule 4, after frequency integral compensation, its phase shift angle only needs to pass through the compensation time Δt to enter the post-fault steady state, and will not cause large transient disturbances to the port voltage and power. However, during the fault ride-through process, the controller of the non-faulty second current source submodule 4 does not form a closed loop with the system. According to the output expression of the distributed control of the current source submodule in formula (8), if the port voltage is precisely controlled at the reference value during the fault ride-through process, the controller frequency will remain unchanged. However, as can be seen from formula (5), without changing other parameters, the output frequency of the voltage source submodule controller in the post-fault steady state has changed, which will cause the controller frequencies of the voltage source submodule and the current source submodule to be inconsistent. If the disconnected first current source submodule 3 is switched back to closed-loop control after the fault ride-through is completed, a new frequency adaptive transient will inevitably be formed, which will cause transient shocks in the system. To suppress transient impacts during closed-loop switching, the voltage of the non-faulty second current source submodule 4 can be set to deviate slightly from the reference value during the fault ride-through process, based on the steady-state frequency value after the fault. This causes the control frequency of the controller of the second current source submodule 4 to deviate directionally due to steady-state error, ultimately achieving smooth switching when the stable frequency value is reached. For example, when the steady-state frequency value... If the voltage is lower than before the fault, the ride-through voltage is set to 0.95 times the reference value. From formula (8), the control frequency of the controller can be determined. It will continue to decrease until it is detected. = Switch back to closed-loop control in time to achieve fault ride-through.

[0161] The frequency integral compensation process is as follows: Figure 11 As shown. Before the fault, the control frequency of the second current source submodule 4 was its original closed-loop controller output frequency. After identifying an open-circuit fault in the first current source submodule 3, it will switch to the port frequency of the compensated first voltage source submodule 1. At this time, the controller of the second current source submodule 4 is operating in open-loop mode, and the port voltage value is related to the phase shift angle of the compensation input. The control frequency of the second current source submodule 4 will shift (e.g., Figure 11 (Black curve, shifting downwards). When the controller frequency of the second current source submodule 4 is detected to have shifted to the system operating frequency (i.e., the control frequency of the voltage source submodule), the system switches back to closed-loop control, thus preventing new transient shocks due to frequency mismatch during controller switching.

[0162] As an example, the specific application and effects of the embodiments of this application are illustrated with simulation results.

[0163] The performance of the fault ride-through strategy of this application embodiment was verified by simulation. A simulation model of a multi-active bridge DC-DC converter with a common high-frequency bus was built in MATLAB / Simulink, and simulation parameters were preset. For simplified analysis, the power allocation ratio of voltage source submodules 1 and 2 was set to 1:1, that is, the power coefficient of the first voltage source submodule 1... The power coefficient of the second voltage source submodule 2 is set to 0.04. The value is also set below 0.04. By simulating two typical open-circuit fault types, the port performance of non-faulty ports under fault conditions and fault crossing conditions is compared.

[0164] A simulation analysis was performed on the case of an open-circuit fault in the first current source submodule 3.

[0165] In the simulation system with configured parameters, the total simulation time was set to 0.6 seconds. At t=0.3 seconds, the first current source submodule 3 experienced an open-circuit fault. Before the fault, the system was running at... , , Under operating conditions, the steady-state frequency of the system can be obtained from the control principle of the voltage source submodule. The phase shift angle between each port in steady state is... , , After the first current source submodule 3 fails, the system operates in a steady state where... , Under the operating condition, the frequency changes as follows: The phase shift angle between each port under steady state can be calculated as follows: , The angle of adaptive adjustment of the transient process can be calculated. Since the steady-state frequency after a fault will be higher than before the fault, it is necessary to set the fault ride-through voltage of the second current source submodule 4 to be higher than the given value, causing its control frequency to deviate upwards. This achieves a smooth switchback to closed-loop control after the fault ride-through ends. This can be achieved by setting a frequency integral compensation value of 1.05 times. During fault ride-through, the port voltage of the second current source submodule 4 will be maintained at an operating value slightly above 48V.

[0166] Under fault-free ride-through conditions, an open circuit in the first current source submodule 3 will cause an overshoot of approximately 35% in the port voltage of the second current source submodule 4, and the peak inductor current of the second current source submodule 4 will surge to about five times its original value at the moment of the fault. After using the fault ride-through strategy, the port voltage of the second current source submodule 4 remains at the voltage deviation value under the set phase shift angle during the ride-through. After about 0.06s, the control frequency of the second current source submodule 4 deviates to be equal to the actual operating frequency of the system (i.e., the preset voltage source submodule control frequency), and the second current source submodule 4 is switched back to closed-loop control. The fault ride-through process ends, and the system resumes operation.

[0167] contrast Figure 12 and Figure 13 During fault ride-through, the transient power surge of the second current source submodule 4 was effectively suppressed, and its operating value remained at approximately 1.1 times the rated operating value. Simultaneously, the transient processes of the first voltage source submodule 1 and the second voltage source submodule 2 were also shortened to some extent under the fault ride-through strategy. Simulation results show that when the first current source submodule 3 experiences an open-circuit fault, this fault ride-through measure can effectively reduce the impact of transient surges during the fault process and prevent damage to non-faulty ports.

[0168] A simulation analysis was performed on the case of an open-circuit fault in the second voltage source submodule 2.

[0169] In the simulation system with configured parameters, the total simulation time was set to 0.6s. At t=0.3s, the second voltage source submodule 2 experienced an open-circuit fault. Before the fault, the steady-state system operation was consistent with the system operation under the condition of an open-circuit fault in the first current source submodule 3. After the open-circuit fault in the second voltage source submodule 2, the system operated in... , , Under the operating condition, the frequency changes as follows: Under steady state, the phase shift angle between each port is , The angle of adaptive adjustment of the transient process can be calculated. , Since the steady-state frequency will be lower than before the fault, it is necessary to set the voltage of the first current source submodule 3 and the second current source submodule 4 to be lower than a given value during the fault ride-through process, causing the control frequency of the second current source submodule 4 to deviate downwards. The compensation value can be set to... , During fault ride-through, the port voltages of the first current source submodule 3 and the second current source submodule 4 will remain at operating values ​​slightly below 220V / 48V.

[0170] In a fault-free ride-through scenario, an open circuit in the second voltage source submodule 2 will cause a transient impact on the two non-faulty current source ports. The magnitude of this impact is inversely proportional to the port power, thus having the greatest impact on the low-power, low-voltage second current source submodule 4. When using the fault ride-through strategy, the port voltages of the first current source submodule 3 and the second current source submodule 4 remain at the voltage deviation value within the set phase shift angle during the ride-through. After approximately 0.08 seconds, the control frequency of the first current source submodule 3 reaches the actual system operating frequency first, and then switches back to closed-loop control. During this process, due to the slight adjustment of the voltage of the first current source submodule 3 from the deviation value to the set value after switching to closed-loop control, a small transient impact will occur on the second current source submodule 4, which is still undergoing fault ride-through. After another 0.05 seconds, the control frequency of the second current source submodule 4 becomes the same as the actual system operating frequency, and then switches back to closed-loop control. The fault ride-through process ends, and the system resumes operation.

[0171] contrast Figure 14 and Figure 15 When the first current source module 3 and the second current source module 4 are not operating during the transient process, the power consumption drops to a maximum of 85% and 60%, respectively, while during fault ride-through, the power consumption remains at 97% and 95%, respectively, and the power transient impact is significantly suppressed.

[0172] When the second voltage source submodule 2 experiences an open-circuit fault, the fault ride-through strategy provided in this application embodiment can effectively reduce the transient impact of the voltage source submodule fault process on the non-faulty current source submodule and prevent damage to the non-faulty ports.

[0173] Based on the above simulation, it can be understood that for the four open-circuit fault scenarios mentioned in the embodiments of this application, namely open-circuit faults occurring at case1, case2, case3 and case4, the fault ride-through strategy with integral compensation proposed in the embodiments of this application can effectively suppress transient overvoltage and overcurrent of non-faulty sub-modules, ensuring the safe and stable operation of the system during transient processes.

[0174] Secondly, embodiments of this application provide an open-circuit fault ride-through device for a common-frequency bus multi-active bridge converter; the open-circuit fault ride-through device includes: an open-circuit fault detection module, used to determine the fault location of a sub-module open-circuit fault when an open-circuit fault is detected in the common-frequency bus multi-active bridge converter; a first calculation and processing module, used to perform sub-module fault disconnection processing according to the fault location, cutting off the fault port to obtain an updated active bridge topology; a second calculation and processing module, used to perform compensation value calculation processing based on the fault location and the acquired circuit parameter information to obtain a frequency integral compensation value; a third calculation and processing module, used to calculate the frequency integral compensation value based on the fault location, A preset offset coefficient is used to perform integral compensation calculation on the frequency integral compensation value to obtain the target compensation frequency. A fault ride-through frequency calculation module adds the preset reference frequency to the target compensation frequency to obtain the compensated fault ride-through frequency. A frequency switching module switches the first control frequency of the non-faulty port in the current source module to the fault ride-through frequency, allowing the updated active bridge topology to enter a stable state after a preset compensation time. A closed-loop control switching module switches back to closed-loop control in the updated active bridge topology when the real-time second control frequency of the non-faulty port is detected to be consistent with the preset voltage source submodule control frequency, thus achieving fault ride-through. The open-circuit fault ride-through device of this application can reduce the impact on non-faulty ports when a submodule is disconnected due to an open-circuit fault, and reduce interference between DC ports and current surges caused by adaptive adjustment.

[0175] It should be noted that since the open-circuit fault traversal device of this embodiment can realize the open-circuit fault traversal method as in any of the previous embodiments, the open-circuit fault traversal device of this embodiment has the same technical principle and the same technical effect as the open-circuit fault traversal method in any of the previous embodiments. In order to avoid repetition and redundancy, it will not be described again here.

[0176] Thirdly, the present invention also provides an electronic device 800, including: a processor 801, which can be implemented using a general-purpose central processing unit, microprocessor, application-specific integrated circuit, or one or more integrated circuits, for executing relevant programs to implement the technical solutions provided in the embodiments of this application; and a memory 802, which can be implemented using a read-only memory, static storage device, dynamic storage device, or random access memory. The memory 802 can store the operating system and other applications. When the technical solutions provided in the embodiments of this specification are implemented by software or firmware, the relevant program code is stored in the memory 802 and is called and executed by the processor 801. The input / output interface 803 is used to realize information input and output. The communication interface 804 is used to realize communication interaction between this device and other devices. Communication can be realized by wired means (e.g., USB, network cable, etc.) or by wireless means (e.g., mobile network, WIFI, Bluetooth, etc.). The bus 805 transmits information between various components of the device (e.g., processor 801, memory 802, input / output interface 803 and communication interface 804). The processor 801, memory 802, input / output interface 803 and communication interface 804 realize communication connection between each other within the device through the bus 805.

[0177] The above provides a detailed description of the preferred embodiments of this application. However, this application is not limited to the above-described embodiments. Those skilled in the art can make various equivalent modifications or substitutions without departing from the spirit of this application. All such equivalent modifications or substitutions are included within the scope defined by this application.

Claims

1. A method for open-circuit fault ride-through in a common high-frequency bus multi-active bridge converter, characterized in that, The common high-frequency bus multi-active bridge converter includes: a high-frequency AC bus, a voltage source module and a current source module connected to the high-frequency AC bus; the voltage source module further includes: a first voltage source sub-module and a second voltage source sub-module connected to the same side of the high-frequency AC bus; the current source module further includes: a first current source sub-module and a second current source module connected to the other side of the high-frequency AC bus. The method includes: When a submodule open-circuit fault is detected in the common high-frequency bus multi-active bridge converter, the fault location of the submodule open-circuit fault is determined; Based on the fault location, the submodule fault disconnection process is performed, the faulty port is cut off, and an updated active bridge topology is obtained. Based on the fault location, a frequency integral compensation value is obtained by calculating the compensation value using the acquired circuit parameter information. Based on the fault location and the preset offset coefficient, the frequency integral compensation value is calculated by integral compensation to obtain the target compensation frequency. The preset reference frequency is added to the target compensation frequency to obtain the compensated fault ride-through frequency; The first control frequency of the non-faulty port in the current source module is switched to the fault ride-through frequency, and after a preset compensation time, the updated active bridge topology enters a stable state. In the updated active bridge topology, when the real-time second control frequency of the non-faulty port is detected to be consistent with the preset voltage source submodule control frequency, the control is switched back to closed-loop control to achieve fault ride-through. The circuit parameter information includes first parameter information before the fault and second parameter information after the fault; the step of calculating the frequency integral compensation value based on the acquired circuit parameter information according to the fault location includes: If the open circuit fault is determined to occur in the first current source submodule based on the fault location, then the first current source submodule is disconnected. The phase shift angle before the fault is obtained by performing phase shift angle calculation based on the first parameter information before the fault and the preset inter-port transmission power expression; The second phase shift angle after the fault is obtained by performing phase shift angle calculation based on the second parameter information after the fault and the preset inter-port transmission power expression; Subtracting the first phase shift angle from the second phase shift angle yields the compensated phase shift angle; The frequency integral compensation value is obtained by dividing the compensation phase shift angle by the preset compensation time.

2. The open-circuit fault ride-through method according to claim 1, characterized in that, The voltage source module includes: a first busbar access terminal connected to the high-frequency AC busbar, and a power supply terminal for connecting to a power source; the first busbar access terminals of both the first voltage source submodule and the second voltage source submodule are connected to the high-frequency AC busbar; The submodule fault disconnection process based on the fault location includes: When the fault location is at the power supply terminal of the first voltage source submodule, the path between the first voltage source submodule and the high-frequency AC bus is closed, and the first voltage source submodule is disconnected from the common high-frequency bus multi-active bridge converter. When the fault location is at the power supply terminal of the second voltage source submodule, the path between the second voltage source submodule and the high-frequency AC bus is closed, and the second voltage source submodule is disconnected from the common high-frequency bus active bridge converter.

3. The open-circuit fault ride-through method according to claim 2, characterized in that, The current source module includes: a second busbar access terminal connected to the high-frequency AC busbar and a load access terminal for connecting a load; the second busbar access terminals of both the first current source submodule and the second current source submodule are connected to the high-frequency AC busbar; The submodule fault disconnection process based on the fault location includes: When the fault location is the load access terminal of the first current source submodule, the path between the first current source submodule and the high-frequency AC bus is closed, and the first current source submodule is disconnected from the common high-frequency bus multi-active bridge converter. When the fault location is the load access terminal of the second current source submodule, the path between the second current source submodule and the high-frequency AC bus is closed, and the second current source submodule is disconnected from the common high-frequency bus multi-active bridge converter.

4. The open-circuit fault ride-through method according to claim 1, characterized in that, The method further includes: In the updated active bridge topology, when it is detected that the real-time second control frequency of the non-faulty current source module is inconsistent with the preset control frequency of the voltage source submodule, no closed-loop control switching is performed. Continue monitoring the real-time second control frequency of non-faulty ports.

5. The open-circuit fault ride-through method according to claim 1, characterized in that, The expression for the inter-port transmission power is: ； ； in, It is the DC side voltage of submodule i's port. It is the DC-side voltage of port j referred to submodule i. The equivalent inductance between submodule i and submodule j It is the phase shift angle between submodule i and submodule j; It is the output power of voltage source submodule i, that is It is the sum of the transmission power of submodule i and the other n-1 submodules, where n is the total number of submodules; The control frequency for submodule i; Equivalent Inductance The expression is: ； in, Let n be the equivalent inductance between submodule i and submodule j, and n be the total number of submodules. For the inductance of submodule i, For the inductance of submodule j, The equivalent inductance of submodule n referred to submodule i.

6. The open-circuit fault-crossing method according to claim 1, characterized in that, The step of performing integral compensation calculation on the frequency integral compensation value based on the fault location and a preset offset coefficient to obtain the target compensation frequency includes: When the open circuit fault is determined to occur in the first current source submodule or the second current source submodule based on the fault location, the first offset coefficient is determined. The target compensation frequency is obtained by multiplying the first offset coefficient by the frequency integral compensation value.

7. The open-circuit fault ride-through method according to claim 6, characterized in that, The step of performing integral compensation calculation on the frequency integral compensation value based on the fault location and a preset offset coefficient to obtain the target compensation frequency includes: When it is determined from the fault location that the open circuit fault occurs in the first voltage source submodule or the second voltage source module, the second offset coefficient is determined; The target compensation frequency is obtained by multiplying the second offset coefficient by the frequency integral compensation value; wherein the second offset coefficient is less than the first offset coefficient.

8. An open-circuit fault ride-through device for a common high-frequency bus multi-active bridge converter, characterized in that, The common high-frequency bus multi-active bridge converter includes: a high-frequency AC bus, a voltage source module and a current source module connected to the high-frequency AC bus; the voltage source module further includes: a first voltage source sub-module and a second voltage source sub-module connected to the same side of the high-frequency AC bus; the current source module further includes: a first current source sub-module and a second current source module connected to the other side of the high-frequency AC bus. The device includes: An open-circuit fault detection module is used to determine the fault location of a submodule open-circuit fault when an open-circuit fault is detected in a common high-frequency bus multi-active bridge converter. The first calculation and processing module is used to perform sub-module fault disconnection processing according to the fault location, disconnect the fault port, and obtain an updated active bridge topology. The second calculation and processing module is used to calculate and process the compensation value based on the obtained circuit parameter information according to the fault location to obtain the frequency integral compensation value. The third calculation and processing module is used to perform integral compensation calculation on the frequency integral compensation value according to the fault location and the preset offset coefficient to obtain the target compensation frequency. The fault ride-through frequency calculation module is used to add the preset reference frequency to the target compensation frequency to obtain the compensated fault ride-through frequency. The frequency switching module is used to switch the first control frequency of the non-faulty port in the current source module to the fault ride-through frequency, and after a preset compensation time, so that the updated active bridge topology enters a stable state. The closed-loop control switching module is used to switch back to closed-loop control in the updated active bridge topology when the real-time second control frequency of the non-faulty port is detected to be consistent with the preset voltage source submodule control frequency, so as to achieve fault ride-through. The circuit parameter information includes first parameter information before the fault and second parameter information after the fault; the step of calculating the frequency integral compensation value based on the acquired circuit parameter information according to the fault location includes: If the open circuit fault is determined to occur in the first current source submodule based on the fault location, then the first current source submodule is disconnected. The phase shift angle before the fault is obtained by performing phase shift angle calculation based on the first parameter information before the fault and the preset inter-port transmission power expression; The second phase shift angle after the fault is obtained by performing phase shift angle calculation based on the second parameter information after the fault and the preset inter-port transmission power expression; Subtracting the first phase shift angle from the second phase shift angle yields the compensated phase shift angle; The frequency integral compensation value is obtained by dividing the compensation phase shift angle by the preset compensation time.

9. An electronic device, characterized in that, It includes at least one processor and a memory for communicatively connecting to the at least one processor; the memory stores instructions executable by the at least one processor to enable the at least one processor to perform the open-circuit fault-crossing method as described in any one of claims 1 to 7.

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