Open-circuit fault ride-through method and device for common high-frequency bus multi-active bridge converter

Abstract

The invention discloses an open-circuit fault ride-through method and device for a common-high-frequency-bus multi-active-bridge converter, and relates to the field of direct-current power distribution network protection. The method comprises the steps that when it is detected that a sub-module open-circuit fault occurs in the common-high-frequency-bus multi-active-bridge converter, a fault port is cut off, and an updated active bridge topology is obtained; performing compensation value calculation based on the circuit parameter information to obtain a frequency integral compensation value; performing integral compensation calculation on the frequency integral compensation value to obtain a target compensation frequency; adding a preset reference frequency and the target compensation frequency to obtain a compensated fault ride-through frequency; switching the first control frequency of a non-fault port to a fault ride-through frequency, and after a preset compensation time, enabling the updated active bridge topology to enter a stable state; and when the real-time second control frequency of the non-fault port is detected to be consistent with the preset control frequency of the voltage source sub-module, the closed-loop control is switched back to realize fault ride-through. Interference between direct-current ports and current impact caused by self-adaptive adjustment can be reduced.

Description

Technical Field

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

[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 topology of multi-voltage DC power electronic converters is mostly based on a common DC bus topology of multiple independent dual active bridges (DAB) or a multi-active bridge (MAB) topology with high-frequency link AC coupling. Among them, the multi-active bridge topology with high-frequency link AC coupling is a common high-frequency bus DC converter based on a modular multi-active bridge structure (MMAB). It has good module scalability and port independence, and the number of power conversion links and components is relatively small, with advantages such as low cost and high power density. However, due to the high-frequency link energy collection, lack of energy buffer storage and strong coupling between ports, this topology needs to be further studied in terms of control strategy optimization and fault impact. In terms of control strategy, the existing control strategies of multi-port DC power electronic converters include: centralized control strategy and decentralized control strategy. Among them, the centralized control strategy is mostly used. Under the centralized control strategy, all measurements, digital control execution and drive signal generation are concentrated in one processor. Although the centralized control architecture is more orderly, computational burden, modularity and scalability become major issues. The decentralized control strategy distributes the computational burden of a central controller to several local controllers, effectively improving the modularity, flexibility and cost-effectiveness of the control system.

[0003] At present, there are relatively few studies on fault analysis and fault ride-through methods for multi-active bridge converters with common high-frequency busbars. The current research is mainly in the field of fault analysis and fault isolation based on centralized control. For example, the power electronic converter in the Zhangbei AC / DC hybrid distribution demonstration project adopts a fault isolation technology based on circuit breakers. In terms of fault ride-through, there are relatively few studies overall, and the proposed methods are relatively simple, which cannot meet the diversified fault protection and fault ride-through requirements of different ports. Summary of the invention

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

[0005] In a first aspect, an embodiment of the present application provides an open-circuit fault ride-through method for a common high-frequency bus multi-active bridge converter, wherein the common high-frequency bus multi-active bridge converter comprises: 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 comprises: a first voltage source submodule and a second voltage source submodule connected to the same side of the high-frequency AC bus; the current source module further comprises: a first current source submodule and a second current source submodule connected to the other same side of the high-frequency AC bus;

[0006] The method comprises:

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

[0008] Performing submodule fault cut-off processing according to the fault location, cutting off the faulty port, and obtaining an updated active bridge topology;

[0009] According to the fault location, a compensation value is calculated based on the acquired circuit parameter information to obtain a frequency integral compensation value;

[0010] Performing integral compensation calculation processing on the frequency integral compensation value according to the fault location and the preset offset coefficient to obtain a target compensation frequency;

[0011] Adding a preset reference frequency to the target compensation frequency to obtain a compensated fault ride-through frequency;

[0012] Switching the first control frequency of the non-fault port in the current source module to the fault ride-through frequency, after a preset compensation time, so that the updated active bridge topology enters a stable state;

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

[0014] In a second aspect, an embodiment of the present application provides an open-circuit fault ride-through device for a common high-frequency bus multi-active bridge converter, wherein the common high-frequency bus multi-active bridge converter comprises: 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 comprises: a first voltage source submodule and a second voltage source submodule connected to the same side of the high-frequency AC bus; the current source module further comprises: a first current source submodule and a second current source submodule connected to the other same side of the high-frequency AC bus;

[0015] The device comprises:

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

[0017] A first calculation processing module, configured to perform submodule fault cut-off processing according to the fault location, cut off the faulty port, and obtain an updated active bridge topology;

[0018] A second calculation processing module, configured to calculate and process the compensation value according to the fault location and based on the acquired circuit parameter information to obtain a frequency integral compensation value;

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

[0020] A fault ride-through frequency calculation module, used for adding a preset reference frequency to the target compensation frequency to obtain a compensated fault ride-through frequency;

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

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

[0023] In a third aspect, an embodiment of the present application provides an electronic device comprising at least one processor and a memory for communicating with the at least one processor; the memory stores instructions executable by the at least one processor, and the instructions are executed by the at least one processor so that the at least one processor can execute the open circuit fault crossing method as described in any one of the embodiments of the first aspect.

[0024] The embodiment of the present application includes: a 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 also includes: a first voltage source submodule and a second voltage source submodule connected to the same side of the high-frequency AC bus; the current source module also includes: a first current source submodule and a second current source submodule connected to the other same side of the high-frequency AC bus; 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; the submodule fault is cut off according to the fault location, the fault port is cut off, and an updated active bridge topology is obtained; according to the fault location, a compensation value is calculated based on the acquired circuit parameter information to obtain a frequency integral compensation value; performing integral compensation calculation processing on the frequency integral compensation value according to the fault position and the preset offset coefficient to obtain the target compensation frequency; adding the preset reference frequency to the target compensation frequency to obtain the compensated fault ride-through frequency; switching the first control frequency of the non-fault port in the current source module to the fault ride-through frequency, after the preset compensation time, so that the updated active bridge topology enters a stable state; in the updated active bridge topology, when it is detected that the real-time second control frequency of the non-fault port is consistent with the preset voltage source sub-module control frequency, switching back to closed-loop control to achieve fault ride-through; thereby reducing current impact; that is, the embodiment of the present application can reduce the impact on the non-fault port caused by the sub-module being cut off due to an open circuit fault, and reduce the interference between DC ports and the current impact caused by adaptive regulation. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1A It is a schematic diagram of the topological structure of a multi-active bridge DC converter provided by an embodiment of the present application;

[0026] Figure 1B It is a schematic diagram of the topological structure of a multi-active bridge converter with a common low-voltage and high-frequency bus provided by an embodiment of the present application;

[0027] Figure 2A This is a schematic diagram of a specific topological structure of a voltage source submodule provided by an embodiment of the present application;

[0028] Figure 2B is a control block diagram of a voltage source submodule provided by an embodiment of the present application;

[0029] Figure 3A This is a schematic diagram of a specific topological structure of a current source submodule provided by an embodiment of the present application;

[0030] Figure 3B This is a schematic diagram of a specific topological structure of a current source submodule provided by an embodiment of the present application;

[0031] Figure 4 It is a flow chart of an open-circuit fault ride-through method of a common high-frequency bus multi-active bridge converter provided by some embodiments of the present application;

[0032] Figure 5 This is a schematic diagram of a submodule open circuit situation provided by an embodiment of the present application;

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

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

[0035] Figure 8 is a schematic diagram of waveform changes of port power of each submodule when an open circuit fault occurs in the first current source submodule;

[0036] Fig. 9 is a schematic diagram of the change in capacitor voltage of the first current source submodule and the second current source submodule when an open circuit fault occurs in the second voltage source submodule;

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

[0038] Fig.11 is a schematic diagram of a frequency integral compensation process of a second current source submodule;

[0039] Fig.12 is a schematic diagram of the change of the port power waveform of each submodule without action when an open circuit fault occurs in the first current source submodule;

[0040] Fig.13 is a schematic diagram of the change of the port power waveform of each submodule under fault ride-through when an open circuit fault occurs in the first current source submodule;

[0041] Fig.14 is a schematic diagram of the change of the port power waveform of each submodule without action when an open circuit fault occurs in the second voltage source submodule;

[0042] Fig.15 It is a schematic diagram of the port power waveform changes of each submodule under fault ride-through when an open circuit fault occurs in the second voltage source submodule. DETAILED DESCRIPTION

[0043] In order to make the purpose, technical scheme and advantages of the present application clearer, the present application is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be noted that although a logical order is shown in the flowchart in the description of the present application, in some cases, the steps shown or described can be performed in an order different from that in the flowchart. In the description of the present application, the meaning of several is one or more, and the meaning of multiple is two or more. The description of "first" and "second" is only used for the purpose of distinguishing technical features, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of indicated technical features or implicitly indicating the order of the indicated technical features. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those generally understood by technicians in the technical field of the present application. The terms used herein are only for the purpose of describing the embodiments of the present application and are not intended to limit the present 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 topology of multi-voltage DC power electronic converters is mostly based on a common DC bus topology of multiple independent dual active bridges (DAB) or a multi-active bridge (MAB) topology with high-frequency link AC coupling. Among them, the multi-active bridge topology with high-frequency link AC coupling is a common high-frequency bus DC converter based on a modular multi-active bridge structure (MMAB). It has good module scalability and port independence, and the number of power conversion links and components is relatively small, with advantages such as low cost and high power density. However, due to the high-frequency link energy collection, lack of energy buffer storage and strong coupling between ports, this topology needs to be further studied in terms of control strategy optimization and fault impact. In terms of control strategy, the existing control strategies of multi-port DC power electronic converters include: centralized control strategy and decentralized control strategy. Among them, the centralized control strategy is mostly used. Under the centralized control strategy, all measurements, digital control execution and drive signal generation are concentrated in one processor. Although the centralized control architecture is more orderly, computational burden, modularity and scalability become major issues. The decentralized control strategy distributes the computational burden of a central controller to several local controllers, effectively improving the modularity, flexibility and cost-effectiveness of the control system.

[0045] At present, there are relatively few studies on fault analysis and fault ride-through methods for multi-active bridge converters with common high-frequency bus. In the related technologies, one document analyzes the instability mechanism of voltage drop at the high-voltage AC port from the perspective of energy based on a four-port power electronic transformer isolated by MMAB, and proposes a low voltage ride-through control scheme, which completes low voltage ride-through by switching the power balance port and the port control strategy during the fault period; another document, based on the demonstration project of common high-frequency bus power router, proposes a master-slave switching control of AC port mode based on duty cycle synchronization, which realizes smooth transition when the control structure of the master and slave inverters has a large difference; in addition, a major challenge of high-frequency coupling multi-port power electronic converters is that all modules are connected to a common high-frequency chain or multi-winding transformer, and the fault-locked module can still maintain the capacitor voltage through uncontrolled rectification. Based on this, a high-frequency oscillation model of the locked module of MMAB under the common high-frequency bus structure is established, and the system oscillation characteristics and module power transmission behavior after the local module is locked are analyzed, and the measure of installing an isolation switch on the AC side of the module is proposed to remove the locked H bridge from the system and prevent power transmission, so as to ensure the safe operation of the system. However, for multi-port DC converters, the exit of submodules under fault conditions may have a significant impact on the continuous operation of the system, and the transient coupling between ports can easily cause the fault to further develop from a single port to multiple ports; in addition, current research is mainly focused on fault analysis and fault isolation based on centralized control. For example, the power electronic converter in the Zhangbei AC / DC hybrid distribution demonstration project uses a circuit breaker-based fault isolation technology. In terms of fault ride-through, there is less overall research, and the proposed methods are relatively simple, which cannot meet the diverse fault protection and fault ride-through requirements of different ports.

[0046] Based on this, the present application provides an open-circuit fault ride-through method, an open-circuit fault ride-through device, and an electronic device for a common high-frequency bus multi-active bridge converter, the method comprising: when a submodule open-circuit fault is detected in a common high-frequency bus multi-active bridge converter, the fault port is removed to obtain an updated active bridge topology; a compensation value is calculated based on circuit parameter information to obtain a frequency integral compensation value; an integral compensation calculation is performed on the frequency integral compensation value to obtain a target compensation frequency; a preset reference frequency is added to the target compensation frequency to obtain a compensated fault ride-through frequency; the first control frequency of the non-fault 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 it is detected that the real-time second control frequency of the non-fault port is consistent with the preset voltage source submodule control frequency, the fault ride-through is switched back to closed-loop control. Interference between DC ports and current shock caused by adaptive regulation can be reduced.

[0047] The embodiments of the present application are further described below in conjunction with the accompanying drawings.

[0048] like Figure 1AAs shown, the multi-active bridge 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. Figure 1A The multi-winding high-frequency transformer of the multi-active bridge DC converter topology in the embodiment 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 a common low voltage and high frequency is shown.

[0049] Figure 1B The design and manufacturing difficulty of the multi-active bridge converter with a common high-frequency bus (i.e., a common high-frequency bus multi-active bridge converter) shown in the figure is reduced, and it is easy to realize the interconnection of any multiple high-frequency transformers. Specifically, the topological structure of 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 also includes: a first voltage source submodule 1 and a second voltage source submodule 2 connected to the same side of the high-frequency AC bus; the current source module also includes: a first current source submodule 3 and a second current source submodule 4 connected to the other same 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 access end of a submodule.

[0050] It should be noted that in each submodule, the full-bridge converter realizes bidirectional interconnection between the DC port and the AC port, which can meet the requirements of bidirectional energy conversion and high-frequency switching of voltage. The high-frequency transformer interconnects the AC port and the AC bus to realize high-frequency AC voltage matching and high-voltage gain conversion, and the DC capacitor provides the necessary voltage support and ripple filtering for the DC bus. The multi-active bridge converter with a common high-frequency bus is also a multi-port power electronic transformer. The topological structure of the multi-active bridge converter with a common high-frequency bus is very suitable for expansion to multiple modules and multiple ports, and the fault module locking has little effect on the normal operation of other modules in the power electronic transformer, which can ensure that the faults between ports are independent of each other. However, the energy collection link between the ports of the multi-active bridge converter with a common high-frequency bus is a high-frequency chain, and there is no energy storage capacitor as an energy buffer, and there is strong coupling between modules and ports. Therefore, it is necessary to conduct in-depth research on the integrated overall design and control of the multi-port power electronic transformer, the coupling and influence under fault conditions, etc.

[0051] Furthermore, combined with Figure 1AThe decentralized control principle of the multi-active bridge DC converter is explained. Specifically, under the traditional centralized control strategy, the global electrical variables of the MMAB converter are measured and transmitted to the central controller, which then determines the phase shift of each submodule. In contrast, the decentralized control strategy uses a variable PWM switching frequency, and the phase angles of the submodules of the MMAB converter will be adaptively adjusted based on local information (such as power and voltage).

[0052] It is understandable that, combined with Figure 1B To ensure the active power balance of the system, the power of each submodule in the multi-active bridge converter with a common high-frequency bus satisfies:

[0053] (P1+P2)+(P3+P4)=0 (1).

[0054] Among them, P1 is the first power of the first voltage source submodule 1, P2 is the second power of the second voltage source submodule 2, P3 is the third power of the first current source submodule 3, and P4 is the fourth power of the second current source submodule 4, and the sum is zero.

[0055] Furthermore, combined with Figure 2A and Figure 2B The control strategy of the voltage source submodule in the common high-frequency bus multi-active converter is described. The voltage source submodule includes: input voltage source, capacitor C dc , a full-bridge converter consisting of four switching tubes, and a two-winding transformer. Among them, the control strategy of the voltage source submodule is: each voltage source submodule determines the power sharing ratio of the voltage source submodule through the maximum switching frequency deviation and power sharing, and adaptively adjusts the switching frequency according to the power droop control. It can be understood that the module switching frequency f of the voltage source submodule si is a variable value, depending on Figure 2B The control block diagram shown shows that the module switching frequency f si The calculation formula is:

[0056]

[0057] Wherein, i is the number of the voltage source submodule, that is, when i=1, it represents the first voltage source submodule 1, and when i=2, it represents the second voltage source submodule 2. i is the DC side power of the voltage source submodule, f sref is the nominal switching frequency. τ is the time constant of the low-pass filter, which is used to reduce the measured P i High frequency ripple. m i is a proportional gain inversely proportional to the output power of each voltage source submodule. The module switching frequency f is obtained siAfter that, it is input into the 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] And when all voltage source submodules are synchronized with each other, the active power of the voltage source submodule is i Inversely proportional, that is:

[0059] m1P1=m2P2 (3);

[0060] Therefore, according to equation (1) and equation (3), we can get:

[0061]

[0062] Substituting equation (4) into equation (2) yields the switching frequency of the module in steady state:

[0063]

[0064] From equation (5), we can see that the module switching frequency of the voltage source submodule is related to both the sum of the power of the current source submodule and m i In order to find the maximum value of the numerator, we can consider the most extreme case, that is, all current source submodules absorb or deliver power at the same time. In addition, m i In order to prevent the change of module switching frequency from affecting the design of the multi-active bridge converter, the proportional gain m should be adjusted appropriately. i At this time, the maximum value of the switching frequency change is shown in formula (6):

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

[0066]

[0067] The module switching frequency of the voltage source submodule i is disturbed and becomes smaller than the module switching frequencies of other submodules. As time goes by, V i The phase angle of the P i The power of other sub-modules increases due to the negative correlation between sub-module power and switching frequency. si The phase angle of submodule i will automatically catch up with other submodules, and the process will continue until the frequencies of all submodules are synchronized.

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

[0069] like Figure 3A As shown, the external circuit is modeled as a current source I in I in The value of can be positive (equivalent to the output power) or negative (equivalent to the absorbed 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 port DC voltage. The switching frequency calculation of the current source submodule is shown in formula (8):

[0070]

[0071] Among them, k p is the proportional coefficient of the PI controller, k i is the integral gain of the PI controller. Assume that the DC terminal voltage V dc Initially less than V ref , at this time, the submodule switching frequency f si The voltage phase of this submodule will lag behind other submodules, resulting in the power P i Reduce, external power input P ext Greater than P i The difference between the two will charge the DC side capacitor, and this process will continue until V dc Equal to V ref .

[0072] Those skilled in the art will appreciate that the system structure shown in the figure does not constitute a limitation on the embodiments of the present application, and may include more or fewer components than shown in the figure, or a combination of certain components, or a different arrangement of components.

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

[0074] Those skilled in the art will appreciate that the system architecture and application scenarios described in the embodiments of the present application are intended to more clearly illustrate the technical solutions of the embodiments of the present application, and do not constitute a limitation on the technical solutions provided in the embodiments of the present application. Those skilled in the art will appreciate that with the evolution of the system architecture and the emergence of new application scenarios, the technical solutions provided in the embodiments of the present application are equally 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 the present application are proposed below.

[0076] First, as Figure 4 As shown, the open circuit fault ride-through method can be applied to Figure 1B In the common high-frequency bus multi-active bridge converter shown, 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 also 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 also includes: a first current source sub-module 3 and a second current source sub-module 4 connected to the other same 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, a fault location of the submodule open circuit fault is determined.

[0078] Step S120: performing submodule fault cut-off processing according to the fault location, cutting off the faulty port, and obtaining an updated active bridge topology.

[0079] Step S130: According to the fault location, a compensation value is calculated based on the acquired circuit parameter information to obtain a frequency integral compensation value.

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

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

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

[0083] Step S170: In the updated active bridge topology, when it is detected that the real-time second control frequency of the non-faulty port is 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 the present application, the method also includes: in an updated active bridge topology, when it is detected that the real-time second control frequency of the non-fault 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-fault port continues to be detected.

[0085] It should be noted that the reference frequency preset 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; the submodule fault is cut off according to the fault location, and the fault port is cut off to obtain an updated active bridge topology; according to the fault location, a compensation value is calculated based on the acquired circuit parameter information to obtain a frequency integral compensation value; the frequency integral compensation value is calculated based on the fault location and a preset offset coefficient to obtain a target compensation frequency; the preset reference frequency is compared with the target compensation frequency. Add together to obtain the compensated fault ride-through frequency; switch the first control frequency of the non-fault port in the current source module to the fault ride-through frequency, and after a preset compensation time, allow the updated active bridge topology to enter a stable state; in the updated active bridge topology, when it is detected that the real-time second control frequency of the non-fault port is consistent with the preset voltage source sub-module control frequency, switch back to closed-loop control to achieve fault ride-through, thereby reducing current impact; therefore, the embodiment of the present application can reduce the impact on the non-fault port caused by the sub-module being cut off due to an open circuit fault, and reduce the interference between DC ports and the current impact caused by adaptive regulation.

[0087] According to some embodiments of the present application, the voltage source module includes: a first bus access terminal connected to the high-frequency AC bus, a power supply terminal for connecting a power supply; the first bus access terminals of the first voltage source submodule 1 and the second voltage source submodule 2 are both connected to the high-frequency AC bus. Further explanation of step S120, wherein the submodule fault cut-off processing 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 end of the first voltage source submodule, the path between the first voltage source submodule and the high-frequency AC bus is controlled to be closed, and the first voltage source submodule is removed from the common high-frequency bus multi-active bridge converter;

[0089] Step S122: When the fault location is the power supply end of the second voltage source submodule, the path between the second voltage source submodule and the high-frequency AC bus is controlled to be closed, and the second voltage source submodule is removed from the common high-frequency bus multi-active bridge converter.

[0090] It can be understood that when the fault location is the first bus access end 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 been directly removed from the common high-frequency bus multi-active bridge converter; therefore, when the fault location is the first bus access end of the first voltage source submodule 1 or the second voltage source submodule 2, no additional operation is required to remove the fault. When the fault location is the power supply end 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 is still in parallel with the high-frequency AC bus, generating a current impact on the non-faulty submodules in the common high-frequency bus multi-active bridge converter, therefore, in this case, additional operations are required to remove the faulty submodules.

[0091] Through step S121 to step S122, when an open circuit fault occurs at the power supply end of the first voltage source submodule 1 or the second voltage source submodule 2, the embodiment of the present application promptly cuts off the fault to protect other non-fault submodules in the common high-frequency bus multi-active bridge converter.

[0092] According to some embodiments of the present application, the current source module includes: a second bus access terminal connected to the high-frequency AC bus and a load access terminal for connecting a load; the second bus access terminals of the first current source submodule 3 and the second current source submodule 4 are both connected to the high-frequency AC bus. Further explaining step S120, wherein the submodule fault cut-off 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 end of the first current source submodule, the path between the first current source submodule and the high-frequency AC bus is controlled to be closed, and the first current source submodule is removed from the common high-frequency bus multi-active bridge converter.

[0094] Step S124: 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 controlled to be closed, and the second current source submodule is removed from the common high-frequency bus multi-active bridge converter.

[0095] It can be understood that when the fault position is the second bus access end 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 been directly removed from the common high-frequency bus multi-active bridge converter; therefore, when the fault position is the second bus access end of the first current source submodule 3 or the second current source submodule 4, no additional operation is required to remove the fault. When the fault position is the load access end 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 is still in parallel with the high-frequency AC bus, generating a current impact on the non-faulty submodules in the common high-frequency bus multi-active bridge converter, therefore, in this case, additional operations are required to remove the faulty submodules.

[0096] In steps S123 to S124, when an open circuit fault occurs at the load access end of the first current source submodule 3 or the second current source submodule 4, the embodiment of the present application promptly removes the fault to protect other non-faulty submodules in the common high-frequency bus multi-active bridge converter.

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

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

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

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

[0101] Third, after an open circuit failure occurs on 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, the present application divides possible open circuit faults into four types, namely: one is that the high-frequency AC bus access end of the current source submodule is open; two is that the load end of the current source submodule is open; three is that the high-frequency AC bus access end of the voltage source submodule is open; and four is that the power supply end of the voltage source submodule is open.

[0103] It should be noted that the fault crossing mode implemented when the first current source submodule 3 has an open circuit fault is consistent with the fault crossing mode implemented when the second current source submodule 4 has an open circuit fault, and the fault crossing mode implemented when the first voltage source submodule 1 has an open circuit fault is consistent with the fault crossing mode implemented when the second voltage source submodule 2 has an open circuit fault. This application specifically discusses the situation where the first current source submodule 3 and the second voltage source submodule 2 have an open circuit fault. The fault crossing modes of the other two fault situations have the same technical principles and the same technical effects, and will not be repeated in order to avoid content duplication and redundancy.

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

[0105] It should be noted that, for both case 1 and case 2, the power of the first current source submodule 3 suddenly changes to 0, and the non-fault submodule is subjected to transient shock at the moment of fault, which is especially reflected in the voltage of the non-fault second current source submodule 4. The difference is that case 1 is equivalent to the entire first current source submodule 3 being removed from the system, while in case 2, the faulty first current source submodule 3 is still in parallel with the high-frequency AC bus. It can be understood that after the case 2 fault, even if there is no load absorbing power under full-bridge lockout, the resonant impedance network composed of the high-frequency transformer leakage inductance and the stray capacitance of each component still has a high-frequency oscillation of hundreds of kHz, which will also cause the fault port at case 2 to still have power transmission, affecting the non-faulty second current source submodule 4. Based on this, in order to protect the non-faulty second current source submodule 4, after detecting that the current source submodule load is open, the first current submodule is temporarily removed from the high-frequency transformer side, the path of the first current submodule is closed, and the system is connected again after the fault is cleared, so case 2 can be equivalent to case 1. In this way, 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, the system reduces the power of part P3, and the remaining first voltage source sub-module 1, second voltage source sub-module 2, and second current source sub-module 4 form a three-active bridge topology (i.e., the updated active bridge topology obtained in step S120).

[0106] Similarly, a similar fault removal method can be used to protect the common high-frequency bus multi-active bridge converter for case 4. Therefore, in the case of timely removal of the faulty second voltage source submodule 2, case 4 is equivalent to case 3. It can be understood that after the second voltage source submodule 2 is removed, for the entire common high-frequency bus multi-active bridge converter, it is equivalent to removing a voltage source with output power, and the system reduces the power of part 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 of the embodiment of the present application are further explained.

[0108] Taking the case 1 where an open circuit fault occurs in the first current source submodule 3, for example, for the fault port (i.e., the second busbar access terminal of the first current source submodule 3), since the inductor loop of the first current source submodule 3 is cut off at the moment of the open circuit fault, the inductor current instantly drops to 0, and the port output capacitor of the first current source submodule 3 releases the stored charge, so that the port voltage drops to 0 after about τ=5RCs, as shown in FIG. Figure 6 This process is mainly manifested in that the first current source submodule 3 loses the power transmission path and shuts down, but does not cause any damage to itself.

[0109] It is understandable that after the first current source submodule 3 fails to open circuit, the power of its port drops to 0 at the moment of opening circuit. For the non-faulty port, the total power released by the voltage source module is greater than the power absorbed by the non-faulty second current source submodule 4, so the voltage of the non-faulty second current source submodule 4 will be Figure 7 The figure shows a transient process that produces values ​​that exceed the original operating values.

[0110] When the secondary side of the transformer of 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 part P3 is reduced in the common high-frequency bus multi-active bridge converter, and 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 short transient state, the non-fault 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 in FIG. 1 , the port power of the first current source submodule 3 changes from the original rated power to 0 after the open circuit fault occurs. For the non-faulty first voltage source submodule 1, the second voltage source submodule 2, and the second current source submodule 4, after a certain period of transient state, the port power of the first voltage source submodule 1 drops from P1 to P 1f , the port power of the second voltage source submodule 2 drops from P2 to P 2f After the 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] In addition, the port power of the second current source submodule 4 is maintained at P4 after the disturbance, and the non-faulty port can still operate normally after the fault transient ends.

[0114] Furthermore, the open circuit fault characteristics of the voltage source submodule of the embodiment of the present application are further explained.

[0115] Taking the case 3 where the second voltage source submodule 2 has an open circuit fault and the fault location is, for example, the fault port (i.e., the first bus access end of the second voltage source submodule 2) will lock the full bridge in time after the open circuit fault occurs, and the second voltage source submodule 2 will lose the power transmission path and shut down. The process is similar to the process of the open circuit fault of the first current source submodule 3 mentioned above. It can be understood that after the second voltage source submodule 2 has an open circuit fault and is removed, the common high-frequency bus multi-active bridge converter loses a voltage source submodule. For the non-faulty submodules, the output power of the first voltage source submodule 1 at the moment of the fault is less than the sum of the absorbed powers of the first current source submodule 3 and the second current source submodule 4. Therefore, the first current source submodule 3 and the second current source submodule 4 will produce a transient process lower than the original operating value, and stabilize at the original operating value after the transient. Fig. 9 shown.

[0116] like Fig.10 As shown in the power waveform, when the second voltage source submodule 2 has an open circuit fault, the system changes from the original first voltage source submodule 1 and the second voltage source submodule 2 jointly emitting power to the first voltage source submodule 1 emitting power alone. In order to restore normal operation after the fault, the power of the first voltage source submodule 1 will increase from the original P1 to P 1f During the transient process, the power of the first current source submodule 3 and the second current source submodule 4 is restored to the original operating value after the transient ends.

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

[0118] Step S131: judging that the open circuit fault occurs in the first current source submodule according to the fault location, the first current source submodule is cut off.

[0119] Step S132: performing phase shift angle calculation processing according to 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: performing phase shift angle calculation processing according to 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: subtracting the first phase shift angle from the second phase shift angle to obtain a compensation phase shift angle.

[0122] Step S135: Obtain a frequency integral compensation value according to the compensation phase shift angle divided by the preset compensation time.

[0123] According to some embodiments of the present application, the expression of the transmission power between ports is:

[0124]

[0125] Among them, U' i is the voltage of port i converted to the first voltage source submodule 1, U' j is the voltage of port j converted to the first voltage source submodule 1, L ij is the equivalent inductance, is the phase shift angle; P i is the output power of voltage source submodule i;

[0126] Equivalent inductance L ij The expression is:

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

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

[0129] It is understandable that when an open circuit fault occurs in the first current source submodule 3 or the second current source submodule 4, after reaching a new steady state, the new steady-state frequency will be higher than the steady-state frequency before the fault. Therefore, it is necessary to set the fault ride-through process voltage higher than a given value, and set the first offset coefficient to make the control frequency of the non-fault port larger, so as to achieve a smooth switch back to closed-loop control effect after the fault ride-through ends. Specifically, the first offset coefficient is 1.05.

[0130] According to some embodiments of the present application, step S140 is further described. Step S140: performing integral compensation calculation processing on the frequency integral compensation value according to the fault location and a preset offset coefficient to obtain a target compensation frequency, including: when it is judged according to the fault location that the open circuit fault occurs in the first voltage source submodule 1 or the second voltage source submodule 2, determining the second offset coefficient; multiplying the second offset coefficient by the frequency integral compensation value to obtain the target compensation frequency; wherein the second offset coefficient is smaller than the first offset coefficient.

[0131] It is understandable that when an open circuit fault occurs in the first voltage source submodule 1 or the second voltage source submodule 2, after reaching a new steady state, the new steady-state frequency will be lower than the steady-state frequency before the fault. Therefore, it is necessary to set the fault ride-through voltage of the non-faulty first current source submodule 3 and the second current source submodule 4 to be lower than a given value, so that the control frequency of the non-faulty port is relatively small, so as to achieve a smooth switch back to closed-loop control effect after the fault ride-through ends. Specifically, the second offset coefficient is 0.95.

[0132] Furthermore, the fault ride-through mechanism involved in the embodiment of the present application is as follows: From the previous analysis, it can be seen that for the fault continuation stage after the capacitor discharge is completed, the current flowing through the fault port device is usually within the rated current range; but for the non-fault port, it should be adjusted in time after the fault occurs to reduce the power transient impact and maintain stable output. The transient impact of the non-fault port is mainly caused by the adjustment of the phase shift angle of the non-fault sub-module after the open circuit occurs, and the phase shift angle of each sub-module is determined by the frequency in the decentralized control strategy. Therefore, by taking corresponding measures to compensate for the phase shift angle of the current source sub-module after the fault occurs, the phase shift angle adaptive adjustment process can be artificially controlled to suppress the transient impact of the voltage.

[0133] Furthermore, the compensation value calculation process provided in the embodiment of the present application is further explained.

[0134] Taking the fault location as Case 1 as an example, the time before the open circuit fault occurs is defined as t0, and the time to reach a new steady state after the fault occurs is defined as t f , 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]

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

[0137]

[0138] Among them, f 1_t0 is the steady-state frequency of cas1 before the fault; Δf is the change in the controller frequency output of the first voltage source submodule 1; f sref is the nominal switching frequency; P4 is the DC side power of the second current source submodule 4; m i It is a proportional gain inversely proportional to the power output of each voltage source submodule; P3 is the DC side power of the first current source submodule 3.

[0139] After case 1 has an open circuit fault, when the second current source submodule 4 returns to the operating value before the fault, by comparing equation (5) with equation (10), it can be seen that the system frequency after the fault will be different from the frequency before the fault. Since the decentralized control reaches stability, the frequencies of each submodule should remain consistent under normal operation, which means that the controller of the non-faulty second current source submodule 4 will undergo a transient adjustment process, changing from the original control frequency to the new control frequency. From the definition of decentralized control, the control frequency f of the first voltage source submodule 1 in this transient process is s1 , the control frequency f of the second current source submodule 4 s4 By integrating the difference of the changes in the transient phase shift angle of the non-fault submodule, the phase shift angle of the steady-state submodule after the fault is:

[0140]

[0141] Among them, f s1 is the control frequency of the first voltage source submodule 1, f s4 is the control frequency of the second current source submodule 4, is the phase shift angle of the second current source submodule 4 before failure.

[0142] In this transient process, the voltage of the second current submodule 4 is disturbed due to the regulation of the controller and then reaches a steady state again.

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

[0144]

[0145] Among them, U i is the DC side voltage of the port of submodule i, U' j is the DC voltage of the port j converted to the submodule i, L ij is the equivalent inductance between submodule i and submodule j, is the phase shift angle between submodule i and submodule j; P i is the output power of submodule i, that is, P i The calculation method of is shown in formula (13), that is, the sum of the transmission power of submodule i and the other n-1 submodules, n is the total number of submodules; f i is the control frequency of submodule i;

[0146] Specifically, the equivalent inductance calculation expression in formula (12) is:

[0147]

[0148] Among them, L ij is the equivalent inductance between submodule i and submodule j, n is the total number of submodules, L i is the inductance of submodule i, L j is the inductance of submodule j, L n is the equivalent inductance of submodule n converted to submodule i, then it can be understood that L1, L2, ... L n They are the equivalent inductances of submodules 1 to n converted to submodule i.

[0149] It can be obtained from formula (12) and formula (14) that after an open circuit fault occurs in case 1, due to the loss of the inductance of the faulty first current source submodule 3, the power of each port will also change due to the loss of the transmission power portion of the faulty port.

[0150] Since the steady-state power of the first current source submodule 3 after the fault is consistent with that before the fault, the system frequency and the voltage source submodule power are both determined by the current source submodule power and the power sharing ratio m i Therefore, the phase shift angle of the port of the second current source submodule 4 before and after the fault can be calculated by the simultaneous equations (12) to (14): and in It is not only the phase shift angle of the port 4 of the second current source submodule 4 after adjustment, but also the phase shift angle of the port 4 finally obtained by the adaptive adjustment of the system under closed-loop control.

[0151] In actual systems, after a fault occurs, the converter often needs a certain amount of time to reach a steady state. When the voltage at the fault port drops to the non-fault port, a transient impact is generated. Since the magnetic link responds slowly, the port 4 of the second current source submodule 4 can be phase-shifted and compensated after the first current source submodule 3 is opened, so as to achieve a smooth transition of the port power. The compensation value calculation method is shown in the following formula:

[0152]

[0153] In decentralized control, the phase shift angle between submodules is obtained by adaptively controlling the frequency of each submodule, as shown in equation (11). Therefore, the phase shift angle cannot be directly compensated in decentralized control, but the same purpose can be achieved by integrating the frequency. The compensation expression obtained from the relationship between the phase shift angle and the frequency is:

[0154]

[0155] Since in the decentralized control, both current source submodules adopt PI constant voltage control, and both voltage source submodules adopt power droop control, there must be a difference in frequency output between the two controls in the transient process when the port open circuit fault occurs, and this difference will affect the integral compensation effect. However, since the frequency outputs of all controllers are the same before the fault, according to the assumed conditions, the control frequency of the first voltage source submodule 1 can be selected as the transient reference frequency in the crossing process, and the compensation frequency can be compensated in the reference frequency, and input into the non-fault current value submodule as the control frequency of the crossing process for control. Taking the case of the first current source submodule 3 being open circuit, 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, and equation (16) is converted to:

[0156]

[0157] Therefore, when the compensation angle is known, the compensation frequency Δf can be calculated by simply setting the compensation time △t. c size.

[0158] Furthermore, the integral compensation calculation process provided in the embodiment of the present application is further explained.

[0159] For the non-faulty second current source submodule 4, after frequency integral compensation, its phase shift angle can enter the post-fault stable state only through the compensation time △t, and will not cause large transient disturbances to the port voltage and power. However, the controller of the non-faulty second current source submodule 4 does not form a closed loop with the system during the fault crossing process. According to the output expression of the distributed control of the current source submodule in formula (8), if the fault crossing process accurately controls the port voltage at the reference value, the controller frequency will remain unchanged. However, it can be seen from formula (5) that 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 voltage source submodule and the current source submodule controller frequency to be inconsistent. If the removed first current source submodule 3 is switched back to closed-loop control after the fault crossing is completed, a new frequency adaptive transient will inevitably be formed, which will cause transient shocks to the system. To suppress the transient impact of the switching closed loop, the voltage of the non-faulty second current source submodule 4 can be set slightly off the reference value during the fault ride-through process according to the steady-state frequency value after the fault, so that the control frequency of the controller of the second current source submodule 4 deviates in a directional manner due to the steady-state error, and finally achieves smooth switching when the stable frequency value is reached. For example, when the steady-state frequency value f 4f If the voltage during the ride-through process is lower than that before the fault, the voltage is set to 0.95 times the reference value. From formula (8), it can be seen that the control frequency f4 of the controller will continue to decrease. When it is detected that f4 = f 4f Switch back to closed-loop control to achieve fault ride-through.

[0160] The frequency integral compensation process is as follows: Fig.11 Before the fault, the control frequency of the second current source submodule 4 is the original closed-loop controller output frequency f s4 After identifying the open circuit fault of 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 in open loop operation, and the port voltage value is related to the phase shift angle of the compensation. The control frequency of the second current source submodule 4 will be offset (such as Fig.11 Black curve, shifted downward). When it is detected that the controller frequency of the second current source submodule 4 is shifted to the system operating frequency (ie, the voltage source submodule control frequency), it switches back to closed-loop control, and no new transient impact occurs due to frequency mismatch when the controller switches.

[0161] An example is given and the specific application and effect of the embodiment of the present application are explained in combination with simulation results.

[0162] The performance of the fault crossing strategy of the embodiment of the present application is verified by simulation. The multi-active bridge DC converter simulation model with a common high-frequency bus built in MATLAB / Simulink is simulated, and the simulation parameters are preset. For a brief analysis, the power distribution ratio of the voltage source submodules 1 and 2 is set to 1:1, that is, the power coefficient m1 of the first voltage source submodule 1 is 0.04, and the power coefficient m2 of the second voltage source submodule 2 is also set to less than 0.04. By simulating two typical open circuit fault types, the port performance of the non-fault port under fault and fault crossing is compared.

[0163] A simulation analysis is performed on the case where the first current source submodule 3 has an open circuit failure.

[0164] In the simulation system with parameter configuration, the total simulation time is set to 0.6s. At t=0.3s, the first current source submodule 3 has an open circuit fault. Before the fault, the system operates under the conditions of P1=P2=5kW, P3=-8kW, P4=-2kW. According to the control principle of the voltage source submodule, the system steady-state frequency f1=f2=f3=f4=19.6kHz can be obtained. The phase shift angle between each port in steady state is φ 12 =0,φ 13 =0.148,φ 14 =0.08. In the steady state after the failure of the first current source submodule 3, the system operates at P 1f =P 2f =1kW, P 4f = -2kW working condition, the frequency changes to f 1f =f 2f =f 4f =19.92kHz, the phase shift angle between each port in steady state can be calculated as φ 12f =0,φ 14f =0.034. The angle Δφ of the transient process adaptive adjustment change can be calculated 14 =-0.046. Since the steady-state frequency after a fault is higher than that before a fault, it is necessary to set the fault ride-through voltage of the second current source submodule 4 higher than a given value to make its control frequency deviate upward, so as to achieve a smooth switch back to closed-loop control effect after the fault ride-through. The compensation value can be set to 1.05Δφ by setting a 1.05 times frequency integral compensation value. 14 During the fault ride-through period, the port voltage of the second current source submodule 4 will be maintained at an operating value slightly higher than 48V.

[0165] In the case of no fault ride-through, the open circuit of the first current source submodule 3 will cause the port voltage of the second current source submodule 4 to overshoot by about 35%, and the peak value of the inductor current of the second current source submodule 4 will impact to about 5 times of the original value at the moment of fault; after using the fault ride-through strategy, the port voltage of the second current source submodule 4 is maintained at the voltage deviation value under the set phase shift angle during the ride-through period. 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.

[0166] contrast Fig.12 and Fig.13 During the fault ride-through period, the transient impact of the power of the second current source submodule 4 is effectively suppressed, and its operating value is maintained at about 1.1 times the rated operating value. At the same time, the transient process of the first voltage source submodule 1 and the second voltage source submodule 2 is also shortened to a certain extent under the fault ride-through strategy. From the simulation results, when an open circuit fault occurs in the first current source submodule 3, the fault ride-through measure can effectively reduce the impact of the transient impact of the fault process and prevent damage to the non-fault port.

[0167] A simulation analysis is performed on the case where the second voltage source submodule 2 has an open circuit failure.

[0168] In the simulation system with parameter configuration, the total simulation time is set to 0.6s. At t=0.3s, the second voltage source submodule 2 has an open circuit fault. In the steady state before the fault, the system operation is consistent with the system operation when the first current source submodule 3 has an open circuit fault. In the steady state after the second voltage source submodule 2 has an open circuit fault, the system operates at P 1f =10kW, P 3f =-2kW, P 4f = -2kW working condition, the frequency changes to f 1f =f 3f =f 4f =19.92kHz, the phase shift angle between each port in steady state is φ 13f =0.205,φ 14f =0.137. The angle Δφ of the transient process adaptive adjustment change can be calculated 13 =0.057, Δφ 14 =0.057. Since the steady-state frequency after a fault will be lower than that before the fault, it is necessary to set the fault ride-through voltage of the first current source submodule 3 and the second current source submodule 4 lower than a given value, so that the control frequency of the second current source submodule 4 deviates downward. The compensation value can be set to 0.95Δφ 13 、0.95Δφ 14During the fault ride-through period, the port voltage of the first current source submodule 3 and the second current source submodule 4 will be maintained at an operating value slightly lower than 220V / 48V.

[0169] In the case of no fault ride-through, the open circuit of the second voltage source submodule 2 will cause a transient impact on the two non-fault current source ports, and the impact size is inversely proportional to the port power size, so the second current source submodule 4 with low power and low voltage has the greatest impact. When using the fault ride-through strategy, the port voltages of the first current source submodule 3 and the second current source submodule 4 are maintained at the voltage deviation value under the set phase shift angle during the ride-through period. After about 0.08s, the control frequency of the first current source submodule 3 first reaches the actual operating frequency of the system, and the first current source submodule 3 switches back to closed-loop control. This process will cause a small transient impact on the second current source submodule 4 that is still in the fault ride-through because the voltage of the first current source submodule 3 is slightly adjusted from the deviation value to the set value after switching the closed loop. After another 0.05s, the control frequency of the second current source submodule 4 is the same as the actual operating frequency of the system, and the second current source submodule 4 switches back to closed-loop control, the fault ride-through process ends, and the system resumes operation.

[0170] contrast Fig.14 and Fig.15 The transient process of the non-faulty first current source submodule 3 and the second current source submodule 4 drops to 85% and 60% at most when there is no action, while they are maintained at 97% and 95% respectively under fault ride-through, and the power transient impact is significantly suppressed.

[0171] When an open circuit fault occurs in the second voltage source submodule 2, the fault ride-through strategy provided in the embodiment of the present application can effectively reduce the transient impact of the voltage source submodule fault process on the non-faulty current source submodule, thereby preventing damage to the non-faulty port.

[0172] Based on the above simulation, it can be understood that for the four open circuit fault conditions mentioned in the embodiments of the present application, namely, the open circuit faults occurring in case 1, case 2, case 3 and case 4, the fault ride-through strategy of integral compensation proposed in the embodiments of the present application can effectively suppress the transient overvoltage and overcurrent of the non-faulty sub-modules, and ensure the safe and stable operation of the system transient process.

[0173] In a second aspect, an embodiment of the present application provides an open-circuit fault ride-through device for a common high-frequency bus multi-active bridge converter; the open-circuit fault ride-through device includes: an open-circuit fault detection module, which is used to determine the fault position of the sub-module open-circuit fault when a sub-module open-circuit fault is detected in the common high-frequency bus multi-active bridge converter; a first calculation and processing module, which is used to perform sub-module fault cut-off processing according to the fault position, remove the faulty port, and obtain an updated active bridge topology; a second calculation and processing module, which is used to calculate and process the compensation value based on the acquired circuit parameter information according to the fault position to obtain a frequency integral compensation value; a third calculation and processing module, which is used to calculate and process the compensation value based on the fault position, The preset offset coefficient performs integral compensation calculation processing on the frequency integral compensation value to obtain the target compensation frequency; the fault crossing frequency calculation module is used to add the preset reference frequency and the target compensation frequency to obtain the compensated fault crossing frequency; the frequency switching module is used to switch the first control frequency of the non-fault port in the current source module to the fault crossing frequency, so that the updated active bridge topology enters a stable state after the preset compensation time; the closed-loop control switching module is used to switch back to closed-loop control in the updated active bridge topology when it is detected that the real-time second control frequency of the non-fault port is consistent with the preset voltage source submodule control frequency to achieve fault crossing. The open-circuit fault crossing device of the present application can reduce the impact on the non-fault port when the submodule is cut off due to an open-circuit fault, and reduce the interference between DC ports and the current impact caused by adaptive regulation.

[0174] It should be noted that since the open-circuit fault ride-through device of this embodiment can implement the open-circuit fault ride-through method of any of the previous embodiments, the open-circuit fault ride-through device of this embodiment and the open-circuit fault ride-through method of any of the previous embodiments have the same technical principles and the same technical effects. In order to avoid redundant content, they will not be repeated here.

[0175] In the third aspect, the present invention also provides an electronic device 800, including: a processor 801, which can be implemented by a general-purpose central processing unit, a microprocessor, an application-specific integrated circuit, or one or more integrated circuits, and is used to execute relevant programs to implement the technical solution provided by the embodiment of the present application; a memory 802, which can be implemented in the form of a read-only memory, a static storage device, a dynamic storage device, or a random access memory. The memory 802 can store an operating system and other application programs. When the technical solution provided in the embodiment of this specification is implemented by software or firmware, the relevant program code is stored in the memory 802, and the processor 801 is called to execute the open circuit fault crossing method of the embodiment of the present application; the input / output interface 803 is used to realize information input and output; the communication interface 804 is used to realize the communication interaction between the present device and other devices, and communication can be realized through wired methods (such as USB, network cables, etc.) or wireless methods (such as mobile networks, WIFI, Bluetooth, etc.); the bus 805 transmits information between the various components of the device (such as the processor 801, the memory 802, the input / output interface 803 and the communication interface 804); wherein the processor 801, the memory 802, the input / output interface 803 and the communication interface 804 realize communication connection with each other within the device through the bus 805.

[0176] The above is a specific description of the preferred implementation of the present application, but the present application is not limited to the above-mentioned implementation mode. Technical personnel familiar with the field can also make various equivalent deformations or substitutions without violating the spirit of the present application. These equivalent deformations or substitutions are all included in the scope defined by the present application.

Claims

1. A method for riding through an open-circuit fault of a common high-frequency bus multi-active bridge converter, characterized in that: The common high-frequency bus multi-active bridge converter comprises: 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 comprises: a first voltage source submodule and a second voltage source submodule connected to the same side of the high-frequency AC bus; the current source module further comprises: a first current source submodule and a second current source submodule connected to the other same side of the high-frequency AC bus; The method comprises: When a submodule open circuit fault is detected in the common high-frequency bus multi-active bridge converter, a fault location of the submodule open circuit fault is determined; Performing submodule fault cut-off processing according to the fault location, cutting off the faulty port, and obtaining an updated active bridge topology; According to the fault location, a compensation value is calculated based on the acquired circuit parameter information to obtain a frequency integral compensation value; Performing integral compensation calculation processing on the frequency integral compensation value according to the fault location and the preset offset coefficient to obtain a target compensation frequency; Adding a preset reference frequency to the target compensation frequency to obtain a compensated fault ride-through frequency; Switching the first control frequency of the non-fault port in the current source module to the fault ride-through frequency, after a preset compensation time, so that the updated active bridge topology enters a stable state; In the updated active bridge topology, when it is detected that the real-time second control frequency of the non-faulty port is consistent with the preset voltage source submodule control frequency, the closed-loop control is switched back to realize fault ride-through.

2. The open circuit fault ride-through method according to claim 1, characterized in that: The voltage source module comprises: a first bus access terminal connected to the high-frequency AC bus, and a power supply terminal for connecting a power supply; the first bus access terminals of the first voltage source submodule and the second voltage source submodule are both connected to the high-frequency AC bus; The performing submodule fault cutting processing according to the fault location includes: When the fault location is the power supply end of the first voltage source submodule, controlling the path between the first voltage source submodule and the high-frequency AC bus to be closed, and removing the first voltage source submodule from the common high-frequency bus multi-active bridge converter; When the fault location is the power supply end of the second voltage source submodule, the path between the second voltage source submodule and the high-frequency AC bus is controlled to be closed, and the second voltage source submodule is removed from the common high-frequency bus multi-active bridge converter.

3. The open circuit fault ride-through method according to claim 2, characterized in that: The current source module comprises: a second bus access terminal connected to the high-frequency AC bus and a load access terminal for connecting a load; the second bus access terminals of the first current source submodule and the second current source submodule are both connected to the high-frequency AC bus; The performing submodule fault cutting processing according to the fault location includes: When the fault position is at the load access end of the first current source submodule, controlling the path between the first current source submodule and the high-frequency AC bus to be closed, and removing the first current source submodule 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 controlled to be closed, and the second current source submodule is removed 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 comprises: 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 submodule control frequency, no closed-loop control switching is performed; Continue to detect the second control frequency of the non-faulty port in real time.

5. The open circuit fault ride-through method according to claim 1, characterized in that: The circuit parameter information includes first parameter information before the fault and second parameter information after the fault; the compensation value calculation process based on the acquired circuit parameter information according to the fault location to obtain the frequency integral compensation value includes: It is determined according to the fault position that the open circuit fault occurs in the first current source submodule, and the first current source submodule is cut off; Performing phase shift angle calculation processing according to the first parameter information before the fault and a preset inter-port transmission power expression to obtain a first phase shift angle before the fault; Performing phase shift angle calculation processing according to the second parameter information after the fault and a preset inter-port transmission power expression to obtain a second phase shift angle after the fault; Subtracting the first phase shift angle from the second phase shift angle to obtain a compensation phase shift angle; The frequency integral compensation value is obtained by dividing the compensation phase shift angle by a preset compensation time.

6. The open circuit fault ride-through method according to claim 5, characterized in that: The expression of the transmission power between ports is: Among them, U i is the DC side voltage of the port of submodule i, U' j is the DC voltage of port j converted to submodule i, L ij is the equivalent inductance between submodule i and submodule j, is the phase shift angle between submodule i and submodule j; P i is the output power of the voltage source submodule i, that is, P i is the sum of the transmission power of submodule i and the other n-1 submodules, where n is the total number of submodules; f i is the control frequency of submodule i; Equivalent inductance L ij The expression is: Among them, L ij is the equivalent inductance between submodule i and submodule j, n is the total number of submodules, L i is the inductance of submodule i, L j is the inductance of submodule j, L n is the equivalent inductance of submodule n converted to submodule i.

7. The open circuit fault ride-through method according to claim 1, characterized in that: The step of performing integral compensation calculation processing on the frequency integral compensation value according to the fault position and the preset offset coefficient to obtain a target compensation frequency includes: When it is determined according to the fault position that the open circuit fault occurs in the first current source submodule or the second current source submodule, determining a first offset coefficient; The first offset coefficient is multiplied by the frequency integral compensation value to obtain the target compensation frequency.

8. The open circuit fault ride-through method according to claim 7, characterized in that: The step of performing integral compensation calculation processing on the frequency integral compensation value according to the fault position and the preset offset coefficient to obtain a target compensation frequency includes: When it is determined according to the fault position that the open circuit fault occurs in the first voltage source submodule or the second voltage source submodule, determining a second offset coefficient; The second offset coefficient is multiplied by the frequency integral compensation value to obtain the target compensation frequency; wherein the second offset coefficient is smaller than the first offset coefficient.

9. 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 comprises: 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 comprises: a first voltage source submodule and a second voltage source submodule connected to the same side of the high-frequency AC bus; the current source module further comprises: a first current source submodule and a second current source submodule connected to the other same side of the high-frequency AC bus; The device comprises: An open circuit fault detection module is used to determine the fault position of the submodule open circuit fault when a submodule open circuit fault is detected in the common high-frequency bus multi-active bridge converter; A first calculation processing module, configured to perform submodule fault cut-off processing according to the fault location, cut off the faulty port, and obtain an updated active bridge topology; A second calculation processing module, configured to calculate and process the compensation value according to the fault location and based on the acquired circuit parameter information to obtain a frequency integral compensation value; A third calculation processing module is used to perform integral compensation calculation processing on the frequency integral compensation value according to the fault location and the preset offset coefficient to obtain a target compensation frequency; A fault ride-through frequency calculation module, used for adding a preset reference frequency to the target compensation frequency to obtain a compensated fault ride-through frequency; A frequency switching module, used for switching the first control frequency of the non-fault port in the current source module to the fault ride-through frequency, so that the updated active bridge topology enters a stable state after a preset compensation time; The closed-loop control switching module is used to switch back to closed-loop control in the updated active bridge topology to achieve fault ride-through when it is detected that the real-time second control frequency of the non-fault port is consistent with the preset voltage source submodule control frequency.

10. An electronic device, characterized in that: It includes at least one processor and a memory for communicating with the at least one processor; the memory stores instructions that can be executed by the at least one processor, and the instructions are executed by the at least one processor so that the at least one processor can execute the open circuit fault crossing method as described in any one of claims 1 to 8.

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