MMC equivalent modeling method and device

Abstract

According to the MMC equivalent modeling method, when an equivalent model is established, a diode is connected to a capacitor of a sub-module in parallel, the diode does not exist in an actual physical structure of an MMC and is only an equivalent mechanism established during modeling, and therefore the capacitor voltage in the sub-module is clamped through the diode; a negative value of the capacitor voltage in the switch simulation process is avoided, and the model stability is improved; according to the method, the sub-modules are equivalent to different switch states according to external trigger pulses, simulation calculation is carried out corresponding to the different switch states, the number of elements needing to be calculated during simulation modeling is greatly reduced through the equivalent mode, the simulation speed of the large-scale power system is remarkably increased, and meanwhile the simulation precision is considered.

Description

Technical Field

[0001] The present invention relates to a simulation analysis technology for a flexible direct current transmission system, and in particular to an MMC equivalent modeling method and device. Background Art

[0002] MMC (Modular Multilevel Converter) is a converter based on a multi-level topology, mainly used for high-voltage and large-capacity DC and AC power transmission. It achieves multi-level output through the series and parallel connection of multiple power modules, making the output voltage waveform closer to a sine wave, reducing harmonic distortion and the need for filters. It is the core device for achieving AC and DC conversion.

[0003] In the MMC structure, the converter valve is composed of many sub-modules (SMs), each of which usually includes power electronic devices (such as IGBT or IGCT) and capacitors. These sub-modules can be dynamically controlled to be turned on and off to form an output voltage waveform with a higher number of levels.

[0004] In flexible DC transmission systems, accurate modeling of MMC valves is crucial for system simulation and analysis. However, traditional detailed modeling methods have large computational complexity and slow simulation speed, making it difficult to meet the needs of large-scale system research. The average-based modeling method simplifies the switching behavior of each submodule and uses the average value to describe its output voltage and current instead of simulating the specific action of each switch, without considering the transient characteristics of the switching device. Therefore, there is an urgent need for an MMC modeling method that can ensure accuracy and significantly improve the calculation speed. Summary of the invention

[0005] Based on this, the present invention provides an MMC equivalent modeling method and device, establishes an equivalent model of MMC, and converts the sub-modules of MMC into different states through external trigger pulses, simplifies the model complexity, and significantly improves the calculation speed.

[0006] The present invention provides an MMC equivalent modeling method, comprising:

[0007] An equivalent model of MMC is established, in which a diode is connected in parallel to the capacitor of each submodule on the MMC valve arm, so that the diode is cut off when the voltage of the capacitor is greater than 0, and the diode is turned on when the voltage of the capacitor is less than 0;

[0008] Receive a trigger pulse input from the outside to the MMC, and determine the equivalent switch state of each submodule according to the trigger pulse;

[0009] The MMC is simulated and calculated based on the equivalent model according to the determined equivalent switch states of each submodule.

[0010] Furthermore, each submodule of the MMC includes a parallel structure consisting of a switch and a diode reversely connected in parallel with the switch. In the equivalent model, the parallel structure is equivalent to a resistor, so that each submodule of the MMC in the equivalent model includes a resistor, a capacitor connected in parallel with the resistor, and a diode connected in parallel with the capacitor.

[0011] Furthermore, the diode connected in parallel to the capacitor in each submodule of the equivalent model is a reverse connection structure.

[0012] Furthermore, when the submodule is a half-bridge structure, the equivalent model of the MMC includes a plurality of submodules connected in series, and a first diode and a second diode connected in parallel to the submodule, the first diode and the second diode are connected in series, and the input current enters the bridge arm of the MMC from the series connection point of the first diode and the second diode.

[0013] Furthermore, when the submodule is equivalent to a locked state, the above equivalent modeling method includes:

[0014] Determine the direction of the bridge arm current;

[0015] The conduction voltage drop of the first diode or the second diode is set according to the direction of the bridge arm current and the number of submodules that are equivalent to the locked state.

[0016] Furthermore, when the submodule is equivalent to the input state, the above equivalent modeling method includes:

[0017] Determine the direction of the bridge arm current to charge or discharge the submodule capacitor in the equivalent model.

[0018] Furthermore, when the submodule is a full-bridge structure, the equivalent model of the MMC includes several submodules connected in series, and a third diode, a fourth diode, a fifth diode and a sixth diode connected in parallel to the submodule. The third diode is connected in series with the fourth diode and connected in parallel on the first side of the submodule. The fifth diode is connected in series with the sixth diode and connected in parallel on the second side of the submodule. The input current enters the bridge arm of the MMC from the series connection point of the third diode and the fourth diode.

[0019] In a second aspect, the present invention provides an MMC equivalent modeling device, comprising:

[0020] A model building module is used to build an equivalent model of the MMC. In the equivalent model, a diode is connected in parallel to the capacitor of each submodule on the MMC valve arm, so that when the voltage of the capacitor is greater than 0, the diode is cut off, and when the voltage of the capacitor is less than 0, the diode is turned on;

[0021] The pulse trigger module is used to receive the trigger pulse input from the outside to the MMC, and determine the equivalent switch state of each submodule according to the trigger pulse;

[0022] The simulation calculation module is used to perform simulation calculation on the MMC according to the determined equivalent switch states of each submodule using an equivalent model.

[0023] In a third aspect, the present invention provides an electronic device, comprising a memory storing computer executable instructions and a processor, wherein when the computer executable instructions are executed by the processor, the device executes each step of the MMC equivalent modeling method provided in the first aspect.

[0024] In a fourth aspect, the present invention provides a readable storage medium storing a computer executable program, which, when executed, can implement the various steps of the MMC equivalent modeling method provided in the first aspect.

[0025] It can be seen from the above technical solutions that the present invention has the following beneficial effects:

[0026] The present invention provides an MMC equivalent modeling method. When establishing an equivalent model, a diode is connected in parallel to the capacitor of a submodule. The diode can be regarded as virtual and does not exist in the actual physical structure. The capacitor voltage is clamped to avoid negative values ​​of the capacitor voltage during a switch simulation process, thereby improving the model stability. The submodule is equivalent to different switch states according to an external trigger pulse, and simulation calculations are performed corresponding to the different switch states. Through this equivalent simplification, the number of components that need to be calculated during simulation modeling is greatly reduced, and the speed of large-scale power system simulation is significantly improved, while taking into account the simulation accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0028] Figure 1 It is the structural diagram of the MMC converter valve;

[0029] Figure 2 It is the topology diagram of the half-bridge submodule;

[0030] Figure 3 It is the topology diagram of the full-bridge submodule;

[0031] Figure 4 It is a flow chart of the MMC equivalent modeling method provided by an embodiment of the present invention;

[0032] Figure 5 It is an equivalent model topology diagram of the MMC submodule provided in an embodiment of the present invention;

[0033] Figure 6 is an equivalent calculation topology diagram of an MMC composed of half-bridge sub-modules provided in an embodiment of the present invention;

[0034] Figure 7 is an equivalent calculation topology diagram of an MMC composed of full-bridge submodules provided in an embodiment of the present invention;

[0035] Figure 8 is a structural diagram of an MMC equivalent modeling device provided in an embodiment of the present invention;

[0036] Fig. 9 This is a diagram of the electronic device architecture provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0037] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0038] See also Figure 1~Figure 3 , which respectively illustrate the typical structure of the MMC converter valve and the internal structure of the sub-module.

[0039] Specific reference Figure 1 The MMC converter valve can be regarded as composed of multiple sub-modules (SM) connected in series. Each sub-module includes power devices and capacitors. These sub-modules can dynamically control the on and off state to form an output voltage waveform with a higher number of levels. Among them, the power device is usually IGBT or IGCT, which is responsible for the switching operation of the current. The capacitor is used to store energy and smooth the output voltage waveform. Each sub-module can provide a voltage unit. Multiple sub-modules are connected in series to form a multi-level output.

[0040] like Figure 2 As shown, it illustrates a submodule topology of a half-bridge structure, including two series-connected IGBTs and a capacitor connected in parallel to the series-connected IGBT structure. By controlling the switching states of the switch tubes T1 and T2, the output voltage of the submodule can be controlled to V C or 0. Figure 3 The topology diagram of a full-bridge submodule is shown, including four IGBTs and a capacitor, where the switch tubes T1 and T2 are connected in series to form a bridge arm, T3 and T4 are connected in series to form a bridge arm, the two bridge arms are connected in parallel, and the capacitor is connected in parallel with the bridge arm structure. Similarly, by controlling the switching state of the switch tubes T1~T4, the output voltage of the submodule can be controlled to V C , 0 or -V C .

[0041] See also Figure 4 An embodiment of the present invention provides an MMC equivalent modeling method, comprising the following steps:

[0042] Step S410: Establish an equivalent model of the MMC, in which a diode is connected in parallel to the capacitor of each submodule on the MMC valve arm, so that the diode is cut off when the capacitor voltage is greater than 0, and the diode is turned on when the capacitor voltage is less than 0.

[0043] Step S420: Receive a trigger pulse input from the outside to the MMC, and determine the equivalent switch state of each submodule according to the trigger pulse.

[0044] Step S430: Perform simulation calculation on the MMC based on the equivalent model according to the determined equivalent switch states of each submodule.

[0045] In a specific embodiment, Figure 5 One of the topological structures of the equivalent model is illustrated. Each submodule of the MMC includes a parallel structure consisting of a switch and a diode reversely connected in parallel with the switch. In the equivalent model, the parallel structure is equivalent to a resistor, so that each submodule of the MMC in the equivalent model includes a resistor, a capacitor connected in parallel with the resistor, and a diode connected in parallel with the capacitor. The diode does not exist in the actual physical structure of the MMC, but is only an equivalent structure when the equivalent model is established.

[0046] The parallel diode in the equivalent model is a reverse connection structure, so that when the capacitor voltage of the submodule is greater than 0, the diode is cut off and does not participate in the calculation. When the capacitor voltage is less than 0, the diode is turned on, forcing the capacitor voltage of the submodule to be clamped at 0.

[0047] In a further embodiment, the trigger pulse can trigger the submodule to the three states of locking, switching on and bypassing, and the submodule is equivalent to the corresponding switch state according to the trigger pulse to perform electromagnetic transient simulation calculation.

[0048] In a further embodiment, when the submodule is a half-bridge structure, the equivalent model of the MMC includes a plurality of submodules connected in series, and a first diode and a second diode connected in parallel to the submodule, the first diode and the second diode are connected in series, and the input current enters the bridge arm of the MMC from the series connection point of the first diode and the second diode.

[0049] In a further embodiment, when the trigger pulse triggers the submodule to enter the locked state, the above equivalent modeling method includes:

[0050] Determine the direction of the bridge arm current;

[0051] The conduction voltage drop of the first diode or the second diode is set according to the direction of the bridge arm current and the number of submodules entering the blocking state in the equivalent model.

[0052] In a further embodiment, when the trigger pulse triggers the submodule to enter the input state, the above equivalent modeling method includes:

[0053] Determine the direction of the bridge arm current to charge or discharge the submodule capacitor in the equivalent model.

[0054] For example, when the bridge arm is a half-bridge submodule, the equivalent calculation of the switching state of the MMC can be simplified as follows: Figure 6 Wherein, submodules SM1 and SM2 indicate submodules in a locked state, SM5 and SM6 indicate submodules in an activated state, and submodules SM3 and SM4 indicate submodules in a bypass state.

[0055] When the submodule is equivalent to the locked state, SM1 and SM2 are connected in series, and diodes D1 and D2 are connected in series and then connected in parallel at both ends of the switch. The input current enters the bridge arm from the series connection point of diodes D1 and D2. When the bridge arm current direction is flowing into the submodule, the submodules SM1 and SM2 on the bridge arm are charged through diode D1, and the conduction voltage drop of diode D1 is set to N times the single diode voltage drop, where N represents the number of submodules equivalent to the locked state in the bridge arm. Conversely, when the bridge arm current direction is flowing out of the submodule, the submodules SM1 and SM2 on the bridge arm are charged through diode D2, and the conduction voltage drop of diode D2 is set to N times the single diode voltage drop, where N represents the number of submodules equivalent to the locked state in the bridge arm.

[0056] When the submodule is equivalent to the input state, such as Figure 6 SM5 and SM6 in the valve arm are connected in series to form a valve arm. When the bridge arm current flows into the submodule, the capacitors of the M submodules in the on-state are directly charged. Conversely, when the bridge arm current flows out of the submodule, the capacitors of the M submodules in the on-state are directly discharged.

[0057] When the submodule is equivalent to the bypass state, the simulation calculation of the submodule is independent of the direction of the bridge arm current, such as Figure 6 In SM3 and SM4, the submodule in bypass state discharges directly through the RC branch, where the RC branch is a branch composed of equivalent resistance and capacitance in the submodule, and the equivalent resistance is obtained by equivalently connecting the IGBT in the original MMC submodule and its reverse-connected parallel diode in parallel.

[0058] In a further embodiment, when the submodule is a full-bridge structure, the equivalent model of the MMC includes several submodules connected in series, and a third diode, a fourth diode, a fifth diode and a sixth diode connected in parallel to the submodules. The third diode is connected in series with the fourth diode and connected in parallel on the first side of the submodule. The fifth diode is connected in series with the sixth diode and connected in parallel on the second side of the submodule. The input current enters the valve arm of the MMC from the series connection point of the third diode and the fourth diode.

[0059] For example, when the submodule is a full-bridge structure, the equivalent calculation of the switching state of the MMC can be simplified as follows: Figure 7 Among them, submodules SM1 and SM6 indicate submodules in the locked state, SM5, SM3 and SM2 indicate submodules in the switched-on state, and submodule SM4 indicates a submodule in the bypass state.

[0060] When the submodule is equivalent to the locked state, SM1 and SM2 are connected in series to form a bridge arm, diodes D1 and D2 are connected in series and then connected in parallel on one side of the bridge arm, and diodes D3 and D4 are connected in series and then connected in parallel on the other side of the bridge arm. The input current enters the bridge arm from the series connection point of diodes D1 and D2. When the direction of the bridge arm current is to flow into the submodule, the submodules SM1 and SM2 on the bridge arm are charged through diodes D1 and D4, and the conduction voltage drop of diodes D1 and D4 is set to N times the single diode voltage drop, where N represents the number of submodules equivalent to the locked state in the bridge arm. Conversely, when the direction of the bridge arm current is to flow out of the submodule, the submodules SM1 and SM2 on the bridge arm are charged through diodes D2 and D3, and the conduction voltage drop of diodes D2 and D3 is set to N times the single diode voltage drop, where N represents the number of submodules equivalent to the locked state in the bridge arm.

[0061] When the submodule is equivalent to the on-state, if the trigger pulse triggers the IGBT corresponding to the diodes D1 and D4, the capacitor voltage of the submodule is on with a positive voltage; if the trigger pulse triggers the IGBT corresponding to the diodes D2 and D3, the capacitor voltage of the submodule is on with a negative voltage; if the trigger pulse triggers the IGBT corresponding to the diodes D1 and D2, or the IGBT corresponding to D3 and D4, the capacitor voltage of the submodule is on with a zero voltage.

[0062] When the submodule is equivalent to the bypass state, the simulation calculation of the submodule is independent of the direction of the bridge arm current, such as Figure 7 In SM4, the submodule in bypass state is discharged directly through the RC branch, where the RC branch is a branch composed of an equivalent resistor and a capacitor in the submodule, and the equivalent resistor is obtained by equivalently connecting the IGBT in the original MMC submodule and its reverse-connected parallel diode in parallel.

[0063] The above disclosed embodiments describe in detail an MMC equivalent modeling method. The above disclosed method can be implemented by various forms of equipment. Therefore, the present invention also discloses a device corresponding to the above method. The following specific embodiments are given for detailed description.

[0064] See also Figure 8 One embodiment of the present invention provides an MMC equivalent modeling device, comprising:

[0065] A model building module 802 is used to build an equivalent model of the MMC, in which a diode is connected in parallel to the capacitor of each submodule on the MMC valve arm, so that when the voltage of the capacitor is greater than 0, the diode is cut off, and when the voltage of the capacitor is less than 0, the diode is turned on;

[0066] The pulse trigger module 804 is used to receive a trigger pulse input from the outside to the MMC, and determine the equivalent switch state of each submodule according to the trigger pulse;

[0067] The simulation calculation module 806 is used to perform simulation calculation on the MMC according to the determined equivalent switch states of each sub-module based on the equivalent model.

[0068] The implementation principle and technical effects of the device provided in the embodiments of the present application are the same as those of the aforementioned method embodiments. For the sake of brief description, for matters not mentioned in the device embodiments, reference may be made to the corresponding contents in the aforementioned method embodiments.

[0069] The methods and related devices mentioned in the above embodiments are described with reference to the method flow charts and / or structural diagrams provided in the embodiments of the present application. Specifically, each process and / or block in the method flow charts and / or structural diagrams, as well as the combination of processes and / or blocks in the flow charts and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the process in the process. Figure 1 A process or multiple processes and / or structures Figure 1 These computer program instructions can also be stored in a computer-readable memory that can guide a computer or other programmable data processing device to work in a specific way, so that the instructions stored in the computer-readable memory produce a product including an instruction device, which implements the functions specified in the process. Figure 1 Schematic diagram of one or more processes and / or structures Figure 1These computer program instructions can also be loaded onto a computer or other programmable data processing device, so that a series of operation steps are executed on the computer or other programmable device to produce a computer-implemented process, so that the instructions executed on the computer or other programmable device provide for implementing the process in the process. Figure 1 A flow or multiple flows and / or structures illustrate the steps of the functions specified in one block or multiple blocks.

[0070] The following embodiments are described by taking the method applied to a computer device as an example. It can be understood that the computer device can be any device with computing and processing functions, and can be but not limited to a server or a personal laptop computer, etc. In one embodiment, the computer device can be an application server, and the application server can be a server for running an application to be tested.

[0071] See also Fig. 9 , shows a hardware block diagram of an electronic device, which is intended to represent various forms of digital computers, such as laptop computers, desktop computers, workstations, personal digital assistants, servers, blade servers, mainframe computers, and other suitable computers. The electronic device may also represent various forms of mobile devices, such as personal digital processing, cellular phones, smart phones, wearable devices, and other similar computing devices. The components shown herein, their connections and relationships, and their functions are merely examples and are not intended to limit the implementation of the present application described and / or required herein.

[0072] like Fig. 9 As shown, the electronic device includes: at least one processor 1, at least one communication interface 2, at least one memory 3 and at least one communication bus 4;

[0073] In the embodiment of the present application, the number of the processor 1, the communication interface 2, the memory 3, and the communication bus 4 is at least one, and the processor 1, the communication interface 2, and the memory 3 communicate with each other through the communication bus 4;

[0074] The processor 1 may be a central processing unit CPU, or an application-specific integrated circuit ASIC (Application Specific Integrated Circuit), or one or more integrated circuits configured to implement the embodiments of the present invention, etc.;

[0075] The memory 3 may include a high-speed RAM memory, and may also include a non-volatile memory (non-volatile memory), etc., such as at least one disk memory;

[0076] The memory stores a program, and the processor can call the program stored in the memory, wherein the program is used to implement each processing flow of the aforementioned MMC equivalent modeling device solution.

[0077] An embodiment of the present invention further provides a readable storage medium having a computer program stored thereon. When the computer program is executed by a processor, the processing flow of the MMC equivalent modeling device solution provided in the above embodiment and / or any possible implementation method in combination with the embodiment is implemented.

[0078] The above-mentioned embodiments have described the present invention in particular detail with respect to possible scenarios, and those skilled in the art will recognize that the present invention can be practiced through other embodiments. The specific naming of components, the capitalization of terms, attributes, data structures, or any other programming or structural aspects are not mandatory or important, and the mechanisms or features of the present invention may have different names, forms, or procedures. The system may be implemented by a combination of hardware and software (as described), entirely by hardware elements, or entirely by software elements. The specific division of functions between the various system components described herein is exemplary only and not mandatory; on the contrary, the functions performed by a single system component may be performed by multiple components, or the functions performed by multiple components may be performed by a single component.

[0079] Those skilled in the art should understand that the various steps of the above disclosed method can be implemented by a general computing device, they can be concentrated on a single computing device, or distributed on a network composed of multiple computing devices, optionally, they can be implemented with program codes executable by the computing device, so that they can be stored in a storage device and executed by the computing device, or they can be made into individual integrated circuit modules, or multiple modules or steps therein can be made into a single integrated circuit module for implementation. Thus, the embodiments of the present invention are not limited to any specific combination of hardware and software.

[0080] These computing device executable programs (also referred to as programs, software, software applications, or code) include machine instructions for programmable processors, and these computing programs can be implemented using high-level procedural and / or object-oriented programming languages, and / or assembly / machine languages. As used herein, the terms "machine-readable medium" and "computer-readable medium" refer to any computer program product, device, and / or device (e.g., disk, optical disk, memory, programmable logic device (PLD)) for providing machine instructions and / or data to a programmable processor, including a machine-readable medium that receives machine instructions as a machine-readable signal. The term "machine-readable signal" refers to any signal for providing machine instructions and / or data to a programmable processor.

[0081] Certain aspects of the present invention include process steps and instructions described herein in the form of algorithms. It should be noted that the process steps and instructions of the present invention can be implemented in software, firmware and / or hardware, and when implemented by software, it can be downloaded, stored on different platforms used by various operating systems and operated from the platforms.

[0082] Those skilled in the art will understand that the structures shown in the accompanying drawings are merely block diagrams of partial structures related to the scheme of the present application, and do not constitute a limitation on the terminal device to which the scheme of the present application is applied. The specific terminal device may include more or fewer components than shown in the figures, or combine certain components, or have a different arrangement of components.

[0083] Some embodiments may be described using "coupled" and "connected" and their derivatives. It should be understood that these terms are not intended to be synonymous with each other. For example, some embodiments may be described using the word "connected" to indicate that two or more elements are in direct physical or electrical contact with each other. In another example, some embodiments may be described using the word "coupled" to indicate that two or more elements are in direct physical or electrical contact with each other. However, the term "coupled" may also mean that two or more elements are not in direct contact with each other, but still cooperate or interact with each other. The embodiments are not limited to this context.

[0084] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "possible design" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0085] Finally, it should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "comprise a ..." do not exclude the presence of other identical elements in the process, method, article or device including the elements.

[0086] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features thereof may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A MMC equivalent modeling method, characterized in that: include: An equivalent model of the MMC is established, in which a diode is connected in parallel to the capacitor of each submodule on the MMC valve arm, so that the diode is cut off when the voltage of the capacitor is greater than 0, and the diode is turned on when the voltage of the capacitor is less than 0; Receive a trigger pulse input from the outside to the MMC, and determine the equivalent switch state of each submodule according to the trigger pulse; Based on the equivalent model, simulation calculation is performed on the MMC according to the determined equivalent switch states of each submodule.

2. The method according to claim 1, characterized in that Each submodule of the MMC includes a parallel structure consisting of a switch and a diode reversely connected in parallel with the switch. In the equivalent model, the parallel structure is equivalent to a resistor, so that each submodule of the MMC in the equivalent model includes a resistor, a capacitor connected in parallel with the resistor, and a diode connected in parallel with the capacitor.

3. The method according to claim 1, characterized in that The diode connected in parallel to the capacitor in each submodule of the equivalent model is a reverse connection structure.

4. The method according to claim 1, characterized in that When the submodule is a half-bridge structure, the equivalent model includes a plurality of submodules connected in series, and a first diode and a second diode connected in parallel to the submodule, the first diode and the second diode are connected in series, and the input current enters the bridge arm of the MMC from the series connection point of the first diode and the second diode.

5. The method according to claim 4, characterized in that When the submodule is equivalent to a locked state, the method further includes: Determine the direction of the bridge arm current; The conduction voltage drop of the first diode or the second diode is set according to the direction of the bridge arm current and the number of submodules that are equivalent to the locked state.

6. The method according to claim 4, characterized in that When the submodule is equivalent to the input state, the method further includes: Determine the direction of the bridge arm current to charge or discharge the submodule capacitor in the equivalent model.

7. The method according to claim 1, characterized in that When the submodule is a full-bridge structure, the equivalent model of the MMC includes a plurality of submodules connected in series, and a third diode, a fourth diode, a fifth diode and a sixth diode connected in parallel to the submodules. The third diode is connected in series with the fourth diode and connected in parallel to the first side of the submodule. The fifth diode is connected in series with the sixth diode and connected in parallel to the second side of the submodule. The input current enters the bridge arm of the MMC from the series connection point of the third diode and the fourth diode.

8. An MMC equivalent modeling device, characterized in that: include: A model building module, used to build an equivalent model of the MMC, in which a diode is connected in parallel to the capacitor of each submodule on the MMC valve arm, so that the diode is cut off when the voltage of the capacitor is greater than 0, and the diode is turned on when the voltage of the capacitor is less than 0; The pulse trigger module is used to receive the trigger pulse input from the outside to the MMC, and determine the equivalent switch state of each submodule according to the trigger pulse; The simulation calculation module is used to perform simulation calculation on the MMC according to the determined equivalent switch states of each submodule based on the equivalent model.

9. An electronic device, characterized in that: The device comprises a memory storing computer executable instructions and a processor, and when the computer executable instructions are executed by the processor, the device executes the MMC equivalent modeling method described in any one of claims 1 to 7.

10. A readable storage medium, characterized in that: A computer executable program is stored, and when the program is executed, the MMC equivalent modeling method described in any one of claims 1 to 7 can be implemented.

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