A method and device for equivalent modeling of MMC

Abstract

The application provides an MMC equivalent modeling method, a diode is connected in parallel with the capacitance of a sub-module when an equivalent model is established, the diode does not exist in the actual physical structure of the MMC, and is only an equivalent mechanism established when modeling, so that the diode is used to clamp the capacitance voltage in the sub-module, the negative value of the capacitance voltage in the simulation process of the switch is avoided, and the model stability is improved; the sub-module is equivalent to different switch states according to external trigger pulses, simulation calculation is carried out corresponding to different switch states, the number of elements that need to be calculated in the simulation modeling is greatly reduced through the equivalent mode, the speed of large-scale power system simulation is significantly improved, and the simulation accuracy is taken into account.

Description

Technical Field

[0001] This invention pertains to simulation analysis technology for flexible DC transmission systems, and particularly relates to an MMC equivalent modeling method and apparatus. Background Technology

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

[0003] In the MMC structure, the converter valve consists of many sub-modules (SMs). Each sub-module typically includes power electronic devices (such as IGBTs or IGCTs) and capacitors. These sub-modules can be dynamically controlled to turn on and off, forming an output voltage waveform with a high level number.

[0004] In flexible DC transmission systems, accurate modeling of MMC valves is crucial for system simulation and analysis. However, traditional detailed modeling methods are computationally intensive and slow, making them unsuitable for large-scale system studies. Average-value-based modeling methods simplify the switching behavior of each submodule, using average values ​​to describe its output voltage and current instead of simulating the specific actions of each switch, thus neglecting the transient characteristics of the switching devices. Therefore, there is an urgent need for an MMC modeling method that can guarantee accuracy while significantly improving computational speed. Summary of the Invention

[0005] Based on this, the present invention provides an equivalent modeling method and apparatus for MMC, which establishes an equivalent model of MMC, and uses external trigger pulses to convert the sub-modules of MMC into different states, thereby simplifying the model complexity and significantly improving the calculation speed.

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

[0007] Establish an equivalent model of MMC. In the equivalent model, a diode is connected in parallel with the capacitor of each sub-module 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 trigger pulses input from the outside to the MMC, and determine the equivalent switching state of each submodule based on the trigger pulses;

[0009] Based on the equivalent model, the MMC is simulated and calculated according to the equivalent switching states of each sub-module.

[0010] Furthermore, each submodule of the MMC includes a parallel structure consisting of a switch and a diode connected in reverse parallel to the switch. In the equivalent model, the parallel structure is equivalent to a resistor, such 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, in the equivalent model, the diodes connected in parallel with the capacitor in each sub-module are in reverse connection.

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

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

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

[0015] The forward voltage drop of the first or 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 engaged state, the above equivalent modeling method includes:

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

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

[0019] Secondly, the present invention provides an MMC equivalent modeling apparatus, comprising:

[0020] The model building module is used to build an equivalent model of MMC. In the equivalent model, a diode is connected in parallel with the capacitor of each sub-module 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.

[0021] The pulse trigger module is used to receive trigger pulses input from the outside to the MMC and determine the equivalent switching state of each sub-module based on the trigger pulses;

[0022] The simulation calculation module is used to perform simulation calculations on the MMC based on the equivalent switching states of each sub-module using an equivalent model.

[0023] Thirdly, the present invention provides an electronic device including a memory storing computer-executable instructions and a processor, wherein when the computer-executable instructions are executed by the processor, the device performs the steps of the MMC equivalent modeling method provided in the first aspect.

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

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

[0026] This invention provides an equivalent modeling method for MMC (Multi-Module Control). When establishing the equivalent model, a diode is connected in parallel with the capacitor of the submodule. This diode can be regarded as virtual and does not exist in the actual physical structure. This clamps the capacitor voltage, preventing the capacitor voltage from becoming negative during the switching simulation and improving the model stability. Based on the external trigger pulse, the submodule is equivalent to different switching states, and simulation calculations are performed for different switching states. This equivalent simplification significantly reduces the number of components that need to be calculated during simulation modeling, significantly improving the speed of large-scale power system simulation while maintaining simulation accuracy. Attached Figure Description

[0027] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0028] Figure 1 This is a structural diagram of an MMC converter valve;

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

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

[0031] Figure 4 This is a flowchart illustrating the implementation of the MMC equivalent modeling method provided in this embodiment of the invention.

[0032] Figure 5 This is the equivalent model topology diagram of the MMC submodule provided in the embodiments of the present invention;

[0033] Figure 6 This is an equivalent computational topology diagram of an MMC composed of half-bridge submodules provided in an embodiment of the present invention;

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

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

[0036] Figure 9 This is an electronic device architecture diagram provided for an embodiment of the present invention. Detailed Implementation

[0037] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0038] See Figures 1-3 The diagrams illustrate the typical structure of the MMC converter valve and the internal structure of its sub-modules.

[0039] For details, please refer to [link / reference]. Figure 1 The MMC converter valve can be viewed as being composed of multiple sub-modules (SMs) connected in series. Each sub-module includes power devices and capacitors. These sub-modules can be dynamically controlled to turn on and off, forming an output voltage waveform with a high number of levels. The power devices commonly used are IGBTs or IGCTs, which are responsible for the switching operation of the current. The capacitors are used for energy storage and smoothing the output voltage waveform. Each sub-module can provide a voltage unit. Multiple sub-modules connected in series form a multi-level output.

[0040] like Figure 2 The diagram illustrates a submodule topology with a half-bridge structure, including two IGBTs connected in series and a capacitor connected in parallel across the series IGBTs. The output voltage of the submodule can be controlled to V by controlling the switching states of transistors T1 and T2. C Or 0. Figure 3 This diagram illustrates a submodule topology with a full-bridge structure, including four IGBTs and one capacitor. Switches T1 and T2 are connected in series to form one bridge arm, and T3 and T4 are connected in series to form another bridge arm. These two bridge arms are connected in parallel, and the capacitor is connected in parallel with the bridge arm structure. Similarly, by controlling the switching states of switches T1-T4, the output voltage of the submodule can be controlled to V. C 0 or -V C .

[0041] See 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 MMC. In the equivalent model, a diode is connected in parallel with the capacitor of each sub-module 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.

[0043] Step S420. Receive the trigger pulse input from the outside to the MMC, and determine the equivalent switching state of each submodule based on the trigger pulse.

[0044] Step S430. Based on the equivalent model, perform simulation calculations on the MMC according to the determined equivalent switching states of each sub-module.

[0045] In a specific embodiment, Figure 5 This diagram illustrates one possible topology of the equivalent model. Each submodule of the MMC includes a parallel structure consisting of a switch and a diode connected in reverse parallel to the switch. In the equivalent model, this parallel structure is represented as a resistor, such 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. This diode does not exist in the actual physical structure of the MMC; it is only an equivalent structure used to establish the equivalent model.

[0046] In the equivalent model, the parallel diodes are reverse-connected, so that when the capacitor voltage of the submodule is greater than 0, the diodes are cut off and do not participate in the calculation, and when the capacitor voltage is less than 0, the diodes are turned on, forcibly clamping the capacitor voltage of the submodule to 0.

[0047] In a further embodiment, the trigger pulse can trigger the submodule to three states: locked, engaged, and bypassed. After the submodule is equivalent to the corresponding switch state based on the trigger pulse, electromagnetic transient simulation calculations are performed.

[0048] In a further embodiment, when the submodule is a half-bridge structure, the equivalent model of the MMC includes several submodules connected in series, and a first diode and a second diode connected in parallel on 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 trigger submodule enters the latching state, the above equivalent modeling method includes:

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

[0051] The forward voltage drop of the first or second diode is set according to the direction of the bridge arm current and the number of sub-modules entering the lockout state in the equivalent model.

[0052] In a further embodiment, when the trigger pulse trigger submodule enters the activated state, the above equivalent modeling method includes:

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

[0054] For example, when the bridge arm is a half-bridge submodule, the equivalent calculation of the MMC's switching state can be simplified as follows: Figure 6 As shown. Submodules SM1 and SM2 represent submodules in the locked state, SM5 and SM6 represent submodules in the engaged state, and submodules SM3 and SM4 represent submodules in the bypass state.

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

[0056] When a submodule is equivalent to being in an engaged state, such as Figure 6 SM5 and SM6 in the bridge arm are connected in series to form a valve arm. When the current direction of the bridge arm is flowing into the submodule, it directly charges the capacitors of the M submodules in the active state. Conversely, when the current direction of the bridge arm is flowing out of the submodule, it directly discharges the capacitors of the M submodules in the active state.

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

[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 on the submodule. The third diode and the fourth diode are connected in series and then in parallel on the first side of the submodule, and the fifth diode and the sixth diode are connected in series and then 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 As shown. Submodules SM1 and SM6 represent submodules in the locked state, SM5, SM3 and SM2 represent submodules in the engaged state, and submodule SM4 represents submodules in the bypass state.

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

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

[0062] When the submodule is equivalent to a bypass state, the simulation calculation of the submodule is independent of the direction of the bridge arm current, such as... Figure 7 In the SM4 submodule, the bypass state submodule discharges directly through the RC branch, where the RC branch is a branch in the submodule consisting of equivalent resistance and capacitance. The equivalent resistance is obtained by equivalence between the parallel structure of the IGBT and its reverse-connected parallel diode in the original MMC submodule.

[0063] The above-disclosed embodiments describe in detail an MMC equivalent modeling method. The disclosed method can be implemented using various types of devices. Therefore, the present invention also discloses an apparatus corresponding to the above method. Specific embodiments are given below for detailed description.

[0064] See Figure 8 An embodiment of the present invention provides an MMC equivalent modeling apparatus, comprising:

[0065] Model building module 802 is used to build an equivalent model of MMC. In the equivalent model, a diode is connected in parallel with the capacitor of each sub-module 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.

[0066] The pulse trigger module 804 is used to receive trigger pulses input from the outside to the MMC and determine the equivalent switching state of each sub-module based on the trigger pulses;

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

[0068] The device provided in this application embodiment has the same implementation principle and technical effect as the aforementioned method embodiment. For the sake of brevity, any parts not mentioned in the device embodiment can be referred to the corresponding content in the aforementioned method embodiment.

[0069] The methods and related apparatuses mentioned in the above embodiments are described with reference to the method flowcharts and / or structural diagrams provided in the embodiments of this application. Specifically, each block of the method flowchart and / or structural diagram, as well as combinations of blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing device to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing device, generate instructions for implementing the process. Figure 1 A schematic diagram of one or more processes and / or structures. Figure 1 The computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to operate in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 A schematic diagram of one or more processes and / or structures. Figure 1The functions specified in one or more boxes. These computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable apparatus for implementing the process. Figure 1 A process or multiple processes and / or structures illustrate the steps of the functions specified in one or more boxes.

[0070] The following embodiments illustrate the application of this method to a computer device. It is understood that the computer device can be any device with computing and processing capabilities, including but not limited to servers or personal laptops. In one embodiment, the computer device can be an application server, which can be a server used to run the application under test.

[0071] See Figure 9 This document illustrates a hardware block diagram of an electronic device intended to represent various forms of digital computers, such as laptops, desktop computers, workstations, personal digital assistants, servers, blade servers, mainframes, and other suitable computers. The electronic device may also represent various forms of mobile devices, such as personal digital processors, cellular phones, smartphones, wearable devices, and other similar computing devices. The components shown herein, their connections and relationships, and their functions are merely illustrative and are not intended to limit the implementation of the present application described and / or claimed herein.

[0072] like Figure 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 this embodiment of the application, the number of processor 1, communication interface 2, memory 3, and communication bus 4 is at least one, and processor 1, communication interface 2, and memory 3 communicate with each other through communication bus 4;

[0074] Processor 1 may be a central processing unit (CPU), an application-specific integrated circuit (ASIC), or one or more integrated circuits configured to implement embodiments of the present invention.

[0075] Memory 3 may include high-speed RAM, and may also include non-volatile memory, such as at least one disk storage device;

[0076] The memory stores a program, which the processor can call. The program is used to implement the various processing flows of the aforementioned MMC equivalent modeling device scheme.

[0077] This invention also provides a readable storage medium storing a computer program thereon. When the computer program is executed by a processor, it implements various processing flows of the MMC equivalent modeling apparatus solution provided in any possible implementation of the above embodiments and / or in combination with the embodiments.

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

[0079] Those skilled in the art should understand that the various steps of the disclosed methods can be implemented using general-purpose computing devices. They can be centralized on a single computing device or distributed across a network of multiple computing devices. Optionally, they can be implemented using device-executable program code, which can then be stored in a storage device for execution by the computing device. Alternatively, they can be fabricated as separate integrated circuit modules, or multiple modules or steps can be fabricated as a single integrated circuit module. Therefore, the embodiments disclosed in this invention are not limited to any specific hardware and software combination.

[0080] The programs (also referred to as programs, software, software applications, or code) executable by these computing devices include machine instructions of a programmable processor and 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 apparatus (e.g., disk, optical disk, memory, programmable logic device (PLD)) used to provide machine instructions and / or data to a programmable processor, including machine-readable media that receive machine instructions as machine-readable signals. The term “machine-readable signal” refers to any signal used to provide machine instructions and / or data to a programmable processor.

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

[0082] Those skilled in the art will understand that the structures shown in the figures are merely block diagrams of some structures related to the present application and do not constitute a limitation on the terminal device to which the present application is applied. Specific terminal devices may include more or fewer components than those shown in the figures, or combine certain components, or have different component arrangements.

[0083] Some embodiments may be described using the terms "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 term "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 term "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. Embodiments are not limited to this context.

[0084] In the description of this specification, the use of terms such as "one embodiment," "some embodiments," "example," "specific example," or "possible design," etc., refers to a specific feature, structure, material, or characteristic described in connection with that embodiment or example, which is included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in a suitable manner in any one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0085] Finally, it should be noted that in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0086] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. An MMC equivalent modeling method, characterized in that, include: An equivalent model of MMC is established. In the equivalent model, the equivalent structure of each sub-module on the MMC valve arm includes a capacitor and a resistor connected in parallel, and a diode connected in reverse parallel to the capacitor. The diode is only used as an equivalent unit in the equivalent structure of the sub-module and does not exist in the actual physical structure of the MMC. Receive external trigger pulses input to the MMC, and convert the switching state of the equivalent structure of the submodule into one of lockout, engagement, or bypass based on the trigger pulses; Based on the equivalent model, the MMC is simulated and calculated according to the determined equivalent switching states of each sub-module, specifically including: When the equivalent switch state of the submodule equivalent structure is locked, a series branch including diodes is connected in parallel at both ends of the submodule equivalent structure, so that the current flows from the connection point of the series branch through the bridge arm where the submodule equivalent structure is located. The forward voltage drop of the diodes in the series branch is set according to the direction of the bridge arm current and the number of submodule equivalent structures in the locked state. When the equivalent switch state of the submodule equivalent structure is in the ON position, the capacitor in the submodule equivalent structure is charged or discharged according to the current direction of the bridge arm where the submodule equivalent structure is in the ON position. When the equivalent switching state of the submodule equivalent structure is bypass, the submodule equivalent structure in the bypass state is discharged through the RC branch. The RC branch is the parallel branch of the capacitor and the equivalent resistance in the actual physical structure of the submodule. The equivalent resistance is obtained by equivalently converting the parallel structure of the IGBT and its reverse-connected parallel diode in the original MMC submodule.

2. The method according to claim 1, characterized in that, When the submodule is a half-bridge structure, the bridge arm in the equivalent model includes several submodule equivalent structures connected in series. The series branches are connected in parallel at both ends of the bridge arm, including a first diode and a second diode. The first diode and the second diode are connected in series, and the current enters the bridge arm of the MMC from the series connection point of the first diode and the second diode.

3. The method according to claim 2, characterized in that, When the equivalent switching state of the submodule equivalent structure is locked, setting the forward voltage drop of the diodes in the series branch according to the bridge arm current direction and the number of submodule equivalent structures in the locked state includes: Determine the direction of the current in the bridge arm; The conducting diode in the first and second diodes is determined based on the direction of the bridge arm current. The forward voltage drop of the conducting diode is set to N times the voltage drop of a single diode, where N is the number of equivalent structures of the sub-modules in the bridge arm that are in a locked state.

4. The method according to claim 1, characterized in that, When the equivalent switch state of the submodule equivalent structure is "on", charging or discharging the capacitor in the submodule equivalent structure according to the current direction of the bridge arm where the submodule equivalent structure is in the "on" state includes: When the bridge arm current flows into the equivalent structure of the submodule, the capacitor in the equivalent structure of the submodule in the active state is charged; when the bridge arm current flows out of the equivalent structure of the submodule, the capacitor in the equivalent structure of the submodule in the active state is discharged.

5. The method according to claim 1, characterized in that, When the submodule is a full-bridge structure, the equivalent model of MMC includes several submodule equivalent structures connected in series, as well as a third diode, a fourth diode, a fifth diode, and a sixth diode connected in parallel on the submodule equivalent structure. The third diode and the fourth diode are connected in series and then in parallel on the first side of the submodule equivalent structure, and the fifth diode and the sixth diode are connected in series and then in parallel on the second side of the submodule equivalent structure. The current enters the bridge arm of MMC from the series connection point of the third diode and the fourth diode.

6. An MMC equivalent modeling device, characterized in that, include: The model building module is used to build an equivalent model of MMC. In the equivalent model, the equivalent structure of each sub-module on the MMC valve arm includes a capacitor and a resistor connected in parallel, and a diode connected in reverse parallel to the capacitor. The diode is only used as an equivalent unit in the equivalent structure of the sub-module and does not exist in the actual physical structure of the MMC. The pulse trigger module is used to receive trigger pulses input to the MMC from the outside, and to convert the switching state of the equivalent structure of the submodule into one of the following: locked, engaged, or bypassed, based on the trigger pulses. The simulation calculation module is used to perform simulation calculations on the MMC based on the equivalent model and the determined equivalent switching states of each sub-module, specifically including: When the equivalent switch state of the submodule equivalent structure is locked, a series branch including diodes is connected in parallel at both ends of the submodule equivalent structure, so that the current flows from the connection point of the series branch through the bridge arm where the submodule equivalent structure is located. The forward voltage drop of the diodes in the series branch is set according to the direction of the bridge arm current and the number of submodule equivalent structures in the locked state. When the equivalent switch state of the submodule equivalent structure is in the ON position, the capacitor in the submodule equivalent structure is charged or discharged according to the current direction of the bridge arm where the submodule equivalent structure is in the ON position. When the equivalent switching state of the submodule equivalent structure is bypass, the submodule equivalent structure in the bypass state is discharged through the RC branch. The RC branch is the parallel branch of the capacitor and the equivalent resistance in the actual physical structure of the submodule. The equivalent resistance is obtained by equivalently converting the parallel structure of the IGBT and its reverse-connected parallel diode in the original MMC submodule.

7. An electronic device, characterized in that, It includes a memory storing computer-executable instructions and a processor, which, when executed by the processor, causes the device to perform the MMC equivalent modeling method according to any one of claims 1 to 5.

8. A readable storage medium, characterized in that, It contains a computer-executable program that, when executed, implements the MMC equivalent modeling method according to any one of claims 1 to 5.

Images