Modularized multilevel converter electromagnetic transient simulation method, device, medium and product

Abstract

The invention discloses a modular multilevel converter electromagnetic transient simulation method and device, a medium and a product, and relates to the technical field of modular multilevel converters, and the method comprises the steps: obtaining a working mode of a modular multilevel converter at a current moment; constructing sub-models corresponding to a plurality of sub-modules in the modular multilevel converter based on the working mode; connecting the sub-models corresponding to all the sub-modules in the same bridge arm in series to obtain a plurality of single-bridge-arm equivalent circuits; building a modular multilevel converter model based on the plurality of single-bridge-arm equivalent circuits; and the switching states of all the sub-modules in the modular multilevel converter at the current moment are input into the modular multilevel converter model, and a simulation result is obtained. According to the invention, the corresponding sub-models are constructed for each sub-module in the modular multilevel converter; the efficiency and precision of electromagnetic transient simulation of the multilevel converter can be improved.

Description

Technical Field

[0001] The present application relates to the technical field of modular multilevel converters, and in particular to a modular multilevel converter electromagnetic transient simulation method, device, medium and product. Background Art

[0002] China's power system is undergoing profound changes, and the electromagnetic transient characteristics of the power system will become increasingly complex. By accurately modeling the relevant components of the power system and conducting detailed and rapid electromagnetic transient simulation analysis, the dynamic characteristics of the power system can be accurately grasped, providing important help for the planning, design, construction, development and operation practice of the power system. With the continuous expansion of the scale of China's AC and DC power grids, the requirements for the rapidity and accuracy of electromagnetic transient simulation are constantly increasing. The electromagnetic transient simulation of new power systems faces the following difficulties: 1) Large system scale. The existing electromagnetic transient simulation numerical algorithms, whether using the state space method or the node voltage method, finally need to solve the linear algebraic equations simultaneously. The amount of calculation is usually in a cubic relationship with the order of the equations. Therefore, the simulation speed will drop sharply as the system scale increases and become unacceptable. At present, China's AC and DC hybrid power grid is large in scale, with many devices, and the total number of simulation nodes is close to 30,000. Taking the Zhangbei Flexible DC Project as an example, each bridge arm of the MMC uses 264 submodules in series (including 20 redundant submodules). The four-terminal bipolar MMC alone contains a total of 12,672 half-bridge submodules. In addition to the transmission lines, control and peripheral large-scale new energy sites, AC power grids, and various loads, its mathematical model will be an ultra-high-order linear algebraic equation group. In the face of electromagnetic transient simulation of such a large-scale flexible DC system, if only the existing numerical methods are used, the efficiency of solving the ultra-high-order linear algebraic equation group will be extremely low. 2) Complex equipment characteristics. With the research and in-depth analysis of various linear and nonlinear models such as converters, new energy sites, complex control systems, and information-physical systems, when researchers use electromagnetic transient simulation as a tool for research, the research objects and purposes are also complex and diverse, and power electronic devices with more complex characteristics have emerged. These power electronic devices have different performances, frequent switching actions, time-varying and nonlinear characteristics, and the computational efficiency of their models is directly related to the electromagnetic transient simulation speed of the entire network. Therefore, it is necessary to study the modeling theory or method of power electronic devices with high computational efficiency. 3) More diverse topologies. With the in-depth study of energy transfer, in order to meet multi-directional flow, power electronic equipment often needs to adopt multi-level and / or multi-port structures. Often, the ports and conversion levels are linked in series or parallel, and the electrical and magnetic coupling between each port and each conversion level is tight, and the equipment topology is more complex and diverse. Therefore, a general modeling method that can unify different topological structures is needed. Electromagnetic transient simulation must be both accurate and fast. However, the changes in the above three aspects make the contradiction between the accuracy and speed of voltage source converter simulation more prominent. The existing methods are difficult to apply, and it is urgent to improve or propose new methods.

[0003] In response to different practical needs, there are different electromagnetic transient simulation models for MMC converters, which are divided into detailed models, switch function models and efficient models based on multi-port equivalents. Different models have different accuracy, calculation speed and application scenarios. (1) Detailed model. Due to the consideration of the transient behavior of semiconductor switches, the detailed model needs to solve a large number of electrical nodes, and also requires an algorithm to quickly solve nonlinear switching events. In addition, the calculation method is required to have the ability to solve "rigid" differential equations. The overall calculation time is still very long. It is mainly used to verify other simplified equivalent models and is not suitable for simulation modeling of large-scale power systems. (2) Dynamic phasor model. In theory, when a sufficient number of orders are taken into account, the dynamic phasor method can approach the accuracy of the detailed model. However, in actual application, as the scale of the system increases, the number of equations increases and the calculation speed decreases due to the hardware capabilities of the computing platform. (3) Multi-port equivalent model. The multi-port Thevenin equivalent is performed on the MMC converter, and the equivalent port circuit is simulated together with the entire circuit. After the entire system simulation is completed, the electrical quantities inside the converter are solved using the information of the converter port after solution. The matrix inversion operation in the forward and inverse solution process of the Thevenin equivalent model limits its solution efficiency. In summary, the shortcomings of the existing technology are mainly: in the context of large-scale power grids, there is a contradiction between accuracy and computational efficiency in the electromagnetic transient simulation of modular multilevel converters.

[0004] The existing MMC converter electromagnetic transient offline simulation speed-up models all strive to achieve a compromise between simulation accuracy and simulation efficiency. The existing MMC converter models can be roughly divided into three categories: (1) Average value model: The average value model also assumes that the capacitor voltages of the submodules are the same. According to the power balance on the AC and DC sides, the AC side uses 6 controlled voltage sources to make them equal, and the DC side uses controlled current sources and virtual capacitors in parallel to make them equal, thereby achieving electrical decoupling of the AC and DC sides, and the AC and DC sides exchange information through the control system. Since the internal circuit of the submodule does not need to be calculated, the average value model has a fast calculation speed, but it cannot simulate the charging and discharging characteristics and circulating current phenomena of the submodule, nor can it take into account the switching loss. Therefore, the simulation accuracy is low and the scope of application in scenarios such as startup, lockout and fault is limited. (2) Dynamic phasor model: The dynamic phasor method uses a phasor with a slow frequency change to represent a signal with a fast frequency change through Fourier transform, thereby increasing the simulation step size and improving the simulation efficiency. Some scholars have improved the dynamic phasor method and proposed a broadband time scale transformation method and a multi-time scale transformation method to improve the simulation efficiency. However, in the simulation of new power systems, due to the large scale of the power grid, a large amount of computing resources will be occupied. In order to ensure the speed of simulation, only the fundamental wave and a few harmonics can be considered, which reduces the simulation accuracy and causes problems of harmonic truncation error and spectrum leakage. (3) Multi-port equivalent model: The process of equalizing the external ports of the converter at the system level and solving the port characteristics of the entire system, as well as the process of inversely solving its internal characteristics at the device level, all involve matrix operations. A large number of matrix operations will reduce the solution efficiency, especially when the system is complex, the simulation efficiency is even lower. In addition, this method also forms the node admittance matrix through matrix operations, and cannot use the physical nature of the circuit to simplify and speed up the process. Summary of the invention

[0005] The purpose of this application is to provide a modular multilevel converter electromagnetic transient simulation method, device, medium and product, which can improve the efficiency and accuracy of multilevel converter electromagnetic transient simulation.

[0006] To achieve the above objectives, this application provides the following solutions:

[0007] In a first aspect, the present application provides a modular multilevel converter electromagnetic transient simulation method, comprising:

[0008] Obtaining the working mode of the modular multilevel converter at the current moment;

[0009] Constructing sub-models corresponding to a plurality of sub-modules in a modular multi-level converter based on the working mode;

[0010] Connect the sub-models corresponding to all sub-modules in the same bridge arm in series to obtain multiple single bridge arm equivalent circuits;

[0011] Build a modular multilevel converter model based on multiple single-bridge equivalent circuits;

[0012] The switch states of all submodules in the modular multilevel converter at the current moment are input into the modular multilevel converter model to obtain simulation results.

[0013] Optionally, after inputting the switch states of all submodules in the modular multilevel converter at the current moment into the modular multilevel converter model to obtain the simulation result, the method further includes:

[0014] Determine whether the simulation is finished based on the simulation result;

[0015] If not, update the current time and return to the step of "obtaining the working mode of the modular multilevel converter at the current time";

[0016] If so, the power system planning is completed based on the dynamic characteristics of the power system reflected by the simulation results.

[0017] Optionally, before obtaining the working mode of the modular multilevel converter at the current moment, the method further includes:

[0018] Initialize the current time t=0.

[0019] Optionally, the working mode includes a first working mode and a second working mode; the first working mode is a high impedance state or an internal fault when locked; the second working mode is normal or forward and reverse charging when locked.

[0020] Optionally, constructing sub-models corresponding to a plurality of sub-modules in a modular multi-level converter based on the working mode includes:

[0021] Acquiring modeling data based on the working mode;

[0022] Determine any submodule in the modular multilevel converter as a current submodule;

[0023] Based on the modeling data, determining a binary resistance equivalent circuit of the current submodule;

[0024] Discretize the binary resistance equivalent circuit of the current submodule to obtain the discretized Norton equivalent circuit:

[0025] According to the discretized Norton equivalent circuit, the switch function equivalent circuit is determined as the sub-model corresponding to the current sub-module using the general modeling principle.

[0026] Optionally, acquiring modeling data based on the working mode includes:

[0027] When the working mode is the first working mode, determining the equivalent resistance as modeling data;

[0028] When the working mode is the second working mode, the working state table of the modular multilevel converter at the current moment is determined as the modeling data.

[0029] Optionally, the single bridge arm equivalent circuit is:

[0030]

[0031] Among them, R inSMs is the equivalent resistance of the equivalent circuit of the switch function corresponding to all sub-modules in a single bridge arm connected in series, k is the serial number of the sub-module in a single bridge arm, N is the total number of sub-modules in a single bridge arm, R inSM，k is the equivalent resistance of the switch function equivalent circuit corresponding to the kth submodule in a single bridge arm, U eqs is the equivalent voltage source of the equivalent circuit of the switch function corresponding to all sub-modules in a single bridge arm connected in series, U eq，k is the equivalent voltage source of the switch function equivalent circuit corresponding to the k sub-modules in a single bridge arm, J eq，k is the equivalent voltage source of the switch function equivalent circuit corresponding to the k sub-modules in a single bridge arm, i arm is the bridge arm current, S k is the switching function of the kth submodule in a single bridge arm, R eqPN，k is the equivalent resistance between the P port and the N port of the switch function equivalent circuit corresponding to the kth submodule in the single bridge arm, R 1，k is the equivalent resistance of the first switch group in the binary resistance equivalent circuit corresponding to the kth submodule in a single bridge arm, R 2，k It is the equivalent resistance of the second switch group in the binary resistance equivalent circuit corresponding to the kth submodule in the single bridge arm.

[0032] In a second aspect, the present application provides a computer device, comprising: a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the computer program to implement the above-mentioned modular multilevel converter electromagnetic transient simulation method.

[0033] In a third aspect, the present application provides a computer-readable storage medium having a computer program stored thereon, which implements the above-mentioned modular multilevel converter electromagnetic transient simulation method when executed by a processor.

[0034] In a fourth aspect, the present application provides a computer program product, including a computer program, which implements the above-mentioned modular multilevel converter electromagnetic transient simulation method when executed by a processor.

[0035] According to the specific embodiments provided in this application, this application discloses the following technical effects:

[0036] The present application provides a modular multi-level converter electromagnetic transient simulation method, equipment, medium and product, which performs equivalent operation on the sub-module circuit of the original MMC converter to obtain a switch function equivalent circuit, forms a number of separately represented sub-module equivalent circuits, and then connects the sub-module equivalent circuits in series to form the entire bridge arm. The switch function is defined, which is essentially a physical expression composed of a binary resistance model of the bridge arm switch, so it can more accurately and universally describe the action state of the switch device, and provide a theoretical basis for the efficient calculation of related elements in the subsequent equivalent model; the parameters are simplified by the MMC converter switch table: the corresponding switch state table is obtained by the corresponding switch combination of the converter under normal working conditions and the selected trapezoidal integration method, and the relevant elements of the equivalent model can be directly modified and calculated according to the switch state table, with high calculation efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0038] Figure 1 This is a flow chart of a modular multilevel converter electromagnetic transient simulation method in one embodiment of the present application.

[0039] Figure 2 This is a topological diagram of the MMC main circuit in one embodiment of the present application.

[0040] Figure 3 This is a structural diagram of a half-bridge circuit in one embodiment of the present application.

[0041] Figure 4 This is a submodule diagram of a half-bridge circuit in one embodiment of the present application.

[0042] Figure 5 This is a diagram of the superposition theorem in one embodiment of the present application.

[0043] Figure 6 This is a discretized Norton equivalent circuit diagram in one embodiment of the present application.

[0044] Figure 7 1 is an equivalent circuit diagram of a switching function in an embodiment of the present application.

[0045] Figure 8 This is a bridge arm decoupling circuit diagram in one embodiment of the present application.

[0046] Fig. 9 It is a structural schematic diagram of a computer device in one embodiment of the present application. DETAILED DESCRIPTION

[0047] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0048] In order to make the above-mentioned objects, features and advantages of the present application more obvious and easy to understand, the present application is further described in detail below with reference to the accompanying drawings and specific implementation methods.

[0049] In an exemplary embodiment, Figure 1 As shown, a modular multilevel converter electromagnetic transient simulation method is provided, comprising:

[0050] Step 101: Obtain the current working mode of the modular multilevel converter. The working mode includes a first working mode and a second working mode. The first working mode is a high impedance state or an internal fault when locked. The second working mode is normal or forward and reverse charging when locked.

[0051] Step 102: construct sub-models corresponding to multiple sub-modules in the modular multi-level converter based on the working mode.

[0052] Step 103: connect the sub-models corresponding to all the sub-modules in the same bridge arm in series to obtain multiple single bridge arm equivalent circuits.

[0053] Step 104: Building a modular multilevel converter model based on multiple single-bridge arm equivalent circuits.

[0054] Step 105: input the switch states of all submodules in the modular multilevel converter at the current moment into the modular multilevel converter model to obtain simulation results.

[0055] Step 106: Determine whether the simulation is finished based on the simulation results. If not, update the current time and return to step 101. If yes, complete the power system planning based on the dynamic characteristics of the power system reflected by the simulation results. The basis for the end of the simulation is that the calculation time is greater than the simulation time.

[0056] Before step 101, the method further includes: initializing the current time t=0.

[0057] Step 102 includes:

[0058] Step 102 - 1 : Acquire modeling data based on the working mode.

[0059] Step 102 - 2 : Determine any submodule in the modular multilevel converter as the current submodule.

[0060] Step 102 - 3 : Based on the modeling data, determine the binary resistance equivalent circuit of the current submodule.

[0061] Step 102 - 4 : discretize the binary resistance equivalent circuit of the current submodule to obtain a discretized Norton equivalent circuit.

[0062] Step 102-5: According to the discretized Norton equivalent circuit, the switching function equivalent circuit is determined to be the sub-model corresponding to the current sub-module using the general modeling principle.

[0063] Step 102-1 includes: when the working mode is the first working mode, determining the equivalent resistance as modeling data. When the working mode is the second working mode, determining the current modular multilevel converter working state table as modeling data.

[0064] Among them, the equivalent circuit of a single bridge arm is:

[0065]

[0066] Among them, R inSMs is the equivalent resistance of the equivalent circuit of the switch function corresponding to all sub-modules in a single bridge arm connected in series, k is the serial number of the sub-module in a single bridge arm, N is the total number of sub-modules in a single bridge arm, R inSM，k is the equivalent resistance of the switch function equivalent circuit corresponding to the kth submodule in a single bridge arm, U eqs is the equivalent voltage source of the equivalent circuit of the switch function corresponding to all sub-modules in a single bridge arm connected in series, U eq，k is the equivalent voltage source of the switch function equivalent circuit corresponding to the k sub-modules in a single bridge arm, J eq，k is the equivalent voltage source of the switch function equivalent circuit corresponding to the k sub-modules in a single bridge arm, i arm is the bridge arm current, S k is the switching function of the kth submodule in a single bridge arm, R eqPN，k is the equivalent resistance between the P port and the N port of the switch function equivalent circuit corresponding to the kth submodule in the single bridge arm, R 1，k is the equivalent resistance of the first switch group in the binary resistance equivalent circuit corresponding to the kth submodule in a single bridge arm, R 2，k It is the equivalent resistance of the second switch group in the binary resistance equivalent circuit corresponding to the kth submodule in the single bridge arm.

[0067] With the continuous advancement of the construction of new power systems, the number of new energy stations is increasing, and a large number of voltage source converters will appear, which brings new challenges to the electromagnetic transient simulation of new power systems. Some existing voltage source converter models, such as detailed models, have high accuracy, but large calculation volume, slow simulation speed, and low efficiency, which are obviously not suitable for the analysis of large systems. In order to solve the problem of fast modeling and efficient solution of multi-port Norton equivalent of converters, in another embodiment, a modular multi-level converter electromagnetic transient simulation method is provided.

[0068] MMC (modular multilevel converter) main circuit topology Figure 2 As shown. Point O represents the zero potential reference point, L arm is the bridge arm reactor, each bridge arm has N submodules connected in series, and C is the submodule capacitance. rj Indicates the total output voltage of the bridge arm composed of all sub-modules of the same bridge arm, i pj and i nj are the upper and lower bridge arm currents respectively (r=p, n, representing the upper and lower bridge arms respectively; j=a, b, c, representing the three phases abc.). V j and i j are the three-phase output voltage and output current of the MMC AC side, U dc is a DC voltage.

[0069] In the MMC main circuit topology, each bridge arm is connected in series with N sub-modules. Each sub-module has different types of circuit results. The half-bridge circuit structure is taken as an example. Figure 3 shown. Figure 3 Part (a) is a single-port submodule. Figure 3 Part (b) is a half-bridge circuit structure, T1 and T2 represent IGBTs of the half-bridge circuit switch group, and D1 and D2 represent diodes of the half-bridge circuit switch group.

[0070] Step 1: Form a binary resistor equivalent circuit.

[0071] Analyze the half-bridge submodule, u c is the capacitor voltage, i arm is the bridge arm current, which is equivalent to the submodule injection current, u sm is the submodule port voltage. Figure 4 Part (a) is the circuit structure. Figure 4 Part (b) is the equivalent circuit of a binary resistor. Figure 4 In part (a), each IGBT / / VD switch group (i.e., an IGBT and a diode in anti-parallel) uses a binary resistance model (when the IGBT or diode is turned on, the resistance is a small resistance R on , when both the IGBT and the diode are turned off, the resistance is a large resistor R off, its typical value is R on =0.01Ω, R off =1MΩ), R1 and R2 are equivalent resistances corresponding to the submodule switch group, thus we get Figure 4 Part (b) shows the equivalent circuit of a binary resistor.

[0072] The superposition theorem is Figure 5 shown. Figure 5 Part (a) is the alternative circuit diagram. Figure 5 Part (b) is the diagram of the constant current source acting alone. Figure 5 Part (c) is the diagram of the constant pressure source acting alone, such as Figure 5 Part (a) is based on the half-bridge binary resistor equivalent model. According to the substitution theorem, the bridge arm current i arm Replace it with a current source and convert the capacitor voltage u c Substitute a voltage source, the reference direction of the voltage source (or current source) is the same as the reference direction of the replaced branch voltage (or current). The superposition theorem can be used to find u sm :

[0073]

[0074] Among them, R eq is the equivalent resistance between the P and N ports, is the equivalent power supply of the n+1th simulation step, n is the simulation step number; S1 is the switching function on the bridge arm of the half-bridge circuit submodule:

[0075]

[0076] Step 2: Discretize the binary resistor equivalent circuit.

[0077] Figure 6 Medium R C ,I hisC are the resistors and historical current sources corresponding to the discretized submodule capacitor C. For the specific expressions of the above resistors and historical current sources, Δt is the time step. The results of the discretization using the trapezoidal method are as follows: R C isI hisC The parameters inside, I hisC All need to be substituted into the following formulas (4) to (8)

[0078]

[0079] Step 3: Form a switching function equivalent circuit.

[0080] Figure 7 The switching function equivalent circuit can be obtained through the UCM general modeling principle. Figure 8 , the object is the submodule of the MMC converter. Figure 6 The Norton equivalent circuit can obtain the corresponding switching function. Figure 7 The switch function model of the submodule port is eq , which is essentially the equivalent voltage source of the submodule's historical current source affecting the submodule port, J eq In essence, it is the equivalent current source that affects the capacitor voltage of the submodule by the submodule port current, so they are not the voltage source or current source in the original equivalent circuit. eq and J eq The effects of these equivalent power supplies cannot be ignored in the calculation and cannot be short-circuited or open-circuited.

[0081] From the equivalent circuit of the switching function, R eqPN is the equivalent resistance between the P and N ports, R eqC For R eqPN and R C Equivalent resistance after parallel connection:

[0082]

[0083] Substituting formula (4) into formula (1), we have:

[0084]

[0085] Let R inSM is the equivalent resistance of the submodule port. For U eq , which is essentially the equivalent voltage source of the submodule's historical current source affecting the submodule port, K sm_JH It is also a switching function, and its definition is different from that of S:

[0086]

[0087] then:

[0088]

[0089] Update of capacitor branch current:

[0090]

[0091] Substituting formula (4) into formula (8), we have:

[0092]

[0093] Equations (7) and (8) can be used to obtain the MMC converter submodule port voltage and capacitor current. The submodule port voltage U sm and the capacitor current i C All with I hisCThe voltage and current are updated with the simulation step size.

[0094] Step 4: Form an equivalent circuit for the entire bridge arm.

[0095] After obtaining the switch function equivalent circuit of a single submodule, the equivalent circuit of the bridge arm side of each submodule is connected in series to obtain the equivalent circuit of the entire bridge arm. Figure 4 Taking any phase bridge arm of the half-bridge submodule MMC as an example, the MMC bridge arm circuit is as follows Figure 8 shown. Figure 8 Part (a) is the bridge arm topology. Figure 8 Part (b) is the bridge arm equivalent circuit. Figure 8 Part (c) is the submodule equivalent circuit.

[0096] Among them, R inSMs The equivalent circuit R of each submodule inSM Equivalent resistance in series, U eqs The equivalent circuit U of each submodule is eq Equivalent voltage sources in series, J eq，k is the equivalent voltage source of each submodule equivalent circuit, R eqPN is the equivalent resistance of each submodule equivalent circuit, S k is the switching function on the bridge arm of the half-bridge circuit submodule:

[0097]

[0098] Figure 7 is the equivalent circuit of any phase bridge arm of the MMC converter, and equation (10) is the parameter of the equivalent diagram. For U eq , which is essentially the equivalent voltage source of the submodule's historical current source affecting the submodule's port. Figure 7 Part (b) U eq and R inSM Parameters can be obtained by Figure 7 The parameters in part (c) are equivalent. For the submodule voltage and current changes, only the Figure 7 Part (b) U eq and R inSM The changes in the modeling method are simplified, the solution process is concise and efficient, and the physical meaning is clear.

[0099] Step 5: Simplify the equivalent model parameters when working normally.

[0100] The switch function equivalence model defines the switch functions S and K sm_JHIts essence is a physical expression composed of the binary resistance model of the bridge arm switch. Therefore, it can more accurately and universally describe the action state of the switching device and reflect all working conditions of the MMC converter.

[0101] When the MMC converter is working in normal state, the equivalent circuit of a single submodule is R eq is Ron or a multiple of Ron (depending on the switch conduction status of the MMC converter in normal state), the switching function S, K sm_JH is 1 or 0. Therefore, when the switch action updates the topology structure, there is no need to recalculate the equivalent resistance R in the binary resistance equivalent circuit. The parameters of the corresponding equivalent model can be quickly updated according to the switch state combination.

[0102] You can simplify U eq , when R1=R on , R2=R off , S1=1,K sm_Jh =1.

[0103] R inSM =R eq +R eqC .

[0104]

[0105] When R1=R off , R2=Ron,S1=0,K sm_Jh =0.

[0106] R inSM =R eq .

[0107]

[0108] After obtaining the switch state table of a single submodule (Table 1), the parameter information of the switch state table of each submodule is substituted into formula (10) to obtain the equivalent parameters of the entire bridge arm.

[0109] Table 1MMC half-bridge circuit switch status table

[0110]

[0111] For the U eq , which is essentially the equivalent voltage source of the submodule's historical current source affecting the submodule's port:

[0112] This application obtains the equivalent circuit corresponding to the original converter based on the fact that the capacitor branch in the MMC converter cannot be open-circuited. Since it is based on the working principle of the converter, the equivalent circuit obtained is both simple in form and universal. When the number of bridge arm sub-modules in the MMC converter changes, only the corresponding sub-circuits need to be added or deleted in the equivalent circuit, which has good scalability. This application simplifies the modeling method, and in each step of the simulation calculation process, the parameter value of the corresponding sub-module can be directly obtained from the physical meaning of the equivalent circuit diagram, which can achieve a speed-up effect. Then, the switch state combination of each sub-module circuit and the corresponding discretization method are used to simplify the solution process, so that the solution process is concise and efficient, and the physical meaning is clear.

[0113] In an exemplary embodiment, a computer device is provided. The computer device may be a server or a terminal. The internal structure diagram thereof may be as follows: Fig. 9 As shown. The computer device includes a processor, a memory, an input / output interface (Input / Output, referred to as I / O) and a communication interface. The processor, the memory and the input / output interface are connected through a system bus, and the communication interface is connected to the system bus through the input / output interface. The processor of the computer device is used to provide computing and control capabilities. The memory of the computer device includes a non-volatile storage medium and an internal memory. The non-volatile storage medium stores an operating system, a computer program and a database. The internal memory provides an environment for the operation of the operating system and the computer program in the non-volatile storage medium. The input / output interface of the computer device is used to exchange information between the processor and an external device. The communication interface of the computer device is used to communicate with an external terminal through a network connection. When the computer program is executed by the processor, a modular multi-level converter electromagnetic transient simulation method is implemented.

[0114] Those skilled in the art will understand that Fig. 9 The structure shown in the figure is only a block diagram of a part of the structure related to the solution of the present application, and does not constitute a limitation on the computer device to which the solution of the present application is applied. The specific computer device may include more or fewer components than those shown in the figure, or combine certain components, or have a different arrangement of components. In an exemplary embodiment, a computer device is provided, including a memory and a processor, wherein a computer program is stored in the memory, and the processor implements the steps in the above-mentioned method embodiments when executing the computer program.

[0115] In an exemplary embodiment, a computer-readable storage medium is provided, storing a computer program, and when the computer program is executed by a processor, the steps in the above method embodiments are implemented.

[0116] In an exemplary embodiment, a computer program product is provided, including a computer program, and when the computer program is executed by a processor, the steps in the above method embodiments are implemented.

[0117] It should be noted that the user information (including but not limited to user device information, user personal information, etc.) and data (including but not limited to data used for analysis, stored data, displayed data, etc.) involved in this application are all information and data authorized by the user or fully authorized by all parties, and the collection, use and processing of relevant data must comply with relevant regulations.

[0118] Those of ordinary skill in the art can understand that all or part of the processes in the above-mentioned embodiment methods can be completed by instructing the relevant hardware through a computer program, and the computer program can be stored in a non-volatile computer-readable storage medium. When the computer program is executed, it can include the processes of the embodiments of the above-mentioned methods. Among them, any reference to the memory, database or other medium used in the embodiments provided in the present application can include at least one of non-volatile and volatile memory. Non-volatile memory can include read-only memory (ROM), magnetic tape, floppy disk, flash memory, optical memory, high-density embedded non-volatile memory, resistive random access memory (ReRAM), magnetic random access memory (MRAM), ferroelectric random access memory (FRAM), phase change memory (PCM), graphene memory, etc. Volatile memory can include random access memory (RAM) or external cache memory, etc. By way of illustration and not limitation, RAM may be in various forms, such as static random access memory (SRAM) or dynamic random access memory (DRAM).

[0119] The database involved in each embodiment provided in this application may include at least one of a relational database and a non-relational database. The non-relational database may include a distributed database based on blockchain, etc., but is not limited thereto. The processor involved in each embodiment provided in this application may be a general-purpose processor, a central processing unit, a graphics processor, a digital signal processor, a programmable logic device, a data processing logic device based on quantum computing, etc., but is not limited thereto.

[0120] The technical features of the above embodiments may be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0121] This article uses specific examples to illustrate the principles and implementation methods of this application. The description of the above embodiments is only used to help understand the method and core ideas of this application. At the same time, for those skilled in the art, according to the ideas of this application, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting this application.

Claims

1. A modular multilevel converter electromagnetic transient simulation method, characterized in that: include: Obtaining the working mode of the modular multilevel converter at the current moment; Constructing sub-models corresponding to a plurality of sub-modules in a modular multi-level converter based on the working mode; Connect the sub-models corresponding to all sub-modules in the same bridge arm in series to obtain multiple single bridge arm equivalent circuits; Build a modular multilevel converter model based on multiple single-bridge equivalent circuits; The switch states of all submodules in the modular multilevel converter at the current moment are input into the modular multilevel converter model to obtain simulation results.

2. The modular multilevel converter electromagnetic transient simulation method according to claim 1, characterized in that: After inputting the switch states of all submodules in the modular multilevel converter at the current moment into the modular multilevel converter model to obtain the simulation result, the method further includes: Determine whether the simulation is finished based on the simulation result; If not, update the current time and return to step "obtaining the working mode of the modular multilevel converter at the current time"; If so, the power system planning is completed based on the dynamic characteristics of the power system reflected by the simulation results.

3. The modular multilevel converter electromagnetic transient simulation method according to claim 1, characterized in that: Before obtaining the working mode of the modular multilevel converter at the current moment, the following steps are also included: Initialize the current time t=0.

4. The modular multilevel converter electromagnetic transient simulation method according to claim 1, characterized in that: The working mode includes a first working mode and a second working mode; the first working mode is a high impedance state or an internal fault when locked; the second working mode is normal or forward and reverse charging when locked.

5. The modular multilevel converter electromagnetic transient simulation method according to claim 1, characterized in that: Based on the working mode, a sub-model corresponding to a plurality of sub-modules in the modular multi-level converter is constructed, including: Acquiring modeling data based on the working mode; Determine any submodule in the modular multilevel converter as a current submodule; Based on the modeling data, determining a binary resistance equivalent circuit of the current submodule; Discretize the binary resistance equivalent circuit of the current submodule to obtain a discretized Norton equivalent circuit; According to the discretized Norton equivalent circuit, the switch function equivalent circuit is determined as the sub-model corresponding to the current sub-module using the general modeling principle.

6. The modular multilevel converter electromagnetic transient simulation method according to claim 5, characterized in that: Acquiring modeling data based on the working mode includes: When the working mode is the first working mode, determining the equivalent resistance as modeling data; When the working mode is the second working mode, the working state table of the modular multilevel converter at the current moment is determined as the modeling data.

7. The modular multilevel converter electromagnetic transient simulation method according to claim 1, characterized in that: The single bridge arm equivalent circuit is: Among them, R inSMs is the equivalent resistance of the equivalent circuit of the switch function corresponding to all sub-modules in a single bridge arm connected in series, k is the serial number of the sub-module in a single bridge arm, N is the total number of sub-modules in a single bridge arm, R inSM，k is the equivalent resistance of the switch function equivalent circuit corresponding to the kth submodule in a single bridge arm, U eqs is the equivalent voltage source of the equivalent circuit of the switch function corresponding to all sub-modules in a single bridge arm connected in series, U eq，k is the equivalent voltage source of the switch function equivalent circuit corresponding to the k sub-modules in a single bridge arm, J eq，k is the equivalent voltage source of the switch function equivalent circuit corresponding to the k sub-modules in a single bridge arm, i arm is the bridge arm current, S k is the switching function of the kth submodule in a single bridge arm, R eqPN，k is the equivalent resistance between the P port and the N port of the switch function equivalent circuit corresponding to the kth submodule in the single bridge arm, R 1，k is the equivalent resistance of the first switch group in the binary resistance equivalent circuit corresponding to the kth submodule in a single bridge arm, R 2，k It is the equivalent resistance of the second switch group in the binary resistance equivalent circuit corresponding to the kth submodule in the single bridge arm.

8. A computer device comprising: A memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the computer program to implement the modular multilevel converter electromagnetic transient simulation method according to any one of claims 1 to 7.

9. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the modular multilevel converter electromagnetic transient simulation method according to any one of claims 1 to 7 is implemented.

10. A computer program product, comprising a computer program, characterized in that When the computer program is executed by a processor, the modular multilevel converter electromagnetic transient simulation method according to any one of claims 1 to 7 is implemented.

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