Flexible direct current power transmission model simulation method and system based on MMC control system

Abstract

The invention relates to the technical field of power system simulation, and particularly discloses a flexible direct current power transmission model simulation method and system based on an MMC control system, and the method comprises the steps: obtaining a trigger pulse signal generated by an improved MMC control system based on a target simulation strategy; and inputting the trigger pulse signal into the flexible direct-current power transmission model for simulation to obtain a simulation result of the flexible direct-current power transmission model. According to the method, on the premise that the simulation precision is guaranteed, the simulation efficiency can be improved, the calculation amount can be reduced, and application and development of the modular multilevel converter technology in actual engineering can be promoted.

Description

Technical Field

[0001] The present invention relates to the technical field of power system simulation, and in particular to a flexible direct current transmission model simulation method and system based on an MMC control system. Background Art

[0002] In the transmission system, electricity is generated by large power plants, usually wind or photovoltaic power plants. Since these power plants are often located far away from urban areas or cities, it is extremely important to transmit the generated electricity efficiently and economically. This is actually achieved by using high-voltage direct current transmission systems to transmit the generated electricity over long distances. The converter is the main component of the high-voltage direct current system. Among the various converter topologies, the modular multilevel converter (MMC) has received considerable attention as the most promising converter technology in high-voltage direct current transmission systems and renewable energy systems such as wind and solar energy.

[0003] The modular multilevel converter consists of multiple submodules connected in series and parallel, which can flexibly control the voltage and current levels. Compared with other traditional converter technologies, this configuration allows a high level of power flow control, improves efficiency, and reduces harmonic distortion. In addition, its modular design facilitates maintenance and replacement, and the study of its control strategy and simulation model is of great significance. The control models of modular multilevel converters in the prior art mostly use detailed models or equivalent circuit models. Although these models can simulate their operating characteristics more accurately, they have a heavy computational burden and slow simulation speed, which is not conducive to the adjustment and optimization of control parameters.

[0004] Therefore, it is urgent to provide a technical solution to solve the above problems. Summary of the invention

[0005] In order to solve the above technical problems, the present invention provides a flexible direct current transmission model simulation method and system based on an MMC control system, which are used to solve the problems of heavy calculation burden and slow simulation speed of the existing model.

[0006] In a first aspect, the present invention provides a flexible direct current transmission model simulation method based on an MMC control system, and the technical solution of the method is as follows:

[0007] Acquire the trigger pulse signal generated by the improved MMC control system based on the target simulation strategy;

[0008] The trigger pulse signal is input into the flexible direct current power transmission model for simulation to obtain a simulation result of the flexible direct current power transmission model.

[0009] The beneficial effects of the flexible direct current transmission model simulation method based on the MMC control system of the present invention are as follows:

[0010] The method of the present invention can improve simulation efficiency and reduce calculation complexity while ensuring simulation accuracy, which is helpful to promote the application and development of modular multi-level converter technology in practical engineering.

[0011] On the basis of the above scheme, the flexible direct current transmission model simulation method based on the MMC control system of the present invention can also be improved as follows.

[0012] In an optional manner, the improved MMC control system includes: a system-level control layer, a converter station-level control layer and a converter valve-level control layer;

[0013] The system-level control layer is used to: receive active component instructions and reactive component instructions generated based on the target simulation strategy, transform to obtain active component reference values ​​according to the active component instructions, and transform to obtain reactive component reference values ​​according to the reactive component instructions;

[0014] The converter station-level control layer is used to: perform vector control on the active component reference value and the reactive component reference value by direct current control to obtain a modulated wave signal;

[0015] The converter valve level control layer is used to: process the modulated wave signal using the nearest level approximation modulation method to obtain the trigger pulse signal.

[0016] In an optional manner, the active component instructions include: active power control, DC voltage control and frequency control; the reactive component instructions include: reactive power control and AC voltage control.

[0017] In an optional manner, the trigger pulse signal includes: a first trigger pulse signal and a second trigger pulse signal; and the step of inputting the trigger pulse signal into the flexible direct current transmission model for simulation includes:

[0018] The first trigger pulse signal is input into the MMC rectifier of the flexible direct current transmission model, and the second trigger pulse signal is input into the MMC inverter of the flexible direct current transmission model, so as to simulate the flexible direct current transmission model.

[0019] In an optional manner, the flexible direct current transmission model includes: a first alternating current power supply, a first alternating current transformer, an MMC rectifier, a direct current transmission line, an MMC inverter, a second alternating current transformer and a second alternating current power supply which are sequentially connected.

[0020] In a second aspect, the present invention provides a flexible direct current transmission model simulation system based on an MMC control system, and the technical solution of the system is as follows:

[0021] Including: acquisition module and simulation module;

[0022] The acquisition module is used to: acquire a trigger pulse signal generated by the improved MMC control system based on a target simulation strategy;

[0023] The simulation module is used to: input the trigger pulse signal into the flexible direct current transmission model for simulation, and obtain the simulation result of the flexible direct current transmission model.

[0024] The beneficial effects of the flexible direct current transmission model simulation system based on the MMC control system of the present invention are as follows:

[0025] The system of the present invention can improve simulation efficiency and reduce calculation complexity while ensuring simulation accuracy, which helps to promote the application and development of modular multi-level converter technology in practical engineering.

[0026] On the basis of the above scheme, the flexible direct current transmission model simulation system based on the MMC control system of the present invention can also be improved as follows.

[0027] In an optional manner, the improved MMC control system includes: a system-level control layer, a converter station-level control layer and a converter valve-level control layer;

[0028] The system-level control layer is used to: receive active component instructions and reactive component instructions generated based on the target simulation strategy, transform to obtain active component reference values ​​according to the active component instructions, and transform to obtain reactive component reference values ​​according to the reactive component instructions;

[0029] The converter station-level control layer is used to: perform vector control on the active component reference value and the reactive component reference value by direct current control to obtain a modulated wave signal;

[0030] The converter valve level control layer is used to: process the modulated wave signal using the nearest level approximation modulation method to obtain the trigger pulse signal.

[0031] In an optional manner, the active component instructions include: active power control, DC voltage control and frequency control; the reactive component instructions include: reactive power control and AC voltage control.

[0032] In an optional manner, the trigger pulse signal includes: a first trigger pulse signal and a second trigger pulse signal; the step of inputting the trigger pulse signal into the flexible direct current transmission model for simulation in the simulation module includes:

[0033] The first trigger pulse signal is input into the MMC rectifier of the flexible direct current transmission model, and the second trigger pulse signal is input into the MMC inverter of the flexible direct current transmission model, so as to simulate the flexible direct current transmission model.

[0034] In an optional manner, the flexible direct current transmission model includes: a first alternating current power supply, a first alternating current transformer, an MMC rectifier, a direct current transmission line, an MMC inverter, a second alternating current transformer and a second alternating current power supply which are sequentially connected.

[0035] The above description is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention, it can be implemented according to the contents of the specification. In order to make the above and other purposes, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are listed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] The accompanying drawings are only used to illustrate the embodiments and are not to be considered as limiting the present invention. In addition, the same reference symbols are used to represent the same components throughout the accompanying drawings. In the accompanying drawings:

[0037] Figure 1 A schematic flow chart of an embodiment of a flexible direct current transmission model simulation method based on an MMC control system of the present invention;

[0038] Figure 2 It is the principle schematic diagram of the improved MMC control system;

[0039] Figure 3 This is one of the structural schematic diagrams of the flexible DC transmission model;

[0040] Figure 4 This is the second structural diagram of the flexible DC transmission model;

[0041] Figure 5 It is the principle schematic diagram of the control system of the MMC average value model;

[0042] Figure 6 It is a schematic diagram of the DC side equivalent circuit of the MMC average value model;

[0043] Figure 7 The present invention is a schematic structural diagram of an embodiment of a flexible direct current transmission model simulation system based on an MMC control system. DETAILED DESCRIPTION

[0044] Exemplary embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. Although exemplary embodiments of the present invention are shown in the drawings, it should be understood that the present invention can be implemented in various forms and should not be limited to the embodiments set forth herein.

[0045] Figure 1 The figure shows a flow chart of an embodiment of a flexible DC transmission model simulation method based on an MMC control system provided by the present invention. Figure 1 As shown, the following steps are included:

[0046] S1. Obtain a trigger pulse signal generated by the improved MMC control system based on a target simulation strategy.

[0047] Among them, Figure 2 As shown, the improved MMC control system includes: system-level control layer, converter station-level control layer and converter valve-level control layer. The target simulation strategy is set according to the simulation requirements of the user, including but not limited to: voltage value, current value, power, etc. The trigger pulse signal is used to control the start and stop of the MMC of the flexible DC transmission model.

[0048] S2. Inputting the trigger pulse signal into the flexible direct current transmission model for simulation to obtain a simulation result of the flexible direct current transmission model.

[0049] Among them, Figure 3 As shown, the flexible direct current transmission model includes: a first AC power source, a first AC transformer, an MMC rectifier, a DC transmission line, an MMC inverter, a second AC transformer and a second AC power source connected in sequence. The trigger pulse signal includes: a first trigger pulse signal and a second trigger pulse signal. The first trigger pulse signal is used to control the start and stop of the MMC rectifier of the flexible direct current transmission model, and the second trigger pulse signal is used to control the MMC inverter of the flexible direct current transmission model. The simulation results are the simulation operation parameters of the flexible direct current transmission model, such as Figure 4As shown in the figure, the input of the flexible DC transmission model includes: ① Control strategy input: active power reference value (P_ref): specifies the active power transmission target of the converter station; reactive power reference value (Q_ref): specifies the reactive power transmission target of the converter station; DC voltage reference value (Udc_ref): used to maintain the stability of the DC voltage. ② Electrical parameter input: AC system parameters: including the voltage level and short-circuit current of the AC system; converter station parameters: such as the capacitance and inductance of the converter submodule; DC line parameters: such as line inductance and line resistance. Fault setting of the flexible DC transmission model: fault conditions such as three-phase short circuit and single-phase grounding can be set to test the stability and fault recovery capability of the system. The output (simulation results) of the flexible DC transmission model includes: ① DC voltage: the DC voltage value (Udc1, Udc2) output by the converter station, which is used to monitor the voltage fluctuation and stability on the DC side. ② Active power and reactive power: Active power output (P1, P2): represents the active power output of each converter station; Reactive power output (Q1, Q2): used to monitor the reactive power compensation effect of the system; ③ System response curve: including the dynamic response curves of voltage, current and power, these data can be used to analyze the effectiveness of the control strategy and the stability of the system. The input and output variables of the above flexible DC transmission model can help analyze the operating performance of the flexible DC transmission system under different working conditions, as well as the response and recovery capabilities of the system under fault conditions through simulation.

[0050] Specifically, the step of inputting the trigger pulse signal into the flexible direct current transmission model for simulation includes:

[0051] The first trigger pulse signal is input into the MMC rectifier of the flexible direct current transmission model, and the second trigger pulse signal is input into the MMC inverter of the flexible direct current transmission model, so as to simulate the flexible direct current transmission model.

[0052] It should be noted that the first trigger pulse signal and the second trigger pulse signal are different. The first trigger pulse signal is used for the AC side, and the second trigger pulse signal is used for the DC side.

[0053] In an optional manner, the system-level control layer is used to: receive active component instructions and reactive component instructions generated based on the target simulation strategy, transform the active component instructions to obtain active component reference values, and transform the reactive component instructions to obtain reactive component reference values.

[0054] The converter station-level control layer is used to: use a direct current control method to perform vector control on the active component reference value and the reactive component reference value to obtain a modulated wave signal.

[0055] The converter valve level control layer is used to: process the modulated wave signal using the nearest level approximation modulation method to obtain the trigger pulse signal.

[0056] Among them, the system-level control layer is responsible for the highest-level control of the flexible DC transmission system. Active component instructions include: active power control, DC voltage control and frequency control; reactive component instructions include: reactive power control and AC voltage control. The system-level control layer is divided into two categories according to the nature of the control quantity: ① Active power control: active power exchanged with the AC system through converter station control, including active power control, DC voltage control, frequency control, etc. ② Reactive power control: reactive power exchanged with the AC system through converter station control, including reactive power control, AC voltage control, etc.

[0057] Among them, the converter station-level control layer adopts a direct current control method (i.e., vector control), which converts three-phase AC quantities into two-phase DC quantities based on the mathematical model of the converter in a synchronous rotating coordinate system (dq coordinates), and directly controls the d-axis and q-axis currents. It has fast current feedback characteristics and inherent current limiting capabilities.

[0058] Among them, the main function of the converter valve level control layer is to receive the modulation wave signal generated by the converter station level control, and generate a trigger pulse signal through the nearest level approximation modulation method to control the opening and closing of the IGBT, so as to make the AC voltage output by the MMC close to the modulation wave by putting in and cutting off the sub-modules.

[0059] In this embodiment, it should be noted that:

[0060] 1) The simulation time of the flexible DC transmission model is set to 10s, the simulation step is 25μs, and the simulation output step is 50μs. During the simulation, a three-phase short-circuit grounding fault occurs on the grid-side busbar of the converter station consisting of the first AC transformer and the MMC rectifier. At 7.1s, the fault is cleared when the current passes through zero. By adjusting the simulation parameters of the target simulation strategy, different faults and operating conditions can be flexibly set.

[0061] 2) Improved MMC control system and benchmark value setting of flexible DC transmission model, including capacity, voltage, current and other parameters. The specific settings are as follows:

[0062] ①Basic capacity: 100MVA.

[0063] ② Reference voltage: 230kV for AC system, ±200kV for DC system.

[0064] ③ Reference current: calculated based on reference capacity and reference voltage.

[0065] 3) The system-level control layer (measurement module) obtains the input variables of the improved MMC control system from the primary circuit of the flexible DC transmission model, and calculates the actual PQ value through dq transformation. The input voltage is the bus voltage on the grid side of the transformer, which is converted to the low-voltage valve side voltage according to the actual transformation ratio of the converter transformer, and then converted based on the set valve side phase voltage effective value. The converter station-level control layer (pole control module) sets the system pole control parameters, including active power reference value, reactive power reference value and DC voltage reference value. The specific parameters are as follows: ① The active control loop of the MMC rectifier selects fixed DC voltage control, and the DC voltage reference value is 400kV. The reactive control loop selects fixed reactive power control, and the reactive power reference value is 20Mvar. ② The active control loop of the MMC inverter selects fixed active power control, and the active power reference value is -100MW. The reactive control loop selects fixed reactive power control, and the reactive power reference value is 30Mvar. The station control module of the improved MMC control system is responsible for active and reactive dual closed-loop control, and the dq inverse transformation generates modulation waves UA, UB, and UC. The coordinated work of the converter station-level control and the converter valve-level control realizes power transmission and voltage control by generating modulation waves and sending them to the converter valve-level control. The converter valve-level control layer (valve control module) adopts the nearest level approximation modulation method, calculates the number of sub-modules put into each valve arm according to the modulation wave, and realizes precise control of the converter by outputting control signals to the MMC valve control. This module can significantly improve the modulation accuracy and reduce the harmonic distortion of the output voltage.

[0066] 4) The flexible DC transmission model can be widely used in fields such as fast control parameter setting, coordinated control strategy development and system-level characteristic research. It helps to promote the application and development of modular multilevel converter technology in practical engineering, especially in the areas of new energy access, grid stability improvement and transmission efficiency improvement.

[0067] 5) If Figure 5 As shown, the improved MMC control system in this embodiment is a control system of the MMC average value model. According to the basic idea of ​​the average value model, in the control system of the MMC average value model, voltage balance control and circulating current suppression control do not need to be used, and the control system outputs the voltage obtained by the nearest level approximation modulation to the six controllable voltage sources of the bridge arm. Compared with the detailed model, the average value model retains the level approximation, that is, the modulation effect of different level numbers can still be reflected; at the same time, the frequent operation of a large number of power electronic devices in the sub-modules and the voltage balancing sorting of the control system and other links with heavy computational burdens are handled in a simplified manner, thereby significantly reducing the simulation time and greatly speeding up the simulation speed. Specifically:

[0068] ① According to the principle of power conservation, the power P input on the AC side ac Equal to the power P on the DC side dcand the converter power loss P loss , that is, formula (1-1): P ac =P dc +P loss ;

[0069] ② Divide both sides of formula (1-1) by the DC voltage U dc The total DC current I dct , DC input current I dc and current consumption I loss The relationship between is formula (1-2): dct =I dc +I loss ;

[0070] ③Substitute the AC side power into the equation to get I dct The expression (1-3):

[0071] ④ The loss of the converter depends on the modulation technology and switching frequency. When operating at rated power, the loss in actual engineering is about 1% of the rated capacity. The loss is closely related to the operating current. If the equivalent resistance of the converter is directly connected in parallel to the DC side, the loss is only related to the DC voltage and has nothing to do with the operating conditions, which is inconsistent with the actual situation. Therefore, the loss of the converter is represented by a controllable current source connected in parallel with the DC voltage, as shown in formula (1-4): R loss is the equivalent loss of the switch and resistor of the MMC.

[0072] ⑤ For DC output current, there is formula (1-5):

[0073] ⑥Introducing two controllable current sources I dct and I loss After that, the DC side equivalent circuit of the MMC average value model can be obtained, as Figure 6 shown. Figure 6 The equivalent concentrated capacitance C in e The capacitor energy storage effect of the submodules of the three-phase six bridge arms is equivalent. Assume that the capacitor voltage of each submodule is uc and there is U dc =N uc , N is the number of bridge arm submodules, then before and after the equivalence, it must satisfy: when the change in DC voltage is the same, the total energy change stored in the dispersed capacitor is the same as the energy change in the concentrated capacitor. When the DC voltage changes △U, there is formula (1-6): After sorting, we can get formula (1-7): It can be seen that the equivalent capacitance after equivalent is proportional to the capacitance value of the submodule and inversely proportional to the MMC level number.

[0074] ⑦ In order to simulate the effect of DC fault, the DC side equivalent circuit diagram of the average value model also adds a e A series switch and a diode on the DC side. In normal operation, the series switch is closed and the diode on the DC side is bypassed, so it can be considered that these two places are inoperative. During a DC fault, all submodules in the MMC form a 6-pulse bridge converter through the freewheeling thyristor K2, and the output is no longer controllable. At this time, the controllable voltage source in the average value model is short-circuited, and the series switch is opened to isolate the equivalent capacitor C on the DC side. e , thus simulating the role of K2 during a fault. At the same time, the diode shunt switch on the DC side is opened and the diode is put into operation to force the current direction.

[0075] The improved MMC control system in this embodiment proposes and implements a three-level hierarchical control structure of system-level control layer, converter station-level control layer and converter valve-level control layer. Each level has different control objectives. The system-level control layer coordinates the operation of each converter station, the converter station-level control layer implements direct current control, and the converter valve-level control layer generates a trigger pulse signal through the nearest level approximation modulation method.

[0076] In this embodiment, the average value model is used to replace the detailed model to simplify the internal characteristics of the MMC. This model greatly improves the simulation speed while maintaining a certain simulation accuracy, and is suitable for system-level research and control strategy verification.

[0077] This embodiment proposes and implements a detailed simulation model and an average value simulation model based on a modular multilevel converter. The detailed model accurately describes the dynamic characteristics of the MMC, while the average value model improves simulation efficiency by simplifying calculations.

[0078] This embodiment adopts the nearest level approximation modulation method to generate the trigger signal of the MMC. This method reduces the number of switch actions and improves the efficiency and stability of the system by selecting the closest level to approximate the modulation wave.

[0079] This embodiment introduces a per-unit method in the improved MMC control system to perform per-unit processing on electrical quantities such as power, voltage, and current, thereby simplifying the parameter debugging process. This method makes the control parameters of MMCs of different capacities and voltage levels consistent, which is convenient for engineering applications.

[0080] In this embodiment, a three-phase short-circuit grounding fault scenario of the converter station AC bus is set during the simulation process to verify the response capability and recovery performance of the system under fault conditions, and prove the effectiveness of the control strategy and the stability of the system.

[0081] Figure 7 FIG. 2 is a schematic diagram showing a structure of an embodiment of a flexible DC transmission model simulation system 200 based on an MMC control system provided by the present invention. Figure 7 As shown, the system 200 includes: an acquisition module 210 and a simulation module 220;

[0082] The acquisition module 210 is used to: acquire a trigger pulse signal generated by the improved MMC control system based on the target simulation strategy;

[0083] The simulation module 220 is used to input the trigger pulse signal into the flexible direct current transmission model for simulation, and obtain a simulation result of the flexible direct current transmission model.

[0084] In an optional manner, the improved MMC control system includes: a system-level control layer, a converter station-level control layer and a converter valve-level control layer;

[0085] The system-level control layer is used to: receive active component instructions and reactive component instructions generated based on the target simulation strategy, transform to obtain active component reference values ​​according to the active component instructions, and transform to obtain reactive component reference values ​​according to the reactive component instructions;

[0086] The converter station-level control layer is used to: perform vector control on the active component reference value and the reactive component reference value by direct current control to obtain a modulated wave signal;

[0087] The converter valve level control layer is used to: process the modulated wave signal using the nearest level approximation modulation method to obtain the trigger pulse signal.

[0088] In an optional manner, the active component instructions include: active power control, DC voltage control and frequency control; the reactive component instructions include: reactive power control and AC voltage control.

[0089] In an optional manner, the trigger pulse signal includes: a first trigger pulse signal and a second trigger pulse signal; the step of inputting the trigger pulse signal into the flexible direct current transmission model for simulation in the simulation module 220 includes:

[0090] The first trigger pulse signal is input into the MMC rectifier of the flexible direct current transmission model, and the second trigger pulse signal is input into the MMC inverter of the flexible direct current transmission model, so as to simulate the flexible direct current transmission model.

[0091] In an optional manner, the flexible direct current transmission model includes: a first alternating current power supply, a first alternating current transformer, an MMC rectifier, a direct current transmission line, an MMC inverter, a second alternating current transformer and a second alternating current power supply which are sequentially connected.

[0092] The technical solution of this embodiment can improve simulation efficiency and reduce calculation complexity while ensuring simulation accuracy, which helps to promote the application and development of modular multi-level converter technology in practical engineering.

[0093] For the above-mentioned parameters in the flexible direct current transmission model simulation system 200 based on the MMC control system of this embodiment and the steps for each module to implement the corresponding functions, reference can be made to the parameters and steps in the embodiment of the flexible direct current transmission model simulation method based on the MMC control system above, and no further details will be given here.

[0094] In the description provided herein, a large number of specific details are described. However, it is understood that embodiments of the present invention can be practiced without these specific details. Similarly, in order to simplify the present invention and help understand one or more of the various inventive aspects, in the above description of exemplary embodiments of the present invention, the various features of the embodiments of the present invention are sometimes grouped together into a single embodiment, figure, or description thereof. Wherein, the claims that follow the specific embodiment are hereby expressly incorporated into the specific embodiment, wherein each claim itself is a separate embodiment of the present invention.

[0095] It should be noted that the above embodiments illustrate the present invention rather than limit it, and that those skilled in the art may devise alternative embodiments without departing from the scope of the appended claims. In the claims, any reference symbol between brackets shall not be construed as a limitation on the claims. The word "comprising" does not exclude the presence of elements or steps not listed in the claims. The word "one" or "an" preceding an element does not exclude the presence of a plurality of such elements. The present invention may be implemented by means of hardware comprising a number of different elements and by means of a suitably programmed computer. In a unit claim enumerating a number of devices, several of these devices may be embodied by the same hardware item. The use of the words first, second, and third, etc. does not indicate any order. These words may be interpreted as names. The steps in the above embodiments, unless otherwise specified, should not be understood as limitations on the order of execution.

Claims

1. A flexible direct current transmission model simulation method based on MMC control system, characterized in that: include: Acquire the trigger pulse signal generated by the improved MMC control system based on the target simulation strategy; The trigger pulse signal is input into the flexible direct current power transmission model for simulation to obtain a simulation result of the flexible direct current power transmission model.

2. The flexible direct current transmission model simulation method based on the MMC control system according to claim 1 is characterized in that: The improved MMC control system comprises: a system-level control layer, a converter station-level control layer and a converter valve-level control layer; The system-level control layer is used to: receive active component instructions and reactive component instructions generated based on the target simulation strategy, transform to obtain active component reference values ​​according to the active component instructions, and transform to obtain reactive component reference values ​​according to the reactive component instructions; The converter station-level control layer is used to: perform vector control on the active component reference value and the reactive component reference value by direct current control to obtain a modulated wave signal; The converter valve level control layer is used to: process the modulated wave signal using the nearest level approximation modulation method to obtain the trigger pulse signal.

3. The flexible direct current transmission model simulation method based on the MMC control system according to claim 2 is characterized in that: The active component instructions include: active power control, DC voltage control and frequency control; the reactive component instructions include: reactive power control and AC voltage control.

4. The flexible direct current transmission model simulation method based on the MMC control system according to any one of claims 1 to 3, characterized in that: The trigger pulse signal includes: a first trigger pulse signal and a second trigger pulse signal; the step of inputting the trigger pulse signal into the flexible direct current transmission model for simulation includes: The first trigger pulse signal is input into the MMC rectifier of the flexible direct current transmission model, and the second trigger pulse signal is input into the MMC inverter of the flexible direct current transmission model, so as to simulate the flexible direct current transmission model.

5. The flexible direct current transmission model simulation method based on the MMC control system according to claim 4 is characterized in that: The flexible direct current power transmission model comprises: a first alternating current power source, a first alternating current transformer, an MMC rectifier, a direct current power transmission line, an MMC inverter, a second alternating current transformer and a second alternating current power source which are sequentially connected.

6. A flexible DC transmission model simulation system based on MMC control system, characterized in that: include: Get modules and simulate modules; The acquisition module is used to: acquire a trigger pulse signal generated by the improved MMC control system based on a target simulation strategy; The simulation module is used to: input the trigger pulse signal into the flexible direct current transmission model for simulation, and obtain the simulation result of the flexible direct current transmission model.

7. The flexible direct current transmission model simulation system based on the MMC control system according to claim 6 is characterized in that: The improved MMC control system comprises: a system-level control layer, a converter station-level control layer and a converter valve-level control layer; The system-level control layer is used to: receive active component instructions and reactive component instructions generated based on the target simulation strategy, transform to obtain active component reference values ​​according to the active component instructions, and transform to obtain reactive component reference values ​​according to the reactive component instructions; The converter station-level control layer is used to: perform vector control on the active component reference value and the reactive component reference value by direct current control to obtain a modulated wave signal; The converter valve level control layer is used to: process the modulated wave signal using the nearest level approximation modulation method to obtain the trigger pulse signal.

8. The flexible direct current transmission model simulation system based on the MMC control system according to claim 7 is characterized in that: The active component instructions include: active power control, DC voltage control and frequency control; the reactive component instructions include: reactive power control and AC voltage control.

9. The flexible direct current transmission model simulation system based on the MMC control system according to any one of claims 6 to 8, characterized in that: The trigger pulse signal includes: a first trigger pulse signal and a second trigger pulse signal; the step of inputting the trigger pulse signal into the flexible direct current transmission model for simulation in the simulation module includes: The first trigger pulse signal is input into the MMC rectifier of the flexible direct current transmission model, and the second trigger pulse signal is input into the MMC inverter of the flexible direct current transmission model, so as to simulate the flexible direct current transmission model.

10. The flexible direct current transmission model simulation system based on the MMC control system according to claim 9, characterized in that: The flexible direct current power transmission model comprises: a first alternating current power source, a first alternating current transformer, an MMC rectifier, a direct current power transmission line, an MMC inverter, a second alternating current transformer and a second alternating current power source which are sequentially connected.

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