Modelling method and system for flexible direct current electromagnetic transient

Abstract

The application discloses a flexible direct-current electromagnetic transient modeling method, comprising the following steps: obtaining data information of a target flexible direct-current power system; performing modular modeling on the target flexible direct-current power system based on simulation software; modeling a structured controller of the target flexible direct-current power system based on the simulation software; establishing an electromagnetic transient simulation model of the target flexible direct-current power system; performing simulation test on the electromagnetic transient simulation model of the target flexible direct-current power system and correcting the electromagnetic transient simulation model; and completing final flexible direct-current electromagnetic transient modeling according to a correction result. The application further discloses a system for realizing the flexible direct-current electromagnetic transient modeling method. The application can not only realize flexible direct-current electromagnetic transient modeling, but also meet simulation requirements of the power system at different stages such as planning, design, dispatching and operation, and has higher reliability and better flexibility.

Description

Technical Field

[0001] The present invention belongs to the field of electrical automation, and in particular relates to a flexible direct current electromagnetic transient modeling method and system. Background Art

[0002] With the development of economy and technology and the improvement of people's living standards, electricity has become an indispensable secondary energy source in people's production and life, bringing endless convenience to people's production and life. Therefore, ensuring a stable and reliable supply of electricity has become one of the most important tasks of the power system.

[0003] Power system simulation is an important way to fully understand the transient and dynamic characteristics of power systems. Its basic principle is to obtain the dynamic behavior and operating characteristics of the power system through calculation based on the established mathematical model of power system components. Power system dynamic simulation technology can be divided into short-term electromagnetic transient simulation, longer-term electromechanical transient simulation, and medium- and long-term dynamic simulation based on the time scale. Among them, electromagnetic transient simulation is mainly used to simulate the mutual conversion between electricity and magnetism in the power system and the transient process of the circuit in detail. It can study the operational transients, resonant transients, fault transients, and transient problems of the control system of the power system. Electromechanical transient simulation starts from the perspective of the power system as a whole and studies three types of stability problems of the power system: synchronous operation stability, frequency stability, and voltage stability.

[0004] Flexible DC technology has been widely used in power systems due to its flexible topology and control strategies. Therefore, power system simulation for flexible DC technology is particularly important. Flexible DC technology has different simulation modeling requirements for electromagnetic transient models in different stages, such as grid planning, design, and dispatching and operation. During the planning and design phase, the model needs to be flexibly and quickly adjusted based on future grid characteristics and DC construction conditions. During the dispatching and operation phase after commissioning, the simulation accuracy of the model needs to be improved to ensure that the model can accurately depict the transient characteristics of the actual flexible DC. However, the current power system simulation solutions are not suitable for the simulation requirements of today's flexible DC technology in terms of simulation flexibility. Summary of the Invention

[0005] One of the objectives of the present invention is to provide a flexible DC electromagnetic transient modeling method with high reliability and good flexibility.

[0006] A second object of the present invention is to provide a system for implementing the flexible DC electromagnetic transient modeling method.

[0007] The flexible DC electromagnetic transient modeling method provided by the present invention comprises the following steps:

[0008] S1. Obtain data information of the target flexible DC power system;

[0009] S2. Based on the data information obtained in step S1, modular modeling of the target flexible DC power system is performed using simulation software;

[0010] S3. Model the structured controller of the target flexible DC power system using simulation software;

[0011] S4. Based on the model obtained in steps S2 and S3, an electromagnetic transient simulation model of the target flexible DC power system is established;

[0012] S5. Perform simulation tests on the electromagnetic transient simulation model of the target flexible DC power system obtained in step S4 and make corrections;

[0013] S6. Based on the correction result obtained in step S5, the final flexible DC electromagnetic transient modeling is completed.

[0014] Step S2, based on the data information obtained in step S1, performs modular modeling of the target flexible DC power system based on simulation software, specifically including the following steps:

[0015] Based on the PSModel simulation software, the topology structure is modified according to the modeling requirements of the electromagnetic transient model; the modification includes modifying the .psm file of electrical component information, modifying the .psm file of node information, and modifying the .sub file of the converter station topology structure;

[0016] Based on the PSModel simulation software, the parameters of each device are modified according to the modeling requirements of the electromagnetic transient model; the modifications include: modifying the .con file to modify the system parameters, and the system parameters include the capacity reference value, DC voltage reference value, grid-side and valve-side line voltage reference values, transformer capacity, reactance value, copper loss, number of converter valve submodules, converter valve submodule capacitance and converter valve bridge arm inductance.

[0017] The step S3 of modeling the structured controller of the target flexible DC power system based on the simulation software specifically includes the following steps:

[0018] Modeling structured controllers;

[0019] Determine the control strategy of each converter station; the control strategy includes passive control mode, DC voltage mode and fixed active power mode;

[0020] Adjust the control system parameters:

[0021] Determine whether the converter station is in constant DC voltage mode:

[0022] If the converter station is in constant DC voltage mode, the DC side line is disconnected and the active output current i dand reactive output current i q Whether it is possible to track the active current reference value i dref and reactive current reference value i qref Adjust the control parameters of the phase-locked loop and the current inner loop according to the change of i dref and i qref Can the system track changes in DC voltage and reactive power or AC voltage and adjust outer loop control parameters?

[0023] If the converter station is not in constant DC voltage mode, the DC circuit is disconnected and a constant voltage source is connected; according to the active output current i d and reactive output current i q Can it track the active current reference value i dref and reactive current reference value i qref According to the change of active current reference value i dref and reactive current reference value i qref Whether it is possible to track changes in active power and reactive power or AC side voltage and adjust the outer loop control parameters.

[0024] The modeling of the structured controller specifically includes the following steps:

[0025] A dual-loop control structure based on Park transformation is adopted to model the structured controller into a measurement unit, an outer-loop control unit, an inner-loop control unit and a valve control unit.

[0026] The measurement unit includes a filtering module, a three-phase-dq conversion module, a power calculation module, a phase-locked loop module, a power synchronization loop module, and a fixed angular frequency module. The output of the filtering module is connected to the power calculation module via the three-phase-dq conversion module. At the same time, the output of the filtering module also outputs the output signal of the measurement unit via the phase-locked loop module, the power synchronization loop module, and the fixed angular frequency module. The output of the power calculation module and the output of the filtering module are also outputs of the measurement unit. The output of the measurement unit serves as a key signal.

[0027] The outer loop control unit includes a d-axis voltage control module, an active power control module, a DC voltage control module, a q-axis voltage control module, a five-power power control module, an AC voltage control module, and a fault ride-through module; the input of the outer loop control unit is the output of the measurement unit; the outputs of the d-axis voltage control module, the active power control module, and the DC voltage control module are all used as inputs to the fault ride-through module; the outputs of the q-axis voltage control module, the five-power power control module, and the AC voltage control module are all used as inputs to the fault ride-through module; the output of the fault ride-through module is the output of the outer loop control unit; and the output of the outer loop control unit is used as the current command;

[0028] The inner loop control unit includes a current inner loop control module, a DC control loop module, and a three-phase-dq conversion module; the input of the inner loop control unit is the output of the outer loop control unit; the output of the current inner loop control module is converted by the three-phase-dq conversion module and serves as the output of the inner loop control unit; the output of the inner loop control unit serves as the voltage command;

[0029] The valve control unit includes a circulation suppression module and a sorting and pressure balancing module; the output of the circulation suppression unit, the output of the inner loop control unit and the output of the DC control loop module are multiplied, and then processed by the sorting and pressure balancing module to obtain the output of the valve control unit; the output of the valve control unit serves as a trigger instruction.

[0030] Step S4, based on the model obtained in steps S2 and S3, establishes an electromagnetic transient simulation model of the target flexible DC power system, which specifically includes the following steps:

[0031] Initialize the target flexible DC power system: first start the fixed DC voltage control, then start the transmitting and receiving converter stations to determine whether the constraints are met:

[0032]

[0033] Where P 送 is the active power output by all sending-end converter stations; P 受 Active power transmitted to all receiving converter stations; is the rated capacity of the constant DC voltage station;

[0034] If the constraints are met, the simulation is performed directly;

[0035] If the constraints are not met, the unlocking sequence of the sending and receiving converter stations is modified and the constraints are checked again.

[0036] Step S5 of performing simulation testing on the electromagnetic transient simulation model of the target flexible DC power system obtained in step S4 and correcting the model specifically includes the following steps:

[0037] Conduct steady-state performance tests on the established electromagnetic transient simulation model of the target flexible DC power system: Connect an ideal voltage source to the AC system and conduct step response tests. Change the active power, reactive power, and DC voltage reference values ​​to determine whether the active power, reactive power, and DC voltage output of each converter station meet the corresponding reference values. If not, modify the model.

[0038] Conduct fault performance tests on the established electromagnetic transient simulation model of the target flexible DC power system: simulate short-circuit faults at the AC-side access points of different converter stations to observe whether the system model can recover and operate normally after the fault. If not, modify the model.

[0039] The present invention also provides a system for implementing the flexible DC electromagnetic transient modeling method, comprising a data acquisition module, a modular modeling module, a controller modeling module, a simulation modeling module, a model correction module and a modeling completion module; the data acquisition module, the modular modeling module, the controller modeling module, the simulation modeling module, the model correction module and the modeling completion module are connected in series in sequence; the data acquisition module is used to acquire data information of the target flexible DC power system and upload the data information to the modular modeling module; the modular modeling module is used to perform modular modeling of the target flexible DC power system based on the received data information and the acquired data information based on the simulation software, and upload the data information to the controller modeling module; the control The controller modeling module is used to model the structured controller of the target flexible DC power system based on the simulation software according to the received data information, and upload the data information to the simulation modeling module; the simulation modeling module is used to establish the electromagnetic transient simulation model of the target flexible DC power system based on the obtained model according to the received data information, and upload the data information to the model correction module; the model correction module is used to simulate and test the electromagnetic transient simulation model of the target flexible DC power system obtained according to the received data information, and correct it, and upload the data information to the modeling completion module; the modeling completion module is used to complete the final flexible DC electromagnetic transient modeling according to the received data information and the obtained correction results.

[0040] The flexible DC electromagnetic transient modeling method and system provided by the present invention not only realizes flexible DC electromagnetic transient modeling by modularly modeling and correcting various parts of the target flexible DC power system, but also can meet the simulation requirements of the power system at different stages such as planning, design, and scheduling and operation, with higher reliability and better flexibility. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 Schematic diagram of the process of the present invention.

[0042] Figure 2 Schematic diagram of the topological structure of the flexible DC structured control system model in the method of the present invention.

[0043] Figure 3 Schematic diagram of a typical scenario of large-scale renewable energy via flexible direct current networking in an embodiment of the method of the present invention.

[0044] Figure 4 Schematic diagram of the DC voltage waveform of the flexible DC system according to the method embodiment of the present invention.

[0045] Figure 5 Schematic diagram of the AC voltage waveform of the flexible DC system according to the method embodiment of the present invention.

[0046] Figure 6Schematic diagram of active power waveform of flexible DC system according to the method embodiment of the present invention.

[0047] Figure 7 Schematic diagram of reactive power waveform of flexible DC system according to the method embodiment of the present invention.

[0048] Figure 8 This is a schematic diagram of the positive high-end power waveform of converter station S2 during fault testing of converter station S2 in a flexible direct current system according to an embodiment of the method of the present invention.

[0049] Figure 9 This is a schematic diagram of the power waveform of the converter station S1 during the fault test of the flexible direct current system S2 according to the method embodiment of the present invention.

[0050] Figure 10 Schematic diagram of the functional modules of the system of the present invention. DETAILED DESCRIPTION

[0051] like Figure 1 The figure shows a schematic flow chart of the method of the present invention: The flexible DC electromagnetic transient modeling method disclosed in the present invention comprises the following steps:

[0052] S1. Obtain data information of the target flexible DC power system;

[0053] S2. Based on the data information obtained in step S1, modular modeling of the target flexible DC power system is performed using simulation software; specifically, the steps include:

[0054] Based on the PSModel simulation software, the topology structure is modified according to the modeling requirements of the electromagnetic transient model; the modification includes modifying the .psm file of electrical component information, modifying the .psm file of node information, and modifying the .sub file of the converter station topology structure;

[0055] Based on the PSModel simulation software, the parameters of various devices are modified according to the modeling requirements of the electromagnetic transient model. The modification includes modifying the .con file to modify the system parameters, which include the capacity reference value, DC voltage reference value, grid-side and valve-side line voltage reference values, transformer capacity, reactance value, copper loss, number of converter valve submodules, converter valve submodule capacitance, and converter valve bridge arm inductance.

[0056] S3. Model the structured controller of the target flexible DC power system using simulation software. This includes the following steps:

[0057] Modeling a structured controller, such as Figure 2 As shown; specifically includes the following steps:

[0058] A dual-loop control structure based on Park transformation is adopted to model the structured controller into a measurement unit, an outer-loop control unit, an inner-loop control unit and a valve control unit.

[0059] The measurement unit includes a filtering module, a three-phase-dq conversion module, a power calculation module, a phase-locked loop module, a power synchronization loop module, and a fixed angular frequency module. The output of the filtering module is connected to the power calculation module via the three-phase-dq conversion module. At the same time, the output of the filtering module also outputs the output signal of the measurement unit via the phase-locked loop module, the power synchronization loop module, and the fixed angular frequency module. The output of the power calculation module and the output of the filtering module are also outputs of the measurement unit. The output of the measurement unit serves as a key signal.

[0060] The outer loop control unit includes a d-axis voltage control module, an active power control module, a DC voltage control module, a q-axis voltage control module, a five-power power control module, an AC voltage control module, and a fault ride-through module; the input of the outer loop control unit is the output of the measurement unit; the outputs of the d-axis voltage control module, the active power control module, and the DC voltage control module are all used as inputs to the fault ride-through module; the outputs of the q-axis voltage control module, the five-power power control module, and the AC voltage control module are all used as inputs to the fault ride-through module; the output of the fault ride-through module is the output of the outer loop control unit; and the output of the outer loop control unit is used as the current command;

[0061] The inner loop control unit includes a current inner loop control module, a DC control loop module, and a three-phase-dq conversion module; the input of the inner loop control unit is the output of the outer loop control unit; the output of the current inner loop control module is converted by the three-phase-dq conversion module and serves as the output of the inner loop control unit; the output of the inner loop control unit serves as the voltage command;

[0062] The valve control unit includes a circulating current suppression module and a sorting and pressure balancing module. The output of the circulating current suppression unit, the output of the inner loop control unit, and the output of the DC control loop module are multiplied and processed by the sorting and pressure balancing module to obtain the output of the valve control unit. The output of the valve control unit serves as a trigger instruction.

[0063] Determine the control strategy of each converter station; the control strategy includes passive control mode, DC voltage mode and fixed active power mode;

[0064] Adjust the control system parameters:

[0065] Determine whether the converter station is in constant DC voltage mode:

[0066] If the converter station is in constant DC voltage mode, the DC side line is disconnected and the active output current i d and reactive output current i q Whether it is possible to track the active current reference value i drefand reactive current reference value i qref Adjust the control parameters of the phase-locked loop and the current inner loop according to the change of i dref and i qref Can the system track changes in DC voltage and reactive power or AC voltage and adjust outer loop control parameters?

[0067] If the converter station is not in constant DC voltage mode, the DC circuit is disconnected and a constant voltage source is connected; according to the active output current i d and reactive output current i q Can it track the active current reference value i dref and reactive current reference value i qref According to the change of active current reference value i dref and reactive current reference value i qref Whether it is possible to track changes in active power and reactive power or AC side voltage and adjust outer loop control parameters;

[0068] S4. Based on the models obtained in steps S2 and S3, an electromagnetic transient simulation model of the target flexible DC power system is established; specifically comprising the following steps:

[0069] Initialize the target flexible DC power system: first start the fixed DC voltage control, then start the transmitting and receiving converter stations to determine whether the constraints are met:

[0070]

[0071] Where P 送 is the active power output by all sending-end converter stations; P 受 Active power transmitted to all receiving converter stations; is the rated capacity of the constant DC voltage station;

[0072] If the constraints are met, the simulation is performed directly;

[0073] If the constraints are not met, the unlocking order of the sending and receiving converter stations is modified and the constraints are checked again;

[0074] S5. Perform simulation testing on the electromagnetic transient simulation model of the target flexible DC power system obtained in step S4 and correct it; specifically comprising the following steps:

[0075] Conduct steady-state performance tests on the established electromagnetic transient simulation model of the target flexible DC power system: Connect an ideal voltage source to the AC system and conduct step response tests. Change the active power, reactive power, and DC voltage reference values ​​to determine whether the active power, reactive power, and DC voltage output of each converter station meet the corresponding reference values. If not, modify the model.

[0076] Conduct fault performance tests on the established electromagnetic transient simulation model of the target flexible DC power system: simulate short-circuit faults at the AC-side access points of different converter stations to observe whether the system model can recover and operate normally after the fault. If not, modify the model.

[0077] S6. Based on the correction result obtained in step S5, the final flexible DC electromagnetic transient modeling is completed.

[0078] The method of the present invention is further described below with reference to an embodiment:

[0079] like Figure 3 The following is a typical scenario of large-scale renewable energy connected via flexible direct current (FDC) grid, including four modes of FDC grid access:

[0080] When the converter station is connected to the clean energy island grid - after the large-scale new energy base is collected through the AC line, the power is directly sent out through the converter station without AC electrical connection to the sending end main grid. The converter station adopts passive or grid-forming control mode;

[0081] The converter station is connected to the sending-end AC main grid. Large-scale new energy bases are connected to the sending-end AC main grid, and then the power is sent out through the converter station. The clean energy base has an AC electrical connection with the main grid. The converter station adopts a grid-following or grid-forming control mode.

[0082] The converter station is connected to the receiving AC main grid. The flexible DC converter station is connected to the load center of the receiving grid, which contains multiple types of equipment such as renewable energy, synchronous machines, static loads, and dynamic loads. The converter station adopts a grid-following control mode with a constant DC voltage or constant active power.

[0083] Converter station access to isolated load grid - The flexible DC converter station accesses an isolated load grid, which only includes static and dynamic loads. The converter station uses a passive or grid-forming control mode to supply power to the isolated load grid.

[0084] The topology and equipment parameters of each flexible DC converter station were preliminarily determined. Considering the large capacity of each flexible DC converter station in this scenario, a true bipolar connection method was adopted. The equipment parameters of each converter station are shown in Table 1 below:

[0085] Table 1 Schematic diagram of flexible DC converter station parameters

[0086] parameter S1 S2 S3 S4 AC side rated frequency 50HZ 50HZ 50HZ 50HZ DC voltage reference value 400kV 400kV 400kV 800kV Capacity benchmark value 500MVA 1000MVA 1000MVA 1000MVA Commutation transformer capacity 600MVA 1200MVA 1200MVA 1200MVA Commutation Reactance 18％ 18％ 18％ 18％ Commutation ratio 525kV / 232.7kV 525kV / 232.7kV 525kV / 232.7kV 230kV / 460kV Number of submodules 244 244 244 244 Bridge arm inductor 0.075H 0.075H 0.075H 0.075H Submodule capacitance 15000μF 15000μF 15000μF 15000μF

[0087] According to the planning scheme, based on the PSModel simulation platform, flexible direct current electromagnetic transient modeling was carried out and the electrical system and control system parameters were modified:

[0088] Build a detailed electromagnetic transient model of a hybrid cascaded multi-terminal DC electrical system, using the flexible direct current (FDC) access scenario 1 as an example, where converter station S1 is connected to the clean energy island grid. Modify electrical parameters in the .con file, including the DC voltage reference value, transmission capacity reference value, and converter transformer and valve parameters.

[0089] Modify the control system parameters based on the access situation. Converter station S1 is connected to the clean energy island grid, where passive control is adopted. Modify the control parameters in the .con file, including the d and q axis control methods, AC and DC voltage reference values, and active power reference values. In addition, in this example, converter stations S1 and S4 adopt passive control, converter station S2 adopts grid-forming control, and converter station S3 adopts fixed DC voltage grid-following control.

[0090] Initialize the flexible direct current electromagnetic transient model and verify the voltage and power of key equipment in the system:

[0091] Determine the unlocking sequence for the flexible DC converter stations: Start the constant DC voltage station first, then start the other sending and receiving converter stations. Unlock the S3 converter station in 0.1s, the S2 converter station in 0.5s, and the S1 and S4 converter stations simultaneously in 1.0s. Based on the control mode of each converter station, determine the initialization strategy for the converter station and grid access as follows:

[0092] For the S1 converter station and the connected AC power grid, it is set to start the clamping voltage source of the new energy side and the S1 converter station at 0.0s, unlock the new energy equipment at 0.1s, unlock the S1 converter station at 1.0s, cut off the clamping voltage source on the new energy side at 2.3s, and cut off the clamping voltage source of the S1 converter station at 3.0s, and merge into the S1 converter station at the same time.

[0093] For the S2 converter station and the connected AC power grid, the time to start the clamped voltage source, synchronous machine and motor on the new energy side is set at 0.0s, the time to unlock the new energy equipment is set at 0.1s, the time to unlock the flexible DC converter station is set at 0.5s, the time to cut off the clamped voltage source on the new energy side is set at 2.3s, the time to unlock the speed of the AC synchronous machine and motor is set at 2.5s, and the time to start the excitation and speed regulation system of the AC synchronous machine is set at 2.8s.

[0094] For the S3 converter station and the connected AC power grid, the time for starting the AC synchronous machine, motor, clamping voltage source on the renewable energy side and flexible DC side is set at 0.0s, unlocking the renewable energy equipment and flexible DC converter station at 0.1s, cutting off the clamping voltage source on the flexible DC side at 1.6s, cutting off the clamping voltage source on the renewable energy side at 2.3s, unlocking the speed of the AC synchronous machine and motor at 2.5s, and starting the excitation and speed regulation system of the AC synchronous machine at 2.8s.

[0095] For the S4 converter station and the connected AC power grid, set the start time of the clamping voltage source at 0.0s, the unlocking of the converter station at 1.0s, the removal of the S4 clamping voltage source at 2.5s and the integration into the converter station, and the unlocking of the motor speed at 3.0s.

[0096] Verify the voltage and power of key system equipment. Figure 4 is the initialization waveform of the multi-terminal flexible DC, Figure 4 is the bipolar DC voltage, the red and blue curves represent the DC voltage of pole 1 and pole 2 respectively; Figure 5 is the AC voltage at the converter station connection point, Figure 6 is the active power of the converter station, Figure 7 The red, blue, green, and pink curves represent the reactive power of the converter stations S1, S2, S3, and S4, respectively. Within 4.0 seconds, the DC voltage, AC voltage, and AC power at each converter station reached a stable state. During initialization, S3 was able to maintain a constant DC voltage, and the flexible DC system was able to maintain stable operation.

[0097] Conduct steady-state performance tests on converter stations S1, S2, S3, and S4 respectively to verify whether the output power and established DC voltage of each converter station meet the requirements;

[0098] Conduct three-phase instantaneous short circuit fault tests at the AC interface of the grid side of converter stations S1, S2, S3 and S4 respectively to observe whether the flexible DC model can operate normally after the fault. If not, continue to adjust the control system to achieve normal operation of the flexible DC model after the fault. Here, the three-phase instantaneous short circuit fault test is conducted on the AC side of the S2 converter station. A short circuit fault is connected 3 seconds after the flexible DC system is started. Figure 8 Output active power and reactive power curves for the positive high-end converter valve of S2 converter station. Figure 9 The active power and reactive power output of the S1 converter station are shown. It can be seen that after a short-circuit fault occurs, the power curve fluctuates and then returns to stable operation. Similarly, the output power of other converters can be tested to see if they can operate normally.

[0099] After completing the above tests, a full electromagnetic transient simulation verification was carried out. The outputs of the flexible DC model normally met the grid operation requirements, and the flexible DC electromagnetic transient modeling based on the PSModel simulation software was completed.

[0100] like Figure 10The figure shows a schematic diagram of the functional modules of the system of the present invention: the system disclosed in the present invention for realizing the flexible DC electromagnetic transient modeling method comprises a data acquisition module, a modular modeling module, a controller modeling module, a simulation modeling module, a model correction module and a modeling completion module; the data acquisition module, the modular modeling module, the controller modeling module, the simulation modeling module, the model correction module and the modeling completion module are connected in series in sequence; the data acquisition module is used to acquire data information of the target flexible DC power system and upload the data information to the modular modeling module; the modular modeling module is used to perform modular modeling of the target flexible DC power system based on the received data information and the acquired data information based on the simulation software, and upload the data information to the controller The controller modeling module is used to model the structured controller of the target flexible DC power system based on the simulation software according to the received data information, and upload the data information to the simulation modeling module; the simulation modeling module is used to establish the electromagnetic transient simulation model of the target flexible DC power system based on the obtained model according to the received data information, and upload the data information to the model correction module; the model correction module is used to simulate and test the electromagnetic transient simulation model of the target flexible DC power system according to the received data information, and correct it, and upload the data information to the modeling completion module; the modeling completion module is used to complete the final flexible DC electromagnetic transient modeling according to the received data information and the obtained correction results.

Claims

1. A flexible DC electromagnetic transient modeling method, comprising the following steps: S1. Obtain data information of the target flexible DC power system; S2. Based on the data information obtained in step S1, modular modeling of the target flexible DC power system is performed using simulation software; S3. Model the structured controller of the target flexible DC power system using simulation software. This includes the following steps: Modeling structured controllers; Determine the control strategy of each converter station; the control strategy includes passive control mode, DC voltage mode and fixed active power mode; Adjust the control system parameters: Determine whether the converter station is in constant DC voltage mode: If the converter station is in constant DC voltage mode, the DC side line is disconnected and the active output current i d and reactive output current i q Whether it is possible to track the active current reference value i dref and reactive current reference value i qref Adjust the control parameters of the phase-locked loop and the current inner loop according to the change of i dref and i qref Can the system track changes in DC voltage and reactive power or AC voltage and adjust outer loop control parameters? If the converter station is not in constant DC voltage mode, the DC circuit is disconnected and a constant voltage source is connected; according to the active output current i d and reactive output current i q Can it track the active current reference value i dref and reactive current reference value i qref Adjust the control parameters of the phase-locked loop and the current inner loop according to the changes in the current; According to the active current reference value i dref and reactive current reference value i qref Whether it is possible to track changes in active power and reactive power or AC side voltage and adjust outer loop control parameters; S4. Based on the model obtained in steps S2 and S3, an electromagnetic transient simulation model of the target flexible DC power system is established; S5. Perform simulation tests on the electromagnetic transient simulation model of the target flexible DC power system obtained in step S4 and make corrections; S6. Based on the correction result obtained in step S5, the final flexible DC electromagnetic transient modeling is completed.

2. The flexible DC electromagnetic transient modeling method according to claim 1 is characterized in that Step S2, based on the data information obtained in step S1, performs modular modeling of the target flexible DC power system based on simulation software, specifically including the following steps: Based on the PSModel simulation software, the topology structure is modified according to the modeling requirements of the electromagnetic transient model; the modification includes modifying the .psm file of electrical component information, modifying the .psm file of node information, and modifying the .sub file of the converter station topology structure; Based on the PSModel simulation software, the parameters of each device are modified according to the modeling requirements of the electromagnetic transient model; the modifications include: modifying the .con file to modify the system parameters, and the system parameters include the capacity reference value, DC voltage reference value, grid-side and valve-side line voltage reference values, transformer capacity, reactance value, copper loss, number of converter valve submodules, converter valve submodule capacitance and converter valve bridge arm inductance.

3. The flexible DC electromagnetic transient modeling method according to claim 2 is characterized in that The modeling of the structured controller specifically includes the following steps: A dual-loop control structure based on Park transformation is adopted to model the structured controller into a measurement unit, an outer-loop control unit, an inner-loop control unit and a valve control unit. The measurement unit includes a filtering module, a three-phase-dq conversion module, a power calculation module, a phase-locked loop module, a power synchronization loop module, and a fixed angular frequency module. The output of the filtering module is connected to the power calculation module via the three-phase-dq conversion module. At the same time, the output of the filtering module also outputs the output signal of the measurement unit via the phase-locked loop module, the power synchronization loop module, and the fixed angular frequency module. The output of the power calculation module and the output of the filtering module are also outputs of the measurement unit. The output of the measurement unit serves as a key signal. The outer loop control unit includes a d-axis voltage control module, an active power control module, a DC voltage control module, a q-axis voltage control module, a five-power power control module, an AC voltage control module, and a fault ride-through module; the input of the outer loop control unit is the output of the measurement unit; the outputs of the d-axis voltage control module, the active power control module, and the DC voltage control module are all used as inputs to the fault ride-through module; the outputs of the q-axis voltage control module, the five-power power control module, and the AC voltage control module are all used as inputs to the fault ride-through module; the output of the fault ride-through module is the output of the outer loop control unit; and the output of the outer loop control unit is used as the current command; The inner loop control unit includes a current inner loop control module, a DC control loop module, and a three-phase-dq conversion module; the input of the inner loop control unit is the output of the outer loop control unit; the output of the current inner loop control module is converted by the three-phase-dq conversion module and serves as the output of the inner loop control unit; the output of the inner loop control unit serves as the voltage command; The valve control unit includes a circulation suppression module and a sorting and pressure balancing module; the output of the circulation suppression unit, the output of the inner loop control unit and the output of the DC control loop module are multiplied, and then processed by the sorting and pressure balancing module to obtain the output of the valve control unit; the output of the valve control unit serves as a trigger instruction.

4. The flexible DC electromagnetic transient modeling method according to claim 3 is characterized in that Step S4, based on the model obtained in steps S2 and S3, establishes an electromagnetic transient simulation model of the target flexible DC power system, which specifically includes the following steps: Initialize the target flexible DC power system: first start the fixed DC voltage control, then start the transmitting and receiving converter stations to determine whether the constraints are met: Where P 送 is the active power output by all sending-end converter stations; P 受 Active power transmitted to all receiving converter stations; is the rated capacity of the constant DC voltage station; If the constraints are met, the simulation is performed directly; If the constraints are not met, the unlocking sequence of the sending and receiving converter stations is modified and the constraints are checked again.

5. The flexible DC electromagnetic transient modeling method according to claim 4 is characterized in that Step S5 of performing simulation testing on the electromagnetic transient simulation model of the target flexible DC power system obtained in step S4 and correcting the model specifically includes the following steps: Conduct steady-state performance tests on the established electromagnetic transient simulation model of the target flexible DC power system: Connect an ideal voltage source to the AC system and conduct step response tests. Change the active power, reactive power, and DC voltage reference values ​​to determine whether the active power, reactive power, and DC voltage output of each converter station meet the corresponding reference values. If not, modify the model. Conduct fault performance tests on the established electromagnetic transient simulation model of the target flexible DC power system: simulate short-circuit faults at the AC-side access points of different converter stations to observe whether the system model can recover and operate normally after the fault. If not, modify the model.

6. A system for implementing the flexible DC electromagnetic transient modeling method according to any one of claims 1 to 5, characterized in that It includes a data acquisition module, a modular modeling module, a controller modeling module, a simulation modeling module, a model correction module and a modeling completion module; the data acquisition module, the modular modeling module, the controller modeling module, the simulation modeling module, the model correction module and the modeling completion module are connected in series in sequence; the data acquisition module is used to acquire data information of the target flexible DC power system and upload the data information to the modular modeling module; The modular modeling module is used to perform modular modeling of the target flexible DC power system based on the received data information and the acquired data information based on the simulation software, and upload the data information to the controller modeling module; The controller modeling module is used to model the structured controller of the target flexible DC power system based on the received data information and the simulation software, and upload the data information to the simulation modeling module; The simulation modeling module is used to establish an electromagnetic transient simulation model of the target flexible DC power system based on the received data information and the obtained model, and upload the data information to the model correction module; The model correction module is used to simulate and test the electromagnetic transient simulation model of the target flexible DC power system based on the received data information, and to correct it, and upload the data information to the modeling completion module; The modeling completion module is used to complete the final flexible DC electromagnetic transient modeling based on the received data information and the obtained correction results.

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