External reactive small-disturbance semi-physical simulation model, system and method
By constructing a semi-physical simulation model of small external reactive power disturbances and an FPGA+CPU co-simulation architecture, the problem of dynamic reactive power support and stability verification of wind turbines in weak grid environments was solved, and accurate reactive power disturbance testing and controller performance evaluation were achieved.
Patent Information
- Application Number
- CN202511775369.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-11-28
- Publication Date
- 2026-01-13
AI Technical Summary
Existing technologies make it difficult to truly integrate physical controllers into wind turbine units, accurately simulate weak grid environments and reactive power disturbance scenarios with multi-stage voltage boosting and low short-circuit ratios, and cannot effectively verify the dynamic reactive power support capability and stability of wind turbine units under weak grid conditions.
A semi-physical simulation model for external reactive power disturbances is constructed, including a direct-drive unit module, a boost transmission module, an equivalent external power grid module, and a reactive power disturbance module. Reactive power disturbances are applied at the generator bus through controllable switching capacitor branches. A high-precision simulation environment is achieved by combining an FPGA and CPU co-simulation architecture.
Without affecting the actual operation of the power grid, this method safely and controllably reproduces reactive power disturbances, accurately verifies the voltage recovery capability and grid connection stability of wind turbine units, and provides a safe testing method.
Smart Images
Figure CN121325645A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of simulation testing technology, and in particular to a hardware-in-the-loop simulation model, system and method for small external reactive disturbances. Background Technology
[0002] Wind turbines typically require multiple step-up transformers and long-distance transmission lines to connect to the main power grid, resulting in the turbine terminals facing a "weak grid" condition characterized by high impedance and low short-circuit ratio (SCR). Under weak grid conditions, the grid voltage is highly sensitive to fluctuations in reactive power, making wind turbines extremely prone to oscillations or grid disconnection.
[0003] Current grid-connected performance testing of wind turbines mainly relies on pure software simulation or field testing. Pure software simulation struggles to accurately simulate the nonlinear characteristics and real-time response of converter controllers, resulting in low simulation reliability. Field testing, constrained by grid safety regulations and operating conditions, makes it difficult to artificially create extreme weak connection conditions with a short-circuit ratio of 1.5 in the actual grid. Furthermore, directly conducting reactive power disturbance tests such as capacitor switching on the existing grid carries the risk of equipment damage and makes fault reproduction and troubleshooting difficult. Therefore, existing technologies lack a testing method that can realistically connect to the physical controller while accurately simulating multi-stage voltage boosting, low short-circuit ratio environments, and reactive power disturbance scenarios, failing to effectively verify the dynamic reactive power support capability and stability of direct-drive units under weak grid conditions. To address these issues, this invention proposes a semi-physical simulation model, system, and method for external reactive power small disturbances. Summary of the Invention
[0004] In this section, as well as in the abstract and title of this application, some simplifications or omissions may be made to avoid obscuring the purpose of this section, the abstract, and the title of this application, and such simplifications or omissions shall not be used to limit the scope of the invention.
[0005] To address the shortcomings of existing technologies, one objective of this invention is to provide a semi-physical simulation model for external reactive power disturbances, comprising a direct-drive generator module for simulating the generator's power generation and conversion characteristics; a boost transmission module connected to the direct-drive generator module for progressively boosting the generator's terminal voltage and transmitting it to the grid side; an equivalent external grid module connected to the end of the boost transmission module for simulating an infinite voltage source; and a reactive power disturbance module connected in parallel at the generator bus of the direct-drive generator module, including a controllable switching capacitor branch, which applies instantaneous reactive power disturbances to the generator bus during testing.
[0006] As a preferred embodiment of the external reactive power small disturbance semi-physical simulation model of the present invention, the step-up transmission module includes a first-stage transformer connected in series, which is used to step up the 0.69kV terminal voltage to the 35kV bus; a second-stage transformer, which is used to step up the 35kV to the 110kV bus; a third-stage transformer, which is used to step up the 110kV to the 330kV bus; a fourth-stage transformer, which is used to step up the 330kV to the first 750kV bus; and a transmission line, which is used to connect the first 750kV bus to the equivalent external power grid module.
[0007] As a preferred embodiment of the external reactive power small disturbance semi-physical simulation model of the present invention, wherein: the capacitor branch in the reactive power disturbance module includes: a capacitor, the capacity of which is set to 5% of the rated capacity of the direct drive unit module and is used to simulate the external reactive power small disturbance scenario; and a circuit breaker, which is used to control the connection and disconnection of the capacitor.
[0008] As a preferred embodiment of the external reactive power small disturbance semi-physical simulation model of the present invention, wherein: the rated voltages of the first-stage transformer, the second-stage transformer, the third-stage transformer, and the fourth-stage transformer are 690V / 35kV, 35 / 110kV, 110 / 330kV, and 330 / 750kV, respectively, and the per-unit impedance values are 0.060, 0.105, 0.105, and 0.180, respectively, with an X / R ratio of 10; the rated voltage of the transmission line is 750kV, the per-unit impedance value is 0.216, and the X / R ratio is 10; by setting the impedances of the first-stage transformer, the second-stage transformer, the third-stage transformer, and the fourth-stage transformer, the short-circuit ratio of the generator terminal bus is set to 1.5; by setting the line impedance, the short-circuit ratio at the second 750kV bus position of the generator is set to 4.6, and the short-circuit capacity is [missing information]. , in For short-circuit capacity, =7.6, The rated capacity of the unit.
[0009] Another objective of this invention is to provide a wind turbine hardware-in-the-loop simulation system, comprising: a real-time simulation host for loading and running an external reactive power small disturbance hardware-in-the-loop simulation model; a controller under test connected to the real-time simulation host; wherein the real-time simulation host adopts an architecture of FPGA and CPU co-simulation, the converter of the direct-drive unit module and the external reactive power small disturbance hardware-in-the-loop simulation model run in the FPGA, and the grid sag and control logic run in the CPU; and a measurement module for acquiring three-phase voltage and current data.
[0010] As a preferred embodiment of the wind turbine hardware-in-the-loop simulation system of the present invention, the simulation step size of the real-time simulation host is configured as follows: the simulation step size of the FPGA is 2 microseconds, and not greater than the minimum step size of 2.5 microseconds required for converter simulation; the simulation step size of the CPU is 20 microseconds, and the simulation output step size is 20 microseconds; the controller under test only connects to the converter control signal during the simulation process, and does not connect to the wind turbine main controller.
[0011] As a preferred embodiment of the wind turbine hardware-in-the-loop simulation system of the present invention, the wind turbine model parameters running in the real-time simulation host are configured as follows: wind turbine rated power 3200kW, rated voltage 690V, grid-side filter capacitor 1337uF, grid-side filter inductor 60uH, and generator type is permanent magnet synchronous generator; the measurement points of the measurement module include 0.4 / 0.96kV at the turbine terminal bus, 35kV at the high-voltage side bus of the transformer substation, and 750kV at the 71-side bus of the line impedance, and the measurement points are used to collect three-phase voltage and current data.
[0012] Another objective of this invention is to provide a method for testing small external reactive power disturbances in a generator unit. The method includes: building a hardware-in-the-loop simulation model of the small external reactive power disturbance in a real-time simulation host, and configuring the system impedance to achieve a short-circuit ratio of 1.5 at the generator terminals; controlling the direct-drive generator unit to operate in parallel with the grid under preset active and reactive power conditions until the system reaches steady state; closing the circuit breaker in the reactive power disturbance module, connecting a capacitor with a capacity of 5% of the generator unit's rated capacity, maintaining operation for a preset time, and then disconnecting the circuit breaker to remove the capacitor; collecting and recording the generator terminal voltage, active power, and reactive power waveforms during the connection and disconnection of the capacitor, and evaluating the stability of the generator unit's operation.
[0013] As a preferred embodiment of the external reactive power small disturbance test method of the unit described in this invention, the preset active power and reactive power conditions are configured as follows: the active power output of the wind turbine unit is adjusted to 0.9 pu and the reactive power is 0.3 pu, and the voltage of the terminal bus is maintained at 1.0 pu. After running for at least 2 seconds, the next step of the operation is performed.
[0014] As a preferred embodiment of the external reactive power small disturbance test method of the present invention, the data acquisition requirements are as follows: use a sampling rate of 10kHz to record the three-phase voltage and current data of the turbine terminal bus, 35kV bus and transmission line side. If the test results show that the turbine terminal voltage can recover to a stable state without continuous oscillation after the disturbance, the test is deemed to have passed. The stability judgment criteria are: during the disturbance, the turbine terminal voltage has no obvious harmonic components, recovers to a steady-state value of 1.0pu within 2000ms, and the direct-drive wind turbine unit maintains uninterrupted grid-connected operation throughout the process.
[0015] The beneficial effects of this invention are as follows: By constructing a hardware-in-the-loop (HIL) simulation model comprising a direct-drive turbine module, a boost transmission module, an equivalent external grid module, and a reactive power disturbance module, this invention can realistically construct the topology of a wind turbine unit connected to an infinite power grid via multi-stage voltage boosting. By connecting a reactive power disturbance module containing a controllable switching capacitor branch in parallel at the turbine bus, the instantaneous reactive power disturbances on the grid side can be safely and controllably reproduced in a hardware-in-the-loop simulation environment. This allows for accurate verification of the voltage recovery capability and grid connection stability of the direct-drive turbine unit under external disturbances without affecting the actual grid operation. Attached Figure Description
[0016] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0017] Figure 1 This is a schematic diagram of the semi-physical simulation model of small external reactive disturbance in Embodiment 1 of the present invention; Figure 2 This is a detailed circuit topology diagram of the boost transmission module and the reactive power disturbance module in Embodiment 2 of the present invention; Figure 3 This is a schematic diagram of the hardware architecture of the wind turbine semi-physical simulation system in Embodiment 3 of the present invention; Figure 4 This is a partial simulation model screenshot of the transformer and measurement components in the simulation model of this invention. Figure 1 ; Figure 5 This is a partial simulation model screenshot of the transformer and measurement components in the simulation model of this invention. Figure 2 ; Figure 6 The waveforms of the terminal voltage, active current, and reactive current obtained in Embodiment 4 of the present invention are shown. Figure 7 The waveforms of active power and reactive power obtained in Embodiment 4 of the present invention are shown. Detailed Implementation
[0018] To make the objectives, features, and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.
[0019] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.
[0020] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that is mutually exclusive with other embodiments.
[0021] Example 1
[0022] Reference Figure 1 and Figure 2 This embodiment is the first embodiment of the invention. This embodiment discloses a semi-physical simulation model for small external reactive power disturbances. The semi-physical simulation model for small external reactive power disturbances is used to simulate the grid-connected operation environment of a direct-drive wind turbine in a semi-physical simulation environment.
[0023] like Figure 1 As shown, the external reactive small disturbance semi-physical simulation model mainly consists of four parts, including the following: Direct drive unit module 100: The direct drive unit module 100 is used to simulate the power generation principle and electrical characteristics of the real direct drive unit M1 in the simulation environment, as the primary side model of the object under test.
[0024] Boost Transmission Module 200: One end of the boost transmission module 200 is connected to the direct drive unit module 100. Its function is to simulate the process in an actual wind farm where the electrical energy generated by the unit M1 needs to go through multiple boosting processes such as transformer substation, collection station, and boosting station, and then transmit the terminal voltage to the grid side M2 after boosting it step by step.
[0025] Equivalent external power grid module 300: The equivalent external power grid module 300 is connected to the end of the boost transmission module 200. In the simulation, it is set as an infinite voltage source to simulate a stable main power grid environment and serve as a voltage reference point.
[0026] Reactive power disturbance module 400: The reactive power disturbance module 400 is connected in parallel at the generator terminal bus M3 of the direct-drive unit module 100. The reactive power disturbance module 400 contains a controllable switching capacitor branch 401. By controlling the on / off state of the capacitor branch 401, instantaneous reactive power disturbances can be artificially applied to the generator terminal bus M3 during the test to simulate the impact of operations such as switching capacitor C2 on the unit M1 in the power grid.
[0027] Example 2
[0028] Reference Figure 1and Figure 2 This embodiment is a further refinement of embodiment 1, focusing on the specific circuit structure and parameter configuration of the boost transmission module 200 and the reactive power disturbance module 400.
[0029] Specifically, in the step-up transmission module 200, to realistically recreate the scenario of a new energy power plant transmitting power through multiple stages of voltage boosting, a four-stage series transformer and a transmission line are designed. Specifically, this includes: First-stage transformer T1: Simulates a box-type transformer, boosting the low-voltage electricity from 0.69kV at the generator terminal to 35kV, connecting to the 35kV bus M4. Second-stage transformer T2: Further boosts the 35kV voltage to 110kV, connecting to the 110kV bus M5. Third-stage transformer T3: Boosts the 110kV voltage to 330kV, connecting to the 330kV bus M6. Fourth-stage transformer T4: Finally boosts the 330kV voltage to the first 750kV bus M7. Transmission line L1: Connects the first 750kV bus M7 and the equivalent external power grid module 300, simulating the line impedance during high-voltage transmission.
[0030] Regarding parameter configuration, to construct a weak grid test environment with a short-circuit ratio (SCR) of 1.5, the parameters of each component are set as follows: the rated voltages of the first-stage transformer T1, the second-stage transformer T2, the third-stage transformer T3, and the fourth-stage transformer T4 are 690V / 35kV, 35 / 110kV, 110 / 330kV, and 330 / 750kV, respectively; their per-unit impedance values are set to 0.060, 0.105, 0.105, and 0.180, respectively, and the X / R ratio is set to 10 for all of them. The rated voltage of the transmission line L1 is 750kV, the per-unit impedance value is set to 0.216, and the X / R ratio is 10. Through the precise tuning of the above impedance parameters, the system short-circuit ratio seen from the generator terminal bus M3 of the direct-drive unit module 100 is 1.5, while the short-circuit ratio at the second 750kV bus M8 is 4.6. The short-circuit capacity is calculated using the formula: SC71 = SCR71 * Sn, where Sn is the rated capacity of unit M1.
[0031] In the reactive power disturbance module 400, the capacitor branch 401 consists of a capacitor C2 connected in series and a circuit breaker 401a. The capacity of capacitor C2 is set to 5% of the rated capacity of the direct-drive unit module 100. The circuit breaker 401a is used to perform closing and opening operations, thereby realizing the instantaneous connection and disconnection of capacitor C2.
[0032] Through the refined modeling of the four-stage transformer and line impedance, a specific weak grid connection condition, SCR=1.5, was reproduced in a hardware-in-the-loop simulation, overcoming the difficulty of setting up such a system in a conventional laboratory environment. Simultaneously, configuring a capacitor C2 with 5% of the rated capacity allows for standardized simulation of a small external reactive power disturbance fault condition, providing an accurate physical model basis for verifying the robustness of the controller.
[0033] Example 3
[0034] Reference Figures 1-5 This embodiment discloses a wind turbine hardware-in-the-loop simulation system for running the above simulation model and connecting to a real controller.
[0035] Specifically, the core of the wind turbine hardware-in-the-loop simulation system includes a real-time simulation host 500, a controller under test 600, and a measurement module 700. The real-time simulation host 500 utilizes an advanced FPGA (Field-Programmable Gate Array), a heterogeneous architecture that co-simulates with a CPU. Due to the high switching frequency of the converter and the high requirements for simulation step size, the main circuit of the converter model in the direct-drive unit module 100 and the external reactive power small disturbance hardware-in-the-loop simulation model are deployed in the FPGA, with a simulation step size configured to be extremely short, 2 microseconds, and no more than 2.5 microseconds, to ensure the simulation accuracy of switching actions. The grid dropout logic, protection logic, and some control logic are deployed in the CPU, with both the simulation step size and output step size configured to be 20 microseconds. The controller under test 600 is a direct-drive wind turbine converter controller, such as model NES5412-3000L, which connects to the real-time simulation host 500 via a physical interface. During the simulation, the system only connects to the converter control signal and not to the main control controller of the wind turbine, so that the impedance characteristics and power response of the unit M1 are completely determined by the controller under test 600, eliminating interference from the main control logic.
[0036] Measurement module 700: Used for real-time acquisition of key electrical quantities in the system. Measurement points are located at the 0.4 / 0.96kV busbar at the turbine end, the 35kV busbar on the high-voltage side of the transformer substation, and the 750kV busbar on the 71 side of line impedance L1. Furthermore, the wind turbine model parameters running in the real-time simulation host 500 are configured as follows: rated power 3200kW, rated voltage 690V, generator is a permanent magnet synchronous generator, grid-side filter capacitor is 1337uF, and filter inductor is 60uH.
[0037] A co-simulation architecture combining FPGA and CPU is adopted to address the high computational demands of high-frequency switching simulation of power electronic devices, achieving microsecond-level real-time response and making the electrical characteristics of the simulation environment highly similar to the real physical environment. Simultaneously, by connecting only the converter controller in a semi-physical manner, the regulation performance of the converter strategy under weak grid conditions can be evaluated.
[0038] Example 4
[0039] Reference Figures 1-7 This embodiment discloses a method for testing small reactive power disturbances outside the generator unit based on the above system.
[0040] The specific steps of this method are as follows: The first step is setup and configuration. Load the simulation model described in Example 1 into the real-time simulation host 500, and configure the transformer and line impedance according to the parameters in Example 2 to ensure that the short-circuit ratio at the machine end is stable at 1.5.
[0041] The second step is steady-state operation. Control the direct-drive unit M1 to enter grid-connected operation mode and adjust the preset operating conditions as follows: the active power output of the fan is 0.9 pu per unit, the reactive power is 0.3 pu, and the voltage at the generator terminal bus is maintained at 1.0 pu. Maintain this state for at least 2 seconds until the system reaches steady state.
[0042] The third step involves applying a disturbance by closing the circuit breaker 401a in the reactive power disturbance module 400 and connecting a 5% capacity capacitor C2 to the system. The system will then experience a reactive power surge. After maintaining this surge for a preset time, such as more than 2 seconds, the circuit breaker 401a is opened, disconnecting capacitor C2 and generating a reverse disturbance again.
[0043] The fourth step is data acquisition and evaluation. The measurement module 700 records data throughout the entire process at a high sampling rate of 10kHz. The focus is on monitoring the three-phase voltage and current waveforms at the generator terminal bus M3, the 35kV bus M4, and the L1 side of the transmission line, as shown below. Figure 6 As shown, the active and reactive power waveforms are as follows: Figure 7 As shown.
[0044] like Figure 6 As shown: Blue curve U: Bus voltage at the turbine terminal, i.e., per-unit value. Before the disturbance, it was stable at around 1.0 pu. At 5 seconds, a small fluctuation occurred due to the switching of capacitor C2, but it quickly recovered to a steady state with no obvious harmonic components, meeting the stability requirement of recovering to around 1.0 pu within 2000 ms. Orange curve Id: Active current component. It remained basically stable throughout, indicating that the active power output of wind turbine unit M1 did not fluctuate significantly due to reactive power disturbances, and the active power control strategy of unit M1 was effective. Cyan curve Iq: Reactive current component. It remained stable before and after the disturbance, demonstrating the stable reactive power support capability of wind turbine unit M1 under small reactive power disturbances, and that the reactive power control logic of the converter did not become unstable.
[0045] like Figure 7The diagram shows the waveforms of active and reactive power. The blue curve P(pu) represents active power, i.e., per-unit value. It remains stable at around 1.0 pu throughout, corresponding to the 0.9 pu active power setting in the test method. Due to a slight deviation in simulation accuracy, this indicates that the active power output of wind turbine unit M1 is unaffected by reactive power disturbances, demonstrating good active power stability during grid-connected operation. The orange curve Q(pu) represents reactive power, i.e., per-unit value. It remains stable at around 0.3 pu, consistent with the 0.3 pu reactive power setting in the test method. There are no significant fluctuations after disturbances, indicating that wind turbine unit M1 can maintain stable reactive power output under external reactive power disturbances, without reactive power oscillations or instability.
[0046] Based on the waveform characteristics of the two graphs, under the condition of small external reactive disturbances, the voltage, active / reactive current, and active / reactive power of the direct-drive wind turbine unit M1 can quickly recover to a steady state without harmonic amplification or power oscillation. It fully meets the stability judgment criteria of no obvious harmonics in the voltage during the disturbance, recovery to a steady state within 2000ms, and uninterrupted grid connection throughout the process, indicating that the wind turbine unit M1 has good grid-connected operation stability under this condition.
[0047] The result judgment criteria are as follows: during the disturbance process of capacitor C2 being connected and disconnected, if the direct drive fan can maintain uninterrupted grid-connected operation throughout the process, and the terminal voltage has no obvious harmonic components, and can stably recover to the steady-state value of 1.0 pu within 2000 ms (2 seconds) without continuous oscillation, then the reactive power small disturbance performance test of the tested controller 600 is judged to have passed.
[0048] By specifying specific initial active / reactive operating conditions (0.9 pu / 0.3 pu) and a high sampling rate (10 kHz) for monitoring, the reproducibility of test results was ensured, and control methods that meet the requirements of the verification procedure for the M1 electrical simulation model of wind turbine units and the guidelines for power grid safety and stability were selected.
[0049] To facilitate understanding of the technical solution of this invention, its working process is briefly described below: The electrical energy generated by the direct-drive unit module 100 is output via the generator bus M3, flowing sequentially through the first-stage transformer T1, the second-stage transformer T2, the third-stage transformer T3, and the fourth-stage transformer T4 for four-stage voltage boosting, and finally fed into the equivalent external power grid module 300 via transmission line L1. During testing, the controller under test 600 controls the generator M1 to generate electricity based on the voltage and current feedback collected by the measurement module 700. When the reactive power disturbance module 400 activates and capacitor C2 is connected, the voltage of the generator bus M3 changes abruptly, and the controller under test 600 needs to quickly adjust the generated reactive current to support the voltage to return to stability. The entire process is carried out in the real-time simulation host 500, which not only simulates the electrical characteristics of a real weak power grid but also verifies the actual performance of the physical controller.
[0050] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.
Claims
1. A hardware-in-the-loop simulation model for small external reactive disturbances, characterized in that: include, A direct-drive unit module (100) is used to simulate the power generation and converter characteristics of the unit (M1); A boost transmission module (200), which is connected to the direct drive unit module (100), is used to boost the terminal voltage of the unit (M1) step by step and transmit it to the grid side (M2). An equivalent external power grid module (300), connected to the end of the boost transmission module (200), is used to simulate an infinite voltage source; and, A reactive power disturbance module (400) is connected in parallel at the generator bus (M3) of the direct-drive unit module (100), and includes a controllable switching capacitor branch (401) for applying instantaneous reactive power disturbance to the generator bus (M3) during the test.
2. The semi-physical simulation model for small external reactive disturbances as described in claim 1, characterized in that: The boost transmission module (200) includes series-connected, The first-stage transformer (T1) is used to step up the 0.69kV voltage at the generator terminals to the 35kV bus (M4). The second-stage transformer (T2) is used to upgrade the 35kV to the 110kV bus (M5). The third-stage transformer (T3) is used to upgrade the 110kV to the 330kV bus (M6). The fourth-stage transformer (T4) is used to step up the 330kV voltage to the first 750kV busbar (M7); and, Transmission line (L1) is used to connect the first 750kV bus (M7) to the equivalent external power grid module (300).
3. The semi-physical simulation model for small external reactive disturbances as described in claim 1 or 2, characterized in that: The capacitor branch (401) in the reactive power disturbance module (400) includes, A capacitor (C2) is used to simulate a small external reactive power disturbance scenario. The capacity of the capacitor (C2) is set to 5% of the rated capacity of the direct drive unit module (100). Circuit breaker (401a), said circuit breaker (401a) is used to control the connection and disconnection of said capacitor (C2).
4. The semi-physical simulation model for small external reactive disturbances as described in claim 2, characterized in that: The rated voltages of the first-stage transformer (T1), the second-stage transformer (T2), the third-stage transformer (T3), and the fourth-stage transformer (T4) are 690V / 35kV, 35 / 110kV, 110 / 330kV, and 330 / 750kV, respectively, and the per-unit impedance values are 0.060, 0.105, 0.105, and 0.180, respectively, with an X / R ratio of 10. The rated voltage of the transmission line (L1) is 750kV, the per-unit impedance value is 0.216, and the X / R ratio is 10. By setting the impedances of the first-stage transformer (T1), the second-stage transformer (T2), the third-stage transformer (T3), and the fourth-stage transformer (T4), the short-circuit ratio of the generator terminal bus (M3) of the unit (M1) is made to be 1.
5. By setting the line impedance (L1), the short-circuit ratio at the second 750kV bus (M8) of the generating unit (M1) is made 4.6, and the short-circuit capacity is... ， in For short-circuit capacity, =7.6, The rated capacity of the unit (M1).
5. A hardware-in-the-loop simulation system for wind turbines, characterized in that: include, The real-time simulation host (500) is used to load and run external reactive small disturbance semi-physical simulation models; The controller under test (600) is connected to the real-time simulation host (500); The real-time simulation host (500) adopts an architecture of FPGA and CPU co-simulation. The converter and external reactive small disturbance semi-physical simulation model of the direct drive unit module (100) run in the FPGA, and the grid sag and control logic run in the CPU. Measurement module (700) is used to acquire three-phase voltage and current data.
6. The wind turbine hardware-in-the-loop simulation system as described in claim 5, characterized in that: The simulation step size of the real-time simulation host (500) is configured as follows: the simulation step size of the FPGA is 2 microseconds, and not greater than the minimum step size of 2.5 microseconds required for converter simulation; the simulation step size of the CPU is 20 microseconds, and the simulation output step size is 20 microseconds; the controller under test (600) only connects to the converter control signal during the simulation process, and does not connect to the wind turbine main control controller.
7. The wind turbine hardware-in-the-loop simulation system as described in claim 5 or 6, characterized in that: The parameters of the wind turbine unit (M1) model running in the real-time simulation host (500) are configured as follows: wind turbine unit (M1) rated power 3200kW, rated voltage 690V, grid-side filter capacitor 1337uF, grid-side filter inductor 60uH, generator type is permanent magnet synchronous generator; The measurement points of the measurement module (700) include the generator end bus 0.4 / 0.96kV, the high voltage side bus of the transformer substation 35kV, and the bus 71 side of the line impedance (L1) 750kV. The measurement points are used to collect three-phase voltage and current data.
8. A method for testing small external reactive power disturbances of a generator unit, characterized in that: include, An external reactive small disturbance semi-physical simulation model was built in the real-time simulation host (500), and the system impedance was configured so that the machine terminal short-circuit ratio was 1.
5. The control unit (M1) operates in parallel with the grid under preset active and reactive power conditions until the system reaches steady state; Close the circuit breaker (401a) in the reactive power disturbance module, put in a capacitor (C2) with a capacity of 5% of the rated capacity of the unit (M1), maintain operation for a preset time, and then disconnect the circuit breaker (401a) to disconnect the capacitor (C2). Collect and record the terminal voltage, active power, and reactive power waveforms during the connection and disconnection of the capacitor (C2) to assess whether the unit (M1) is operating stably.
9. The method for testing small reactive power disturbances outside the generating unit as described in claim 8, characterized in that: The preset active and reactive power operating conditions are configured as follows: adjust the active power output of the fan unit (M1) to 0.9 pu and the reactive power to 0.3 pu, and maintain the terminal bus voltage at 1.0 pu. After running for at least 2 seconds, the next operation will be performed.
10. The method for testing small reactive power disturbances outside the generator unit as described in claim 8 or 9, characterized in that: The requirements for data collection are as follows: use a sampling rate of 10kHz to record the three-phase voltage and current data of the generator terminal bus (M3), 35kV bus (M4) and transmission line (L1). If the test results show that the generator terminal voltage can recover to a stable state without continuous oscillation after the disturbance, the test is considered to have passed. The criteria for judging stability are: during the disturbance, the terminal voltage of the wind turbine unit (M1) has no obvious harmonic components, recovers to a steady-state value of 1.0 pu within 2000 ms, and the direct-drive wind turbine unit (M1) maintains uninterrupted grid-connected operation throughout the process.