Quasi-Steady-State Voltage Control Method, Device and Control System for Wind Farm with Coordinated Energy Storage

Abstract

The present invention discloses a quasi-steady-state voltage control method, device and control system for a wind farm with coordinated energy storage, belonging to the technical field of wind power generation control. The method includes: during the voltage support process after system fault clearing, first, based on the voltage information at the point of common coupling of the wind farm, start the quasi-steady-state voltage support control, and the wind turbine group and the centralized energy storage enter the first voltage support stage; the energy storage quickly absorbs active power, and the wind turbine group generates reactive power according to their respective capabilities; when the support reaches a small active-power to voltage coupling degree, enter the second voltage support stage, the energy storage exits the absorption of active power, the wind turbine group resumes active power and exits reactive power compensation until the voltage recovery of the wind farm is completed. The present invention coordinates the power output of the wind turbine group and the energy storage in the wind farm, and utilizes the coupling effect of active power and voltage, which can improve the effect and stability of quasi-steady-state voltage support, and finally realize the rapid recovery of the quasi-steady-state voltage of the wind farm after system fault clearing.

Description

Technical Field

[0001] The present invention belongs to the technical field of wind power generation control, and more specifically, relates to a quasi-steady-state voltage control method, device and control system for a wind farm that coordinates energy storage. Background Art

[0002] Wind power has developed rapidly due to advantages such as cleanliness and low cost. However, as synchronous machines in the system are gradually replaced by wind power, the voltage support capacity of the system weakens and the grid strength decreases. When a fault is cleared, the quasi-steady-state voltage recovery of the wind farm is slow, and in severe cases, the disconnection of the wind farm will further deteriorate the system stability. Providing quasi-steady-state voltage support for the wind farm is of great significance for the stable operation of the power grid.

[0003] During the low voltage period, the wind farm units can support the voltage at the point of common coupling of the station by flexibly controlling the output power of the power electronic converters. Existing voltage support mostly adopts the control of increasing reactive power output. The reactive power droop control based on the measured voltage is the most common in engineering. The dynamic reactive power support control considering current limitation and the maximum voltage support control using reactive power have also been studied. However, in the quasi-steady state after the fault is cleared, the wind turbines still need to recover active power to avoid wind abandonment and system instability. Therefore, the influence of active power on voltage in the quasi-steady state voltage support should also be considered. Research shows that the recovery of active power during the quasi-steady state process will deteriorate the voltage recovery. Therefore, the quasi-steady state voltage of the wind farm needs to design and control the active and reactive power dynamics simultaneously.

[0004] However, how to coordinate the centralized energy storage in the wind farm to design a method that can simultaneously utilize the active and reactive power dynamics to control the quasi-steady state voltage of the wind farm is an urgent problem to be solved. Summary of the Invention

[0005] In view of the above-mentioned defects or improvement requirements of the prior art, the present invention provides a quasi-steady-state voltage control method, device and control system for a wind farm that coordinates energy storage, aiming to solve the technical problem of how to design a method that can simultaneously utilize the active and reactive power dynamics to control the quasi-steady state voltage of the wind farm.

[0006] To achieve the above object, according to one aspect of the present invention, a quasi-steady-state voltage control method for a wind farm that coordinates energy storage is provided, including:

[0007] S1: When the voltage at the point of common coupling of the system wind farm meets the quasi-steady state support start criterion, control the wind turbine group and the centralized energy storage in the wind farm to enter the first voltage support stage;

[0008] S2: In the first voltage support stage, control each wind turbine in the wind turbine group to increase reactive power output, and control the centralized energy storage to absorb active power until the maximum value;

[0009] S3: If the voltage at the common coupling point of the system wind farm satisfies the active - voltage weak coupling condition during the first voltage support stage, then control the wind turbine group and the centralized energy storage to enter the second voltage support stage;

[0010] S4: During the second voltage support stage, control the centralized energy storage to stop absorbing active power until the absorbed power is zero; then, control the wind turbines to resume active power until each wind turbine resumes the active power corresponding to its maximum power tracking, and withdraw from reactive power compensation;

[0011] S5: When the voltage recovery completion condition is met, control the wind turbine group and the centralized energy storage to withdraw from the quasi - steady - state voltage support control.

[0012] In one embodiment, the quasi - steady - state support start criterion includes: the voltage U at the common coupling point PCC is lower than the first voltage threshold and suddenly increases by a value ΔU within the first preset time period PCC and is greater than the second voltage threshold.

[0013] In one embodiment, the control of each wind turbine in the wind turbine group to increase the reactive power in S2 includes:

[0014] Control the total reactive power reference value of the wind turbine group to be ;

[0015] Control the reactive power reference value of the i - th wind turbine in the wind turbine group to be

[0016] ;

[0017] where, K0, are the boundary coefficient and the droop coefficient respectively, U PCC is the voltage at the common coupling point, U ref is the reference voltage of the common coupling point, S max is the maximum capacity of the grid - side converter of a single wind turbine, and S WTi is the actual apparent power generated by the i - th wind turbine.

[0018] In one embodiment, the control of the centralized energy storage to absorb active power until the maximum value in S2 includes: controlling the centralized energy storage to absorb active power at a preset rate according to a ramp until the maximum value.

[0019] In one embodiment, the active - voltage weak coupling condition includes: the coupling degree between the output active power of the wind farm and the voltage at the common coupling point is less than the coupling threshold, and within a continuous second preset time period, the voltage U at the common coupling point PCCGreater than the third voltage threshold.

[0020] In one embodiment, the coupling degree Utilize

[0021]

[0022] Calculated; where P WF and Q WF are the total active power and reactive power output by the wind farm respectively, is the calculation formula simplification identifier, , is the ratio of the line impedance of the wind farm connected to the system to the equivalent impedance of the system, U K is the voltage of the node where the wind farm is connected to the system via the line, and SCR is the short-circuit ratio of the wind farm connected to the system.

[0023] In one embodiment, the voltage recovery completion condition includes: the voltage U of the point of common coupling PCC is not lower than the third voltage threshold and not higher than the fourth voltage threshold within the third preset time period.

[0024] According to another aspect of the present invention, there is provided a quasi-steady-state voltage control device for a wind farm coordinating energy storage, including:

[0025] A start-up module, configured to control the wind turbine groups and the centralized energy storage in the wind farm to enter the first voltage support stage when the voltage of the point of common coupling of the system wind farm meets the quasi-steady-state support start criterion;

[0026] A first support module, configured to control each wind turbine in the wind turbine groups to increase reactive power generation and control the centralized energy storage to absorb active power until the maximum value during the first voltage support stage;

[0027] A switching module, configured to control the wind turbine groups and the centralized energy storage to enter the second voltage support stage if the voltage of the point of common coupling of the system wind farm meets the active-voltage weak coupling condition during the first voltage support stage;

[0028] A second support module, configured to control the centralized energy storage to stop absorbing active power until the absorbed power is zero during the second voltage support stage; then, control the wind turbines to resume active power until each wind turbine resumes the active power corresponding to its maximum power tracking and exits reactive power compensation;

[0029] An exit module, configured to control the wind turbine groups and the centralized energy storage to exit the quasi-steady-state voltage support control when the voltage recovery completion condition is met.

[0030] According to another aspect of the present invention, there is provided a control system for a wind farm, including a memory and a processor. The memory stores a computer program, and when the processor executes the computer program, the steps of the method are implemented.

[0031] According to another aspect of the present invention, there is provided a computer-readable storage medium, on which a computer program is stored. When the computer program is executed by a processor, the steps of the method are implemented.

[0032] Generally speaking, compared with the prior art by the above technical solutions conceived by the present invention, the following beneficial effects can be achieved:

[0033] (1) This solution provides a quasi-steady-state voltage support strategy for a wind farm that coordinates energy storage. During the voltage support process after the system fault is cleared, first, based on the voltage information at the point of common coupling (PCC) of the wind farm, the quasi-steady-state voltage support control is started, and the wind turbine group and the energy storage enter the first voltage support stage; the energy storage quickly absorbs active power, and the wind turbine group generates reactive power according to their respective capabilities; when the support reaches a small active-voltage coupling degree, it enters the second voltage support stage, the energy storage exits the absorption of active power, the wind turbine group resumes active power and exits reactive power compensation until the voltage recovery of the wind farm is completed. The present invention coordinates the power output of the wind turbine group and the energy storage in the wind farm, and utilizes the coupling effect of active power and voltage, which can improve the effect and stability of quasi-steady-state voltage support, and finally realize the rapid recovery of the quasi-steady-state voltage of the wind farm after the system fault is cleared.

[0034] (2) The quasi-steady-state support start criterion described in this solution includes: the voltage U at the point of common coupling PCC is lower than the first voltage threshold and the sudden increase value ΔU within the first preset time period PCC is greater than the second voltage threshold. This method considers that the detection information comes from the point of common coupling of the wind farm, does not require detailed fault information, and realizes the start of quasi-steady-state voltage support based on local information.

[0035] (3) This solution designs the reactive power control of the wind turbine group based on the Logistic function. This method considers the problem that a large amount of reactive power decreases when the voltage difference decreases during the support, and through the design, the wind farm can still smoothly provide more reactive power, realizing quasi-steady-state rapid voltage support, which is beneficial to reducing the recovery period.

[0036] (4) The conditions of weak active-voltage coupling considered in this solution include: the coupling degree between the output active power of the wind farm and the voltage at the point of common coupling is less than the coupling threshold and within the continuous second preset time period, the voltage U at the point of common coupling PCCGreater than the third voltage threshold. This method designs an automatic switching during the quasi-steady-state voltage support stage based on the change in the coupling strength between active power and voltage during the voltage support process, facilitating the recovery of active power and deteriorating the voltage to a lesser extent.

[0037] (5) This solution quantifies the coupling relationship between the active power and voltage of the wind farm by considering the coupling degree calculation formula in the condition of weak active-voltage coupling, taking into account information such as the system short-circuit ratio and real-time voltage, which is beneficial to obtaining the coupling strength between active power and voltage in the current state.

[0038] (6) The voltage recovery completion condition described in this solution includes: the voltage U at the point of common coupling PCC is not lower than the third voltage threshold and not higher than the fourth voltage threshold within the third preset time period. This method designs to identify the situation of voltage recovery based on local information and realizes the automatic exit from the quasi-steady-state voltage support. Description of the Drawings

[0039] Figure 1 It is a flowchart of the quasi-steady-state voltage support strategy for a wind farm coordinating energy storage provided by an embodiment of the present invention.

[0040] Figure 2 It is a schematic framework diagram of the quasi-steady-state voltage support control strategy for a wind farm provided by an embodiment of the present invention.

[0041] Figure 3 It is a schematic diagram of the power coordination principle between a wind turbine and energy storage provided by an embodiment of the present invention.

[0042] Figure 4 It is a topological diagram of the wind farm grid-connected system for quasi-steady-state voltage support testing in an embodiment of the present invention.

[0043] Figure 5a It is the voltage result of the wind farm point of common coupling after a system fault in an embodiment of the present invention.

[0044] Figure 5b It is the active power output result of the wind farm with energy storage in an embodiment of the present invention.

[0045] Figure 5c It is the reactive power output result of the wind farm with energy storage in an embodiment of the present invention.

[0046] Figure 5d It is the active power output result of the energy storage in the wind farm in an embodiment of the present invention.

[0047] Figure 5e It is the real-time calculation result of the coupling degree of the wind farm in an embodiment of the present invention. Detailed Embodiment

[0048] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0049] Taking the actual wind farm parameters in a certain area as an example prototype. Based on the Matlab / Simulink platform, a wind farm with energy storage connected to the IEEE four-machine two-area model is built, and the wind farm replaces a synchronous machine in the original system. The wind farm consists of 15 equivalent wind turbines and a centralized energy storage. Each wind turbine is composed of a set of 10 direct-drive wind turbines with a capacity of 3.33 MW. The installed wind power penetration rate is 24.3%. The energy storage capacity is 10% of the capacity of the wind turbine cluster, that is, 50 MW. The wind speed of the wind farm is set to 16.0 m / s. The downstream wind turbines are affected by the wake effect. The disturbance is set to a three-phase short-circuit fault occurring at 1 / 3 of the near-bus 8 of the tie line 7-8 at t = 5 s, and the fault is cleared at t = 5.28 s.

[0050] As Figure 1 shown, a quasi-steady-state voltage support strategy for a wind farm coordinating energy storage is provided, which is applied to a wind farm with a centralized energy storage connected to the grid connection point. The quasi-steady-state voltage support strategy specifically includes:

[0051] S1: When the voltage at the point of common coupling of the system wind farm meets the quasi-steady-state support start criterion, control the wind turbine cluster and the centralized energy storage in the wind farm to enter the first voltage support stage;

[0052] S2: In the first voltage support stage, control each wind turbine in the wind turbine cluster to increase the reactive power output, and control the centralized energy storage to absorb the active power until the maximum value;

[0053] S3: If the voltage at the point of common coupling of the system wind farm meets the active-power-voltage weak coupling condition in the first voltage support stage, control the wind turbine cluster and the centralized energy storage to enter the second voltage support stage;

[0054] S4: In the second voltage support stage, control the centralized energy storage to stop absorbing the active power until the absorbed power is zero; then, control the wind turbines to resume the active power until each wind turbine resumes the active power corresponding to its maximum power tracking, and withdraw the reactive power compensation;

[0055] S5: When the voltage recovery completion condition is met, control the wind turbine cluster and the centralized energy storage to withdraw from the quasi-steady-state voltage support control.

[0056] Refer to Figure 1 and Figure 2, the design method is as follows:

[0057] S1: When the voltage at the point of common coupling of the system wind farm meets the quasi-steady-state support start criterion, generate a quasi-steady-state voltage support start signal;

[0058] As an optional implementation, the quasi-steady-state support start criterion in S1 is: the voltage U at the point of common coupling of the wind farm PCC is lower than 0.9 and the sudden increase value ΔU within 0.01 s PCC is greater than 0.2. It should be noted that the above numerical design is only for illustrative purposes, and the actual parameters can be near the example parameters.

[0059] Specifically, in the test system, the fault time is t = 5 s, and the fault clearing time is t = 5.28 s. By monitoring the voltage amplitude at the point of common coupling of the wind farm, the voltage amplitude increment at t = 5.29 s meets the quasi-steady-state voltage support start criterion, and the quasi-steady-state voltage support strategy is started.

[0060] S2: When receiving the quasi-steady-state voltage support start signal, the wind turbine group and the energy storage enter the first voltage support stage; among them, each wind turbine increases the reactive power according to the control based on the Logistic function, and the energy storage quickly absorbs the active power according to a ramp until the maximum value;

[0061] As an optional implementation, the reactive power control of the wind turbine group based on the Logistic function in S2 is specifically:

[0062] The total reactive power output of the wind turbine group is , and the reactive power reference value of each wind turbine is further calculated ; where Q WF is the total reactive power output reference value of the wind turbine group, Q WTi is the reactive power output reference value of the i-th wind turbine, K0, are the boundary coefficient and the droop coefficient respectively, U ref is the reference voltage of the point of common coupling, S max is the maximum capacity of the grid-side converter of a single wind turbine, S WTi is the actual apparent power generated by the i-th wind turbine. Specifically, in the embodiment, K0 = 5 is selected, , U ref = 1, S max is 3.33 MW.

[0063] S3: When the active-voltage weak coupling condition is met, generate a voltage support stage switching signal;

[0064] As an optional implementation, the active-voltage weak coupling condition in S3 is: the coupling degree between the active power output of the wind farm and the voltage at the point of common coupling and the voltage U at the point of common coupling of the wind farm is PCC > 0.97 within 300 ms continuously. It should be noted that the above numerical design is only for illustrative purposes, and the actual parameters can be near the example parameters.

[0065] The coupling degree is calculated using ; where P WF , Q WF are the total active power and reactive power output by the wind farm respectively, is the simplified identifier of the calculation formula, , is the ratio of the impedance of the line connecting the wind farm to the system to the equivalent impedance of the system, U K is the voltage at the node where the wind farm is connected to the system via the line, and SCR is the short-circuit ratio of the wind farm connected to the system.

[0066] Specifically, as shown in Figure 5a and Figure 5e , when t = 6.51 s, the voltage at the point of common coupling of the wind farm recovers to 0.97 and is not lower than 0.97 within 300 ms. The calculated coupling degree satisfies at t = 5.43 s and afterwards. Therefore, a voltage support stage switching signal is generated at t = 6.81 s.

[0067] S4: When receiving the voltage support stage switching signal, the wind turbine group and the energy storage enter the second voltage support stage, and the energy storage quickly exits the active power absorption according to a ramp until the absorption power is 0;

[0068] Specifically, after receiving the voltage support stage switching signal, the energy storage quickly exits the active power absorption according to a ramp and completely exits at t = 7.01 s.

[0069] Furthermore, when the centralized energy storage completely exits the active power absorption, the wind turbine group recovers the active power according to a ramp until the active power of each wind turbine unit recovers to the corresponding active power of its maximum power tracking, and at the same time gradually exits the reactive power compensation;

[0070] Specifically, the wind turbine group starts to recover the active power and exit the reactive power compensation at t = 7.01 s, and the active power recovers to the maximum power tracking reference value at t = 7.25 s.

[0071] S5: When the voltage recovery completion condition is satisfied, the wind turbine group and the energy storage exit the quasi-steady state voltage support control;

[0072] It should be noted that Figure 3 is the schematic diagram of the power coordination between the wind turbine unit and the energy storage provided by an embodiment of the present invention. Figure 4: is a wind farm grid-connected system topology diagram for quasi-steady-state voltage support test in an embodiment of the present invention. As an optional implementation, the voltage recovery completion condition in S5 is: the wind farm common coupling point voltage U PCC The voltage U of the common coupling point is not less than 0.97 and not more than 1.07 for a period of 2 seconds. PCC All of them are in the range of 0.97~1.07, so the quasi-steady-state voltage support control is exited at t = 9.01s. It should be noted that the above numerical design is only for example, and the actual parameters can be close to the example parameters.

[0073] The following is an explanation of the simulation data: The voltage results of the common coupling point of the wind farm after the system failure are as follows: Figure 5a As shown in Figure 2, the output active power of the wind farm with energy storage is as follows: Figure 5b As shown, the output reactive power result is as follows Figure 5c As shown, the output active power of the energy storage is as follows Figure 5d As shown, the real-time calculation results of coupling degree are as follows Figure 5e When the wind farm does not participate in voltage support, it does not generate reactive power during and after the system fault is cleared. Since the dynamic load in the comprehensive load absorbs a large amount of reactive power during this period, the voltage continues to be low, with a value of 0.66, and the voltage is unstable.

[0074] When dynamic voltage support control is adopted, the wind turbine increases reactive current according to the droop function after the fault is cleared. Since the reactive power increase is small near 0.9, the time to recover to the normal operation range is slow. The voltage recovery time from fault clearance to voltage recovery to the normal operation range is t3=2.97s; when dynamic reactive power control is adopted, the reactive current increases according to the step time to support, but after the fault is cleared, the short-term voltage reaches above 0.9 and automatically exits reactive compensation. The subsequent voltage recovery is slow, and the voltage recovery time is t2=4.98s; the proposed quasi-steady-state voltage support control starts at t=5.29s and enters the first stage of voltage support. While the energy storage absorbs active power, the wind turbine quickly increases reactive power according to the proposed function and enters the second stage of voltage support at t=6.81s. The voltage recovery time is t1=1.23s. The voltage recovery time is the shortest, thus achieving fast quasi-steady-state voltage support.

[0075] In another embodiment, a quasi-steady-state voltage control device for a wind farm coordinated with energy storage is provided, comprising:

[0076] A start-up module, used to control the wind turbines and centralized energy storage in the wind farm to enter the first voltage support stage when the voltage at the common coupling point of the system wind farm meets the quasi-steady-state support start-up criterion;

[0077] The first support module is used to control each wind turbine in the wind turbine group to increase reactive power generation during the first voltage support stage, and control the centralized energy storage to absorb active power until the maximum value;

[0078] The switching module is used to control the wind turbine group and the centralized energy storage to enter the second voltage support stage if the voltage at the common coupling point of the system wind farm satisfies the active-voltage weak coupling condition during the first voltage support stage;

[0079] The second support module is used to control the centralized energy storage to stop absorbing active power until the absorbed power is zero during the second voltage support stage; then, control the wind turbines to resume active power until each wind turbine resumes the active power corresponding to its maximum power tracking, and exit reactive power compensation;

[0080] The exit module is used to control the wind turbine group and the centralized energy storage to exit the quasi-steady state voltage support control when the voltage recovery completion condition is met.

[0081] In another embodiment, a control system for a wind farm is provided, including a memory and a processor. The memory stores a computer program, and when the processor executes the computer program, the steps of the method are implemented.

[0082] In another embodiment, a computer-readable storage medium is provided, on which a computer program is stored. When the computer program is executed by a processor, the steps of the method are implemented.

[0083] Those skilled in the art can easily understand that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A quasi-steady-state voltage control method for a wind farm coordinated with energy storage, characterized in that Including: S1: When the voltage at the point of common coupling of the system wind farm meets the quasi-steady-state support start criterion, control the wind turbine group and the centralized energy storage in the wind farm to enter the first voltage support stage; S2: In the first voltage support stage, control each wind turbine in the wind turbine group to increase the reactive power output, and control the centralized energy storage to absorb active power until the maximum value; S3: If the voltage at the point of common coupling of the system wind farm meets the active-voltage weak coupling condition in the first voltage support stage, control the wind turbine group and the centralized energy storage to enter the second voltage support stage; S4: In the second voltage support stage, control the centralized energy storage to stop absorbing active power until the absorbed power is zero; then, control the wind turbines to resume active power output until each wind turbine resumes the active power corresponding to its maximum power tracking, and stop the reactive power compensation; S5: When the voltage recovery completion condition is met, control the wind turbine group and the centralized energy storage to exit the quasi-steady-state voltage support control; The quasi-steady-state support starting criterion includes: the voltage U at the point of common coupling PCC is lower than the first voltage threshold and suddenly increases by a value ΔU within the first preset time period PCC and is greater than the second voltage threshold; The active-power-voltage weak coupling condition includes that the coupling degree between the output active power of the wind farm and the voltage at the point of common coupling is less than a coupling threshold value, and the voltage U at the point of common coupling is greater than a third voltage threshold value within a continuous second preset time period. PCC is greater than a third voltage threshold value.

2. The quasi-steady-state voltage control method for a wind farm with coordinated energy storage according to claim 1, characterized in that The step of controlling each wind turbine in the wind turbine group to increase the reactive power output in S2 includes: The total reactive power reference value for controlling the wind turbine group is ; Controlling the reactive power reference value of the i-th wind turbine in the wind turbine group to be ； Among them, K0, are the boundary coefficient and the droop coefficient respectively, U PCC is the voltage at the common coupling point, U ref is the reference voltage of the common coupling point, S max is the maximum capacity of the grid-side converter of a single wind turbine, S WTi is the actual apparent power output by the i-th wind turbine.

3. The quasi-steady-state voltage control method for a wind farm with coordinated energy storage according to claim 2, characterized in that, The step of controlling the centralized energy storage to absorb active power until the maximum value in S2 includes: controlling the centralized energy storage to absorb active power at a preset rate in a ramp until the maximum value.

4. The quasi-steady-state voltage control method for a wind farm with coordinated energy storage according to claim 1, characterized in that, The coupling degree Utilize Calculated; Among them, P WF , Q WF are the total active power and reactive power output by the wind farm respectively, is the simplified identifier of the calculation formula, , is the ratio of the impedance of the line connecting the wind farm to the system to the equivalent impedance of the system, U K is the voltage of the node where the wind farm is connected to the system through the line, and SCR is the short-circuit ratio of the wind farm connected to the system.

5. The quasi-steady-state voltage control method for a wind farm with coordinated energy storage according to claim 1, characterized in that, The voltage recovery completion condition includes: the common coupling point voltage U PCC is not lower than the third voltage threshold and not higher than the fourth voltage threshold within the third preset time period.

6. A quasi-steady-state voltage control device for a wind farm that coordinates energy storage, characterized in that, Including: A start module, used to control the wind turbine group and the centralized energy storage in the wind farm to enter the first voltage support stage when the voltage at the point of common coupling of the system wind farm meets the quasi-steady-state support start criterion; A first support module, used to control each wind turbine in the wind turbine group to increase the reactive power output and control the centralized energy storage to absorb active power until the maximum value in the first voltage support stage; A switching module, used to control the wind turbine group and the centralized energy storage to enter the second voltage support stage if the voltage at the point of common coupling of the system wind farm meets the active-voltage weak coupling condition in the first voltage support stage; A second support module, used to control the centralized energy storage to stop absorbing active power until the absorbed power is zero in the second voltage support stage; then, control the wind turbines to resume active power output until each wind turbine resumes the active power corresponding to its maximum power tracking, and stop the reactive power compensation; An exit module, used to control the wind turbine group and the centralized energy storage to exit the quasi-steady-state voltage support control when the voltage recovery completion condition is met; The quasi-steady-state support starting criterion includes: the voltage U at the point of common coupling PCC is lower than the first voltage threshold and suddenly increases by a value ΔU within the first preset time period PCC and is greater than the second voltage threshold; The active-power-voltage weak coupling condition includes: the coupling degree between the output active power of the wind farm and the voltage at the point of common coupling is less than a coupling threshold value, and the voltage U at the point of common coupling is greater than a third voltage threshold value within a continuous second preset time period. PCC is greater than a third voltage threshold value.

7. A control system for a wind farm, comprising a memory and a processor, the memory storing a computer program, characterized in that, When the processor executes the computer program, it implements the steps of the method described in any one of claims 1 to 5.

8. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by the processor, it implements the steps of the method described in any one of claims 1 to 5.

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