A fault ride-through coordination control method for a grid-forming wind storage system

Abstract

The application discloses a kind of network type wind storage system fault ride-through coordination control methods, comprising the following steps: S1, the main circuit topology model of network type wind storage system is established;S2, the influence on the transient stability of wind storage system under system fault state is considered based on the control method of main circuit topology model;S3, establish a variety of wind storage system transient stability promotion control strategy;S4, combined switch control realizes the fault ride-through coordination control of a variety of wind storage system transient stability promotion control strategy.The application significantly improves the transient stability and safety of the system through active power reference value switching, energy storage power regulation, power angle compensation and voltage amplitude switching strategy, effectively suppresses wind turbine speed fluctuation, power angle instability and short-circuit current impact and other problems, and has important theoretical significance and engineering value.

Description

Technical Field

[0001] This invention belongs to the field of new energy power generation and power system control technology, specifically, it relates to a fault ride-through coordinated control method for a grid-type wind-storage system. Background Technology

[0002] With the continuous increase in the grid-connected capacity of wind turbines, the safety and stability issues brought about by the high proportion of wind power connected to the grid have become a research hotspot. Traditional grid-connected wind turbines lack active support capabilities when the grid is disturbed, while grid-connected wind turbines, due to their ability to simulate the operating characteristics of synchronous generators and exhibiting "voltage source" characteristics, have gradually attracted widespread attention. To achieve energy balance within the wind turbine and improve transient and steady-state control capabilities, scholars at home and abroad have proposed an operation mode that equips the DC side of the grid-connected wind turbine converter with energy storage. However, in the event of a voltage drop in the grid, how to achieve fault ride-through through coordinated wind and energy storage operation control remains an urgent problem to be solved.

[0003] Currently, research on fault ride-through strategies for grid-connected converters mainly focuses on the withstand current of the grid-connected converter after a fault, the transient stability of the system, and reactive power support during the fault. Existing technologies include some studies proposing to suppress short-circuit current surges by introducing virtual impedance, but the current-limiting effect depends on the virtual impedance setting method; other studies reduce overcurrent problems through phase compensation and amplitude switching control, or reduce unbalanced power by urgently adjusting the pitch angle to change the output power of the generator-side converter. Furthermore, some studies propose transferring the active power deviation in virtual synchronization control to the energy storage control stage to absorb redundant energy, thereby improving the transient stability of the system. However, these methods have certain limitations in practical applications. For example, the change in equivalent impedance after a line short-circuit fault is not fully considered when deriving the dynamic compensation value of active power; while some new topologies can improve transient power angle stability and reactive power support capability, they increase equipment costs and are difficult to promote on a large scale.

[0004] Further analysis reveals that changes in turbine speed and converter port power angle during a fault may trigger system safety issues. Although the power difference can be reduced by adjusting the active power reference value or utilizing energy storage to absorb unbalanced power, the presence of virtual inertia, damping, and proportional-integral control elements results in a slow response speed, making it difficult to quickly achieve system stability. Furthermore, existing technologies lack sophisticated strategies for controlling the amplitude and phase of virtual voltage during faults, leading to limited fault current suppression and requiring further improvement in transient power angle stability. Therefore, developing a fault ride-through coordinated control strategy that comprehensively considers turbine speed, energy storage status, and virtual voltage and phase regulation has significant theoretical and engineering value. Summary of the Invention

[0005] The purpose of this invention is to provide a fault ride-through coordinated control method for grid-type wind and energy storage systems, which mainly solves the problems of wind turbine speed fluctuation, power angle instability and short-circuit current impact in existing grid-type wind and energy storage systems under grid voltage sag.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] A method for coordinated control of fault ride-through in a grid-type wind-storage system includes the following steps:

[0008] S1. Establish the main circuit topology model of the grid-type wind-storage system;

[0009] S2, The control method based on the main circuit topology model considers the impact of system fault conditions on the transient stability of the wind storage system;

[0010] S3, establish multiple control strategies to improve the transient stability of wind storage systems;

[0011] S4, combined with switch control, enables fault ride-through coordinated control of various wind and storage system transient stability enhancement control strategies.

[0012] Furthermore, in this invention, the main circuit topology model includes a permanent magnet direct-drive wind turbine, a machine-side converter, a grid-side converter, a DC-DC step-up transformer, and a supercapacitor; the permanent magnet direct-drive wind turbine is connected to the external wind farm collection bus via the machine-side converter and the grid-side converter; the supercapacitor is connected to the DC bus of the back-to-back machine-side converter and the grid-side converter via the DC-DC step-up transformer.

[0013] Furthermore, in step S2, the control method for the main circuit topology model includes:

[0014] The grid-side converter is controlled by adjusting the terminal voltage through the exciter control system of a synchronous generator, simulating the primary frequency regulation process and inertial damping characteristics of a synchronous generator to regulate the active power and frequency of the wind-storage system. At the same time, voltage and current dual-loop control is used to realize current vector limiting and voltage limiting.

[0015] The control of the generator-side converter is achieved by DC bus voltage control;

[0016] The supercapacitor is controlled by controlling the reference current with constant power. The size of the charge and discharge is controlled to achieve this.

[0017] Furthermore, in step S2, the transient stability of the wind-storage system is affected by the reduction of active power at the grid connection point during grid faults, which causes safety issues for the wind-storage system.

[0018] Furthermore, in step S3, the various transient stability improvement control strategies for the wind-storage system include:

[0019] The active power reference value switching control switches the active power reference value generation of the grid-side converter from the maximum power point tracking mode to the constant power mode.

[0020] Transient power regulation control that balances wind turbine speed and energy storage SOC, dynamically adjusting the energy storage power command value based on unbalanced power and energy storage SOC. Absorb redundant power;

[0021] Transient power angle compensation control uses a PI controller to generate a phase compensation amount to compensate for the virtual synchronization phase and stabilize the power angle. ;

[0022] Voltage amplitude switching control switches the virtual voltage reference value to the grid connection point voltage amplitude to suppress short-circuit current.

[0023] Furthermore, in this invention, the power in the constant power mode is the power value corresponding to the optimal speed before the fault.

[0024] Furthermore, in this invention, the formula for calculating the unbalanced power is:

[0025]

[0026] In the formula, For the input power of the machine-side converter, The active power at the grid connection point. This is the energy storage power command value before the fault; This is unbalanced power;

[0027] The energy storage power command value The adjustment rules are as follows:

[0028] When the energy storage is in the power absorption state and has not reached the SOC upper limit ;

[0029] When the energy storage is in the power output state ;

[0030] In the formula, This represents the upper limit of the power absorbed during operation.

[0031] Furthermore, in voltage amplitude regulation, the conditional expression for voltage amplitude switching is:

[0032]

[0033] In the formula, and These are the real-time measured amplitude of the grid connection point voltage and the rated voltage amplitude, respectively. This is the voltage reference value. This is the virtual voltage reference value after the switch; where pu is the per-unit value.

[0034] Furthermore, the fault ride-through coordination control process is as follows: after receiving the fault start signal, the active power reference value switching control, transient power adjustment control, transient power angle compensation control and voltage amplitude switching control are executed sequentially.

[0035] Compared with the prior art, the present invention has the following beneficial effects:

[0036] (1) This invention effectively absorbs redundant power during faults by switching active power reference values ​​and combining transient power regulation control that takes into account both wind turbine speed and energy storage SOC. This avoids large fluctuations in wind turbine speed due to power imbalance, solves the equipment safety problem caused by speed exceeding limits in traditional control, and improves the transient stability of the system.

[0037] (2) The present invention adopts transient power angle compensation control to control the power angle fluctuation within a safe range; at the same time, through voltage amplitude switching control, the voltage difference between the converter outlet and the grid connection point is significantly reduced, effectively suppressing the short circuit current and avoiding equipment overcurrent damage.

[0038] (3) This invention achieves orderly coordination of four transient stability improvement strategies through switch control, overcoming the shortcomings of slow response speed and limited stability improvement of a single control strategy. For example, in simulations where the voltage drops to 0.4 pu and 0.2 pu, the system's active power recovery speed is accelerated, and the fluctuation amplitudes of power angle, current, and speed during transient processes are significantly reduced, comprehensively improving the fault ride-through capability and operational safety of the grid-type wind-storage system under grid faults, and has important engineering application value. Attached Figure Description

[0039] Figure 1 This is a diagram of the main circuit topology of a grid-type wind-storage system in an embodiment of the present invention.

[0040] Figure 2 This is a schematic diagram of the machine-side converter control method in an embodiment of the present invention.

[0041] Figure 3 This is a schematic diagram of the grid-side converter control method in an embodiment of the present invention.

[0042] Figure 4 This is a schematic diagram of the supercapacitor control method in an embodiment of the present invention.

[0043] Figure 5 As described in the embodiments of the present invention Greater than A schematic diagram of active power at that time.

[0044] Figure 6As described in the embodiments of the present invention Less than A schematic diagram of active power at that time.

[0045] Figures 7-9 The transient response waveforms of active power in three modes are shown in the embodiments of the present invention when the voltage drops to 0.2 pu.

[0046] Figures 10-12 The transient response waveforms of the fan speed under three modes when the voltage drops to 0.2 pu in the embodiments of the present invention are shown.

[0047] Figures 13-15 The transient response waveforms of the wind turbine port power angle under three modes when the voltage drops to 0.2 pu in the embodiments of the present invention are shown.

[0048] Figures 16-18 The transient response waveforms of the grid connection point current under three modes when the voltage drops to 0.2 pu in the embodiments of the present invention are shown.

[0049] Figure 19 This is the transient power angle curve for conventional control in this embodiment of the invention.

[0050] Figure 20 This is a voltage phasor diagram under fault conditions in an embodiment of the present invention.

[0051] Figure 21 This is a block diagram of the fault traversal coordination control strategy in an embodiment of the present invention.

[0052] Figure 22 This is a flowchart illustrating the implementation of the fault traversal coordination control strategy in an embodiment of the present invention.

[0053] Figures 23-26 The simulated waveforms of active power, wind turbine speed, wind turbine port power angle, and grid connection point current when the voltage drops to 0.4 pu under the fault ride-through coordinated control strategy in this embodiment of the invention are shown.

[0054] Figures 27-30 The simulated waveforms of active power, wind turbine speed, wind turbine port power angle, and grid connection point current when the voltage drops to 0.2 pu under the fault ride-through coordinated control strategy in this embodiment of the invention are shown. Detailed Implementation

[0055] The present invention will be further described below with reference to the accompanying drawings and embodiments. The embodiments of the present invention include, but are not limited to, the following embodiments.

[0056] like Figure 1As shown, this invention discloses a fault ride-through coordinated control method for a grid-type wind-storage system. The main circuit topology of the grid-type wind-storage system includes a permanent magnet direct-drive wind turbine, a turbine-side converter, a grid-side converter, a DC-DC step-up transformer, and a supercapacitor. The permanent magnet direct-drive wind turbine captures wind energy and converts it into electrical energy. The turbine-side converter converts AC to DC and connects it to the DC bus. The turbine-side converter is an AC-DC converter, and the grid-side converter is a DC-AC converter; their connection forms a back-to-back bidirectional DC-DC converter. The back-to-back bidirectional DC-DC converter regulates the DC bus voltage to ensure efficient energy transfer. The grid-side converter inverts the DC to AC and connects it to the external power grid via the step-up transformer. The supercapacitor is connected to the DC bus via the DC-DC step-up transformer to absorb or release unbalanced power, enhancing the system's dynamic response capability.

[0057] Control methods for the main circuit topology model, such as Figures 2-4 As shown, the grid-side converter is controlled by simulating the exciter control system of a synchronous generator to regulate the terminal voltage, while simultaneously simulating the primary frequency regulation process and inertial damping characteristics of a synchronous generator to achieve regulation of the active power and frequency of the wind-storage system. Furthermore, a dual-loop voltage and current control module is used to implement current vector limiting and voltage limiting. The generator-side converter is controlled using DC bus voltage control to maintain DC bus voltage stability. The supercapacitor is controlled by constant power control of the reference current to achieve its charging and discharging process.

[0058] Transient stability issues in wind-storage systems arise during grid faults due to reduced active power at the grid connection point, leading to safety concerns. In the virtual synchronous control of the grid-side converter for the wind turbine, the active power-frequency regulation control equation is:

[0059] (1)

[0060] In the formula, , These are the active power and active power reference value at the grid connection point, respectively. , For virtual inertia and damping coefficient, Virtual synchronous angular velocity and rated angular velocity difference, This is a virtual synchronization phase.

[0061] From equation (1), we can see that, and The relative magnitudes of these factors affect the changes in virtual synchronous speed and virtual synchronous phase. Under normal operating conditions, Maximum Power Point Tracking (MPPT) mode is used to maximize the output power of the wind turbine, with an active power reference value. The expression is:

[0062] (2)

[0063] In the formula, air density; Where is the blade radius; The wind energy utilization coefficient, For the tip speed ratio, To determine the optimal rotational speed corresponding to the maximum power point at the given wind speed, This is the maximum power of the wind turbine. Approximate pitch angle Speed ​​ratio of leaf tip The nonlinear function is described by formula (3).

[0064] (3)

[0065] In the formula, For the introduction of intermediate variables; This refers to wind speed.

[0066] In the initial stage of a power grid fault, the active power at the grid connection point Reduce, and at the same time, the pitch angle control strategy will be based on Actual value control The increase leads to a higher wind energy utilization coefficient. The decrease leads to a reduction in the active power reference value under MPPT control. Reduce. That is, when a fault occurs, and Both will decrease, but the degree of decrease will differ, which may result in two situations: Greater than situation, Reduce to less than The situation. When Greater than The fan speed increases; when Less than The fan speed decreased.

[0067] In addition, according to formula (1), and Imbalance will cause The change in voltage phase at the grid connection point during a fault. It will also change, and the power angle at the wind turbine converter port is:

[0068] (4)

[0069] From formula (4), we can see that the angle of work It will change after the failure.

[0070] Therefore, after a fault, both the fan speed and power angle will change, and both may cause system safety issues. During a fault, if adjustments are made... The size and the utilization of energy storage to absorb part of the unbalanced power can both reduce and The power difference is used to adjust the fan speed and converter port power angle. However, this involves virtual inertia, damping, and proportional-integral control, resulting in a slow response. Therefore, adjusting the virtual phase and virtual voltage can be considered to provide transient stability of the power angle and limit short-circuit circuits.

[0071] Therefore, this embodiment presents several control strategies to improve the transient stability of the wind-storage system. The first control strategy is active power reference value switching control.

[0072] Before the malfunction, Generated under MPPT control; during fault period and fault recovery period, It can maintain MPPT control mode or operate in constant power mode. Therefore, settings are configured separately during the fault period and after the fault recovery. The following three operating modes will be discussed: Mode I - During the fault period and the initial stage of fault recovery, the MPPT operating mode will still be maintained, and the power reference value will be marked as... Mode II - Maintains the optimal speed during both the fault period and the initial recovery phase. The corresponding power is constant power operation, and the power reference value is marked as follows. Mode III - Maintain optimal speed during faults The corresponding power is constant during operation. In the initial stage of fault recovery, it is switched to MPPT operation mode, and the power reference value is marked as follows. . Figure 5 and Figure 6 These represent the initial stages of the fault. Greater than situation, Less than Under these conditions, the curves showing the changes in wind power captured by the wind turbine, the power reference value, and the active power at the grid connection point over time are shown. , , The wind power captured by the wind turbine in three modes. , , The output active power of the grid connection point under the three modes are respectively the active power output. The time of the failure This is the time when the fault is cleared.

[0073] Figure 5 In Mode I, during a fault, the active power at the grid connection point becomes... The bc segment of the curve, and The DC segment forms a speed acceleration zone; in the initial stage of fault recovery, the control strategy controls the active power tracking at the grid connection point. Power becomes The clg segment of the curve, and The cg segment forms a speed acceleration zone; therefore, in this mode, the wind turbine continuously accelerates from the moment the fault occurs until the initial stage of fault termination. In modes II and III, the active power at the grid connection point becomes [missing information - likely a value or parameter]. and The bi segment of the curve, and and The first segment forms the fan speed acceleration zone; in the middle of the fault, and Corresponding to the ie segment, and and The ije section forms a deceleration zone for the fan speed; in the later stages of the fault and during the fault recovery phase... and track and ,and and A speed reduction zone is formed, and the deceleration process in Mode II is faster than in Mode III during the initial stage of fault recovery. Meanwhile, during the fault, the active power reference value in Mode I... The decrease, with The area of ​​the angular acceleration region decreases; although the active power reference values ​​for Modes II and III do not decrease, due to... and Tracking the active power command value reduces the area of ​​the power angle acceleration region accordingly, which is beneficial to the stability of the transient power angle.

[0074] Figure 6 In Mode I, during a fault, the active power at the grid connection point becomes... The kdi segment of the curve, and The BDI segment forms a speed deceleration zone; in the initial stage of fault recovery, the control strategy controls the active power tracking at the grid connection point. Power becomes In the fkh segment of the curve, the speed tends to stabilize. Therefore, in this mode, the wind turbine continuously decelerates from the moment the fault occurs until the moment the fault ends. In modes II and III, during the initial stage of the fault, the active power at the grid connection point is... and The kl segment of the curve, and and The bl section forms a deceleration zone for the fan speed; during the middle and later stages of the fault, and Corresponding to the lf segment, and and The ljef section forms a zone where the fan speed accelerates; during the fault recovery phase... and track and ,and and A speed reduction zone is formed, and the deceleration process in Mode II is faster than in Mode III during the initial stage of fault recovery. This is because under Mode I... and Both decrease, resulting in a smaller area of ​​the power acceleration zone; in Mode II and Mode III, the area of ​​the power acceleration zone formed by the active power reference value and the active power at the grid connection point increases during the fault period.

[0075] Figures 7-18 The transient response waveforms of active power, turbine speed, turbine port power angle, and grid connection point current are presented under three modes when the grid voltage drops to 0.2 pu. The fault time is 6 seconds, and the fault duration is 4 seconds. It can be seen that when the voltage drops to 0.2 pu, in the initial stage of the fault, Less than In Mode I, the fan speed decreases; in Modes II and III, during the fault... track During the process, Greater than The wind turbine accelerates. When the voltage drops to 0.2 pu, the power angle fluctuations are relatively large during the fault period. In addition, the peak three-phase current at the grid connection point before the fault was 0.467 kA. When the voltage drops to 0.2 pu, the current at the initial stage of the fault is 1.31 times that before the fault; in the initial stage of fault recovery, the current reaches 1.23 times in Mode I, and 1.89 times in Modes II and III.

[0076] Based on the above analysis, it can be seen that using Mode II during the fault period and the initial stage of fault recovery is beneficial to power recovery, and the increase in fan speed is not too high.

[0077] Therefore, in this embodiment, active power reference value switching control is adopted to switch the active power reference value of the grid-side converter from Maximum Power Point Tracking (MPPT) mode to constant power mode. The power value in constant power mode is set to the power value corresponding to the optimal speed before the fault. This strategy suppresses turbine speed fluctuations and power angle instability by reducing the difference between the active power reference value and the actual output power.

[0078] The second control strategy is transient power regulation control that takes into account both turbine speed and energy storage SOC. The wind-storage system as a whole outputs power to the AC grid through the grid-side converter port, while the energy captured by the wind turbine is fed into the DC bus through the turbine-side converter, and the energy storage also exchanges energy through the DC bus. Therefore, during fault transients, some of the unbalanced power can be absorbed by adjusting the charging of the energy storage connected in parallel at the DC bus, reducing the wind turbine's rotational reserve or wind curtailment.

[0079] Since the energy storage is a supercapacitor with a fast response speed, it is considered to prioritize the absorption of unbalanced power by the energy storage. Simultaneously, the wind turbine speed is monitored in real time; if it exceeds 1.2 pu, the pitch angle is increased through pitch angle control. Assuming... This is the input power of the machine-side converter. For grid-side power at the grid connection point, Calculate the unbalanced power based on the power command value of the stored energy before the fault:

[0080] (5)

[0081] By combining the current state of power (SOP) and state of charge (SOC) of the energy storage, the power regulation capability is assessed, and the command value for switching after a fault is calculated and given. .

[0082] If it is in the power absorption state, that is, the power command at this time If the capacitor voltage at this time The voltage required to reach the designed SOC upper limit If the current operating state is maintained, then the current operating state will be maintained; otherwise, the absorption of unbalanced power will be allowed. Assume... This is the upper limit of the power absorbed during operation. for:

[0083] (6)

[0084] If it is in the power output state, that is ,calculate for:

[0085] (7).

[0086] The third control strategy is transient power angle compensation control. Considering the fast response of transient power angle compensation, direct compensation of the virtual phase angle is adopted. To achieve angular stability. Figure 19 This diagram illustrates the power angle curve of a grid-side converter under conventional control during a fault transient. The figure shows the power angle curve before the fault. It operates on curve I, and after a fault, the voltage drops and it operates on curve II. The power angle during normal operation. The power angle at the time of fault clearing is crucial. If the area of ​​the acceleration region formed at the time of fault clearing is larger than the maximum deceleration area, transient stability will be lost. If the power angle is controlled during the fault period, ensuring that at the time of fault clearing... Do not deviate Too far a distance will reduce the acceleration area, which is beneficial to system stability.

[0087] like Figure 20 As shown, assuming the grid-side converter port voltage was before the fault occurred, The grid connection point voltage is Before the fault, the phase difference between the two was The equivalent impedance between the grid-side converter and the grid connection point is After the fault, due to changes in network topology and the influence of control strategies, the voltage at the grid-side converter port becomes... The grid connection point voltage becomes After the fault, the phase difference between the two is If during the fault period, Do not deviate Too far, consider using power angle compensation control to ( Generated after proportional-integral control Direct compensation to virtual phase angle Above. By adopting power angle compensation control, the power angle stability can be improved and the fault current can be reduced. However, when the voltage drop is low, other control strategies are needed to further suppress the fault current.

[0088] The fourth control strategy is voltage amplitude switching control. The control equation for the virtual excitation voltage regulation module in the grid-side controller is:

[0089] (8)

[0090] In the formula, For virtual voltage, This is the voltage reference value. and These are the reference and actual values ​​for reactive power. and For proportionality coefficient and integral coefficient, This is the droop coefficient.

[0091] To reduce the voltage difference between the converter outlet and the grid connection point and suppress short-circuit current during fault voltage dips, voltage amplitude switching control is employed to reduce the voltage difference during faults. Switch to the grid connection point voltage amplitude to make the converter output voltage amplitude track the grid connection point voltage amplitude, as shown in the following expression:

[0092] (9)

[0093] In the formula, and These are the real-time measured amplitude of the grid connection point voltage and the rated voltage amplitude, respectively.

[0094] Fault traversal coordination control strategy block diagram as follows Figure 21 As shown, the active power reference value switching control, transient power regulation control, power angle compensation control, and voltage amplitude switching control are respectively controlled by switches. , , , control.

[0095] After receiving the fault start signal, via Switch to constant power reference value ; Calculate using formulas (6) and (7) ,Depend on accomplish Switch to ;Calculated under normal operating conditions and stored by memory elements Compensation phase difference after fault track After being output by the proportional-integral controller, it generates The virtual phase angle is compensated for in the virtual synchronization control. In this process, an improved virtual phase angle is formed. *;pass Depend on Switch to It is worth mentioning that during fault recovery, a sudden change in phase difference will still occur between the grid connection point and the converter port voltage. Therefore, the phase difference compensation control strategy will continue during this stage until steady state is reached after fault recovery. The specific implementation process is as follows: Figure 22 As shown.

[0096] To verify the effectiveness of the fault-crossing coordinated control strategy proposed in this paper, a system was built in PSCAD / EMTDC software as follows: Figure 1 A grid-connected simulation model of wind and energy storage was developed. The model includes a thermal power plant with three 350MW equivalent thermal power units (SCR=2); and 50 wind and energy storage systems, each consisting of a single 2MW direct-drive wind turbine and a supercapacitor with a rated capacity of 0.4MW*40s. A three-phase short-circuit fault is assumed to occur at t=6s, and the fault is cleared at t=10s. Figures 23-26 , Figures 27-30 Simulations were conducted to verify the implementation of the fault ride-through coordinated control strategy proposed in this invention when the grid connection point voltage dropped to 0.4 pu and 0.2 pu during a fault.

[0097] After the fault, the active power reference value is constant power. When the voltage drops to 0.2 pu, compare... Figures 27-30 and Figures 13-15 In Mode II, the speed increase is smaller; the power angle is controlled within a certain range during the fault. After the fault is recovered, The maximum current at the grid connection point during the transient process is 1.55 pu.

[0098] In summary, this invention significantly improves the transient stability of the system through active power reference value switching control, transient power regulation control, power angle compensation control, and voltage amplitude switching control. Voltage amplitude switching control effectively suppresses short-circuit current during faults. By dynamically adjusting the energy storage power command value, it fully utilizes energy storage to absorb unbalanced power, reducing the conversion of the wind turbine's rotational kinetic energy. Combining virtual phase and voltage amplitude regulation achieves rapid response and improves the overall system performance. This invention provides a fault ride-through coordinated control strategy that comprehensively considers wind turbine speed, energy storage status, and virtual voltage and phase regulation, possessing significant theoretical and engineering value.

[0099] The above embodiments are merely one of the preferred embodiments of the present invention and should not be used to limit the scope of protection of the present invention. Any modifications or refinements made to the main design concept and spirit of the present invention that are not of substantial significance, but solve the same technical problem as the present invention, should be included within the scope of protection of the present invention.

Claims

1. A method for coordinated control of fault ride-through of a grid-forming wind storage system, characterized in that, The method comprises the following steps: S1, establishing a main circuit topology model of the networked wind storage system; S2, considering the influence of the control method based on the main circuit topology model on the transient stability of the wind storage system under system fault state; S3, establishing multiple wind storage system transient stability improvement control strategies, including: active power reference value switching control, which controls the active power reference value of the grid-side converter to switch from maximum power point tracking mode to constant power mode; The transient power regulation control considers the fan rotating speed and the energy storage SOC, and dynamically adjusts the energy storage power instruction value according to the unbalanced power and the energy storage SOC , absorbs redundant power; Transient power angle compensation control, generating phase compensation through a PI controller to compensate for virtual synchronous phase to stabilize power angle ; voltage amplitude switching control, which switches the virtual voltage reference value to the grid point voltage amplitude to suppress short-circuit current; S4, combining switch control to realize the fault ride-through coordination control of multiple wind storage system transient stability improvement control strategies. 2.The method of claim 1, wherein, The main circuit topology model comprises a permanent magnet direct drive wind turbine, a machine-side converter, a grid-side converter, a DC-DC booster transformer and a super capacitor; the permanent magnet direct drive wind turbine is connected to the external wind farm collection bus through the machine-side converter and the grid-side converter; the super capacitor is connected to the DC bus of the back-to-back machine-side converter and grid-side converter through the DC-DC booster transformer.

3. The network-constructed wind storage system fault ride-through coordination control method according to claim 2, characterized in that, In the step S2, the control method of the main circuit topology model comprises: The control of the grid-side converter adjusts the terminal voltage by simulating the exciter control system of the synchronous generator, realizes the regulation of active power and frequency of the wind storage system by simulating the primary frequency regulation process and inertia damping characteristics of the synchronous generator, and realizes current vector limiting and voltage limiting by adopting voltage and current double-loop control; The control of the machine-side converter is realized by adopting DC bus voltage control; The control of the supercap is achieved by controlling the reference current of a constant power control The size of the reference current controls the charge and discharge of the supercap.

4. The network-constructed wind storage system fault ride-through coordination control method according to claim 3, characterized in that, In the step S2, the transient stability of the wind storage system causes safety problems of the wind storage system due to the decrease of active power at the grid point when the power grid fails.

5. The network-constructed wind storage system fault ride-through coordination control method according to claim 4, characterized in that, The power in the constant power mode is the power value corresponding to the optimal speed before the fault.

6. The network-constructed wind storage system fault ride-through coordination control method of claim 1, wherein, The calculation formula of the unbalanced power is: In the formula, is the input power of the machine-side converter, is the active power of the grid point, is the energy storage power command value before the fault; is the unbalanced power; The energy storage power instruction value The adjustment rule is that: When the energy storage is in the power absorption state and has not reached the upper SOC limit, ; When the energy storage is in a power delivery state, ; In the formula, is the upper limit value of the power absorbed for operation.

7. The network-constructed wind storage system fault ride-through coordination control method of claim 1, wherein, In the voltage amplitude regulation, the condition expression for voltage amplitude switching is: wherein, and are the amplitude of the real-time measurement of the grid-connected point voltage and the rated voltage amplitude, respectively; is the voltage reference value, is the virtual voltage reference value after switching, wherein p.u. is the per unit. 8.The method of claim 1, wherein, In the step S4, the fault ride-through coordination control process is: after receiving the fault start signal, the active power reference value switching control, transient power regulation control, transient power angle compensation control and voltage amplitude switching control are executed in sequence.

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