High-low voltage continuous ride-through control system and method for direct-drive fan

Abstract

The invention relates to the technical field of wind power generation grid-connected control, in particular to a direct-drive fan high-low voltage continuous ride-through control system and method, which comprises an instruction generation unit, a fault simulation unit, an electrical quantity acquisition unit, a fan protection execution unit and a continuous ride-through coordination unit, the fault simulation unit simulates various voltage faults through opening and closing combination, the electrical quantity acquisition unit captures parameter characteristics through multi-rate sampling and marks the faults, and the fan protection execution unit reduces active power and enhances reactive absorption for voltage rise, raises reactive current for drop and generates reverse reactive current to counteract negative sequence components during two-phase faults. And the continuous ride-through coordination unit switches a fault identifier and resets a strategy during voltage alternation, and outputs a ride-through signal and an authentication report after returning to normal, thereby solving the problems of insufficient adaptability to alternation faults and no difference in phase fault processing in traditional control, improving the grid-connected stability of a fan, and ensuring that wind power is safely accessed to a power grid.

Description

Technical Field

[0001] The present invention relates to the technical field of wind power generation grid-connected control, and in particular to a direct-drive wind turbine high and low voltage continuous ride-through control system and method. Background Art

[0002] Wind power grid-connected control is an important technology. In wind power generation systems, grid voltage often rises or falls suddenly due to faults. Direct-drive wind turbines must have the ability to ride through these voltage anomalies to maintain grid stability and avoid large-scale grid disconnection accidents. This technology is of great significance to ensuring the security of the grid after large-scale wind power access and improving the efficiency of renewable energy utilization. Traditional ride-through control methods for single voltage faults are no longer able to cope with the voltage fluctuation scenarios that may occur in the power grid.

[0003] However, the traditional direct-drive wind turbine voltage ride-through technology has the core problem of insufficient adaptability to continuous faults and conflicting control strategies. The existing scheme can only deal with a single type of voltage rise or drop fault, and does not consider the alternating occurrence of the two. When the grid first experiences a voltage rise and then quickly turns to a drop, the wind turbine's original power reduction and reactive absorption increase strategy cannot be switched in time, resulting in insufficient reactive power regulation capability and causing equipment overcurrent. At the same time, the same control logic is used for two-phase faults and three-phase faults, and no differentiated adjustment is performed for the negative sequence voltage component, which aggravates the voltage waveform distortion and causes the wind turbine protection system to malfunction and trigger disconnection. The combination of these problems causes the wind turbine to have a sudden drop in stability under complex voltage faults, which not only affects the continuity of wind power output, but may also cause grid chain failures, making it difficult to meet the stringent requirements of a high proportion of new energy grids for wind turbine ride-through capability. To solve this problem, we provide a direct-drive wind turbine high and low voltage continuous ride-through control system and method. Summary of the Invention

[0004] The object of the present invention is to provide a direct-drive wind turbine high and low voltage continuous ride-through control system and method to solve the problems raised in the above background technology.

[0005] 1. Because traditional systems cannot cope with alternating voltage rises and falls, untimely control strategy switching can lead to equipment overcurrent. Therefore, this case uses a continuous through-coordination unit to monitor voltage alternations and reset the control strategy, ensuring the stability of the wind turbine under complex fault conditions.

[0006] 2. Because traditional systems use the same control logic for two-phase and three-phase faults and do not differentiate between adjusting the negative-sequence component, which exacerbates waveform distortion, this case uses the wind turbine protection execution unit to calculate the negative-sequence component and generate reverse reactive current, which can reduce voltage distortion and avoid malfunction of the protection system.

[0007] To achieve the above objectives, a direct-drive wind turbine high and low voltage continuous ride-through control system is provided, including: An instruction generation unit, configured to generate a circuit breaker action timing instruction according to a target fault type; The fault simulation unit is connected to the instruction generation unit and actively generates any of the following voltage fault conditions on the high-voltage side of the direct-drive wind turbine chassis by performing the circuit breaker opening or closing operation: No-load boost fault, two-phase boost fault or three-phase boost fault in which the voltage is boosted to a preset boost ratio of the rated voltage; The voltage drops to a preset drop ratio of the rated voltage or zero in a no-load drop fault, a two-phase drop fault, or a three-phase drop fault; An electrical quantity collection unit, connected to the fault simulation unit, collects line voltage, positive sequence voltage, active power, reactive power and reactive current parameters on the high-voltage side of the box-type transformer in real time; The fan protection execution unit is connected to the electrical quantity acquisition unit and dynamically executes the fan control strategy according to the collected electrical quantity parameters: When a voltage rise fault is detected, the wind turbine's active power output is reduced and reactive power absorption is increased; When a voltage drop fault is detected, the wind turbine’s reactive current output is increased and the active power ramp-up rate is limited; The continuous crossing coordination unit is connected to the wind turbine protection execution unit. During the duration of a single fault: If it is detected that the voltage rises and falls alternately, the voltage fault type identifier is switched and the control strategy of the wind turbine protection execution unit is reset; When the electrical quantity parameters return to the rated range, the control strategy restrictions are released and a crossing success signal is output.

[0008] A second object of the present invention is to provide a method for implementing a high and low voltage continuous ride-through control system for a direct-drive wind turbine including any one of the above, comprising the following steps: S1. The instruction generation unit generates circuit breaker action sequence instructions based on the target fault type. The fault simulation unit actively generates a voltage fault condition with a preset rise or fall ratio on the high-voltage side of the box-type transformer through a combination of opening and closing operations. The no-load rise only operates the collector line circuit breaker. Differentiated impedance control is implemented for two-phase faults. Current-limiting reactors are synchronously connected for three-phase faults. All circuit breakers operate sequentially at adjustable time intervals. S2, the electrical quantity acquisition unit uses a multi-rate sampling mechanism to capture the high-frequency distortion characteristics of line voltage and the changing trends of power parameters in real time. When the positive sequence voltage continuously exceeds the threshold, the fault type is marked and a protection reference benchmark is generated based on the sliding average of the pre-fault parameters. S3: The wind turbine protection execution unit responds to voltage rises by reducing active power output in stages and increasing reactive power absorption in steps. In response to voltage drops, it increases reactive current output and limits the active power ramp rate. Under two-phase faults, it generates reverse reactive current to offset the negative sequence component and dynamically limits the active power upper limit. When high and low voltages alternate, it switches the fault flag and resets the control strategy through the continuous crossing coordination unit, retaining reactive power in reserve or resetting the power reduction starting point. S4. When the electrical quantity parameters return to the rated range, the continuous ride-through coordination unit releases the control restrictions and outputs a ride-through success signal, and simultaneously generates a certification report containing the fault type, line voltage waveform, and power curve.

[0009] Compared with the prior art, the present invention has the following beneficial effects: 1. The continuous ride-through coordination unit monitors the alternating changes of voltage rise and fall in real time. Once the alternation is identified, the fault type identifier is immediately switched and the control strategy is reset according to the switching direction. When the voltage changes from rise to fall, some reactive power absorption capacity is retained as a backup. When the voltage changes from fall to rise, power reduction control is performed with the current active power as the new starting point. This avoids the insufficient reactive power regulation capability caused by the switching lag of the traditional strategy, effectively prevents equipment overcurrent, and ensures the stable operation of the wind turbine under complex voltage fluctuations.

[0010] 2. For two-phase faults, the wind turbine protection execution unit calculates the negative-sequence voltage component in real time, generates a reactive current in the opposite phase to offset the negative-sequence effect, and dynamically adjusts the upper limit of active power output according to the severity of the negative-sequence component, solving the problem of voltage waveform distortion caused by traditional unified control logic. For three-phase faults, proportional voltage suppression is achieved by synchronously connecting current-limiting inductors, reducing the risk of malfunction of the protection system caused by waveform distortion and lowering the risk of grid disconnection.

[0011] 3. The fault simulation unit and the electrical quantity acquisition unit work together to enhance efficiency. The fault simulation unit performs opening and closing operations in a sequenced manner according to the preset circuit breaker combination logic, accurately simulating the transient process of various voltage faults. The electrical quantity acquisition unit adopts a multi-rate sampling mechanism, capturing voltage waveform distortion at high frequency and tracking power change trends at medium frequency, and generates a protection benchmark based on the sliding average before the fault, providing accurate data support for the control strategy, improving the accuracy and reliability of ride-through control, ensuring the continuity of wind power output, and adapting to the stringent requirements of a high-proportion new energy power grid. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 It is an overall block diagram of the present invention; Figure 2 It is the overall flow chart of the present invention.

[0013] The meaning of each number in the figure is: 1. Instruction generation unit; 2. Fault simulation unit; 3. Electrical quantity acquisition unit; 4. Fan protection execution unit; 5. Continuous crossing coordination unit. DETAILED DESCRIPTION

[0014] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0015] The present invention provides a high and low voltage continuous ride-through control system for direct-drive wind turbines. Figure 1 As shown, including: Instruction generation unit 1, used to generate circuit breaker action timing instructions according to the target fault type; The fault simulation unit 2 is connected to the instruction generation unit 1 and actively generates any of the following voltage fault conditions on the high-voltage side of the direct-drive wind turbine chassis by performing the circuit breaker opening or closing operation: No-load boost fault, two-phase boost fault or three-phase boost fault in which the voltage is boosted to a preset boost ratio of the rated voltage; The voltage drops to a preset drop ratio of the rated voltage or zero in a no-load drop fault, a two-phase drop fault, or a three-phase drop fault; To accurately simulate different types of voltage faults, the fault simulation unit 2 matches the preset circuit breaker combination logic according to the fault type when performing opening and closing operations, and generates fault conditions close to the actual power grid through differentiated operations. The specific implementation method is as follows: Among them, for the no-load rise fault, that is, the abnormal voltage rise that occurs when the fan is not loaded, only the collector line connection circuit breaker is operated to reduce power interference. The voltage needs to be raised to a preset proportion of the rated voltage, and ensure that there is no active power fluctuation interference during the fault process. Disconnect the connection circuit breaker between the collector line and the fan to put the fan in a no-load state to avoid the fan output power affecting the voltage detection. By adjusting the voltage regulator on the grid side, the voltage is gradually raised. At the same time, the high and low voltage side circuit breakers of the box transformer are kept in a closed state to ensure that the voltage rise only acts on the high-voltage side of the box transformer. When the voltage stabilizes and reaches the preset rise ratio, this state is maintained until the end of the fault simulation. In the no-load state, only the collector line circuit breaker is controlled by opening and closing to isolate the influence of the fan power output on the voltage, ensuring the simulated rise fault. The fault is pure and repeatable. For a two-phase rise fault, that is, a voltage rise occurs on any two phases in a three-phase circuit, differentiated impedance control is performed to raise the voltage of the specified phase, so that the voltage of phases A and B is raised to 110% of the rated voltage, and phase C maintains the rated voltage. This simulates an asymmetric grid fault, disconnects the corresponding line circuit breakers of A and B, and connects a current-limiting resistor with a preset resistance in its circuit. For example, phase A is connected to 5 ohms, phase B is connected to 5 ohms, and the phase C circuit breaker remains closed without impedance connection. The A and B circuit breakers are reclosed, and the connected impedance causes the voltage of these two phases to rise due to the voltage divider effect, while phase C maintains the rated voltage due to the lack of impedance connection. The line voltage is monitored in real time, and the impedance value is adjusted to stabilize the voltage of phases A and B at the preset rise ratio. The logic of differentiated impedance control is: By connecting impedance to the fault phase separately, an asymmetric voltage distribution is artificially created, accurately simulating the common two-phase voltage anomalies in the power grid, providing a typical scenario for the verification of subsequent wind turbine protection strategies. For three-phase drop faults, that is, when the three-phase voltages drop to a preset proportion of the rated voltage at the same time, the current-limiting reactor is synchronously connected to achieve proportional voltage suppression, and all circuit breaker operations are sequenced at adjustable time intervals to simulate the transient process of the power grid, so that the voltages of phases A, B, and C drop to 20% of the rated voltage at the same time, simulating a serious symmetrical fault in the power grid. Current-limiting reactors of the same specifications are connected in series in the three-phase lines on the high-voltage side of the box-type transformer, such as 10 millihenry per phase. The instruction generation unit 1 sends a synchronous opening and closing signal to control the three-phase circuit breakers to open and close at the same time, ensuring that the reactors are synchronously connected to the three-phase circuit. The inductive reactance characteristics of the reactor are used to reduce the three-phase voltage drop due to the inductive reactance at the same time, while maintaining the symmetry of the three-phase voltage and the consistent drop ratio. The logic of synchronous connection is: Three-phase faults require voltage symmetry. Reactors with identical parameters and synchronous operation are used to ensure equal voltage drops across the three phases. This prevents the introduction of additional negative sequence components due to asynchronous operation, which could affect the accuracy of fault simulation. Circuit breaker operations for all types of faults are sequenced at adjustable time intervals to simulate grid transients. The operation sequence table is set as follows: For example, in a three-phase drop fault, the sequence of "opening the three-phase circuit breaker (50 milliseconds) → connecting the reactor (50 milliseconds) → closing the three-phase circuit breaker (50 milliseconds)" takes a total of 150 milliseconds, which is close to the rapid change characteristics of actual power grid faults. A verification link is set between each operation step. After the circuit breaker is disconnected, the loop current is checked to see if it is zero. This ensures that the operation is in place before executing the next step to avoid fault simulation distortion caused by incorrect operation. For example, when simulating a continuous fault of "two phases rising first, then three phases falling", the two-phase rising sequence is first executed (total time 200 milliseconds), and the three-phase falling sequence operation is automatically started after an interval of 100 milliseconds. The dynamic evolution process of the power grid fault is restored by time interval control. The fault simulation unit 2 can accurately generate various voltage fault conditions, which not only ensures the diversity of fault types, but also restores the transient characteristics of the power grid through serialized operations, providing a real and reliable fault environment for electrical quantity acquisition and verification of wind turbine protection strategies.

[0016] The electrical quantity acquisition unit 3 is connected to the fault simulation unit 2 to collect the line voltage, positive sequence voltage, active power, reactive power and reactive current parameters of the high-voltage side of the box-type transformer in real time; To accurately capture the dynamic characteristics of electrical parameters on the high-voltage side of the direct-drive wind turbine chassis, the electrical quantity acquisition unit 3 adopts a multi-rate sampling mechanism, combined with a fault marking system and benchmark generation logic, to provide reliable data support for the wind turbine protection strategy. The specific implementation is as follows: Differentiated sampling rates are used based on the changing characteristics of different electrical parameters to ensure that key features are not missed. Voltage signals are sampled at high frequencies to capture waveform distortion. For voltage signals such as line voltage and positive-sequence voltage, high-frequency sampling is used, sampling 10 times per millisecond. This focuses on capturing voltage waveform distortion features, such as spikes during voltage swells, dips during voltage dips, and asymmetric waveforms during two-phase faults. For example, in the event of a two-phase surge fault, high-frequency sampling can clearly record the instantaneous jump details of the faulted phase voltage, while also accurately capturing the slight fluctuations in the normal phase voltage, providing raw data for subsequent negative-sequence component calculations. Power parameters are sampled at intermediate frequencies to track trend changes. For power parameters such as active power, reactive power, and reactive current, intermediate-frequency sampling is used, sampling 100 times per second, to track their changing trends, including the gradual decrease in active power and the step-by-step increase in reactive current during voltage surges. For example, during a voltage sag, intermediate-frequency sampling can record the continuous change curve of reactive current slowly rising from the rated value to the safety limit, reflecting its regulation trend without the need for high-frequency sampling and avoiding data redundancy. The logic of multi-rate sampling is as follows: Voltage waveform distortion is often instantaneous (millisecond level), and high-frequency capture is required to retain details, while power parameter changes are relatively slow (second level), and medium-frequency sampling can reflect trends. The combination of the two reduces data processing pressure while ensuring data integrity. At the same time, a fault marking system is established to monitor the positive-sequence voltage status in real time and trigger the corresponding fault identification. When the positive-sequence voltage exceeds the high-voltage threshold or falls below the low-voltage threshold within a preset time range, the corresponding fault identification is triggered. The high-voltage threshold (such as 110% of the rated voltage) and the low-voltage threshold (such as 90% of the rated voltage) are preset, and the duration condition is set at the same time. The positive-sequence voltage exceeds the high-voltage threshold for 20 milliseconds, or falls below the low-voltage threshold for 20 milliseconds to avoid false marking caused by instantaneous interference. When the positive-sequence voltage exceeds the high-voltage threshold and meets the duration condition, it is marked as a "voltage rise fault", and is further combined with the line voltage data to distinguish whether it is a two-phase rise or a two-phase rise. If the three phases are raised and only the voltages of phases A and B exceed the threshold, it is marked as "two-phase rise". When the positive sequence voltage is lower than the low voltage threshold and meets the duration condition, it is marked as "voltage drop fault". Similarly, two-phase drop or three-phase drop is distinguished. For example, if the positive sequence voltage is at 115% of the rated voltage (ultra-high voltage threshold) for 30 milliseconds and the line voltage shows that all three phases exceed the threshold, the system marks it as "three-phase rise fault", providing clear fault type information for the wind turbine protection execution unit 4, and generating a protection strategy reference benchmark based on the sliding average value of the parameters before the fault occurs. The reference benchmark of the protection strategy is generated to ensure the rationality of the strategy adjustment, and the sliding window length before the fault is set. The window contains all sampling data 1 second before the fault occurs, that is, the historical values ​​of voltage and power. The parameters in the sliding window, that is, the active power and reactive current during normal operation, are calculated with an average value as the "reference state" before the fault occurs. For example, the sliding average of active power within 1 second before a fault is 800 kilowatts. This value serves as the reference starting point for power reduction operations when the voltage rises. Starting from 800 kilowatts, the power is reduced in stages. The reference benchmark is updated in real time as the window scrolls, ensuring that it always reflects the stable operating state before the fault occurs. For example, if the wind turbine is in a power fluctuation stage before the fault, the sliding average value will be dynamically adjusted to avoid the benchmark distortion caused by the use of a single fixed value. The electrical quantity acquisition unit 3 not only accurately captures the voltage distortion details and power change trends through multi-rate sampling, but also clarifies the fault type through the fault marking system. It also provides an adjustment starting point for the protection strategy based on the sliding average value, making the subsequent control of the wind turbine protection execution unit 4 more in line with the actual operating state, improving the accuracy and reliability of high and low voltage ride-through control.

[0017] The fan protection execution unit 4 is connected to the electrical quantity acquisition unit 3 and dynamically executes the fan control strategy according to the collected electrical quantity parameters: When a voltage rise fault is detected, the wind turbine's active power output is reduced and reactive power absorption is increased; When a voltage drop fault is detected, the wind turbine’s reactive current output is increased and the active power ramp-up rate is limited; To ensure stable operation of the wind turbine during voltage anomalies, the wind turbine protection execution unit 4 adopts differentiated dynamic adjustment strategies for voltage rise and fall faults, achieving high and low voltage ride-through through phased and stepped power control. The specific implementation methods are as follows: When the wind turbine protection execution unit 4 responds to a voltage rise fault, the wind turbine protection execution unit 4 reduces active power and increases reactive power absorption according to preset stages, as follows: The system reduces wind turbine active power output in stages and increases reactive power absorption in a step-by-step manner. In response to a voltage sag fault, reactive current output is increased to a safe limit and the active power ramp-up rate is limited. The power change rate in each stage is set to a configurable gradient value. The system is divided into three stages based on the voltage rise: Stage 1 (a 10%-20%), Stage 2 (20%-30%), and Stage 3 (above 30%). Each stage corresponds to a configurable power change rate gradient. For example, in Stage 1, the rated active power is reduced by 10% per minute, in Stage 2 by 20%, and in Stage 3 by 30%. The reactive power absorption intensity is also set in a stepped manner: absorbing 20% ​​of the rated reactive power in Stage 1, 40% in Stage 2, and 60% in Stage 3. The maximum absorption intensity does not exceed the rated reactive capacity of the wind turbine.

[0018] Phase 1: When a voltage rise of 15% (Phase 1 range) is detected, the active power is reduced at a rate of 10% per minute, from the rated 1000 kW to 900 kW, while absorbing 20% ​​of the rated reactive power to prevent further voltage rise; Phase 2: If the voltage continues to rise to 25% (Phase 2 range), the active power reduction rate is accelerated to 20% per minute, from 900 kW to 720 kW, and reactive power absorption is increased to 40%. The voltage rise is suppressed by increasing reactive power consumption. Phase 3: If the voltage exceeds 30%, the active power is reduced to a safe value (300 kilowatts) at a rate of 30% per minute, and reactive power absorption is increased to 60% to maximize grid voltage stability. The greater the voltage rise, the more significant the impact on the grid. By gradually increasing the regulation intensity, secondary disturbances caused by power surges can be avoided and voltage anomalies can be specifically suppressed. When a "voltage sag fault" is detected, that is, the positive sequence voltage falls below 90% of the rated value, a strategy of increasing reactive current is implemented, supplemented by limiting active power increases: The voltage dip is divided into stages according to its depth, i.e., a dip of 10%-30% is Stage A, 30%-50% is Stage B, and more than 50% is Stage C. Each stage corresponds to a reactive current output gradient: Stage A outputs 30% of the rated current, Stage B outputs 60%, and Stage C outputs 90%, all of which do not exceed the rated current safety limit. For example, if the voltage dips by 20% (Stage A), the reactive current is immediately increased from the rated 200 amperes to 30% (60 amperes); if it drops to 40% (Stage B), it is increased to 60% (120 amperes). Reactive power is injected to support the grid voltage recovery. The maximum active power ramp-up rate is set to no more than 10% of the rated value per minute to avoid a rapid increase in active power during a voltage dip, which would increase the grid burden. For example, during voltage recovery, when the active power recovers from 300 kilowatts, it can increase by a maximum of 100 kilowatts (10% of the rated value) per minute to ensure that no voltage drop occurs before the voltage stabilizes. When new power fluctuations occur and the voltage drops, the voltage is supported by reactive current first, while the active power climbing speed is limited to prevent the grid from bearing additional load in a fragile state and ensure the stability of voltage recovery. The power change rate gradient value of each stage can be flexibly configured according to the wind turbine model and grid requirements. For large-capacity wind turbines (such as 5 MW and above), the gradient value can be set small (such as a 5% reduction per minute in stage 1) to avoid excessive adjustment range affecting grid stability. For wind turbines connected to weak grids, the gradient value can be set large (such as a 15% reduction per minute in stage 1) to speed up the response speed and suppress the spread of voltage anomalies. For example, a 2 MW wind turbine is connected to a strong grid, and the active power reduction gradient in the voltage rise stage 1 is set to 8% per minute, while the gradient in the same stage when connected to a weak grid is set to 12% per minute. This ensures that the adjustment strategy matches the actual operating environment, effectively supports grid stability while ensuring the safety of the wind turbine itself, and achieves continuous riding through high and low voltages.

[0019] When processing a two-phase lift fault or a two-phase drop fault, the wind turbine protection execution unit 4 calculates the negative sequence voltage component in real time and generates a reverse phase reactive current based on it, and dynamically adjusts the active power output upper limit value according to the severity of the negative sequence voltage component.

[0020] To address the voltage waveform distortion caused by the negative-sequence voltage component in two-phase faults, the wind turbine protection execution unit 4 achieves precise suppression of two-phase rise or fall faults by real-time calculation of the negative-sequence component, generation of reverse reactive current, and dynamic adjustment of the active power upper limit. The specific implementation is as follows: When the electrical quantity acquisition unit 3 marks a "two-phase rise fault" (e.g., the voltages of phases A and B rise, and phase C is normal) or a "two-phase drop fault" (e.g., the voltages of phases A and B drop, and phase C is normal), the fan protection execution unit 4 immediately starts the calculation of the negative sequence voltage component: The real-time line voltage values ​​of the three phases A, B, and C on the high-voltage side of the box-type transformer are obtained through high-frequency sampling (such as 1100 volts for phase A, 1100 volts for phase B, and 1000 volts for phase C, with a rated voltage of 1000 volts). Based on the asymmetric characteristics of the three-phase voltage, the symmetrical component method, a method of decomposing asymmetrical three-phase quantities into symmetrical components, is used to extract the negative-sequence voltage component. The magnitude of the negative-sequence component reflects the degree of asymmetry of the three-phase voltage. The larger the component, the more serious the disturbance to the power grid caused by the two-phase fault. That is, the calculated negative-sequence voltage component is 100 volts, indicating a high degree of asymmetry. The core feature of a two-phase fault is the asymmetry of the three-phase voltage. The negative-sequence component is a key indicator for quantifying this asymmetry. Its value directly determines the strength of the subsequent suppression strategy. According to the calculation The negative sequence voltage component generated generates a reactive current of the opposite phase to offset its influence. The phase of the reverse phase reactive current is opposite to the phase of the negative sequence voltage component, that is, the phase of the negative sequence voltage component is 60 degrees, and the current phase is 240 degrees. The amplitude is proportional to the size of the negative sequence voltage component. For example, a negative sequence component of 100 volts corresponds to a reverse reactive current of 200 amperes, and a component of 50 volts corresponds to 100 amperes, ensuring that the current can accurately neutralize the interference of the negative sequence component. The generated reverse phase reactive current is injected into the power grid through the wind turbine's converter, a device for power conversion, with priority given to the fault phase, i.e., phase A and B. The symmetry changes of the three-phase voltage are monitored in real time. After injection, the voltages of phases A and B gradually drop to 1050 volts, and phase C maintains 10 00 volts, the degree of three-phase asymmetry is reduced. For example, in a two-phase lifting fault, the negative sequence voltage component is 80 volts, and a reactive current with an opposite phase and an amplitude of 160 amperes is generated and injected into phases A and B, so that the negative sequence component is offset to below 30 volts, and the voltage waveform distortion is significantly improved. At the same time, according to the severity of the negative sequence voltage component, the active power output upper limit is adjusted in stages to avoid active power fluctuations aggravating voltage asymmetry. The negative sequence component threshold range is preset, 0-50 volts is mild, 50-100 volts is moderate, and above 100 volts is severe, corresponding to different active upper limit adjustment ratios. When it is mild, the upper limit is 90% of the rated value, when it is moderate, it is 70%, and when it is severe, it is 50%. If the negative sequence component is 60 volts, moderate, then the active power output upper limit will be increased from the rated value to 1000 kilowatts is reduced to 700 kilowatts, limiting the active power transmitted by the wind turbine to the grid; if the component drops to 40 volts, which is mild, the upper limit will rise back to 900 kilowatts, reducing power generation losses while ensuring grid stability. The more serious the negative sequence component is, the weaker the grid's ability to withstand active power fluctuations. By lowering the active power upper limit, additional impacts on the grid can be reduced, and combined with the injection of reverse reactive current, a coordinated control of "suppressing negative sequence + stabilizing active power" is formed. The wind turbine protection execution unit 4 targets the asymmetric characteristics of two-phase faults, directly offsetting negative sequence interference through reverse reactive current, and avoiding secondary fluctuations by dynamically adjusting the active power upper limit, effectively improving voltage waveform distortion, reducing the risk of false operation of the wind turbine protection system, and ensuring grid stability under two-phase faults.

[0021] The reactive power absorption intensity of the wind turbine protection execution unit 4 increases with the increase of the positive sequence voltage, and the reactive current output intensity increases with the depth of the positive sequence voltage drop. The maximum regulation intensity does not exceed the safety limit of the wind turbine's rated reactive capacity and rated current.

[0022] To ensure that the reactive power regulation of the wind turbine when the voltage rises or falls can effectively stabilize the power grid while not exceeding its own safe operating range, the positive sequence voltage change amplitude and reactive power regulation intensity are dynamically matched, and the upper limit of the regulation is strictly limited. The specific implementation method is as follows: When a positive sequence voltage rise is detected, the reactive power absorption intensity is enhanced in stages according to the magnitude of the rise. The steps are as follows: The positive sequence voltage rise is divided into multiple intervals, that is, 10%-20% of the rated voltage is interval 1, 20%-30% is interval 2, and more than 30% is interval 3. Each interval corresponds to a preset reactive absorption ratio. Interval 1 absorbs 20% of the rated reactive capacity, interval 2 absorbs 40%, and interval 3 absorbs 60%. The electrical quantity acquisition unit 3 continuously monitors the positive sequence voltage value. When the rise increases from 15% (interval 1) to 25% (interval 2), the wind turbine protection execution unit 4 automatically increases the reactive absorption intensity from 20% to 40%, that is, when the rated reactive capacity is 1000 kvar, it is adjusted from absorbing 200 kvar to 400 kvar, and each time Before adjustment, check whether the current reactive absorption intensity exceeds the rated reactive capacity of the wind turbine, that is, the maximum does not exceed 1000 kVar. If the increase is too large and the calculated absorption intensity exceeds the limit, the rated capacity is automatically used as the upper limit. For example, interval 3 theoretically needs to absorb 600 kVar, and it is executed if it does not exceed the limit. If the calculated value reaches 1200 kVar due to special circumstances, it is absorbed as 1000 kVar. The greater the voltage increase, the more excess reactive power in the grid. It is necessary to balance the grid by enhancing the absorption intensity, but it must be limited to the reactive capacity of the wind turbine itself to avoid equipment overload. When a positive sequence voltage drop is detected, the reactive current output intensity is increased in grades according to the drop depth. The steps are as follows: The positive sequence voltage drop depth is divided into multiple intervals, that is, 10%-30% of the rated voltage is interval A, 30%-50% is interval B, and more than 50% is interval C. Each interval corresponds to a preset reactive current output ratio. Interval A outputs 30% of the rated current, interval B outputs 60%, and interval C outputs 90%. When the voltage drop deepens from 20% (interval A) to 40% (interval B), the execution unit increases the reactive current from 30% of the rated current, that is, when the rated current is 500 amperes, the reactive current is output. Output 150 amperes, increase to 60% (300 amperes), support voltage recovery by injecting reactive power, check whether the current output current exceeds the rated current of the wind turbine before each adjustment, that is, the maximum does not exceed 500 amperes. If the drop is too deep and the calculated output intensity exceeds the limit, the rated current is used as the upper limit, that is, the interval C theoretically needs to output 450 amperes, and it is executed if it does not exceed the limit. If the calculated value reaches 550 amperes, it is output at 500 amperes. The greater the voltage drop, the more urgent the grid's demand for reactive power, and the need to increase the output intensity. Reactive power is replenished at a moderate rate, but must be kept within the rated current range to prevent damage to components such as the converter due to overcurrent. To ensure the safety and continuity of the regulation process, the actuator unit has a built-in real-time monitoring and feedback mechanism that continuously compares the current reactive power absorption / output values ​​with the rated capacity / current. When the value reaches 90%, an early warning is issued, prompting caution in subsequent adjustments. If the regulation intensity approaches the limit momentarily due to a sudden voltage surge, the buffer mechanism is automatically triggered, gradually increasing the intensity to the limit within 0.5 seconds rather than an instantaneous jump, thus avoiding current or power surges. For example, if the calculated reactive power absorption intensity reaches 95% of the rated capacity due to a sudden positive-sequence voltage surge, the actuator unit will initially absorb the reactive power at 90% and then gradually increase it to 95% within 1 second. Simultaneously, the actuator unit monitors the device temperature and current waveform, maintaining stable output after confirming that there are no abnormalities. Through this dynamic regulation and limit control, the wind turbine protection actuator unit 4 can not only accurately match the reactive power regulation intensity to the degree of voltage anomaly, but also prevent equipment damage through safety limit constraints, thus ensuring safe operation of the wind turbine itself while ensuring grid stability.

[0023] If it is detected that the voltage rises and falls alternately, the voltage fault type identifier is switched and the control strategy of the wind turbine protection execution unit 4 is reset; When the electrical quantity parameters return to the rated range, the control strategy restrictions are released and a crossing success signal is output.

[0024] When the continuous crossing coordination unit 5 detects alternating voltage rises and falls, it immediately switches the voltage fault type identifier and resets the control strategy of the wind turbine protection execution unit 4, wherein part of the reactive power absorption capacity is retained for standby when the voltage changes from rise to fall, and power reduction control is performed with the current active power value as the new starting point when the voltage changes from fall to rise.

[0025] To cope with complex fault scenarios where voltage rises and falls occur alternately, the continuous ride-through coordination unit 5 ensures that the control logic of the wind turbine protection execution unit 4 quickly adapts to changes in fault types through real-time monitoring and policy reset. The specific implementation is as follows: The continuous ride-through coordination unit 5 continuously receives the positive sequence voltage data transmitted by the electrical quantity acquisition unit 3. When it is detected that the voltage state changes from rising to falling or from falling to rising, it immediately performs the following operations: Set the judgment condition for state switching. When the positive sequence voltage drops from exceeding the high voltage threshold, that is, 110% of the rated voltage, to below the low voltage threshold, that is, 90% of the rated voltage, and the change is completed within 50 milliseconds, it is judged as "lifting to falling"; when the positive sequence voltage rises from below the low voltage threshold to exceeding the high voltage threshold, and the change is completed within 50 milliseconds, it is judged as "falling to lifting". Once the state switching is determined, the wind turbine protection execution unit 4 immediately switches the "voltage lifting fault" to "voltage falling fault" and synchronizes the new identifier to it as the basis for adjusting its control strategy. For example, the positive sequence voltage drops from 115% of the rated voltage (lifting state) to 85% (falling state) within 30 milliseconds. The coordination unit determines it as "lifting to falling", updates the fault identifier to "voltage falling fault", and notifies the execution unit to switch to the falling response strategy. When the fault When the fault type changes from voltage rise to voltage drop, the continuous crossing coordination unit 5 instructs the wind turbine protection execution unit 4 to reset the strategy according to the following logic. When switching from the rising state to the falling state, the reactive absorption function is not completely shut down immediately. Instead, 30%-50% of the current reactive absorption intensity is retained, that is, 150 kVar is retained instead of the original absorption of 400 kVar as a backup adjustment capacity to cope with the possibility of another rise. While retaining the backup capacity, the core control logic of the voltage drop is executed first to quickly increase the reactive current output, that is, output reactive current according to the gradient value corresponding to the drop depth, and limit the active power climbing rate. The voltage change is monitored in real time. If the drop state continues to be stable, that is, it is maintained for more than 100 milliseconds, the retained reactive absorption backup capacity is gradually reduced, such as reducing it by 10% every 20 milliseconds until it is completely shut down to ensure full support for the voltage recovery;If a rise occurs again in a short period of time, the backup capacity will be immediately activated to enhance the absorption intensity. For example, when the voltage rises and then drops, 200 kVar of reactive absorption reserve will be retained, and 300 amperes of reactive current will be output to support the voltage. After 100 milliseconds, the voltage will stabilize, and the backup absorption capacity will be gradually reduced to 0, focusing on responding to drops. When the fault type changes from voltage drop to rise, the continuous crossing coordination unit 5 instructs the execution unit to reset the strategy according to the following logic, and sets the active power output value at the moment of switching, such as the current active power of 600 kilowatts, as the new starting point for power reduction, and no longer traces the baseline value before the fault, to avoid grid fluctuations caused by rapid power callback. Starting from the current active value, the power is reduced in stages according to the gradient value corresponding to the voltage rise. For example, a 20% rise corresponds to a 20% drop per minute, starting from 600 kilowatts, and every minute the power is reduced by 20%. The power is reduced to 480 kW and 384 kW per minute. Simultaneously, reactive power absorption is increased in steps corresponding to the increase in power. A 20% increase corresponds to 40% of the rated reactive power absorption, ensuring coordinated suppression of voltage increases with power reduction. For example, when switching from a drop to a rise, if the current active power is 500 kW and the increase is 25%, the system starts at 500 kW and reduces it to 400 kW and 320 kW at a rate of 20% per minute. Simultaneously, reactive power absorption is gradually increased from 0 to 40% of the rated capacity. The continuous crossing coordination unit 5 solves the problem of strategy switching lag in traditional control: when switching from a rise to a drop, reserve capacity is retained to cope with repeated fluctuations. When switching from a drop to a rise, the current active power is used as the starting point to avoid power surges. This ensures that the wind turbine maintains stable regulation under alternating faults, ensuring grid connection security.

[0026] To ensure that the direct-drive wind turbine can stably recover to normal operation after voltage anomaly, the continuous ride-through coordination unit 5 strictly determines the successful ride-through conditions through multi-dimensional parameter monitoring. The specific implementation method is as follows: The positive sequence voltage is continuously stable within the rated range, and the active power fluctuation rate and reactive power deviation rate meet the preset tolerance threshold. The continuous crossing coordination unit 5 receives the positive sequence voltage data transmitted by the electrical quantity collection unit 3 in real time. The primary judgment condition is that the positive sequence voltage must be continuously stable within the rated range, such as 90%-110% of the rated voltage. The upper and lower limits of the rated range of the positive sequence voltage are set, that is, when the rated voltage is 1000 volts, the lower limit is 900 volts and the upper limit is 1100 volts. When the positive sequence voltage is detected to return to the range, the timing starts, and the positive sequence voltage is required to continue to operate stably within the rated range for a preset time, such as 2 seconds, during which no fluctuations outside the range occur, that is, the voltage is always between 950-1050 volts within 2 seconds. If the voltage exceeds the range again during the process, the timer will be reset to ensure the stability of voltage recovery rather than instantaneous fluctuations. Positive sequence voltage is the core indicator reflecting the overall state of the power grid. Its continued stability is the basis for the wind turbine to resume normal operation, avoiding misjudgment of successful crossing due to temporary voltage compliance. On the basis of voltage stability, the fluctuation of active power is monitored to ensure that its fluctuation rate is within the preset tolerance threshold. The active power fluctuation rate is the ratio of the maximum change in active power per unit time, such as 1 second, to the current average active power value. For example, if the active power increases from 800 kW to 820 kW in 1 second, the average value is 810 kW, and the fluctuation rate is 20 / 810. The preset tolerance threshold is when the calculated active power fluctuation rate is lower than the threshold for 3 consecutive unit times, such as 3 seconds, it is determined that the active power fluctuation meets the standard. For example, if the threshold is 5%, and the fluctuation rate is 3%, 4%, and 2% for three consecutive seconds, the condition is met. Excessive active power fluctuations will cause a secondary impact on the power grid. It is necessary to ensure that it remains stable during the recovery phase to prevent the voltage from becoming unstable again due to power fluctuations just after it stabilizes. At the same time, the deviation of reactive power is monitored to ensure that its deviation rate from the rated reactive power is within the preset range. The reactive power deviation rate is the difference between the current reactive power and the rated reactive power, and the ratio of the current reactive power to the rated reactive power. For example, if the rated reactive power is 500 kVar and the current value is 520 kVar, the deviation rate is 20 / 500. A preset tolerance threshold, such as 10%, is set. When the reactive power deviation rate is below the threshold for three consecutive time units, such as 3 seconds, it is determined that the reactive power deviation meets the standard.For example, when the threshold is 10%, the conditions are met if the deviation rates for three consecutive seconds are 6%, 8%, and 5% respectively. When the above three conditions, the positive sequence voltage is continuously stable, the active power fluctuation rate meets the standard, and the reactive power deviation rate meets the standard, are met at the same time, the continuous crossing coordination unit 5 immediately outputs a crossing success signal. The signal contains key information such as the fault type, voltage recovery time, and power stability time, and is synchronously sent to the wind turbine control system and the power grid dispatching center, indicating that the wind turbine has the conditions for normal grid-connected operation. At the same time, the control strategy restrictions on the wind turbine protection execution unit 4 are lifted, and the active power climbing rate and the reactive power regulation are no longer restricted. The normal mode of the power supply section allows the wind turbine to gradually return to normal operating conditions. For example, after a wind turbine experiences a voltage drop fault, the positive sequence voltage remains stable at 950-1050 volts for 2 seconds, the active power fluctuation rate is less than 5% for 3 consecutive seconds, and the reactive power deviation rate is less than 10% for 3 consecutive seconds. The coordination unit determines that the ride-through is successful, outputs a signal and releases the control restriction. Through such multi-condition verification, the continuous ride-through coordination unit 5 ensures the recovery quality of the wind turbine after the voltage anomaly is crossed, avoiding grid instability caused by premature judgment and preventing excessive delays from affecting the wind turbine's power generation efficiency, providing reliable protection for the safe access of wind power to the grid.

[0027] When the crossing success signal is generated, a certification report including the fault type, the line voltage waveform, the active power curve and the reactive current curve recorded by the electrical quantity acquisition unit 3 is output synchronously.

[0028] In the present invention, the instruction generation unit 1 generates the circuit breaker action sequence, the fault simulation unit 2 simulates various voltage faults through the combination of opening and closing, the electrical quantity acquisition unit 3 captures parameter characteristics and marks faults with multi-rate sampling, the wind turbine protection execution unit 4 reduces active power and enhances reactive absorption in response to voltage rise, and increases reactive current in response to voltage drop. In the event of a two-phase fault, a reverse reactive current is generated to offset the negative sequence component. The continuous crossing coordination unit 5 switches the fault identifier and resets the strategy when the voltage alternates, and outputs a crossing signal and a certification report after returning to normal, thereby solving the problems of insufficient adaptability of traditional control to alternating faults and no difference in phase fault processing, improving the grid-connected stability of wind turbines, and ensuring the safe access of wind power to the power grid.

[0029] A second object of the present invention is to provide a method for implementing a high and low voltage continuous ride-through control system for a direct-drive wind turbine including any one of the above, comprising the following steps: S1. Instruction generation unit 1 generates circuit breaker action sequence instructions based on the target fault type. Fault simulation unit 2 actively generates a voltage fault condition with a preset rise ratio or drop ratio on the high-voltage side of the box-type transformer through a combination of opening and closing operations. No-load rise only operates the collector line circuit breaker. Differentiated impedance control is performed for two-phase faults. Current-limiting reactors are synchronously connected for three-phase faults. All circuit breakers operate sequentially at adjustable time intervals. S2, electrical quantity acquisition unit 3 uses a multi-rate sampling mechanism to capture the high-frequency distortion characteristics of line voltage and the trend of power parameter changes in real time. When the positive sequence voltage continuously exceeds the threshold, the fault type is marked and a protection reference benchmark is generated based on the sliding average of the pre-fault parameters; S3, the wind turbine protection execution unit 4 responds to voltage rise by reducing active power output in stages and increasing reactive power absorption strength in steps. In response to voltage drop, it increases reactive current output and limits the active power ramp rate. In the event of a two-phase fault, it generates reverse reactive current to offset the negative sequence component and dynamically limits the active power upper limit. When high and low voltages alternate, it switches the fault flag and resets the control strategy through the continuous crossing coordination unit 5, retaining reactive power reserve or resetting the power reduction starting point. S4. When the electrical quantity parameters return to the rated range, the continuous ride-through coordination unit 5 releases the control restriction and outputs a ride-through success signal, and simultaneously generates a certification report containing the fault type, line voltage waveform, and power curve.

[0030] The above shows and describes the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The above embodiments and descriptions are merely preferred examples of the present invention and are not intended to limit the present invention. Various changes and improvements may be made to the present invention without departing from the spirit and scope of the present invention. Such changes and improvements fall within the scope of the present invention. The scope of protection claimed in the present invention is defined by the appended claims and their equivalents.

Claims

1. Direct drive wind turbine high and low voltage continuous ride-through control system, characterized by: include: An instruction generation unit (1) is used to generate a circuit breaker action sequence instruction according to a target fault type; The fault simulation unit (2) is connected to the instruction generation unit (1) and actively generates any of the following voltage fault conditions on the high-voltage side of the direct-drive wind turbine chassis by performing a circuit breaker opening or closing operation: No-load boost fault, two-phase boost fault or three-phase boost fault in which the voltage is boosted to a preset boost ratio of the rated voltage; The voltage drops to a preset drop ratio of the rated voltage or zero in a no-load drop fault, a two-phase drop fault, or a three-phase drop fault; An electrical quantity acquisition unit (3) is connected to the fault simulation unit (2) and collects line voltage, positive sequence voltage, active power, reactive power and reactive current parameters of the high-voltage side of the box transformer in real time; The fan protection execution unit (4) is connected to the electrical quantity acquisition unit (3) and dynamically executes the fan control strategy according to the acquired electrical quantity parameters: When a voltage rise fault is detected, the wind turbine's active power output is reduced and reactive power absorption is increased; When a voltage drop fault is detected, the wind turbine’s reactive current output is increased and the active power ramp-up rate is limited; The continuous crossing coordination unit (5) is connected to the wind turbine protection execution unit (4), and during the duration of a single fault: If it is detected that voltage rises and falls alternately occur, the voltage fault type identifier is switched and the control strategy of the wind turbine protection execution unit (4) is reset; When the electrical quantity parameters return to the rated range, the control strategy restrictions are released and a crossing success signal is output.

2. The direct-drive wind turbine high and low voltage continuous ride-through control system according to claim 1 is characterized in that: When performing opening and closing operations, the preset circuit breaker combination logic is matched according to different fault types: For no-load rise faults, only the collector line connection circuit breaker is operated to reduce power interference. For two-phase rise faults, differentiated impedance control is performed to increase the voltage of the specified phase. For three-phase drop faults, current-limiting reactors are synchronously connected to achieve proportional voltage suppression. All circuit breaker operations are sequenced at adjustable time intervals to simulate grid transient processes.

3. The direct-drive wind turbine high and low voltage continuous ride-through control system according to claim 1, characterized in that: The electrical quantity acquisition unit (3) uses a multi-rate sampling mechanism to capture the dynamic characteristics of electrical parameters: The voltage signal is sampled at high frequency to capture waveform distortion, and the power parameters are sampled at medium frequency to track trend changes. At the same time, a fault marking system is established. When the positive sequence voltage exceeds the high voltage threshold or falls below the low voltage threshold within a preset time range, the corresponding fault mark is triggered, and a protection strategy reference benchmark is generated based on the sliding average value of the parameters before the fault occurs.

4. The direct-drive wind turbine high and low voltage continuous ride-through control system according to claim 1, characterized in that: The wind turbine protection execution unit (4) reduces the wind turbine active power output in stages and increases the reactive power absorption intensity in a step-by-step manner when responding to a voltage rise fault, and increases the reactive current output to a safe limit and limits the active power climbing rate when responding to a voltage drop fault, wherein the power change rate in each stage is set to a configurable gradient value.

5. The direct-drive wind turbine high and low voltage continuous ride-through control system according to claim 4 is characterized in that: When processing a two-phase lift fault or a two-phase drop fault, the wind turbine protection execution unit (4) calculates the negative sequence voltage component in real time and generates a reverse phase reactive current based on the negative sequence voltage component, and dynamically adjusts the active power output upper limit value according to the severity of the negative sequence voltage component.

6. The direct-drive wind turbine high and low voltage continuous ride-through control system according to claim 1, characterized in that: When the continuous crossing coordination unit (5) detects that the voltage rises and falls alternately, it immediately switches the voltage fault type identifier and resets the control strategy of the wind turbine protection execution unit (4), wherein a portion of the reactive power absorption capacity is reserved for standby when the voltage rises and falls, and power reduction control is performed with the current active power value as a new starting point when the voltage falls and rises.

7. The direct-drive wind turbine high and low voltage continuous ride-through control system according to claim 3, characterized in that: The reactive power absorption intensity of the wind turbine protection execution unit (4) increases with the positive sequence voltage rise amplitude, and the reactive current output intensity increases with the positive sequence voltage drop depth, and the maximum regulation intensity does not exceed the safety limit of the wind turbine rated reactive capacity and rated current.

8. The direct-drive wind turbine high and low voltage continuous ride-through control system according to claim 1, characterized in that: The conditions for the continuous crossing coordination unit (5) to output a crossing success signal are: The positive sequence voltage remains stable within the rated range, while the active power fluctuation rate and reactive power deviation rate meet the preset tolerance thresholds.

9. The direct-drive wind turbine high and low voltage continuous ride-through control system according to claim 1, characterized in that: When the crossing success signal is generated, a certification report including the fault type, the line voltage waveform, the active power curve and the reactive current curve recorded by the electrical quantity acquisition unit (3) is output synchronously.

10. A method for implementing a high and low voltage continuous ride-through control system for a direct-drive wind turbine according to any one of claims 1 to 9, characterized in that: The following steps are involved: S1, the instruction generation unit (1) generates a circuit breaker action sequence instruction according to the target fault type, and the fault simulation unit (2) actively generates a voltage fault condition with a preset lifting ratio or drop ratio on the high-voltage side of the box-type transformer through a combination of opening and closing operations, wherein the no-load lifting only operates the collector line circuit breaker, the two-phase fault performs differentiated impedance control, the three-phase fault synchronously connects the current limiting reactor, and all circuit breakers are sequentially operated according to an adjustable time interval; S2, electrical quantity acquisition unit (3) uses a multi-rate sampling mechanism to capture the high-frequency distortion characteristics of line voltage and the trend of power parameter changes in real time, marks the fault type when the positive sequence voltage continuously exceeds the threshold, and generates a protection reference benchmark based on the sliding average of the parameters before the fault; S3, the wind turbine protection execution unit (4) responds to voltage rise by reducing active power output in stages and increasing reactive power absorption intensity in steps; responds to voltage drop by increasing reactive current output and limiting active power climbing rate; generates reverse reactive current to offset negative sequence component and dynamically limits active power upper limit under two-phase fault; switches fault identification and resets control strategy through continuous crossing coordination unit (5) when high and low voltage alternate, retains reactive power standby or resets power reduction starting point; S4. When the electrical quantity parameters return to the rated range, the continuous crossing coordination unit (5) releases the control restriction and outputs a crossing success signal, and simultaneously generates a certification report containing the fault type, line voltage waveform and power curve.

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