Automatic identification method for substation fault voltage ride-through index based on step response analysis

Abstract

The application provides a kind of station fault voltage ride through index automatic identification method based on step response analysis, the measured data before and after fault voltage ride through is collected, the measured data is preprocessed, the line voltage effective value is obtained, and the line voltage effective value curve, active power curve and reactive current curve are drawn;Look for split1-4 on the line voltage effective value curve, find point1, 3, 5, 6 according to split1-4 on the voltage effective value curve, and the line voltage effective value eligibility index is calculated based on the coordinate value of point1, 3, 5, 6;Look for point7-16 on the active power curve according to split1-4, and the active power eligibility index is calculated based on the coordinate value of point7-16;Look for point17-22 on the reactive current curve according to split1-4, and the reactive current eligibility index is calculated based on the coordinate value of point17-22;The line voltage effective value eligibility index, active power eligibility index and reactive current eligibility index are stored, and the fault voltage ride through of new energy station can be quickly and accurately analyzed.

Description

Technical Field

[0001] This invention relates to the field of power system automation technology, and in particular to an automatic identification method for power station fault voltage ride-through index based on step response analysis. Background Technology

[0002] Voltage fault ride-through testing is a key test in power systems to evaluate the grid-connected operation capability of new energy power generation equipment, including wind turbine generators and photovoltaic inverters. The core purpose of the test is to verify whether the equipment can maintain grid connection without disconnecting from the grid within a specified time by dynamically adjusting its output power when the grid experiences short-term voltage fluctuations or faults—such as voltage drops, rises, or momentary interruptions. This capability not only prevents the equipment from disconnecting from the grid due to protection mechanisms, but more importantly, it ensures the stability of the grid during fault recovery and prevents chain reactions caused by individual equipment disconnection.

[0003] The test strictly followed a series of grid connection technical standards, which are divided into two major systems based on the type of new energy: wind power and photovoltaic. For wind power equipment, commonly used standards include GB / T 19963-2021 "Technical Regulations for Wind Farm Connection to Power Systems", GB / T 36995-2018 "Test Procedure for Fault Voltage Ride-through Capability of Wind Turbine Generators", NB / T 31111-2017 "Test Procedure for High Voltage Ride-through of Wind Turbine Generators", Q / CSG 1211017-2018 "Technical Specifications for Wind Farm Connection to Power Grid" and "Technical Principles for New Energy Power Station Connection System of Yunnan Power Grid (2023 Edition)", focusing on assessing the control strategies and hardware protection mechanisms of the units during voltage anomalies. For photovoltaic applications, standards include GB / T 19964-2024 "Technical Regulations for Photovoltaic Power Station Connection to Power Systems", GB / T 31365-2015 "Test Procedure for Photovoltaic Power Station Connection to Power Grid", and NB / T Standards such as 10324-2019 "Technical Specification for High Voltage Ride-through Detection of Photovoltaic Power Stations" use fault voltage generators to simulate voltage disturbances of different amplitudes and durations to ensure that power generation equipment has the ability to withstand transient voltage changes in the power grid. This is an important technical guarantee for the safe grid connection of new energy on a large scale and is directly related to the stability and reliability of the power system.

[0004] However, the current calculation method for fault voltage ride-through index of new energy power plants still has significant shortcomings. The existing process relies on manual processing of 64 standard operating conditions. Technicians need to identify voltage threshold points, record time parameters, and complete complex calculations one by one in the waveform diagram. This manual operation mode brings multiple problems: First, it is inefficient. Full-condition testing of a single power plant often takes a lot of time, which seriously prolongs the project cycle. Second, it has accuracy deviation. The unavoidable subjectivity in the manual diagram interpretation process will introduce measurement errors, affecting key indicators. Finally, it has quality risks. The inconsistency of manual operation leads to a decrease in the standardization of test reports and the reliability of data, making it difficult to meet the requirements of high-precision testing. Summary of the Invention

[0005] In view of this, the present invention proposes an automatic identification method for power station fault voltage ride-through index based on step response analysis, which can automatically and quickly identify the fault voltage ride-through index of new energy power stations and is easy to promote and apply.

[0006] The technical solution of this invention is implemented as follows:

[0007] An automatic identification method for power station fault voltage ride-through index based on step response analysis includes the following steps:

[0008] Step S1: Collect measurement data before and after fault voltage ride-through, preprocess the measurement data, obtain the effective value of line voltage, and plot the effective value curve of line voltage.

[0009] Step S2: Query the points on the line voltage RMS curve where voltage ride-through begins and ends, and record them as split1-4. split1-4 divides the line voltage RMS curve into five parts: before the fault, the voltage boost response segment, during the fault, the voltage drop response segment, and after the fault.

[0010] Step S3: Locate points 1, 3, 5, and 6 on the voltage RMS curve according to split1-4, and calculate the line voltage RMS pass index based on the coordinate values ​​of points 1, 3, 5, and 6.

[0011] Step S4: Plot the active power curve based on the measurement data. Locate point 7-16 on the active power curve according to split1-4. Calculate the active power qualification index based on the coordinate value of point 7-16.

[0012] Step S5: Plot the reactive current curve based on the measurement data. Locate point 17-22 on the reactive current curve according to split1-4. Calculate the reactive current compliance index based on the coordinate values ​​of point 17-22.

[0013] Step S6: Store the line voltage RMS value qualification index, active power qualification index, and reactive current qualification index.

[0014] Preferably, before collecting measurement data in step S1, the following parameters need to be set: rated voltage, rated capacity, data voltage unit, data current unit, current starting column, voltage starting column, data starting row, data file format, data form, and data file name.

[0015] Preferably, the specific steps of step S1 are as follows:

[0016] Step S11: Collect measurement data 4 seconds before and after fault voltage ride-through. The data resolution is 0.ms. After analyzing the statistical characteristics of the data, determine the filter size and filter the measurement data.

[0017] Step S12: Replace outliers in the measurement data with reasonable values ​​using outlier detection methods;

[0018] Step S13: Obtain the effective value of the line voltage from the processed measurement data and plot the effective value curve of the line voltage.

[0019] Preferably, the specific steps of step S2 are as follows: based on the threshold value of high voltage ride-through, find the points of entering and exiting voltage ride-through from the voltage effective value curve, and record them as split1-4, where the part before split1 is the pre-fault part, the part between split1-2 is the boost response segment part, the part between split2-3 is the middle part of the fault, the part between split3-4 is the buck response segment part, and the part after the fault is the post-fault part.

[0020] Preferably, the specific steps of step S3 are as follows:

[0021] Step S31: Take the midpoint between split1 and the starting point of the line voltage RMS curve, and denote it as point1. Take the midpoint between split2 and split3, and denote it as point3.

[0022] Step S32: In the range [split2, split2+1000], set the sliding window size to 2000, the sliding algorithm is the variance of all points in the window and the starting point of the window, and the threshold is the peak-to-peak value of the line voltage RMS curve in [split2+1000, split3-1000]. The sliding window slides from left to right to find the first point with a variance less than the threshold, which is denoted as point5.

[0023] Step S33: In the range [split3-1000, split3], set the sliding window size to 2000, the sliding algorithm is the variance of all points in the window and the starting point of the window, and the threshold is the peak-to-peak value of the curve in [split2+1000, split3-1000]. The sliding window slides from right to left to find the first point with a variance less than the threshold, which is denoted as point6.

[0024] Step S34: Calculate the line voltage effective value qualification index based on the coordinate values ​​of point1, 3, 5, and 6.

[0025] Preferably, the line voltage RMS value qualification index includes the voltage rise amplitude U. T and voltage rise duration t T The voltage rise amplitude U T and voltage rise duration t T The expression is:

[0026]

[0027] t T = (point6_x - point5_x) * 1000

[0028] Where point1_y and point3_y are the ordinate values ​​of point1 and point3, respectively, and point5_x and point6_x are the abscissa values ​​of point5 and point6, respectively. n This is the system's nominal voltage.

[0029] Preferably, the specific steps of step S4 are as follows:

[0030] Step S41: Plot the active power curve based on the measurement data, and synchronize the active power curve with the line voltage RMS value curve in time.

[0031] Step S42: Take the maximum and minimum points on the active power curve located in the interval [split2-400, split2+400], and denote them as point8 and point9 respectively;

[0032] Step S43: Take the maximum and minimum points on the active power curve located in the interval [(split2+split3) / 2-1500, (split2+split3) / 2+1500], and record them as point11 and point12 respectively;

[0033] Step S44: Find the maximum and minimum points on the active power curve located in the interval [split3-400, split3+400], and record them as point14 and point15 respectively;

[0034] Step S45: Set the upper bound as the maximum value of the active power curve in the interval [point8-3500, point8-500], and the lower bound as the minimum value of the active power curve in the interval [point8-3500, point8-500]. Find the first point in the interval [point8-500, point8] where the active power exceeds the upper and lower bounds from left to right, and denot it as ponit7.

[0035] Step S46: Set the upper bound as the maximum value of the active power curve in the interval [point9+500, point9+2500], and the lower bound as the minimum value of the active power curve in the interval [point9+500, point9+2500]. Find the first point in the interval [point9, point9+500] where the active power exceeds the upper and lower bounds from right to left, and record it as point10.

[0036] Step S47: Set the upper bound as the maximum value of the active power curve in the interval [point14-2500, point14-500], and the lower bound as the minimum value of the active power curve in the interval [point14-2500, point14-500]. Find the first point in the interval [point14-500, point14] where the active power exceeds the upper and lower bounds from left to right, and record it as point13.

[0037] Step S48: Set the upper bound as the maximum value of the active power curve in the interval [point15+500, point15+3500], and the lower bound as the minimum value of the active power curve in the interval [point15+500, point15+3500]. Find the first point in the interval [point15, point15+500] where the active power exceeds the upper and lower bounds from right to left, and record it as point16.

[0038] Step S49: Calculate the active power qualification index based on the coordinate values ​​of point7-16.

[0039] Preferably, the active power qualification index includes the active power fluctuation range M at the time of voltage rise. up Active power fluctuation time t at the moment of voltage rise up Active power fluctuation range M at the moment of voltage drop down Active power fluctuation time t at the moment of voltage drop down and the active power fluctuation range M during voltage rise. mid The active power fluctuation range M during voltage rise. up Active power fluctuation time t at the moment of voltage rise up Active power fluctuation range M at the moment of voltage dropdown Active power fluctuation time t at the moment of voltage drop down and the active power fluctuation range M during voltage rise. mid The expression is:

[0040]

[0041] Where point7_x, point10_x, point13_x, and point16_x are the x-coordinates of point7, point10, point13, and point16, respectively; and point8_y, point9_y, point11_y, point12_y, point14_y, and point15_y are the y-coordinates of point8, point9, point11, point12, point14, and point15, respectively. n This refers to the system's nominal active power.

[0042] Preferably, the specific steps of step S5 are as follows:

[0043] Step S51: Plot the reactive current curve based on the measurement data, and synchronize the reactive current curve with the effective value curve of the line voltage in time.

[0044] Step S52: Take the midpoint between split1 and the starting point of the reactive current curve on the reactive current curve, and denote it as point17.

[0045] Step S53: Take the midpoint between split1 and split3 on the reactive current curve and denote it as point20;

[0046] Step S54: Locate the data point index of all reactive current values ​​within the high voltage ride-through range, and record the moment when the threshold is first exceeded as point19 and the moment when the threshold is last exceeded as point21.

[0047] Step S55: Take the peak-to-peak value of the interval [split2-3000, split2-1000] as the threshold, take the average value of the interval [split2-3000, split2-1000] as the target value, and find the first point from left to right in the range [split2-200, point19_x] whose difference from the target value is greater than the threshold, and record it as point18, where point19_x is the x-coordinate value of point19;

[0048] Step S56: Take the peak-to-peak value of the interval [split3+1000, split3+3000] as the threshold, take the average value of the interval [split3+1000, split3+3000] as the target value, and find the first point from right to left in the range [point21_x, split3+200] whose difference from the target value is greater than the threshold, and record it as point22, where point21_x is the x-coordinate value of point21;

[0049] Step S57: Calculate the reactive current compliance index based on the coordinate values ​​of point17-22.

[0050] Preferably, the reactive current compliance index includes the reactive current response time t. xy Reactive current withdrawal time t tc Reactive current duration t cx and the steady-state mean value of reactive current I wt The reactive current response time t xy Reactive current withdrawal time t tc Reactive current duration t cx and the steady-state mean value of reactive current I wt The expression is:

[0051] t xy = (point19_x - point18_x) * 1000

[0052] t tc = (point22_x - point4_x) * 1000

[0053] t cx = (point21_x - point19_x) * 1000

[0054]

[0055] Where point4_x, point18_x, point19_x, point21_x, and point22_x are the x-coordinates of point4, point18, point19, point21, and point22, respectively; point17_y and point20_y are the y-coordinates of point17 and point20, respectively; and P... n U n These are the system's nominal active power and voltage, respectively.

[0056] Compared with the prior art, the beneficial effects of the present invention are:

[0057] This invention discloses an automatic identification method for power plant fault voltage ride-through indicators based on step response. After collecting measurement data before and after a fault voltage ride-through, the method can plot the line voltage RMS curve, active power curve, and reactive current curve. The line voltage RMS curve can be divided into five parts based on the points of entry and exit from the voltage ride-through. This division helps to limit the range during subsequent point calculations. Points 1-22 can then be located on the line voltage RMS, active power, and reactive power curves based on these points. The voltage RMS compliance indicators, active power compliance indicators, and reactive current compliance indicators are calculated based on the coordinates of these points. Finally, the calculated RMS, active power, and reactive current compliance indicators are stored. This allows for rapid and accurate compliance analysis of fault voltage ride-through at new energy power plants, freeing test analysts from repetitive calculations. Attached Figure Description

[0058] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only preferred embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0059] Figure 1 The flowchart shows the automatic identification method for station fault voltage ride-through index based on step response analysis according to the present invention.

[0060] Figure 2 This is a schematic diagram showing the selection of points for the line voltage RMS curve of the automatic identification method for station fault voltage ride-through index based on step response analysis according to the present invention.

[0061] Figure 3 This is a schematic diagram of point 6 in the automatic identification method for station fault voltage ride-through index based on step response analysis of the present invention.

[0062] Figure 4 This is a schematic diagram of selecting points for the active power curve in the automatic identification method of station fault voltage ride-through index based on step response analysis of the present invention.

[0063] Figure 5 This is a schematic diagram showing the selection of point 10 in the automatic identification method for station fault voltage ride-through index based on step response analysis of the present invention.

[0064] Figure 6This is a schematic diagram showing the selection of point 16 in the automatic identification method for station fault voltage ride-through index based on step response analysis of the present invention.

[0065] Figure 7 This is a schematic diagram of selecting points for the reactive current curve in the automatic identification method of station fault voltage ride-through index based on step response analysis of the present invention.

[0066] Figure 8 This is the automatic identification result of the high voltage ride-through test index for a 120% three-phase heavy load in application example 1 of the present invention;

[0067] Figure 9 This is the result of automatic identification of active power index in the 120% three-phase heavy load 2 high voltage ride-through test of the present invention, Example 1.

[0068] Figure 10 This is the second result of the automatic identification of active power index in the 120% three-phase heavy load 2 high voltage ride-through test of the application example 1 of this invention;

[0069] Figure 11 This is a distribution map of key points for the fault voltage ride-through index of new energy power plants. Detailed Implementation

[0070] To better understand the technical content of this invention, a specific embodiment is provided below, and the invention will be further described in conjunction with the accompanying drawings.

[0071] See Figures 1 to 7 The present invention provides an automatic identification method for power station fault voltage ride-through index based on step response analysis, comprising the following steps:

[0072] Step S1: Collect measurement data before and after fault voltage ride-through, preprocess the measurement data, obtain the effective value of line voltage, and plot the effective value curve of line voltage.

[0073] Step S2: Query the points on the line voltage RMS curve where voltage ride-through begins and ends, and record them as split1-4. split1-4 divides the line voltage RMS curve into five parts: before the fault, the voltage boost response segment, during the fault, the voltage drop response segment, and after the fault.

[0074] Step S3: Locate points 1, 3, 5, and 6 on the voltage RMS curve according to split1-4, and calculate the line voltage RMS pass index based on the coordinate values ​​of points 1, 3, 5, and 6.

[0075] Step S4: Plot the active power curve based on the measurement data. Locate point 7-16 on the active power curve according to split1-4. Calculate the active power qualification index based on the coordinate value of point 7-16.

[0076] Step S5: Plot the reactive current curve based on the measurement data. Locate point 17-22 on the reactive current curve according to split1-4. Calculate the reactive current compliance index based on the coordinate values ​​of point 17-22.

[0077] Step S6: Store the line voltage RMS value qualification index, active power qualification index, and reactive current qualification index.

[0078] In the automatic identification method of station fault voltage ride-through index based on step response backwashing of the present invention, the measurement data before and after fault voltage ride-through are collected first, and then the measurement data are preprocessed to ensure that the data is accurate and free of noise. The processed measurement data can be converted into line voltage effective value. Based on the time change, the line voltage effective value curve can be plotted. In addition, based on the measurement data, active power curve and reactive current curve are also plotted. After obtaining the line voltage effective value curve, four split points can be obtained according to the points on the curve that enter and exit voltage ride-through, denoted as split1-4. Split1-4 can divide the line voltage effective value curve into five parts, which can play a role in limiting the range when searching for points in the later stage.

[0079] After obtaining split1-4, points 1, 3, 5, and 6 can be located on the line voltage RMS curve based on the coordinate values ​​of split1-4. Then, the line voltage RMS compliance index can be calculated based on the coordinate values ​​of points 1, 3, 5, and 6. Next, the active power curve and reactive current curve are compared with the line voltage RMS curve. Based on the changes in the coordinate values ​​of split1-4, points 7-16 and 17-22 can be located on the active power curve and reactive current curve, respectively. Then, the active power compliance index and reactive current compliance index can be obtained based on the coordinate values ​​of points 7-16 and 17-22, respectively. Based on the line voltage RMS compliance index, active power compliance index, and reactive current compliance index, the compliance analysis of fault voltage ride-through at new energy power plants can be performed quickly and accurately. By quickly locating points, manual searching can be avoided, improving efficiency, freeing test analysts from repetitive calculations, reducing workload, and improving the accuracy of point location.

[0080] Preferably, before collecting measurement data in step S1, the following parameters need to be set: rated voltage, rated capacity, data voltage unit, data current unit, current starting column, voltage starting column, data starting row, data file format, data form, and data file name.

[0081] After setting the rated parameters, it is easy to compare and calculate with the measured data to determine whether the measured data is within the normal range of the rated data.

[0082] Preferably, the specific steps of step S1 are as follows:

[0083] Step S11: Collect measurement data 4 seconds before and after fault voltage ride-through. The data resolution is 0.ms. Analyze the statistical characteristics of the data, such as mean, variance and distribution, and then determine the filter size and filter the measurement data.

[0084] Step S12: Use outlier detection methods, such as Z-Score and IQR, to replace outliers in the measurement data with reasonable values;

[0085] Step S13: Obtain the effective value of the line voltage from the processed measurement data and plot the effective value curve of the line voltage.

[0086] By preprocessing the measurement data, noise can be removed and outliers can be replaced with reasonable values, thus ensuring the accuracy of the measurement data and enabling the plotting of a line voltage RMS curve with high accuracy.

[0087] Preferably, the specific steps of step S2 are as follows: based on the threshold value of high voltage ride-through, find the points of entering and exiting voltage ride-through from the voltage effective value curve, and record them as split1-4, where the part before split1 is the pre-fault part, the part between split1-2 is the boost response segment part, the part between split2-3 is the middle part of the fault, the part between split3-4 is the buck response segment part, and the part after the fault is the post-fault part.

[0088] After obtaining the line voltage RMS curve, based on the high voltage ride-through threshold, the points for entering and exiting voltage ride-through can be directly found on the line voltage RMS curve. These points are denoted as split1-4. Split1-4 divides the line voltage RMS curve into 5 parts in sequence to facilitate the limitation of the range when calculating points later.

[0089] Preferably, the specific steps of step S3 are as follows:

[0090] Step S31: Take the midpoint between split1 and the starting point of the line voltage RMS curve, and denote it as point1. Take the midpoint between split2 and split3, and denote it as point3.

[0091] Step S32: In the range [split2, split2+1000], set the sliding window size to 2000, the sliding algorithm is the variance of all points in the window and the starting point of the window, and the threshold is the peak-to-peak value of the line voltage RMS curve in [split2+1000, split3-1000]. The sliding window slides from left to right to find the first point with a variance less than the threshold, which is denoted as point5.

[0092] Step S33: In the range [split3-1000, split3], set the sliding window size to 2000, the sliding algorithm is the variance of all points in the window and the starting point of the window, and the threshold is the peak-to-peak value of the curve in [split2+1000, split3-1000]. The sliding window slides from right to left to find the first point with a variance less than the threshold, which is denoted as point6.

[0093] Step S34: Calculate the line voltage RMS value compliance index based on the coordinate values ​​of points 1, 3, 5, and 6. The line voltage RMS value compliance index includes the voltage rise amplitude U. T and voltage rise duration t T The voltage rise amplitude U T and voltage rise duration t T The expression is:

[0094]

[0095] t T = (point6_x - point5_x) * 1000

[0096] Where point1_y and point3_y are the ordinate values ​​of point1 and point3, respectively, and point5_x and point6_x are the abscissa values ​​of point5 and point6, respectively. n This is the system's nominal voltage.

[0097] The effective line voltage is a voltage signal emitted by the device to simulate the line voltage at the grid connection point during a real high-voltage crossing. The effective line voltage first rises from the nominal voltage to the target crossing voltage, and then returns to the nominal voltage after a period of time. The two key qualification indicators of the effective line voltage are the voltage rise amplitude and the voltage rise duration. After obtaining points 1, 3, 5, and 6, the effective line voltage can be directly calculated based on the coordinate values ​​of points 1, 3, 5, and 6. By calculating the qualification indicators using the coordinate values ​​of points on the curve, different operating conditions at the substation can be accurately represented, and the data is accurate. Compared with manually finding the points, it is more efficient and accurate.

[0098] When the fundamental positive sequence voltage reaches 1.1, the system enters the high-voltage crossing threshold, and the active and reactive power of the system begin to adjust. Point 2 and point 4 are the start and end times when the fundamental voltage exceeds the 1.1 times threshold. The specific algorithm for finding these points is as follows:

[0099] (1) Condition detection: By locating the index of all data points with fundamental positive sequence voltage values ​​within the range of 1.1±0.001, with a tolerance of 0.001, we avoid missing detections caused by floating-point precision errors.

[0100] (2) Validity verification: Check whether at least two points that meet the conditions are found to ensure that the time interval can be extracted.

[0101] (3) Key point extraction: The moment when the threshold is first exceeded is point2, and the moment when the threshold is last exceeded is point4.

[0102] Preferably, the specific steps of step S4 are as follows:

[0103] Step S41: Plot the active power curve based on the measurement data, and synchronize the active power curve with the line voltage RMS value curve in time.

[0104] Step S42: Take the maximum and minimum points on the active power curve located in the interval [split2-400, split2+400], and denote them as point8 and point9 respectively;

[0105] Step S43: Take the maximum and minimum points on the active power curve located in the interval [(split2+split3) / 2-1500, (split2+split3) / 2+1500], and record them as point11 and point12 respectively;

[0106] Step S44: Find the maximum and minimum points on the active power curve located in the interval [split3-400, split3+400], and record them as point14 and point15 respectively;

[0107] Step S45: Set the upper bound as the maximum value of the active power curve in the interval [point8-3500, point8-500], and the lower bound as the minimum value of the active power curve in the interval [point8-3500, point8-500]. Find the first point in the interval [point8-500, point8] where the active power exceeds the upper and lower bounds from left to right, and denot it as ponit7.

[0108] Step S46: Set the upper bound as the maximum value of the active power curve in the interval [point9+500, point9+2500], and the lower bound as the minimum value of the active power curve in the interval [point9+500, point9+2500]. Find the first point in the interval [point9, point9+500] where the active power exceeds the upper and lower bounds from right to left, and record it as point10.

[0109] Step S47: Set the upper bound as the maximum value of the active power curve in the interval [point14-2500, point14-500], and the lower bound as the minimum value of the active power curve in the interval [point14-2500, point14-500]. Find the first point in the interval [point14-500, point14] where the active power exceeds the upper and lower bounds from left to right, and record it as point13.

[0110] Step S48: Set the upper bound as the maximum value of the active power curve in the interval [point15+500, point15+3500], and the lower bound as the minimum value of the active power curve in the interval [point15+500, point15+3500]. Find the first point in the interval [point15, point15+500] where the active power exceeds the upper and lower bounds from right to left, and record it as point16.

[0111] Step S49: Calculate the active power qualification index based on the coordinate values ​​of point7-16. The active power qualification index includes the active power fluctuation range M at the voltage rise time. up Active power fluctuation time t at the moment of voltage rise up Active power fluctuation range M at the moment of voltage drop dowb Active power fluctuation time t at the moment of voltage drop down and the active power fluctuation range M during voltage rise. mid The active power fluctuation range M during voltage rise. up Active power fluctuation time t at the moment of voltage rise up Active power fluctuation range M at the moment of voltage drop down Active power fluctuation time t at the moment of voltage drop down and the active power fluctuation range M during voltage rise. mid The expression is:

[0112]

[0113] Where point7_x, point10_x, point13_x, and point16_x are the x-coordinates of point7, point10, point13, and point16, respectively; and point8_y, point9_y, point11_y, point12_y, point14_y, and point15_y are the y-coordinates of point8, point9, point11, point12, point14, and point15, respectively. n This refers to the system's nominal active power.

[0114] During high-voltage ride-through, the main risks to the active power of wind turbines are DC bus overvoltage, converter overload, and excessive mechanical power input caused by a sudden rise in grid voltage. These risks may lead to equipment damage or grid disconnection. To address these risks, the turbines need to actively reduce active power output by rapidly limiting the converter (e.g., by activating the DC unloading circuit to dissipate excess energy), dynamically adjust the pitch angle to reduce mechanical power input, and inject capacitive reactive power to suppress voltage fluctuations. During a fault, the active power fluctuation amplitude must be strictly limited within a threshold. After the fault is cleared, the active power should return to normal with a gradual slope to ensure no grid disconnection. To meet the grid dynamic response standards, wind turbines should have the ability to operate continuously without disconnecting from the grid. For wind turbines that are not disconnected from the grid, the active power fluctuation amplitude should be within ±50% Pn during voltage rise and voltage recovery, with the fluctuation amplitude greater than zero and the fluctuation time not exceeding 80ms. During voltage rise, the output active power fluctuation amplitude should be within ±5% Pn. After voltage recovery, the output power should be the output power corresponding to the actual wind conditions. There are five indicators to verify the compliance of high voltage ride-through active power, namely the active power fluctuation range M during voltage rise. up Active power fluctuation time t at the moment of voltage rise up Active power fluctuation range M at the moment of voltage drop down Active power fluctuation time t at the moment of voltage drop down and the active power fluctuation range M during voltage rise. mid After synchronizing the active power curve with the line voltage RMS curve in time, point7-16 can be obtained based on the coordinate changes of split1-4 on the line voltage RMS curve. Finally, the active power qualification index can be obtained based on the coordinate values ​​of point7-16.

[0115] Preferably, the specific steps of step S5 are as follows:

[0116] Step S51: Plot the reactive current curve based on the measurement data, and synchronize the reactive current curve with the effective value curve of the line voltage in time.

[0117] Step S52: Take the midpoint between split1 and the starting point of the reactive current curve on the reactive current curve, and denote it as point17.

[0118] Step S53: Take the midpoint between split1 and split3 on the reactive current curve and denote it as point20;

[0119] Step S54: Locate the data point index of all reactive current values ​​within the high voltage ride-through range, and record the moment when the threshold is first exceeded as point19 and the moment when the threshold is last exceeded as point21.

[0120] Step S55: Take the peak-to-peak value of the interval [split2-3000, split2-1000] as the threshold, take the average value of the interval [split2-3000, split2-1000] as the target value, and find the first point from left to right in the range [split2-200, point19_x] whose difference from the target value is greater than the threshold, and record it as point18, where point19_x is the x-coordinate value of point19;

[0121] Step S56: Take the peak-to-peak value of the interval [split3+1000, split3+3000] as the threshold, take the average value of the interval [split3+1000, split3+3000] as the target value, and find the first point from right to left in the range [point21_x, split3+200] whose difference from the target value is greater than the threshold, and record it as point22, where point21_x is the x-coordinate value of point21;

[0122] Step S57: Calculate the reactive current compliance index based on the coordinate values ​​of point 17-22. The reactive current compliance index includes the reactive current response time t. xy Reactive current withdrawal time t tc Reactive current duration t cx and the steady-state mean value of reactive current I wt The reactive current response time t xy Reactive current withdrawal time t tc Reactive current duration t cx and the steady-state mean value of reactive current I wt The expression is:

[0123] t xy = (point19_x - point18_x) * 1000

[0124] t tc = (point22_x - point4_x) * 1000

[0125] t cx = (point21_x - point19_x) * 1000

[0126]

[0127] Where point4_x, point18_x, point19_x, point21_x, and point22_x are the x-coordinates of point4, point18, point19, point21, and point22, respectively; point17_y and point20_y are the y-coordinates of point17 and point20, respectively; and P... n U n These are the system's nominal active power and voltage, respectively.

[0128] During high-voltage ride-through in power systems, to maintain grid voltage stability and meet grid connection requirements, wind turbines need to dynamically adjust reactive current to suppress voltage surges. According to the voltage-reactive power control strategy, when the grid voltage exceeds the rated threshold, the equipment should actively inject reactive current in the opposite direction to the voltage deviation. Specifically, during high-voltage ride-through, after the system detects a voltage rise, it dynamically increases the injection of capacitive reactive current (or reduces the output of inductive reactive current) based on the preset voltage-reactive power response curve, thereby absorbing reactive power to offset the voltage rise trend. Vector control enables rapid tracking of reactive current, effectively suppressing transient overvoltages, ensuring the equipment does not disconnect from the grid during faults and supporting dynamic grid recovery. From the moment the voltage rise occurs at the grid connection point, the response time of dynamic inductive reactive current control should not exceed 40ms, and inductive reactive current should be continuously injected during voltage faults. The dynamic inductive reactive current provided by the wind turbine should meet the requirements of the formula:

[0129] I TL ≥1.5×(U T -1.1) / I n , (1.1≤U T ≤1.3)

[0130] During the period of voltage rise at the grid connection point, the reactive current output by the wind farm to the power system should be the difference between the reactive current output before the voltage rise and the dynamic reactive current increment. The maximum reactive current output capacity of the wind farm should not be less than 1.05 times the rated current of the wind farm. From the moment the voltage rise occurs at the grid connection point, the rise time of the dynamic reactive current of the wind farm should not exceed 40ms. From the moment the voltage at the grid connection point recovers to below 110% of the nominal voltage, the wind farm should withdraw the actively supplied dynamic reactive current increment within 40ms. The four indicators for verifying the qualification of high voltage ride-through reactive current are the reactive current response time t. xyReactive current withdrawal time t tc Reactive current duration t cx and the steady-state mean value of reactive current I wt Point 17-22 is obtained based on the coordinate changes of split 1-4 on the line voltage RMS curve. Finally, the reactive current qualification index can be obtained based on the coordinate values ​​of point 17-22.

[0131] The following is a practical verification example:

[0132] The high-voltage ride-through qualification index for a certain wind farm is calculated. This wind farm has a rated voltage of 35kV and a rated capacity of 5MW. Instantaneous three-phase voltage and current values ​​of a certain turbine in the wind farm are measured using current transformers and voltage transformers and stored in an Excel spreadsheet. The format is: voltage unit V, current unit A, voltage data starting column 2, current data starting column 5, data starting row 3. The high-voltage fault ride-through conditions are shown in Table 1.

[0133] Table 1

[0134]

[0135] For the fault voltage ride-through condition 120% three-phase heavy load 2 data of this wind farm, the automatic identification method of the fault voltage ride-through index based on step response analysis of the present invention was used to obtain the reactive current baseline value: 12.37, 0.9 reactive current value: -17.49; the coordinates of each key point are split1: 50018, split2: 50185, split3: 150342, split4: 150547, point1: x-coordinate = 2.50, y-coordinate = 35.04, point2: x-coordinate = 5.01, y-coordinate = 1 .10, point3: x-coordinate = 10.03, y-coordinate = 40.76, point4: x-coordinate = 15.04, y-coordinate = 1.10, point5: x-coordinate = 5.02, y-coordinate = 40.41, point6: x-coordinate = 15.03, y-coordinate = 40.43, point7: x-coordinate = 5.00, y-coordinate = 4.75, point8: x-coordinate = 5.05, y-coordinate = 4.93, point9: x-coordinate = 5.03, y-coordinate = 4.66, point10: x-coordinate = 5. Point 08: Y-coordinate = 4.89; Point 11: X-coordinate = 6.24, Y-coordinate = 4.75; Point 12: X-coordinate = 10.33, Y-coordinate = 4.47; Point 13: X-coordinate = 15.01, Y-coordinate = 4.58; Point 14: X-coordinate = 15.08, Y-coordinate = 4.73; Point 15: X-coordinate = 15.06, Y-coordinate = 4.26; Point 16: X-coordinate = 15.08, Y-coordinate = 4.72; Point 17: X-coordinate = 2.50, Y-coordinate = -6.35 Point 18: x-coordinate = 4.99, y-coordinate = -6.55; Point 19: x-coordinate = 5.01, y-coordinate = -17.38; Point 20: x-coordinate = 10.03, y-coordinate = -29.41; Point 21: x-coordinate = 15.05, y-coordinate = -17.36; Point 22: x-coordinate = 15.06, y-coordinate = -5.95; Point 23: x-coordinate = 17.52, y-coordinate = -5.06. The results of comparing the coordinates identified by this method with standard coordinates and manually found coordinates are shown in Table 2.

[0136] Table 2

[0137]

[0138]

[0139] The table only shows the error on the horizontal axis because the data curves for the three point-finding algorithms remain unchanged. The horizontal axis can represent the accuracy of point finding, and the position of the point in the data for the qualification index is shown below. Figure 8As shown, the active power identification status is as follows: Figure 9-10 As shown in the diagram, the standard compliance indicator points are illustrated below. Figure 11 As shown in Tables 3 and 4, the final automatically generated report containing the RMS value qualification index, active power qualification index, and reactive current qualification index is as follows:

[0140] Table 3

[0141]

[0142]

[0143] Table 4

[0144]

[0145] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. An automatic identification method for power station fault voltage ride-through index based on step response analysis, characterized in that, Includes the following steps: Step S1: Collect measurement data before and after fault voltage ride-through, preprocess the measurement data, obtain the effective value of line voltage, and plot the effective value curve of line voltage. Step S2: Query the points on the line voltage RMS curve where voltage ride-through begins and ends, and record them as split1-4. split1-4 divides the line voltage RMS curve into five parts: before the fault, the voltage boost response segment, during the fault, the voltage drop response segment, and after the fault. Step S3: Locate points 1, 3, 5, and 6 on the voltage RMS curve according to split1-4, and calculate the line voltage RMS pass index based on the coordinate values ​​of points 1, 3, 5, and 6. Step S4: Plot the active power curve based on the measurement data. Locate point 7-16 on the active power curve according to split1-4. Calculate the active power qualification index based on the coordinate value of point 7-16. Step S5: Plot the reactive current curve based on the measurement data. Locate point 17-22 on the reactive current curve according to split1-4. Calculate the reactive current compliance index based on the coordinate values ​​of point 17-22. Step S6: Store the line voltage RMS value qualification index, active power qualification index, and reactive current qualification index.

2. The automatic identification method for station fault voltage ride-through index based on step response analysis according to claim 1, characterized in that, Before collecting measurement data in step S1, the following parameters need to be set: rated voltage, rated capacity, data voltage unit, data current unit, current starting column, voltage starting column, data starting row, data file format, data form, and data file name.

3. The automatic identification method for station fault voltage ride-through index based on step response analysis according to claim 1, characterized in that, The specific steps of step S1 are as follows: Step S11: Collect measurement data 4 seconds before and after fault voltage ride-through. The data resolution is 0.ms. After analyzing the statistical characteristics of the data, determine the filter size and filter the measurement data. Step S12: Replace outliers in the measurement data with reasonable values ​​using outlier detection methods; Step S13: Obtain the effective value of the line voltage from the processed measurement data and plot the effective value curve of the line voltage.

4. The automatic identification method for station fault voltage ride-through index based on step response analysis according to claim 1, characterized in that, The specific steps of step S2 are as follows: based on the threshold value of high voltage ride-through, find the points of entering and exiting voltage ride-through from the voltage effective value curve and record them as split1-4. The part before split1 is the pre-fault part, the part between split1-2 is the boost response segment, the part between split2-3 is the middle part of the fault, the part between split3-4 is the buck response segment, and the part after the fault is the post-fault part.

5. The automatic identification method for station fault voltage ride-through index based on step response analysis according to claim 1, characterized in that, The specific steps of step S3 are as follows: Step S31: Take the midpoint between split1 and the starting point of the line voltage RMS curve, and denote it as point1. Take the midpoint between split2 and split3, and denote it as point3. Step S32: In the range [split2, split2+1000], set the sliding window size to 2000, the sliding algorithm is the variance of all points in the window and the starting point of the window, and the threshold is the peak-to-peak value of the line voltage RMS curve in [split2+1000, split3-1000]. The sliding window slides from left to right to find the first point with a variance less than the threshold, which is denoted as point5. Step S33: In the range [split3-1000, split3], set the sliding window size to 2000, the sliding algorithm is the variance of all points in the window and the starting point of the window, and the threshold is the peak-to-peak value of the curve in [split2+1000, split3-1000]. The sliding window slides from right to left to find the first point with a variance less than the threshold, which is denoted as point6. Step S34: Calculate the line voltage effective value qualification index based on the coordinate values ​​of point1, 3, 5, and 6.

6. The automatic identification method for station fault voltage ride-through index based on step response analysis according to claim 1 or 5, characterized in that, The line voltage RMS value qualification index includes the voltage rise amplitude U. T and voltage rise duration t T The voltage rise amplitude U T and voltage rise duration t T The expression is: t T =(point6_x-point5_x)*1000 Where point1_y and point3_y are the ordinate values ​​of point1 and point3, respectively, and point5_x and point6_x are the abscissa values ​​of point5 and point6, respectively. n This is the system's nominal voltage.

7. The automatic identification method for station fault voltage ride-through index based on step response analysis according to claim 1, characterized in that, The specific steps of step S4 are as follows: Step S41: Plot the active power curve based on the measurement data, and synchronize the active power curve with the line voltage RMS value curve in time. Step S42: Take the maximum and minimum points on the active power curve located in the interval [split2-400, split2+400], and denote them as point8 and point9 respectively; Step S43: Take the maximum and minimum points on the active power curve located in the interval [(split2+split3) / 2-1500, (split2+split3) / 2+1500], and record them as point11 and point12 respectively; Step S44: Find the maximum and minimum points on the active power curve located in the interval [split3-400, split3+400], and record them as point14 and point15 respectively; Step S45: Set the upper bound as the maximum value of the active power curve in the interval [point8-3500, point8-500], and the lower bound as the minimum value of the active power curve in the interval [point8-3500, point8-500]. Find the first point in the interval [point8-500, point8] where the active power exceeds the upper and lower bounds from left to right, and denot it as ponit7. Step S46: Set the upper bound as the maximum value of the active power curve in the interval [point9+500, point9+2500], and the lower bound as the minimum value of the active power curve in the interval [point9+500, point9+2500]. Find the first point in the interval [point9, point9+500] where the active power exceeds the upper and lower bounds from right to left, and record it as point10. Step S47: Set the upper bound as the maximum value of the active power curve in the interval [point14-2500, point14-500], and the lower bound as the minimum value of the active power curve in the interval [point14-2500, point14-500]. Find the first point in the interval [point14-500, point14] where the active power exceeds the upper and lower bounds from left to right, and record it as point13. Step S48: Set the upper bound as the maximum value of the active power curve in the interval [point15+500, point15+3500], and the lower bound as the minimum value of the active power curve in the interval [point15+500, point15+3500]. Find the first point in the interval [point15, point15+500] where the active power exceeds the upper and lower bounds from right to left, and record it as point16. Step S49: Calculate the active power qualification index based on the coordinate values ​​of point7-16.

8. The automatic identification method for station fault voltage ride-through index based on step response analysis according to claim 1 or 7, characterized in that, The active power compliance index includes the active power fluctuation range M at the time of voltage rise. up Active power fluctuation time t at the moment of voltage rise up Active power fluctuation range M at the moment of voltage drop down Active power fluctuation time t at the moment of voltage drop down and the active power fluctuation range M during voltage rise. mid The active power fluctuation range M during voltage rise. up Active power fluctuation time t at the moment of voltage rise up Active power fluctuation range M at the moment of voltage drop down Active power fluctuation time t at the moment of voltage drop down and the active power fluctuation range M during voltage rise. mid The expression is: Where point7_x, point10_x, point13_x, and point16_x are the x-coordinates of point7, point10, point13, and point16, respectively; and point8_y, point9_y, point11_y, point12_y, point14_y, and point15_y are the y-coordinates of point8, point9, point11, point12, point14, and point15, respectively. n This refers to the system's nominal active power.

9. The automatic identification method for station fault voltage ride-through index based on step response analysis according to claim 1, characterized in that, The specific steps of step S5 are as follows: Step S51: Plot the reactive current curve based on the measurement data, and synchronize the reactive current curve with the effective value curve of the line voltage in time. Step S52: Take the midpoint between split1 and the starting point of the reactive current curve on the reactive current curve, and denote it as point17. Step S53: Take the midpoint between split1 and split3 on the reactive current curve and denote it as point20; Step S54: Locate the data point index of all reactive current values ​​within the high voltage ride-through range, and record the moment when the threshold is first exceeded as point19 and the moment when the threshold is last exceeded as point21. Step S55: Take the peak-to-peak value of the interval [split2-3000, split2-1000] as the threshold, take the average value of the interval [split2-3000, split2-1000] as the target value, and find the first point from left to right in the range [split2-200, point19_x] whose difference from the target value is greater than the threshold, and record it as point18, where point19_x is the x-coordinate value of point19; Step S56: Take the peak-to-peak value of the interval [split3+1000, split3+3000] as the threshold, take the average value of the interval [split3+1000, split3+3000] as the target value, and find the first point from right to left in the range [point21_x, split3+200] whose difference from the target value is greater than the threshold, and record it as point22, where point21_x is the x-coordinate value of point21; Step S57: Calculate the reactive current compliance index based on the coordinate values ​​of point17-22.

10. The automatic identification method for station fault voltage ride-through index based on step response analysis according to claim 6, characterized in that, The reactive current compliance index includes the reactive current response time t. xy Reactive current withdrawal time t tc Reactive current duration t cx and the steady-state mean value of reactive current I wt The reactive current response time t xy Reactive current withdrawal time t tc Reactive current duration t cx and the steady-state mean value of reactive current I wt The expression is: t xy =(point19_x-point18_x)*1000 t tc =(point22_x-point4_x)*1000 t cx =(point21_x-point19_x)*1000 Where point4_x, point18_x, point19_x, point21_x, and point22_x are the x-coordinates of point4, point18, point19, point21, and point22, respectively; point17_y and point20_y are the y-coordinates of point17 and point20, respectively; and P... n U n These are the system's nominal active power and voltage, respectively.

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