Station fault voltage ride-through index automatic identification method based on step response analysis

Abstract

The invention provides a station fault voltage ride-through index automatic identification method based on step response analysis, and the method comprises the steps: collecting measurement data before and after fault voltage ride-through, carrying out the preprocessing of the measurement data, obtaining a line voltage effective value, and drawing a line voltage effective value curve, an active power curve, and a reactive current curve; searching split1-4 on the line voltage effective value curve, searching point1, point3, point5 and point6 on the voltage effective value curve according to the split1-4, and calculating to obtain a line voltage effective value qualification index based on coordinate values of the point1, the point3, the point5 and the point6; according to the split1-4, point7-16 is searched on the active power curve, and an active power eligibility index is obtained through calculation based on the coordinate value of the point7-16; according to the split1-4, point17-22 is searched on the reactive current curve, and on the basis of the coordinate value of the point17-22, a reactive current eligibility index is obtained through calculation; a line voltage effective value eligibility index, an active power eligibility index and a reactive current eligibility index are stored, and eligibility analysis can be rapidly and accurately carried out on fault voltage ride-through of the new energy station.

Description

Technical Field

[0001] The present invention relates to the technical field of power system automation, and in particular to a method for automatically identifying a station fault voltage ride-through index based on step response analysis. Background Art

[0002] The voltage fault ride-through test is a key test in the power system to evaluate the grid-connected operation capability of renewable energy power generation equipment, including wind turbines and photovoltaic inverters. The core purpose of the test is to verify whether the equipment can maintain grid connection within the specified time by dynamically adjusting the output power when the grid experiences short-term voltage fluctuations or faults, such as voltage sags, surges, or momentary interruptions. This capability not only prevents equipment from being disconnected from the grid due to the triggering of protection mechanisms, but more importantly, it ensures the stability of the grid during fault recovery and prevents individual equipment from being disconnected from the grid and triggering a chain reaction.

[0003] The implementation of this test strictly follows a series of grid-connected technical standards. These standards are divided into two major systems, wind power and photovoltaics, according to the type of renewable energy. For wind power generation equipment, commonly used standards include GB / T 19963-2021 "Technical Regulations for Wind Farm Access to Power System", GB / T 36995-2018 "Test Procedure for Fault Voltage Ride-Through Capability of Wind Turbines", NB / T 31111-2017 "Test Procedure for High Voltage Ride-Through of Wind Turbines", Q / CSG 1211017-2018 "Technical Specification for Wind Farm Access to Grid" and "Yunnan Power Grid New Energy Site Access System Technical Principles (2023 Edition)", focusing on the control strategy and hardware protection mechanism of the unit in the event of voltage anomalies; in the photovoltaic field, the standards are based on GB / T 19964-2024 "Technical Regulations for Photovoltaic Power Station Access to Power System", GB / T31365-2015 "Test Procedure for Photovoltaic Power Station Access to Grid", NB / T 10324-2019 "Technical Regulations for High Voltage Ride-Through Detection in Photovoltaic Power Stations", etc., simulate voltage disturbances of different amplitudes and durations through fault voltage generating devices 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 large-scale and safe grid connection of new energy and is directly related to the stability and reliability of the power system.

[0004] However, the current calculation method for fault voltage ride-through indicators of new energy stations still has significant deficiencies. 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-operation condition testing of a single station often takes a lot of time, seriously extending the project cycle; second, it is accuracy deviation. The inevitable subjectivity in the manual image recognition process will introduce measurement errors and affect key indicators; finally, it is quality risk. The inconsistency of manual operation leads to a decrease in the standardization of test reports and the credibility of data, making it difficult to meet high-precision detection needs. Summary of the Invention

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

[0006] The technical solution of the present invention is achieved as follows:

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

[0008] Step S1: Collect measurement data before and after the fault voltage ride-through, pre-process the measurement data, obtain the effective value of the line voltage, and draw a line voltage effective value curve;

[0009] Step S2: query the points on the line voltage RMS curve at which voltage ride-through is entered and exited, and record them as split 1-4. Split 1-4 divides the line voltage RMS curve into five parts: pre-fault, boost response segment, fault, buck response segment, and post-fault segment.

[0010] Step S3: Search points 1, 3, 5, and 6 on the voltage effective value curve according to split 1-4, and calculate the line voltage effective value qualification index based on the coordinate values of points 1, 3, 5, and 6;

[0011] Step S4: Draw an active power curve based on the measured data, search for point 7-16 on the active power curve according to split 1-4, and calculate the active power qualification index based on the coordinate values of point 7-16;

[0012] Step S5: Draw a reactive current curve based on the measured data, search for points 17-22 on the reactive current curve according to splits 1-4, and calculate the reactive current qualification index based on the coordinate values of points 17-22;

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

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

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

[0016] Step S11: collect measurement data 4 seconds before and after the fault voltage ride-through with a data resolution of 0.ms, analyze the statistical characteristics of the data to determine the filter size, and filter the measurement data;

[0017] Step S12: using an outlier detection method to replace outliers in the measurement data with reasonable values;

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

[0019] Preferably, the specific steps of step S2 are: according to the threshold value of high voltage ride-through, find the points of entering voltage ride-through 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 reaction segment part, the part between split2-3 is the fault part, the part between split3-4 is the buck reaction segment part, and the part between split4-5 is the post-fault part.

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

[0021] Step S31, take the midpoint between split1 and the starting point of the line voltage effective value curve, record it as point1, take the midpoint between split2 and split3, record it as point3;

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

[0023] Step S33: In the range [split3-1000, split3], set the sliding window size to 2000, the sliding algorithm to the variance of all points in the window and the window starting point, the threshold to the peak-to-peak value of the curve at [split2+1000, split3-1000], and slide the sliding window from right to left to find the first point whose variance is less than the threshold, recorded as point6;

[0024] Step S34: Calculate the line voltage effective value qualification index according to the coordinate values of point 1, 3, 5, and 6.

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

[0026]

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

[0028] Among them, point1_y and point3_y are the vertical coordinate values of point1 and 3, point5_x and point6_x are the horizontal coordinate values of point5 and 6, and U n is the nominal system voltage.

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

[0030] Step S41: Draw an active power curve based on the measurement data, and perform time alignment and synchronization between the active power curve and the line voltage effective value curve;

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

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

[0033] Step S44: Take the maximum and minimum points in the interval [split3-400, split3+400] on the active power curve and record them as point 14 and point 15 respectively;

[0034] Step S45: Set the upper bound to the maximum value of the active power curve in the interval [point8-3500, point8-500] and the lower bound to 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 record it as ponit7.

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

[0036] Step S47: Set the upper bound to the maximum value of the active power curve in the interval [point14-2500, point14-500], and the lower bound to 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 to the maximum value of the active power curve in the interval [point15+500, point15+3500], and the lower bound to 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 point 7-16.

[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 when voltage rises up , Active power fluctuation range M at the time of voltage drop down , Active power fluctuation time t at voltage drop down And the active power fluctuation range M during voltage rise mid , where the active power fluctuation range M at the time of voltage rise up , Active power fluctuation time t when voltage rises up , Active power fluctuation range M at the time of voltage dropdown , Active power fluctuation time t at voltage drop down And the active power fluctuation range M during voltage rise mid The expression is:

[0040]

[0041] Among them, point7_x, point10_x, point13_x, point16_x are the horizontal coordinate values of point7, point10, point13, and point16 respectively, and point8_y, point9_y, point11_y, point12_y, point14_y, and point15_y are the vertical coordinate values of point8, point9, point11, point12, point14, and point15 respectively. n is the nominal active power of the system.

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

[0043] Step S51: Draw a reactive current curve based on the measurement data, and synchronize the reactive current curve with the line voltage effective value curve 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 record it as point17;

[0045] Step S53: Take the midpoint between split 1 and split 3 on the reactive current curve and record it as point 20;

[0046] Step S54: Locate the indexes of all data points where the reactive current value is within the high voltage ride-through range, record the time when the reactive current value first exceeds the threshold as point 19, and record the time when the reactive current value last exceeds the threshold as point 21;

[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 in the range [split2-200, point19_x] from left to right whose difference from the target value is greater than the threshold, and record it as point18, where point19_x is the horizontal 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 in the range [point21_x, split3+200] from right to left whose difference from the target value is greater than the threshold, and record it as point22, where point21_x is the horizontal coordinate value of point21;

[0049] Step S57: Calculate the reactive current qualification index according to the coordinate values of point 17-22.

[0050] Preferably, the reactive current qualification index includes reactive current response time t xy , reactive current exit 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 exit 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] Among them, point4_x, point18_x, point19_x, point21_x, point22_x are the horizontal coordinate values of point4, point18, point19, point21, and point22, point17_y, point20_y are the vertical coordinate values of point17 and point20, P n 、U n are the system nominal active power and voltage respectively.

[0056] Compared with the prior art, the present invention has the following beneficial effects:

[0057] The present invention discloses an automatic identification method for station fault voltage ride-through indicators based on step response. After collecting measurement data before and after the fault voltage ride-through, the line voltage effective value curve, the active power curve, and the reactive current curve can be drawn respectively. In the line voltage effective value curve, points split1-4 can be determined based on entering voltage ride-through and exiting voltage ride-through. Split1-4 can divide the line voltage effective value curve into five parts to limit the range in the subsequent point solution process. Then, based on split1-4, points 1-22 can be found on the line voltage effective value curve, the active power curve, and the reactive power curve respectively. Then, according to the coordinate values of the points found respectively, the voltage effective value qualification index, the active power qualification index, and the reactive current qualification index are calculated. Finally, the calculated effective value qualification index, the active power qualification index, and the reactive current qualification index are stored, so that the qualification analysis of the new energy station fault voltage ride-through can be performed quickly and accurately, freeing the test analyst from simple repetitive calculations. BRIEF DESCRIPTION OF THE DRAWINGS

[0058] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only preferred embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0059] Figure 1 This is a flow chart of the method for automatically identifying station fault voltage ride-through indicators based on step response analysis of the present invention;

[0060] Figure 2 A schematic diagram of selecting points on a line voltage effective value curve in the method for automatically identifying station fault voltage ride-through indicators based on step response analysis of the present invention;

[0061] Figure 3 Schematic diagram of point 6 selection in the method for automatically identifying station fault voltage ride-through indicators based on step response analysis of the present invention

[0062] Figure 4 A schematic diagram of selecting points on an active power curve in the method for automatically identifying station fault voltage ride-through indicators based on step response analysis of the present invention;

[0063] Figure 5 Schematic diagram of selecting point 10 of the method for automatically identifying station fault voltage ride-through indicators based on step response analysis of the present invention;

[0064] Figure 6This is a schematic diagram of selecting point 16 of the method for automatically identifying station fault voltage ride-through indicators based on step response analysis of the present invention;

[0065] Figure 7 A schematic diagram of selecting points on a reactive current curve in the method for automatically identifying station fault voltage ride-through indicators based on step response analysis of the present invention;

[0066] Figure 8 This is the automatic identification result of the 120% three-phase heavy load 2 high voltage ride through test indicator of Application Example 1 of the present invention;

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

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

[0069] Figure 11 This is the distribution map of key points of fault voltage ride-through indicators in new energy stations. DETAILED DESCRIPTION

[0070] In order to better understand the technical content of the present invention, a specific embodiment is provided below, and the present invention is further described in conjunction with the accompanying drawings.

[0071] See also Figures 1 to 7 The method for automatically identifying the fault voltage ride-through index of a station based on step response analysis provided by the present invention comprises the following steps:

[0072] Step S1: Collect measurement data before and after the fault voltage ride-through, pre-process the measurement data, obtain the effective value of the line voltage, and draw a line voltage effective value curve;

[0073] Step S2: query the points on the line voltage RMS curve at which voltage ride-through is entered and exited, and record them as split 1-4. Split 1-4 divides the line voltage RMS curve into five parts: pre-fault, boost response segment, fault, buck response segment, and post-fault segment.

[0074] Step S3: Search points 1, 3, 5, and 6 on the voltage effective value curve according to split 1-4, and calculate the line voltage effective value qualification index based on the coordinate values of points 1, 3, 5, and 6;

[0075] Step S4: Draw an active power curve based on the measured data, search for point 7-16 on the active power curve according to split 1-4, and calculate the active power qualification index based on the coordinate values of point 7-16;

[0076] Step S5: Draw a reactive current curve based on the measured data, search for points 17-22 on the reactive current curve according to splits 1-4, and calculate the reactive current qualification index based on the coordinate values of points 17-22;

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

[0078] In a method for automatically identifying fault voltage ride-through indicators at a station based on step response backwashing of the present invention, measurement data before and after the fault voltage ride-through are first collected, 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 values, and a line voltage effective value curve can be drawn based on time changes. In addition, an active power curve and a reactive current curve are also drawn based on the measurement data. After obtaining the line voltage effective value curve, four split points can be obtained based on the points on the curve at which voltage ride-through enters and exits the voltage ride-through, which are recorded as split1-4. Split1-4 can divide the line voltage effective value curve into five parts, which can serve to limit the range when searching for points in the subsequent search.

[0079] After obtaining split1-4, point1, 3, 5, and 6 can be found on the line voltage effective value curve based on the coordinate values of split1-4, and then the line voltage effective value qualification index can be calculated based on the coordinate values of point1, 3, 5, and 6. Then, the active power curve and reactive current curve are compared with the line voltage effective value curve. According to the change of the coordinate values of split1-4, point7-16 and point17-22 can be found on the active power curve and reactive current curve respectively. Then, according to the coordinate values of point7-16 and point17-22 respectively, the active power qualification index and reactive current qualification index can be obtained after calculation. Based on the line voltage effective value qualification index, active power qualification index, and reactive current qualification index, the fault voltage ride-through of the new energy station can be quickly and accurately analyzed. By quickly finding the point, manual search can be avoided, efficiency can be improved, and the test analyst can be separated from repeated calculations, reducing labor and improving the accuracy of point search.

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

[0081] After setting the rated parameters, you can easily compare and calculate with the measured data to ensure that the measured data is within the normal range of the rated data.

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

[0083] Step S11: Collect measurement data 4 seconds before and after the fault voltage ride-through with a data resolution of 0.1ms, 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 an outlier detection method to replace outliers in the measurement data with reasonable values by using Z-Score and IQR.

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

[0086] By preprocessing the measurement data, the noise in the measurement data can be removed, and the abnormal values can be replaced with reasonable values to ensure the accuracy of the measurement data, so that a line voltage effective value curve with high accuracy can be drawn.

[0087] Preferably, the specific steps of step S2 are: according to the threshold value of high voltage ride-through, find the points of entering voltage ride-through 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 reaction segment part, the part between split2-3 is the fault part, the part between split3-4 is the buck reaction segment part, and the part between split4-5 is the post-fault part.

[0088] After obtaining the line voltage RMS curve, the points entering and exiting voltage ride-through can be directly found on the line voltage RMS curve based on the high voltage ride-through threshold. These points are recorded as split 1-4. Split 1-4 divides the line voltage RMS curve into five parts in sequence, facilitating the range limitation of subsequent point calculations.

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

[0090] Step S31, take the midpoint between split1 and the starting point of the line voltage effective value curve, record it as point1, take the midpoint between split2 and split3, record it as point3;

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

[0092] Step S33: In the range [split3-1000, split3], set the sliding window size to 2000, the sliding algorithm to the variance of all points in the window and the window starting point, the threshold to the peak-to-peak value of the curve at [split2+1000, split3-1000], and slide the sliding window from right to left to find the first point whose variance is less than the threshold, recorded as point6;

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

[0094]

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

[0096] Among them, point1_y and point3_y are the vertical coordinate values of point1 and 3, point5_x and point6_x are the horizontal coordinate values of point5 and 6, and U n is the nominal system voltage.

[0097] The effective value of the line voltage is the voltage signal emitted by the device, which is used to simulate the line voltage at the grid connection point during actual high-voltage ride-through. The effective value of the line voltage first rises from the nominal voltage to the ride-through target value voltage, and then returns to the nominal voltage for a period of time. The two key qualification indicators of the effective value of the line voltage are the voltage rise amplitude and the voltage rise duration. After obtaining point 1, 3, 5, and 6, they can be directly calculated based on the coordinate values of point 1, 3, 5, and 6. The calculation of the qualification indicators through the coordinate values of the points on the curve can accurately represent the different working conditions of the station, and the data is accurate. Compared with manual search for points, it is more efficient and more accurate.

[0098] When the fundamental positive sequence voltage reaches 1.1, the high voltage ride-through threshold is reached and the system's active and reactive powers begin to adjust. Point 2 and point 4 are the start and end times when the fundamental voltage exceeds 1.1 times the threshold. The specific point calculation algorithm is as follows:

[0099] (1) Conditional detection: By locating the data point indexes of all fundamental positive sequence voltage values within the range of 1.1±0.001, the tolerance is 0.001 to avoid missed detection 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 first time the threshold is exceeded is point 2, and the last time the threshold is exceeded is point 4.

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

[0103] Step S41: Draw an active power curve based on the measurement data, and perform time alignment and synchronization between the active power curve and the line voltage effective value curve;

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

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

[0106] Step S44: Take the maximum and minimum points in the interval [split3-400, split3+400] on the active power curve and record them as point 14 and point 15 respectively;

[0107] Step S45: Set the upper bound to the maximum value of the active power curve in the interval [point8-3500, point8-500] and the lower bound to 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 record it as ponit7.

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

[0109] Step S47: Set the upper bound to the maximum value of the active power curve in the interval [point14-2500, point14-500], and the lower bound to 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 to the maximum value of the active power curve in the interval [point15+500, point15+3500], and the lower bound to 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 point 7-16. The active power qualification index includes the active power fluctuation range M at the time of voltage rise. up , Active power fluctuation time t when voltage rises up , Active power fluctuation range M at the time of voltage drop dowb , Active power fluctuation time t at voltage drop down And the active power fluctuation range M during voltage rise mid , where the active power fluctuation range M at the time of voltage rise up , Active power fluctuation time t when voltage rises up , Active power fluctuation range M at the time of voltage drop down , Active power fluctuation time t at voltage drop down And the active power fluctuation range M during voltage rise mid The expression is:

[0112]

[0113] Among them, point7_x, point10_x, point13_x, point16_x are the horizontal coordinate values of point7, point10, point13, and point16 respectively, and point8_y, point9_y, point11_y, point12_y, point14_y, and point15_y are the vertical coordinate values of point8, point9, point11, point12, point14, and point15 respectively. n is the nominal active power of the system.

[0114] During the high-voltage ride-through process, the main risks faced by the active power of wind turbines are DC bus overvoltage, converter overload and excessive mechanical power input caused by the sudden rise of grid voltage, which may cause equipment damage or disconnection from the grid. To cope with the risks, the unit needs to actively reduce the active power output through the converter's rapid amplitude limiting (such as enabling the DC unloading circuit to dissipate excess energy), dynamically adjust the pitch angle to reduce mechanical power input, and collaboratively inject capacitive reactive power to suppress voltage fluctuations; the active power fluctuation amplitude during the fault period must be strictly limited within the threshold, and after the fault is cleared, it must return to normal with a gentle slope to ensure that it does not disconnect from the grid and In accordance with the grid dynamic response standard, 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 the range of ±50% Pn when the voltage rises and when the voltage returns to normal, and the fluctuation amplitude should be greater than zero, and the fluctuation time should not exceed 80ms. During the voltage rise period, the output active power fluctuation amplitude should be within the range of ±5% Pn. After the voltage returns to normal, the output power should be the output power corresponding to the actual wind conditions. There are five indicators to verify the high voltage ride-through active power qualification, namely, the active power fluctuation range M at the time of voltage rise ... up , Active power fluctuation time t when voltage rises up , Active power fluctuation range M at the time of voltage drop down , Active power fluctuation time t at voltage drop down And the active power fluctuation range M during voltage rise mid After the active power curve and the line voltage RMS curve are time-aligned and synchronized, point 7-16 can be obtained based on the coordinate value changes of split 1-4 on the line voltage RMS curve. Finally, the various active power qualification indicators can be obtained according to the coordinate values of point 7-16.

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

[0116] Step S51: Draw a reactive current curve based on the measurement data, and synchronize the reactive current curve with the line voltage effective value curve 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 record it as point17;

[0118] Step S53: Take the midpoint between split 1 and split 3 on the reactive current curve and record it as point 20;

[0119] Step S54: Locate the indexes of all data points where the reactive current value is within the high voltage ride-through range, record the time when the reactive current value first exceeds the threshold as point 19, and record the time when the reactive current value last exceeds the threshold as point 21;

[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 in the range [split2-200, point19_x] from left to right whose difference from the target value is greater than the threshold, and record it as point18, where point19_x is the horizontal 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 in the range [point21_x, split3+200] from right to left whose difference from the target value is greater than the threshold, and record it as point22, where point21_x is the horizontal coordinate value of point21;

[0122] Step S57: Calculate the reactive current qualification index based on the coordinate values of point 17-22. The reactive current qualification index includes the reactive current response time t xy , reactive current exit 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 exit 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] Among them, point4_x, point18_x, point19_x, point21_x, point22_x are the horizontal coordinate values of point4, point18, point19, point21, and point22, point17_y, point20_y are the vertical coordinate values of point17 and point20, P n 、U n are the system nominal active power and voltage respectively.

[0128] During the high-voltage ride-through of the power system, in order to maintain the voltage stability of the grid and meet the requirements of the grid-connected specifications, wind turbines need to dynamically adjust the reactive current to suppress the voltage surge. According to the voltage-reactive control strategy, when the grid voltage exceeds the rated threshold, the equipment should actively inject reactive current in the opposite direction of the voltage deviation. Specifically, during the high-voltage ride-through, after the system detects the voltage rise, it dynamically increases the injection of capacitive reactive current (or reduces the output of inductive reactive current) according to the preset voltage-reactive response curve, thereby offsetting the voltage rise trend through the absorption of reactive power. Rapid tracking of reactive current through vector control can effectively suppress transient overvoltages, ensure that the equipment does not go off-grid during the fault and support the dynamic recovery of the grid. From the moment the voltage rises at the grid connection point, the response time of the dynamic inductive reactive current control is no more than 40ms, and the inductive reactive current is continuously injected during the voltage fault. 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 when the voltage at the grid connection point increases, the reactive current output by the wind farm to the power system should be the difference between the reactive current output before the voltage at the grid connection point increases and the dynamic reactive current increment. The maximum output capacity of the wind farm's reactive current should not be less than 1.05 times the rated current of the wind farm. From the moment the voltage at the grid connection point increases, the dynamic reactive current rise time of the wind farm shall not exceed 40ms; from the moment the voltage at the grid connection point recovers to below 110% of the nominal voltage, the wind farm shall withdraw the dynamic reactive current increment actively provided within 40ms. The four indicators for verifying the qualification of the high voltage ride-through reactive current are the reactive current response time t xy, reactive current exit time t tc , reactive current duration t cx And the steady-state mean value of reactive current I wt Based on the change of the coordinate values of split1-4 on the line voltage effective value curve, point17-22 is obtained, and finally, the various reactive current qualification indicators can be obtained according to the coordinate values of point17-22.

[0131] The following is a practical verification example:

[0132] The HVRT compliance index for a wind farm with a rated voltage of 35 kV and a rated capacity of 5 MW was calculated. Current and voltage transformers were used to measure the instantaneous three-phase voltage and current values of a turbine in the wind farm. The values were stored in an Excel spreadsheet in the following format: voltage unit V, current unit A, voltage data starting in column 2, current data starting in column 5, and data starting in row 3. The HVRT operating conditions are shown in Table 1.

[0133] Table 1

[0134]

[0135] The data of the fault voltage ride-through condition 120% three-phase large load 2 of this wind farm is used to use the automatic identification method of the station fault voltage ride-through index based on step response analysis of the present invention, and the reactive current reference value is: 12.37, 0.9 reactive current value: -17.49; the coordinates of each key point split1: 50018, split2: 50185, split3: 150342, split4: 150547, point1: abscissa = 2.50, ordinate = 35.04, point2: abscissa = 5.01, ordinate = 1 .10, point3: abscissa = 10.03, ordinate = 40.76, point4: abscissa = 15.04, ordinate = 1.10, point5: abscissa = 5.02, ordinate = 40.41, point6: abscissa = 15.03, ordinate = 40.43, point7: abscissa = 5.00, ordinate = 4.75, point8: abscissa = 5.05, ordinate = 4.93, point9: abscissa = 5.03, ordinate = 4.66, point10: abscissa = 5. 08, ordinate = 4.89, point11: abscissa = 6.24, ordinate = 4.75, point12: abscissa = 10.33, ordinate = 4.47, point13: abscissa = 15.01, ordinate = 4.58, point14: abscissa = 15.08, ordinate = 4.73, point15: abscissa = 15.06, ordinate = 4.26, point16: abscissa = 15.08, ordinate = 4.72, point17: abscissa = 2.50, ordinate = -6.35 , point18: abscissa = 4.99, ordinate = -6.55, point19: abscissa = 5.01, ordinate = -17.38, point20: abscissa = 10.03, ordinate = -29.41, point21: abscissa = 15.05, ordinate = -17.36, point22: abscissa = 15.06, ordinate = -5.95, point23: abscissa = 17.52, ordinate = -5.06, the comparison results of the coordinates identified by this method with the standard coordinates and the manually found point coordinates are shown in Table 2:

[0136] Table 2

[0137]

[0138]

[0139] In the table, only the error of the horizontal axis is reflected. Since the data curves of the three point-finding algorithms remain unchanged, the horizontal axis can represent the accuracy of point-finding. The position of the point of the qualification index in the data is as follows: Figure 8As shown in the figure, the identification of active power is as follows Figure 9-10 As shown, the schematic diagram of the standard qualification index point is as follows Figure 11 As shown, the final automatically generated report containing the effective value qualification index, active power qualification index and reactive current qualification index is shown in Table 3 and Table 4:

[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 in the scope of protection of the present invention.

Claims

1. The automatic identification method of station fault voltage ride-through index based on step response analysis is characterized by: The following steps are involved: Step S1: Collect measurement data before and after the fault voltage ride-through, pre-process the measurement data, obtain the effective value of the line voltage, and draw a line voltage effective value curve; Step S2: query the points on the line voltage RMS curve at which voltage ride-through is entered and exited, and record them as split 1-4. Split 1-4 divides the line voltage RMS curve into five parts: pre-fault, boost response segment, fault, buck response segment, and post-fault segment. Step S3: Search points 1, 3, 5, and 6 on the voltage effective value curve according to split 1-4, and calculate the line voltage effective value qualification index based on the coordinate values of points 1, 3, 5, and 6; Step S4: Draw an active power curve based on the measured data, search for point 7-16 on the active power curve according to split 1-4, and calculate the active power qualification index based on the coordinate values of point 7-16; Step S5: Draw a reactive current curve based on the measured data, search for points 17-22 on the reactive current curve according to splits 1-4, and calculate the reactive current qualification index based on the coordinate values of points 17-22; Step S6: storing the line voltage effective value qualification index, the active power qualification index, and the reactive current qualification index.

2. The method for automatically identifying fault voltage ride-through indicators of a station based on step response analysis according to claim 1 is characterized in that: Before collecting the measurement data, the step S1 needs to set the following parameters: rated voltage, rated capacity, data voltage unit, data current unit, current starting column, voltage starting column, data starting row, data file format, data table and data file name.

3. The method for automatically identifying fault voltage ride-through indicators of a station based on step response analysis according to claim 1 is characterized in that: The specific steps of step S1 are: Step S11: collect measurement data 4 seconds before and after the fault voltage ride-through with a data resolution of 0.ms, analyze the statistical characteristics of the data to determine the filter size, and filter the measurement data; Step S12: using an outlier detection method to replace outliers in the measurement data with reasonable values; Step S13: Obtain the effective value of the line voltage from the processed measurement data, and draw a line effective value curve of the line voltage.

4. The method for automatically identifying fault voltage ride-through indicators of a station based on step response analysis according to claim 1 is characterized in that: The specific steps of step S2 are: according to the high voltage ride-through threshold value, the points of entering and exiting voltage ride-through are found on the voltage effective value curve, and are recorded as split1-4, where the part before split1 is the pre-fault part, the part between split1-2 is the boost reaction part, the part between split2-3 is the fault part, the part between split3-4 is the buck reaction part, and the part between split4-5 is the post-fault part.

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

6. The method for automatically identifying station fault voltage ride-through indicators based on step response analysis according to claim 1 or 5, characterized in that: The line voltage effective value qualification index includes the voltage rise amplitude U T and the voltage rise duration t T , the voltage increase amplitude U T and the voltage rise duration t T The expression is: t T =(point6_x-point5_x)*1000 Among them, point1_y and point3_y are the vertical coordinate values of point1 and 3, point5_x and point6_x are the horizontal coordinate values of point5 and 6, and U n is the nominal system voltage.

7. The method for automatically identifying fault voltage ride-through indicators of a station based on step response analysis according to claim 1 is characterized in that: The specific steps of step S4 are: Step S41: Draw an active power curve based on the measurement data, and perform time alignment and synchronization between the active power curve and the line voltage effective value curve; Step S42: Take the maximum point and the minimum point in the interval [split2-400, split2+400] on the active power curve and record them as point8 and point9 respectively; Step S43: Take the maximum point and the minimum point on the active power curve in the interval [(split2+split3) / 2-1500, (split2+split3) / 2+1500] and record them as point11 and point12 respectively; Step S44: Take the maximum and minimum points in the interval [split3-400, split3+400] on the active power curve and record them as point 14 and point 15 respectively; Step S45: Set the upper bound to the maximum value of the active power curve in the interval [point8-3500, point8-500] and the lower bound to 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 record it as ponit7. Step S46: Set the upper bound to the maximum value of the active power curve in the interval [point9+500, point9+2500], and the lower bound to 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] from right to left where the active power exceeds the upper and lower bounds, and record it as point10. Step S47: Set the upper bound to the maximum value of the active power curve in the interval [point14-2500, point14-500], and the lower bound to 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 to the maximum value of the active power curve in the interval [point15+500, point15+3500], and the lower bound to 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 point 7-16.

8. The method for automatically identifying station fault voltage ride-through indicators based on step response analysis according to claim 1 or 7, characterized in that: The active power qualification index includes the active power fluctuation range M at the time of voltage rise up , Active power fluctuation time t when voltage rises up , Active power fluctuation range M at the time of voltage drop down , Active power fluctuation time t at voltage drop down And the active power fluctuation range M during voltage rise mid , where the active power fluctuation range M at the time of voltage rise up , Active power fluctuation time t when voltage rises up , Active power fluctuation range M at the time of voltage drop down , Active power fluctuation time t at voltage drop down And the active power fluctuation range M during voltage rise mid The expression is: Among them, point7_x, point10_x, point13_x, point16_x are the horizontal coordinate values of point7, point10, point13, and point16 respectively, and point8_y, point9_y, point11_y, point12_y, point14_y, and point15_y are the vertical coordinate values of point8, point9, point11, point12, point14, and point15 respectively. n is the nominal active power of the system.

9. The method for automatically identifying fault voltage ride-through indicators of a station based on step response analysis according to claim 1 is characterized in that: The specific steps of step S5 are: Step S51: Draw a reactive current curve based on the measurement data, and synchronize the reactive current curve with the line voltage effective value curve in time; Step S52: Take the midpoint between split1 and the starting point of the reactive current curve on the reactive current curve, and record it as point17; Step S53: Take the midpoint between split 1 and split 3 on the reactive current curve and record it as point 20; Step S54: Locate the indexes of all data points where the reactive current value is within the high voltage ride-through range, record the time when the reactive current value first exceeds the threshold as point 19, and record the time when the reactive current value last exceeds the threshold as point 21; 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 in the range [split2-200, point19_x] from left to right whose difference from the target value is greater than the threshold, and record it as point18, where point19_x is the horizontal 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 in the range [point21_x, split3+200] from right to left whose difference from the target value is greater than the threshold, and record it as point22, where point21_x is the horizontal coordinate value of point21; Step S57: Calculate the reactive current qualification index according to the coordinate values of point 17-22.

10. The method for automatically identifying fault voltage ride-through indicators of a station based on step response analysis according to claim 6, characterized in that: The reactive current qualification index includes reactive current response time t xy , reactive current exit 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 exit 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 Among them, point4_x, point18_x, point19_x, point21_x, point22_x are the horizontal coordinate values of point4, point18, point19, point21, and point22, point17_y and point20_y are the vertical coordinate values of point17 and point20, P n 、U n are the system nominal active power and voltage respectively.

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