A matlab-based fault ride-through time judgment method

Abstract

The application discloses a matlab-based fault ride-through time judgment method, a fault ride-through type judgment module judges and confirms the type of the input fault ride-through of the power grid, a fault ride-through starting and ending time judgment module obtains the time value of the starting moment of the fault ride-through or the fault ride-through ending time value or the time value of both according to the waveform diagram or the fault ride-through type; when the fault ride-through type is high-voltage ride-through, the time value of the point with the maximum phase voltage effective value slope of the power grid is the time value of the starting moment of the fault ride-through; when the fault ride-through type is low-voltage ride-through, the time value of the point with the minimum phase voltage effective value slope of the power grid is the time value of the starting moment of the fault ride-through; the matlab-based fault ride-through time judgment method can realize the full-automatic judgment of the power grid fault from the data import to the output report, can improve the efficiency of the fault ride-through test of the converter, and can improve the accuracy and stability of the fault index judgment.

Description

Technical Field

[0001] This invention relates to the field of testing technology in the wind power industry, and in particular to a fault ride-through time determination method based on MATLAB. Background Technology

[0002] Post-fault ride-through data processing is mainly applied in the testing technology field of the wind power industry. In this application, the core of the fault ride-through calculation algorithm lies in the judgment of the fault ride-through entry time and exit time.

[0003] In converter fault ride-through testing, since the laboratory cannot realistically simulate the fault ride-through conditions of the power grid, it is necessary to introduce a fault ride-through simulation device to simulate the actual power grid fault ride-through. Generally, the laboratory can simulate fault ride-through in two ways: the first is the basic principle of resistive-inductive voltage division and resistive-capacitive voltage boost; the second is to directly simulate the power grid by controlling the output voltage of the ACsource source.

[0004] Currently, the fault ride-through test of converters only involves collecting voltage and current signals at the grid end during the fault ride-through period. Then, the collected data is analyzed and the effective value waveform is calculated using an algorithm. Finally, the data is manually judged to determine whether each key parameter meets the national standard requirements. This method is more convenient than the earlier purely manual calculation, but a large number of indicators still require human judgment. The entire test cycle is long, time-consuming, inefficient, and has significant human error and unstable test accuracy.

[0005] Therefore, it is necessary to design a fault ride-through time determination method that can realize the fully automatic judgment of power grid faults from data import to output report, which can improve the efficiency of converter fault ride-through test, as well as the accuracy and stability of fault indicator judgment. Summary of the Invention

[0006] The technical problem to be solved by this invention is to propose a fault ride-through time judgment method based on MATLAB. This MATLAB-based fault ride-through time judgment method can realize fully automatic judgment of power grid faults from data import to output report. It can improve the efficiency of converter fault ride-through test, and at the same time improve the accuracy and stability of fault indicator judgment.

[0007] To address the aforementioned technical problems, this invention provides a MATLAB-based method for determining fault ride-through time, comprising a data reading module, a data conversion and calculation module, a slope calculation and waveform output module, a fault ride-through type determination module, and a fault ride-through start and end time determination module. The method includes the following steps: the data reading module collects instantaneous grid line voltage values ​​at N sampling points during the fault ride-through period input to the power grid and outputs them to the data conversion and calculation module; the data conversion and calculation module converts the N instantaneous grid line voltage values ​​into effective grid phase voltage values; then, the N effective grid phase voltage values ​​are filtered; and the slope calculation and waveform output module further filters the values. The slope algorithm calculates the slope values ​​of N filtered grid phase voltage RMS values ​​and generates a waveform diagram from all the obtained slope values. The fault ride-through type judgment module judges and confirms the type of fault ride-through input from the grid. The fault ride-through start and end time judgment module obtains the fault ride-through start time value or fault ride-through end time value or both based on the waveform diagram or the fault ride-through type. When the fault ride-through type is high-voltage ride-through, the time value of the point with the largest slope of the grid phase voltage RMS value is the fault ride-through start time value. When the fault ride-through type is low-voltage ride-through, the time value of the point with the smallest slope of the grid phase voltage RMS value is the fault ride-through start time value.

[0008] Preferably, the filtering slope algorithm is: df(i) = U(i+3) - U(i), where df(i) is the slope of the effective value of the phase voltage at the i-th sampling point of the power grid, U(i+3) is the effective value of the phase voltage at the (i+3)-th sampling point of the power grid, and U(i) is the effective value of the phase voltage at the i-th sampling point of the power grid.

[0009] Preferably, when the fault ride-through type determination module determines that the type of power grid input fault ride-through is low-voltage fault ride-through, the fault ride-through start and end time determination module extracts the time value of the minimum slope point in the waveform diagram output by the slope calculation and waveform diagram output module as the start time of the low-voltage fault ride-through, and extracts the time value of the maximum point in the waveform diagram as the end time of the low-voltage fault ride-through.

[0010] Preferably, when the fault ride-through type determination module determines that the type of fault ride-through input to the power grid is a low-voltage fault ride-through, it further determines whether the fault ride-through is an unbalanced ride-through. If the fault ride-through is determined to be an unbalanced ride-through, the data conversion and calculation module calculates the positive and negative sequence active current and reactive current of the fault ride-through input to the power grid, and obtains the response time of the power grid requiring reactive power compensation based on the calculation results of the positive and negative sequence active current and reactive current.

[0011] Preferably, when the fault ride-through type determination module determines that the type of power grid input fault ride-through is a high-voltage fault ride-through, the fault ride-through start and end time determination module extracts the time value of the maximum slope point in the waveform diagram output by the slope calculation and waveform diagram output module as the start time of the high-voltage fault ride-through, and extracts the time value of the minimum point in the waveform diagram as the end time of the high-voltage fault ride-through.

[0012] Preferably, the data conversion and calculation module calculates the positive and negative sequence active and reactive currents of the fault ride-through input to the power grid, and obtains the response time of the power grid requiring reactive power compensation based on the calculation results of the positive and negative sequence active and reactive currents, and calculates the fault duration; wherein, the fault duration is: the end time of high-voltage fault ride-through minus the start time of high-voltage fault ride-through.

[0013] Preferably, when the fault ride-through type judgment module determines that the type of power grid input fault ride-through is a composite fault ride-through, the fault ride-through start and end time judgment module extracts the waveform diagram output by the slope calculation and waveform diagram output module, extracts the first two seconds of the first fault ride-through start time from the sampled data of the data reading module, selects a time from the time between the first fault ride-through start time and the time before the second ride-through start time as the start time, extracts the time value of the minimum slope from the start time as the end time of the high-voltage ride-through fault and the start time of the low-voltage ride-through fault, and extracts the time value of the maximum slope as the start time of the high-voltage ride-through fault and the end time of the low-voltage ride-through fault.

[0014] Preferably, when the fault ride-through type determination module determines that the type of power grid input fault ride-through is a composite ride-through fault ride-through, specifically a composite ride-through where a high-voltage ride-through fault precedes a low-voltage ride-through fault, then the module first determines the start time of the high-voltage ride-through fault and then determines the start time of the low-voltage ride-through fault.

[0015] Preferably, when the fault ride-through type determination module determines that the type of power grid input fault ride-through is a composite ride-through fault, specifically a composite ride-through of low-voltage ride-through fault followed by high-voltage ride-through fault, then the low-voltage ride-through fault initiation time is determined first, followed by the high-voltage ride-through fault initiation time.

[0016] Preferably, the method further includes a test result judgment module and a test result output module. The MATLAB-based fault ride-through time judgment method further includes: the data conversion and calculation module, the slope calculation and waveform output module, the fault ride-through type judgment module, and the fault ride-through start and end time judgment module outputting the obtained data to the test result judgment module. The test result judgment module performs a power grid input test based on the obtained data and sends the obtained test results to the test result output module for output.

[0017] After adopting the above method, the data reading module collects the instantaneous values ​​of the grid line voltage at N sampling points during the fault ride-through of the grid input and outputs them to the data conversion and calculation module. The data conversion and calculation module converts the N instantaneous grid line voltage values ​​into effective values ​​of the grid phase voltages, and then filters the N effective values ​​of the grid phase voltages. The slope calculation and waveform output module calculates the slope values ​​of the N filtered effective values ​​of the grid phase voltages using a filtering slope algorithm, and generates a waveform graph from all the obtained slope values. The fault ride-through type judgment module judges and confirms the type of fault ride-through input to the grid, and the fault ride-through start and end time judgment module determines the type of fault ride-through based on the fault ride-through start and end time. The waveform or fault ride-through type yields the fault ride-through start time, fault ride-through end time, or both. When the fault ride-through type is high-voltage ride-through, the time value of the point with the largest effective slope of the grid phase voltage is the fault ride-through start time. When the fault ride-through type is low-voltage ride-through, the time value of the point with the smallest effective slope of the grid phase voltage is the fault ride-through start time. This MATLAB-based fault ride-through time judgment method can achieve fully automatic judgment of grid faults from data import to output report, which can improve the efficiency of converter fault ride-through testing, as well as the accuracy and stability of fault indicator judgment. Attached Figure Description

[0018] Figure 1 This is an overall flowchart of a fault travel time determination method based on MATLAB according to the present invention.

[0019] Figure 2 This is an overall interface diagram of a fault travel time determination method based on MATLAB according to the present invention. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0021] Example 1

[0022] Please see Figure 1 and Figure 2 , Figure 1 This is an overall flowchart of a fault travel time determination method based on MATLAB according to the present invention. Figure 2 This is an overall interface diagram of a fault travel time determination method based on MATLAB according to the present invention.

[0023] This embodiment discloses a fault ride-through time determination method based on MATLAB, including a data reading module, a data conversion and calculation module, a slope calculation and waveform output module, a fault ride-through type determination module, and a fault ride-through start and end time determination module. The method includes the following steps: the data reading module collects the instantaneous values ​​of the grid line voltage at N sampling points during the fault ride-through period input to the grid and outputs them to the data conversion and calculation module. The data conversion and calculation module converts the N instantaneous grid line voltage values ​​into effective values ​​of grid phase voltages, and then filters the N effective values ​​of grid phase voltages. The slope calculation and waveform output module calculates the filtered slope... The method calculates the slope values ​​of N filtered grid phase voltage RMS values ​​and generates a waveform diagram of all obtained slope values. The fault ride-through type judgment module judges and confirms the type of fault ride-through input by the grid. The fault ride-through start and end time judgment module obtains the fault ride-through start time value or fault ride-through end time value or both based on the waveform diagram or fault ride-through type. When the fault ride-through type is high voltage ride-through, the time value of the point with the largest slope of the grid phase voltage RMS value is the fault ride-through start time value. When the fault ride-through type is low voltage ride-through, the time value of the point with the smallest slope of the grid phase voltage RMS value is the fault ride-through start time value.

[0024] Example 2

[0025] This embodiment is based on Embodiment 1. In this embodiment, the filtering slope algorithm is: df(i) = U(i+3) - U(i), where df(i) is the slope of the effective value of the phase voltage at the i-th sampling point of the power grid, U(i+3) is the effective value of the phase voltage at the (i+3)-th sampling point of the power grid, and U(i) is the effective value of the phase voltage at the i-th sampling point of the power grid. This method can effectively filter out high-frequency oscillation waveforms within 3fs.

[0026] The data conversion and calculation module filters the effective values ​​of N grid phase voltages and extracts the slope between two points within the selected range. By increasing the number of interval points between the selected two points, the slope value of the effective value of grid phase voltage is filtered accordingly to remove voltage oscillations in the high-frequency part, so that the slope value at the actual low-voltage break-through moment is unique. Then, the maximum or minimum value of the slope can be determined.

[0027] Example 3

[0028] This embodiment is based on Embodiment 1. In this embodiment, when the fault ride-through type judgment module determines that the type of power grid input fault ride-through is low-voltage fault ride-through, the fault ride-through start and end time judgment module extracts the time value of the minimum slope point in the waveform graph output by the slope calculation and waveform graph output module as the start time of the low-voltage fault ride-through, and extracts the time value of the maximum point in the waveform graph as the end time of the low-voltage fault ride-through.

[0029] Example 4

[0030] This embodiment is based on Embodiment 3. In this embodiment, when the fault ride-through type judgment module determines that the type of fault ride-through input to the power grid is a low-voltage fault ride-through, it further determines whether the fault ride-through is an unbalanced ride-through. If the fault ride-through is determined to be an unbalanced ride-through, the data conversion and calculation module calculates the positive and negative sequence active current and reactive current of the fault ride-through input to the power grid, and obtains the response time of the power grid requiring reactive power compensation based on the calculation results of the positive and negative sequence active current and reactive current.

[0031] Example 5

[0032] This embodiment is based on Embodiment 1. In this embodiment, when the fault ride-through type judgment module determines that the type of power grid input fault ride-through is high-voltage fault ride-through, the fault ride-through start and end time judgment module takes the time value of the maximum slope in the waveform graph output by the slope calculation and waveform graph output module as the start time of its high-voltage fault ride-through, and takes the time value of the minimum point in the waveform graph as the end time of its high-voltage fault ride-through.

[0033] In this embodiment, the data conversion and calculation module calculates the positive and negative sequence active and reactive currents of the fault crossing input to the power grid, and obtains the response time of the power grid requiring reactive power compensation based on the calculation results of the positive and negative sequence active and reactive currents, and calculates the fault duration; wherein, the fault duration is: the end time of high-voltage fault crossing minus the start time of high-voltage fault crossing.

[0034] Example 6

[0035] This embodiment is based on Embodiment 1. In this embodiment, when the fault ride-through type judgment module determines that the type of power grid input fault ride-through is a composite fault ride-through, the fault ride-through start and end time judgment module extracts the waveform diagram output by the slope calculation and waveform diagram output module, extracts the first two seconds of the first fault ride-through start time from the sampled data of the data reading module, selects a time from the time between the first fault ride-through start time and the time before the second ride-through start time as the start time, extracts the time value of the minimum slope from the start time as the end time of the high-voltage ride-through fault and the start time of the low-voltage fault ride-through, and extracts the time value of the maximum slope as the start time of the high-voltage ride-through fault and the end time of the low-voltage fault ride-through.

[0036] In this embodiment, when the fault ride-through type determination module determines that the type of power grid input fault ride-through is a composite ride-through fault ride-through, specifically a composite ride-through where a high-voltage ride-through fault precedes a low-voltage ride-through fault, then the module first determines the start time of the high-voltage ride-through fault and then determines the start time of the low-voltage ride-through fault.

[0037] In this embodiment, when the fault ride-through type determination module determines that the type of power grid input fault ride-through is a composite ride-through fault ride-through, specifically a composite ride-through of low-voltage ride-through fault followed by high-voltage ride-through fault, it first determines the start time of the low-voltage ride-through fault and then determines the start time of the high-voltage ride-through fault.

[0038] Example 7

[0039] This embodiment is based on Embodiment 1. In this embodiment, the fault ride-through time judgment method based on MATLAB further includes a test result judgment module and a test result output module. The fault ride-through time judgment method based on MATLAB further includes: the data conversion and calculation module, the slope calculation and waveform output module, the fault ride-through type judgment module, and the fault ride-through start and end time judgment module output the obtained data to the test result judgment module. The test result judgment module performs a power grid input test based on the obtained data and sends the obtained test results to the test result output module for output.

[0040] This MATLAB-based fault ride-through time determination method can achieve fully automated fault determination of the entire power grid from data import to output report. It can improve the efficiency of converter fault ride-through testing, as well as the accuracy and stability of fault indicator determination.

[0041] It should be understood that the above are merely preferred embodiments of the present invention and should not be construed as limiting the scope of the patent. Any equivalent structural or procedural transformations made based on the description and drawings of the present invention, or direct or indirect applications in other related technical fields, are similarly included within the scope of patent protection of the present invention.

Claims

1. A matlab-based fault ride-through time determination method, characterized in that, The method comprises a data reading module, a data conversion and calculation module, a slope calculation and waveform chart output module, a fault ride-through type judgment module and a fault ride-through start and end time judgment module, and the method comprises the following steps: the data reading module collects N sampling point grid line voltage instantaneous values during the grid input fault ride-through and outputs to the data conversion and calculation module, the data conversion and calculation module converts the N grid line voltage instantaneous values into grid phase voltage effective values, and then filters the N grid phase voltage effective values, the slope calculation and waveform chart output module calculates the slope values of the N filtered grid phase voltage effective values through a filtering slope algorithm, and generates a waveform chart from all the obtained slope values, the fault ride-through type judgment module judges and confirms the type of the grid input fault ride-through, and the fault ride-through start and end time judgment module obtains the time value of the fault ride-through start time or the fault ride-through end time or both from the waveform chart and the fault ride-through type; when the fault ride-through type is high voltage ride-through, the time value of the point with the maximum grid phase voltage effective value slope is the time value of the fault ride-through start time; when the fault ride-through type is low voltage ride-through, the time value of the point with the minimum grid phase voltage effective value slope is the time value of the fault ride-through start time.

2. The matlab-based fault clearance time determination method of claim 1, wherein, The filtering slope algorithm is: df(i)=U(i+3)-U(i), wherein df(i) is the slope of the phase voltage effective value of the i-th sampling point of the grid, U(i+3) is the phase voltage effective value of the i+3-th sampling point of the grid, and U(i) is the phase voltage effective value of the i-th sampling point of the grid.

3. The matlab-based fault clearance time determination method of claim 1, wherein, When the fault ride-through type judgment module judges that the type of the grid input fault ride-through is low voltage fault ride-through, the fault ride-through start and end time judgment module takes the time value of the minimum point in the waveform chart as the start time of the grid low voltage fault ride-through, and takes the time value of the maximum point in the waveform chart as the end time of the grid low voltage fault ride-through.

4. The matlab-based fault clearance time determination method of claim 3, wherein, When the fault ride-through type judgment module judges that the type of the grid input fault ride-through is low voltage fault ride-through, it further judges whether the fault ride-through is unbalanced ride-through, and if it is judged that the fault ride-through is unbalanced ride-through, the data conversion and calculation module calculates the positive and negative sequence active current and reactive current of the grid input fault ride-through, and obtains the response time of the grid required reactive compensation according to the calculation results of the positive and negative sequence active current and reactive current.

5. The matlab-based fault ride-through time judgment method according to claim 1, wherein When the fault ride-through type judgment module judges that the type of the grid input fault ride-through is high voltage fault ride-through, the fault ride-through start and end time judgment module takes the time value of the maximum point in the waveform chart as the start time of the high voltage fault ride-through, and takes the time value of the minimum point in the waveform chart as the end time of the high voltage fault ride-through.

6. The matlab-based fault clearance time determination method of claim 5, wherein, The data conversion and calculation module calculates the positive and negative sequence active current and reactive current of the grid input fault ride-through, and obtains the response time of the grid requiring reactive compensation and the fault duration according to the calculation results of the positive and negative sequence active current and reactive current, wherein the fault duration is the end time of high-voltage fault ride-through minus the start time of high-voltage fault ride-through.

7. The matlab-based fault clearance time determination method of claim 1, wherein , When the fault ride-through type judgment module judges that the type of the grid input fault ride-through is composite fault ride-through, the fault ride-through start and end time judgment module takes the waveform from the waveform chart output by the slope calculation and waveform chart output module, intercepts the first two seconds of the first fault ride-through start time in the sampling data of the data reading module, selects a time as the start time from the first fault ride-through start time to the time before the second fault ride-through, takes the time value of the minimum point of the slope as the end time of the high-low fault ride-through and the start time of the low fault ride-through, and takes the time value of the maximum point of the slope as the end time of the low fault ride-through.

8. The matlab-based fault clearance time determination method of claim 7, wherein When the fault ride-through type judgment module judges that the type of the grid input fault ride-through is composite fault ride-through and is the composite ride-through of high-voltage fault ride-through first and then low-voltage fault ride-through, the high-voltage fault ride-through start time is judged first, and then the low-voltage fault ride-through start time is judged.

9. The matlab-based fault clearance time determination method of claim 7, wherein When the fault ride-through type judgment module judges that the type of the grid input fault ride-through is composite fault ride-through and is the composite ride-through of low-voltage fault ride-through first and then high-voltage fault ride-through, the low-voltage fault ride-through start time is judged first, and then the high-voltage fault ride-through start time is judged.

10. The matlab-based fault clearance time determination method of claim 1, wherein, The test result judgment module and the test result output module are further included, and the fault ride-through time judgment method based on matlab further includes that the data conversion and calculation module, the slope calculation and waveform chart output module, the fault ride-through type judgment module and the fault ride-through start and end time judgment module output the obtained data to the test result judgment module, the test result judgment module performs grid input test according to the obtained data, and sends the obtained test result to the test result output module for output.

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