Harmonic impedance detection method and system of power system

Abstract

The invention provides a harmonic impedance detection method and system of a power system, and belongs to the technical field of harmonic impedance detection. The method comprises the steps of obtaining first harmonic current, first harmonic voltage, first harmonic impedance, second harmonic current, second harmonic voltage, second harmonic impedance, third harmonic current, third harmonic voltage, third harmonic impedance, theoretical harmonic impedance and an average difference value, and performing curved surface fitting to obtain first to sixth reference fitting curved surfaces; and obtaining two first harmonic impedance reference values, two second harmonic impedance reference values and two third harmonic impedance reference values based on the first reference fitting curved surface to the sixth reference fitting curved surface, the average difference, the real-time harmonic current and the real-time harmonic voltage, and taking a mean value among the two first harmonic impedance reference values, the two second harmonic impedance reference values and the two third harmonic impedance reference values as a harmonic impedance detection result. According to the invention, harmonic impedance detection is carried out from multiple dimensions, and the accuracy and reliability of a detection result are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of harmonic impedance detection, and in particular to a harmonic impedance detection method and system for an electric power system. Background Art

[0002] Harmonic impedance detection of power systems is an important means of evaluating the harmonic characteristics of power systems. The detection methods mainly include:

[0003] 1. Direct injection method

[0004] The direct injection method calculates the harmonic impedance by injecting a harmonic current of a specific frequency into the power system and measuring the resulting harmonic voltage. This method is applicable to low-voltage power systems and can measure the single-phase equivalent harmonic impedance of a three-phase system by injecting a single-phase harmonic current between two phase lines.

[0005] 2. Measure the harmonic source in the system (direct measurement)

[0006] When nonlinear loads are present in a power system, they inject harmonic currents into the system. These existing harmonic sources can be used as input signals to calculate the harmonic impedance of the system by measuring the harmonic currents and harmonic voltages. This method is non-intrusive and does not cause additional disturbance to the system.

[0007] 3. Spectral Analysis Method

[0008] The spectrum analysis method is to analyze the disturbance signal in the power system and use algorithms such as Fast Fourier Transform (FFT) to obtain the frequency response function of the system, thereby determining the harmonic impedance. This method can be performed without adding disturbance to the system and has high accuracy and reliability.

[0009] 4. Interpolation method

[0010] In some cases, due to the limitations of actual measurement conditions, it may not be possible to directly measure the harmonic impedance at all frequencies. In this case, the interpolation method can be used to deduce the harmonic impedance at other frequencies based on the measured data at known frequencies. This method requires the selection of appropriate interpolation functions and algorithms to ensure the accuracy of the deduced results.

[0011] However, these methods basically perform harmonic impedance detection from a single dimension, and the accuracy and reliability of the detection results need to be improved. Summary of the invention

[0012] The present invention provides a harmonic impedance detection method and system for an electric power system, which perform harmonic impedance detection from multiple dimensions to improve the accuracy and reliability of the detection result.

[0013] This specification discloses a harmonic impedance detection method for an electric power system, comprising:

[0014] Measuring the first harmonic current and the first harmonic voltage generated by the nonlinear load, and calculating the first harmonic impedance;

[0015] Collect the second harmonic current and second harmonic voltage in the power system and determine the second harmonic impedance using spectrum analysis method;

[0016] Inject the third harmonic current into the power system, measure the third harmonic voltage generated thereby, and calculate the third harmonic impedance;

[0017] Establish an equivalent circuit model of the power system, collect harmonic voltage and harmonic current data, and calculate the theoretical harmonic impedance;

[0018] The differences between the first harmonic impedance, the second harmonic impedance and the third harmonic impedance and the theoretical harmonic impedance are respectively taken as the first difference, the second difference and the third difference, and the averages among the first difference, the second difference and the third difference are calculated to obtain the average difference;

[0019] The first harmonic current is used as a row vector, the average difference is used as a column vector, a matrix is ​​constructed, and the first harmonic impedance is imported to perform surface fitting to obtain a first reference fitting surface;

[0020] The first harmonic voltage is used as a row vector, the average difference is used as a column vector, a matrix is ​​constructed, and the first harmonic impedance is imported to perform surface fitting to obtain a second reference fitting surface;

[0021] The second harmonic current is used as a row vector, the average difference is used as a column vector, a matrix is ​​constructed, and the second harmonic impedance is imported to perform surface fitting to obtain a third reference fitting surface;

[0022] The second harmonic voltage is used as a row vector, the average difference is used as a column vector, a matrix is ​​constructed, and the second harmonic impedance is imported to perform surface fitting to obtain a fourth reference fitting surface;

[0023] The third harmonic current is used as a row vector, the average difference is used as a column vector, a matrix is ​​constructed, and the third harmonic impedance is imported to perform surface fitting to obtain a fifth reference fitting surface;

[0024] The third harmonic voltage is used as a row vector, the average difference is used as a column vector, a matrix is ​​constructed, and the third harmonic impedance is imported to perform surface fitting to obtain a sixth reference fitting surface;

[0025] Based on the real-time first harmonic current, the real-time first harmonic voltage, the average difference, the first reference fitting surface and the second reference fitting surface, two first harmonic impedance reference values ​​are obtained;

[0026] Based on the real-time second harmonic current, the real-time second harmonic voltage, the average difference, the third reference fitting surface and the fourth reference fitting surface, two second harmonic impedance reference values ​​are obtained;

[0027] Based on the real-time third harmonic current, the real-time third harmonic voltage, the average difference, the fifth reference fitting surface and the sixth reference fitting surface, two third harmonic impedance reference values ​​are obtained;

[0028] An average value among the two first harmonic impedance reference values, the two second harmonic impedance reference values ​​and the two third harmonic impedance reference values ​​is taken as a harmonic impedance detection result.

[0029] In this specification, the transformer capacity in the power system is obtained;

[0030] Calculate the average value of the first harmonic impedance, the second harmonic impedance and the third harmonic impedance to obtain the harmonic impedance average value;

[0031] The transformer capacity is used as a row vector, the average difference is used as a column vector, a matrix is ​​constructed, and the harmonic impedance mean is imported to perform surface fitting, thereby obtaining the seventh reference fitting surface;

[0032] Based on the real-time transformer capacity, the average difference and the seventh reference fitting surface, a fourth harmonic impedance reference value is obtained;

[0033] An average value among the fourth harmonic impedance reference value, the two first harmonic impedance reference values, the two second harmonic impedance reference values ​​and the two third harmonic impedance reference values ​​is taken as a harmonic impedance detection result.

[0034] In this specification, the load distance in the power system is obtained;

[0035] Calculate the average value of the first harmonic impedance, the second harmonic impedance and the third harmonic impedance to obtain the harmonic impedance average value;

[0036] The load distance is used as a row vector, the average difference is used as a column vector, a matrix is ​​constructed, and the harmonic impedance mean is imported to perform surface fitting to obtain an eighth reference fitting surface;

[0037] Based on the real-time load distance, the average difference and the eighth reference fitting surface, a fifth harmonic impedance reference value is obtained;

[0038] An average value among the fifth harmonic impedance reference value, the two first harmonic impedance reference values, the two second harmonic impedance reference values ​​and the two third harmonic impedance reference values ​​is taken as a harmonic impedance detection result.

[0039] In this specification, the harmonic order in the power system is obtained;

[0040] Calculate the average value of the first harmonic impedance, the second harmonic impedance and the third harmonic impedance to obtain the harmonic impedance average value;

[0041] The harmonic order is used as a row vector, the average difference is used as a column vector, a matrix is ​​constructed, and the harmonic impedance mean is imported to perform surface fitting to obtain a ninth reference fitting surface;

[0042] Based on the real-time harmonic order, average difference and ninth reference fitting surface, a sixth harmonic impedance reference value is obtained;

[0043] An average value among the sixth harmonic impedance reference value, the two first harmonic impedance reference values, the two second harmonic impedance reference values ​​and the two third harmonic impedance reference values ​​is taken as a harmonic impedance detection result.

[0044] In this specification, the line and equipment impedance in the power system is obtained;

[0045] Calculate the average value of the first harmonic impedance, the second harmonic impedance and the third harmonic impedance to obtain the harmonic impedance average value;

[0046] The line and equipment impedances are taken as row vectors, the average difference is taken as column vector, a matrix is ​​constructed, and the harmonic impedance mean is imported to perform surface fitting, and the tenth reference fitting surface is obtained;

[0047] Based on the real-time line and equipment impedance, the average difference and the tenth reference fitting surface, the seventh harmonic impedance reference value is obtained;

[0048] An average value among the seventh harmonic impedance reference value, the two first harmonic impedance reference values, the two second harmonic impedance reference values ​​and the two third harmonic impedance reference values ​​is taken as a harmonic impedance detection result.

[0049] In this specification, the harmonic frequencies in the power system are obtained;

[0050] Calculate the average value of the first harmonic impedance, the second harmonic impedance and the third harmonic impedance to obtain the harmonic impedance average value;

[0051] The harmonic frequency is used as a row vector, the average difference is used as a column vector, a matrix is ​​constructed, and the harmonic impedance mean is imported to perform surface fitting, and the eleventh reference fitting surface is obtained;

[0052] Based on the real-time harmonic frequency, the average difference and the eleventh reference fitting surface, an eighth harmonic impedance reference value is obtained;

[0053] An average value among the eighth harmonic impedance reference value, the two first harmonic impedance reference values, the two second harmonic impedance reference values ​​and the two third harmonic impedance reference values ​​is taken as a harmonic impedance detection result.

[0054] In this specification, the distributed capacitance of the lines in the power system is obtained;

[0055] Calculate the average value of the first harmonic impedance, the second harmonic impedance and the third harmonic impedance to obtain the harmonic impedance average value;

[0056] The line distributed capacitance is taken as a row vector, the average difference is taken as a column vector, a matrix is ​​constructed, and the harmonic impedance mean value is imported to perform surface fitting, and a twelfth reference fitting surface is obtained;

[0057] Based on the real-time line distributed capacitance, the average difference and the twelfth reference fitting surface, a ninth harmonic impedance reference value is obtained;

[0058] An average value among the ninth harmonic impedance reference value, the two first harmonic impedance reference values, the two second harmonic impedance reference values ​​and the two third harmonic impedance reference values ​​is taken as a harmonic impedance detection result.

[0059] In this specification, the transformer distributed capacitance in the power system is obtained;

[0060] Calculate the average value of the first harmonic impedance, the second harmonic impedance and the third harmonic impedance to obtain the harmonic impedance average value;

[0061] The transformer distributed capacitance is used as a row vector, the average difference is used as a column vector, a matrix is ​​constructed, and the harmonic impedance mean is imported to perform surface fitting, and a thirteenth reference fitting surface is obtained;

[0062] Based on the real-time transformer distributed capacitance, the average difference and the thirteenth reference fitting surface, a tenth harmonic impedance reference value is obtained;

[0063] An average value among the tenth harmonic impedance reference value, the two first harmonic impedance reference values, the two second harmonic impedance reference values ​​and the two third harmonic impedance reference values ​​is taken as a harmonic impedance detection result.

[0064] In this specification, harmonic current is injected into the power system, and the power parameters are gradually increased or decreased, the harmonic voltage generated thereby is measured, and the amplitude of the harmonic impedance change is calculated;

[0065] Based on the variation amplitude of the injected harmonic current, the variation amplitude of the power parameters and the variation amplitude of the harmonic impedance, a variation amplitude fitting surface is obtained by using a surface fitting method;

[0066] Based on the real-time injected harmonic current, the real-time adjusted power parameters and the variation amplitude fitting surface, the variation amplitude of the harmonic impedance is obtained, and then the real-time harmonic impedance is calculated;

[0067] The real-time harmonic impedance, the average of the two first harmonic impedance reference values, the two second harmonic impedance reference values ​​and the two third harmonic impedance reference values ​​are taken as the harmonic impedance detection result;

[0068] Power parameters include transformer capacity, load distance, harmonic order, line and equipment impedance, harmonic frequency, line distributed capacitance and transformer distributed capacitance.

[0069] This specification also discloses a harmonic impedance detection system for an electric power system, which is used to implement any of the above-mentioned harmonic impedance detection methods for an electric power system. The harmonic impedance detection system for an electric power system comprises:

[0070] A direct measurement module is used to measure the first harmonic current and the first harmonic voltage generated by the nonlinear load, and calculate the first harmonic impedance;

[0071] A spectrum analysis module, used for collecting the second harmonic current and the second harmonic voltage in the power system, and determining the second harmonic impedance using a spectrum analysis method;

[0072] A direct injection module is used to inject the third harmonic current into the power system, measure the third harmonic voltage generated thereby, and calculate the third harmonic impedance;

[0073] Theoretical harmonic impedance acquisition module is used to establish an equivalent circuit model of the power system, collect harmonic voltage and harmonic current data, and calculate the theoretical harmonic impedance;

[0074] An average difference acquisition module is used to take the differences between the first harmonic impedance, the second harmonic impedance and the third harmonic impedance and the theoretical harmonic impedance as the first difference, the second difference and the third difference respectively, calculate the average of the first difference, the second difference and the third difference, and obtain the average difference;

[0075] Surface fitting module for:

[0076] The first harmonic current is used as a row vector, the average difference is used as a column vector, a matrix is ​​constructed, and the first harmonic impedance is imported to perform surface fitting to obtain a first reference fitting surface;

[0077] The first harmonic voltage is used as a row vector, the average difference is used as a column vector, a matrix is ​​constructed, and the first harmonic impedance is imported to perform surface fitting to obtain a second reference fitting surface;

[0078] The second harmonic current is used as a row vector, the average difference is used as a column vector, a matrix is ​​constructed, and the second harmonic impedance is imported to perform surface fitting to obtain a third reference fitting surface;

[0079] The second harmonic voltage is used as a row vector, the average difference is used as a column vector, a matrix is ​​constructed, and the second harmonic impedance is imported to perform surface fitting to obtain a fourth reference fitting surface;

[0080] The third harmonic current is used as a row vector, the average difference is used as a column vector, a matrix is ​​constructed, and the third harmonic impedance is imported to perform surface fitting to obtain a fifth reference fitting surface;

[0081] The third harmonic voltage is used as a row vector, the average difference is used as a column vector, a matrix is ​​constructed, and the third harmonic impedance is imported to perform surface fitting to obtain a sixth reference fitting surface;

[0082] Detection module for:

[0083] Based on the real-time first harmonic current, the real-time first harmonic voltage, the average difference, the first reference fitting surface and the second reference fitting surface, two first harmonic impedance reference values ​​are obtained;

[0084] Based on the real-time second harmonic current, the real-time second harmonic voltage, the average difference, the third reference fitting surface and the fourth reference fitting surface, two second harmonic impedance reference values ​​are obtained;

[0085] Based on the real-time third harmonic current, the real-time third harmonic voltage, the average difference, the fifth reference fitting surface and the sixth reference fitting surface, two third harmonic impedance reference values ​​are obtained;

[0086] An average value among the two first harmonic impedance reference values, the two second harmonic impedance reference values ​​and the two third harmonic impedance reference values ​​is taken as a harmonic impedance detection result.

[0087] This manual can at least achieve the following beneficial effects:

[0088] By acquiring the first harmonic current, the first harmonic voltage, the first harmonic impedance, the second harmonic current, the second harmonic voltage, the second harmonic impedance, the third harmonic current, the third harmonic voltage, the third harmonic impedance, the theoretical harmonic impedance and the average difference, the surface fitting is performed respectively to obtain the first reference fitting surface to the sixth reference fitting surface; based on the first reference fitting surface to the sixth reference fitting surface, the average difference, the real-time harmonic current and harmonic voltage, two first harmonic impedance reference values, two second harmonic impedance reference values ​​and two third harmonic impedance reference values ​​are obtained; the mean between the two first harmonic impedance reference values, the two second harmonic impedance reference values ​​and the two third harmonic impedance reference values ​​is used as the harmonic impedance detection result. The present invention performs harmonic impedance detection from multiple dimensions, thereby improving the accuracy and reliability of the detection results. BRIEF DESCRIPTION OF THE DRAWINGS

[0089] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative work.

[0090] Figure 1 It is a schematic diagram of the harmonic impedance detection method of the power system involved in the present invention. DETAILED DESCRIPTION

[0091] In the following, only some exemplary embodiments are briefly described. As those skilled in the art will appreciate, the described embodiments may be modified in various ways without departing from the spirit or scope of the embodiments of the present invention. Therefore, the drawings and descriptions are considered to be exemplary and non-restrictive in nature.

[0092] The disclosure below provides many different embodiments or examples to implement different structures of the embodiments of the present invention. In order to simplify the disclosure of the embodiments of the present invention, the parts and settings of specific examples are described below. Of course, they are only examples, and the purpose is not to limit the embodiments of the present invention. In addition, the embodiments of the present invention can repeat reference numbers and / or reference letters in different examples, and this repetition is for the purpose of simplification and clarity, which itself does not indicate the relationship between the various embodiments and / or settings discussed.

[0093] The embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0094] like Figure 1 As shown, the embodiment of this specification discloses a harmonic impedance detection method for an electric power system, comprising:

[0095] Measuring the first harmonic current and the first harmonic voltage generated by the nonlinear load, and calculating the first harmonic impedance;

[0096] Collect the second harmonic current and second harmonic voltage in the power system and determine the second harmonic impedance using spectrum analysis method;

[0097] Inject the third harmonic current into the power system, measure the third harmonic voltage generated thereby, and calculate the third harmonic impedance;

[0098] Establish an equivalent circuit model of the power system, collect harmonic voltage and harmonic current data, and calculate the theoretical harmonic impedance;

[0099] The differences between the first harmonic impedance, the second harmonic impedance and the third harmonic impedance and the theoretical harmonic impedance are respectively taken as the first difference, the second difference and the third difference, and the averages among the first difference, the second difference and the third difference are calculated to obtain the average difference;

[0100] The first harmonic current is used as a row vector, the average difference is used as a column vector, a matrix is ​​constructed, and the first harmonic impedance is imported to perform surface fitting to obtain a first reference fitting surface;

[0101] The first harmonic voltage is used as a row vector, the average difference is used as a column vector, a matrix is ​​constructed, and the first harmonic impedance is imported to perform surface fitting to obtain a second reference fitting surface;

[0102] The second harmonic current is used as a row vector, the average difference is used as a column vector, a matrix is ​​constructed, and the second harmonic impedance is imported to perform surface fitting to obtain a third reference fitting surface;

[0103] The second harmonic voltage is used as a row vector, the average difference is used as a column vector, a matrix is ​​constructed, and the second harmonic impedance is imported to perform surface fitting to obtain a fourth reference fitting surface;

[0104] The third harmonic current is used as a row vector, the average difference is used as a column vector, a matrix is ​​constructed, and the third harmonic impedance is imported to perform surface fitting to obtain a fifth reference fitting surface;

[0105] The third harmonic voltage is used as a row vector, the average difference is used as a column vector, a matrix is ​​constructed, and the third harmonic impedance is imported to perform surface fitting to obtain a sixth reference fitting surface;

[0106] Based on the real-time first harmonic current, the real-time first harmonic voltage, the average difference, the first reference fitting surface and the second reference fitting surface, two first harmonic impedance reference values ​​are obtained;

[0107] Based on the real-time second harmonic current, the real-time second harmonic voltage, the average difference, the third reference fitting surface and the fourth reference fitting surface, two second harmonic impedance reference values ​​are obtained;

[0108] Based on the real-time third harmonic current, the real-time third harmonic voltage, the average difference, the fifth reference fitting surface and the sixth reference fitting surface, two third harmonic impedance reference values ​​are obtained;

[0109] An average value among the two first harmonic impedance reference values, the two second harmonic impedance reference values ​​and the two third harmonic impedance reference values ​​is taken as a harmonic impedance detection result.

[0110] In some embodiments, obtaining a transformer capacity in a power system;

[0111] Calculate the average value of the first harmonic impedance, the second harmonic impedance and the third harmonic impedance to obtain the harmonic impedance average value;

[0112] The transformer capacity is used as a row vector, the average difference is used as a column vector, a matrix is ​​constructed, and the harmonic impedance mean is imported to perform surface fitting, and the seventh reference fitting surface is obtained;

[0113] Based on the real-time transformer capacity, the average difference and the seventh reference fitting surface, a fourth harmonic impedance reference value is obtained;

[0114] An average value among the fourth harmonic impedance reference value, the two first harmonic impedance reference values, the two second harmonic impedance reference values ​​and the two third harmonic impedance reference values ​​is taken as a harmonic impedance detection result.

[0115] In some embodiments, obtaining a load distance in the power system;

[0116] Calculate the average value of the first harmonic impedance, the second harmonic impedance and the third harmonic impedance to obtain the harmonic impedance average value;

[0117] The load distance is used as a row vector, the average difference is used as a column vector, a matrix is ​​constructed, and the harmonic impedance mean is imported to perform surface fitting to obtain an eighth reference fitting surface;

[0118] Based on the real-time load distance, the average difference and the eighth reference fitting surface, a fifth harmonic impedance reference value is obtained;

[0119] An average value among the fifth harmonic impedance reference value, the two first harmonic impedance reference values, the two second harmonic impedance reference values ​​and the two third harmonic impedance reference values ​​is taken as a harmonic impedance detection result.

[0120] In some embodiments, obtaining harmonic orders in the power system;

[0121] Calculate the average value of the first harmonic impedance, the second harmonic impedance and the third harmonic impedance to obtain the harmonic impedance average value;

[0122] The harmonic order is used as a row vector, the average difference is used as a column vector, a matrix is ​​constructed, and the harmonic impedance mean is imported to perform surface fitting to obtain a ninth reference fitting surface;

[0123] Based on the real-time harmonic order, average difference and ninth reference fitting surface, a sixth harmonic impedance reference value is obtained;

[0124] An average value among the sixth harmonic impedance reference value, the two first harmonic impedance reference values, the two second harmonic impedance reference values ​​and the two third harmonic impedance reference values ​​is taken as a harmonic impedance detection result.

[0125] In some embodiments, obtaining line and equipment impedances in the power system;

[0126] Calculate the average value of the first harmonic impedance, the second harmonic impedance and the third harmonic impedance to obtain the harmonic impedance average value;

[0127] The line and equipment impedances are taken as row vectors, the average difference is taken as column vector, a matrix is ​​constructed, and the harmonic impedance mean is imported to perform surface fitting, and the tenth reference fitting surface is obtained;

[0128] Based on the real-time line and equipment impedance, the average difference and the tenth reference fitting surface, the seventh harmonic impedance reference value is obtained;

[0129] An average value among the seventh harmonic impedance reference value, the two first harmonic impedance reference values, the two second harmonic impedance reference values ​​and the two third harmonic impedance reference values ​​is taken as a harmonic impedance detection result.

[0130] In some embodiments, obtaining harmonic frequencies in the power system;

[0131] Calculate the average value of the first harmonic impedance, the second harmonic impedance and the third harmonic impedance to obtain the harmonic impedance average value;

[0132] The harmonic frequency is used as a row vector, the average difference is used as a column vector, a matrix is ​​constructed, and the harmonic impedance mean is imported to perform surface fitting, and the eleventh reference fitting surface is obtained;

[0133] Based on the real-time harmonic frequency, the average difference and the eleventh reference fitting surface, an eighth harmonic impedance reference value is obtained;

[0134] An average value among the eighth harmonic impedance reference value, the two first harmonic impedance reference values, the two second harmonic impedance reference values ​​and the two third harmonic impedance reference values ​​is taken as a harmonic impedance detection result.

[0135] In some embodiments, obtaining distributed capacitance of lines in a power system;

[0136] Calculate the average value of the first harmonic impedance, the second harmonic impedance and the third harmonic impedance to obtain the harmonic impedance average value;

[0137] The line distributed capacitance is taken as a row vector, the average difference is taken as a column vector, a matrix is ​​constructed, and the harmonic impedance mean value is imported to perform surface fitting, and a twelfth reference fitting surface is obtained;

[0138] Based on the real-time line distributed capacitance, the average difference and the twelfth reference fitting surface, a ninth harmonic impedance reference value is obtained;

[0139] An average value among the ninth harmonic impedance reference value, the two first harmonic impedance reference values, the two second harmonic impedance reference values ​​and the two third harmonic impedance reference values ​​is taken as a harmonic impedance detection result.

[0140] In some embodiments, obtaining transformer distributed capacitance in a power system;

[0141] Calculate the average value of the first harmonic impedance, the second harmonic impedance and the third harmonic impedance to obtain the harmonic impedance average value;

[0142] The transformer distributed capacitance is used as a row vector, the average difference is used as a column vector, a matrix is ​​constructed, and the harmonic impedance mean is imported to perform surface fitting, and a thirteenth reference fitting surface is obtained;

[0143] Based on the real-time transformer distributed capacitance, the average difference and the thirteenth reference fitting surface, a tenth harmonic impedance reference value is obtained;

[0144] An average value among the tenth harmonic impedance reference value, the two first harmonic impedance reference values, the two second harmonic impedance reference values ​​and the two third harmonic impedance reference values ​​is taken as a harmonic impedance detection result.

[0145] In some embodiments, harmonic current is injected into the power system, and the power parameters are gradually increased or decreased, the harmonic voltage generated thereby is measured, and the amplitude of the harmonic impedance change is calculated;

[0146] Based on the variation amplitude of the injected harmonic current, the variation amplitude of the power parameters and the variation amplitude of the harmonic impedance, a variation amplitude fitting surface is obtained by using a surface fitting method;

[0147] Based on the real-time injected harmonic current, the real-time adjusted power parameters and the variation amplitude fitting surface, the variation amplitude of the harmonic impedance is obtained, and then the real-time harmonic impedance is calculated;

[0148] The real-time harmonic impedance, the average of the two first harmonic impedance reference values, the two second harmonic impedance reference values ​​and the two third harmonic impedance reference values ​​are taken as the harmonic impedance detection result;

[0149] Power parameters include transformer capacity, load distance, harmonic order, line and equipment impedance, harmonic frequency, line distributed capacitance and transformer distributed capacitance.

[0150] In summary, the various embodiments can be applied in combination, that is, the real-time harmonic impedance, one or more values ​​of the fourth harmonic impedance reference value to the tenth harmonic impedance reference value, the average of two first harmonic impedance reference values, two second harmonic impedance reference values ​​and two third harmonic impedance reference values ​​are used as the harmonic impedance detection result.

[0151] It should be understood that the above surface fitting operation can use existing software tools, such as the Curve Fitting tool in Matlab. The above modules can be existing data detection / measurement devices / sensors or data reading modules of the power system (transmission and distribution substations, etc.), which can directly obtain data in the power system.

[0152] It is clear that by obtaining the data of the power system in advance through existing equipment, a large amount of test data can be obtained. These test data can be simulation test data in the laboratory or actual measured or operating data of the power system in practice.

[0153] The embodiment of this specification also discloses a harmonic impedance detection system of an electric power system, which is used to implement any of the above-mentioned harmonic impedance detection methods of the electric power system. The harmonic impedance detection system of the electric power system includes:

[0154] A direct measurement module is used to measure the first harmonic current and the first harmonic voltage generated by the nonlinear load, and calculate the first harmonic impedance;

[0155] A spectrum analysis module, used for collecting the second harmonic current and the second harmonic voltage in the power system, and determining the second harmonic impedance using a spectrum analysis method;

[0156] A direct injection module is used to inject the third harmonic current into the power system, measure the third harmonic voltage generated thereby, and calculate the third harmonic impedance;

[0157] Theoretical harmonic impedance acquisition module is used to establish an equivalent circuit model of the power system, collect harmonic voltage and harmonic current data, and calculate the theoretical harmonic impedance;

[0158] An average difference acquisition module is used to take the differences between the first harmonic impedance, the second harmonic impedance and the third harmonic impedance and the theoretical harmonic impedance as the first difference, the second difference and the third difference respectively, calculate the average of the first difference, the second difference and the third difference, and obtain the average difference;

[0159] Surface fitting module for:

[0160] The first harmonic current is used as a row vector, the average difference is used as a column vector, a matrix is ​​constructed, and the first harmonic impedance is imported to perform surface fitting to obtain a first reference fitting surface;

[0161] The first harmonic voltage is used as a row vector, the average difference is used as a column vector, a matrix is ​​constructed, and the first harmonic impedance is imported to perform surface fitting to obtain a second reference fitting surface;

[0162] The second harmonic current is used as a row vector, the average difference is used as a column vector, a matrix is ​​constructed, and the second harmonic impedance is imported to perform surface fitting to obtain a third reference fitting surface;

[0163] The second harmonic voltage is used as a row vector, the average difference is used as a column vector, a matrix is ​​constructed, and the second harmonic impedance is imported to perform surface fitting to obtain a fourth reference fitting surface;

[0164] The third harmonic current is used as a row vector, the average difference is used as a column vector, a matrix is ​​constructed, and the third harmonic impedance is imported to perform surface fitting to obtain a fifth reference fitting surface;

[0165] The third harmonic voltage is used as a row vector, the average difference is used as a column vector, a matrix is ​​constructed, and the third harmonic impedance is imported to perform surface fitting to obtain a sixth reference fitting surface;

[0166] Detection module for:

[0167] Based on the real-time first harmonic current, the real-time first harmonic voltage, the average difference, the first reference fitting surface and the second reference fitting surface, two first harmonic impedance reference values ​​are obtained;

[0168] Based on the real-time second harmonic current, the real-time second harmonic voltage, the average difference, the third reference fitting surface and the fourth reference fitting surface, two second harmonic impedance reference values ​​are obtained;

[0169] Based on the real-time third harmonic current, the real-time third harmonic voltage, the average difference, the fifth reference fitting surface and the sixth reference fitting surface, two third harmonic impedance reference values ​​are obtained;

[0170] An average value among the two first harmonic impedance reference values, the two second harmonic impedance reference values ​​and the two third harmonic impedance reference values ​​is taken as a harmonic impedance detection result.

[0171] When implementing the methods of the above embodiments, it is only necessary to add corresponding functional modules.

[0172] The above-described embodiments are used to illustrate the present invention, not to limit the present invention, so changes in the exemplified values ​​or replacement of equivalent elements should still fall within the scope of the present invention.

[0173] From the above detailed description, it can be understood by those skilled in the art that the present invention can indeed achieve the aforementioned objectives and is in compliance with the provisions of the Patent Law.

[0174] Although the preferred embodiments of the present invention have been described, those skilled in the art may make additional changes and modifications to these embodiments once they are aware of the basic creative concepts. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention. The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. It should be pointed out that any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

[0175] It should be noted that the above description of the relevant process is only for example and explanation, and does not limit the scope of application of this specification. For those skilled in the art, various modifications and changes can be made to the process under the guidance of this specification. However, these modifications and changes are still within the scope of this specification.

[0176] The basic concepts have been described above. Obviously, for those of ordinary skill in the art who have read this application, the above invention disclosure is only for example and does not constitute a limitation of this application. Although not explicitly stated here, those of ordinary skill in the art may make various modifications, improvements and amendments to this application. Such modifications, improvements and amendments are suggested in this application, so such modifications, improvements and amendments still belong to the spirit and scope of the exemplary embodiments of this application.

[0177] At the same time, the present application uses specific words to describe the embodiments of the present application. For example, "one embodiment", "an embodiment", and / or "some embodiments" refer to a certain feature, structure or characteristic related to at least one embodiment of the present application. Therefore, it should be emphasized and noted that "one embodiment" or "an embodiment" or "an alternative embodiment" mentioned twice or more in different positions in this specification does not necessarily refer to the same embodiment. In addition, some features, structures or characteristics in one or more embodiments of the present application can be appropriately combined.

[0178] In addition, it will be appreciated by those skilled in the art that various aspects of the present application may be illustrated and described by a number of patentable categories or situations, including any new and useful combination of processes, machines, products or substances, or any new and useful improvements thereto. Therefore, various aspects of the present application may be implemented entirely by hardware, entirely by software (including firmware, resident software, microcode, etc.), or by a combination of hardware and software. The above hardware or software may all be referred to as "units", "modules" or "systems". In addition, various aspects of the present application may take the form of a computer program product embodied in one or more computer-readable media, wherein computer-readable program code is contained therein.

[0179] The computer program code required for the operation of each part of the application can be written in any one or more programming languages, including object-oriented programming languages ​​such as Java, Scale, Smalltalk, Elffell, JADE, Emerald, C++, C#, VB.NET, Python, etc., such as C programming language, Visual Basic, Fortran2103, Perl, COBOL2102, PHP, ABAP, such as Python, Ruby and Groovy dynamic programming language or other programming languages. The program code can be run completely on the user's computer, or run on the user's computer as an independent software package, or partly run on the user's computer and partly run on the remote computer, or run completely on the remote computer or server. In the latter case, the remote computer can be connected to the user's computer by any network form, such as local area network (LAN) or wide area network (WAN), or be connected to an external computer (such as by the Internet), or in a cloud computing environment, or as a service, such as software as a service (SaaS).

[0180] In addition, unless explicitly stated in the claims, the order of the processing elements and sequences described in this application, the use of alphanumeric characters, or the use of other names are not intended to limit the order of the processes and methods of this application. Although the above disclosure discusses some invention embodiments that are currently considered useful through various examples, it should be understood that such details are only for illustrative purposes, and the attached claims are not limited to the disclosed embodiments. On the contrary, the claims are intended to cover all modifications and equivalent combinations that are consistent with the essence and scope of the embodiments of this application. For example, although the implementation of the various components described above can be embodied in a hardware device, it can also be implemented as a pure software solution, for example, installation on an existing server or mobile device.

[0181] Similarly, it should be noted that in order to simplify the description disclosed in this application and thus help understand one or more embodiments of the invention, in the above description of the embodiments of the application, multiple features are sometimes combined into one embodiment, figure or description thereof. However, this method of the application should not be interpreted as reflecting the intention that the claimed object requires more features than those explicitly stated in each claim. On the contrary, the subject of the invention should have fewer features than the above single embodiment.

Claims

1. A method for detecting harmonic impedance of an electric power system, characterized in that: include: Measuring the first harmonic current and the first harmonic voltage generated by the nonlinear load, and calculating the first harmonic impedance; Collect the second harmonic current and second harmonic voltage in the power system and determine the second harmonic impedance using spectrum analysis method; Inject the third harmonic current into the power system, measure the third harmonic voltage generated thereby, and calculate the third harmonic impedance; Establish an equivalent circuit model of the power system, collect harmonic voltage and harmonic current data, and calculate the theoretical harmonic impedance; The differences between the first harmonic impedance, the second harmonic impedance and the third harmonic impedance and the theoretical harmonic impedance are respectively taken as the first difference, the second difference and the third difference, and the averages among the first difference, the second difference and the third difference are calculated to obtain the average difference; The first harmonic current is used as a row vector, the average difference is used as a column vector, a matrix is ​​constructed, and the first harmonic impedance is imported to perform surface fitting to obtain a first reference fitting surface; The first harmonic voltage is used as a row vector, the average difference is used as a column vector, a matrix is ​​constructed, and the first harmonic impedance is imported to perform surface fitting to obtain a second reference fitting surface; The second harmonic current is used as a row vector, the average difference is used as a column vector, a matrix is ​​constructed, and the second harmonic impedance is imported to perform surface fitting to obtain a third reference fitting surface; The second harmonic voltage is used as a row vector, the average difference is used as a column vector, a matrix is ​​constructed, and the second harmonic impedance is imported to perform surface fitting to obtain a fourth reference fitting surface; The third harmonic current is used as a row vector, the average difference is used as a column vector, a matrix is ​​constructed, and the third harmonic impedance is imported to perform surface fitting to obtain a fifth reference fitting surface; The third harmonic voltage is used as a row vector, the average difference is used as a column vector, a matrix is ​​constructed, and the third harmonic impedance is imported to perform surface fitting to obtain a sixth reference fitting surface; Based on the real-time first harmonic current, the real-time first harmonic voltage, the average difference, the first reference fitting surface and the second reference fitting surface, two first harmonic impedance reference values ​​are obtained; Based on the real-time second harmonic current, the real-time second harmonic voltage, the average difference, the third reference fitting surface and the fourth reference fitting surface, two second harmonic impedance reference values ​​are obtained; Based on the real-time third harmonic current, the real-time third harmonic voltage, the average difference, the fifth reference fitting surface and the sixth reference fitting surface, two third harmonic impedance reference values ​​are obtained; An average value among the two first harmonic impedance reference values, the two second harmonic impedance reference values ​​and the two third harmonic impedance reference values ​​is taken as a harmonic impedance detection result.

2. The harmonic impedance detection method of the power system according to claim 1, characterized in that: Get the transformer capacity in the power system; Calculate the average value of the first harmonic impedance, the second harmonic impedance and the third harmonic impedance to obtain the harmonic impedance average value; The transformer capacity is used as a row vector, the average difference is used as a column vector, a matrix is ​​constructed, and the harmonic impedance mean is imported to perform surface fitting, thereby obtaining the seventh reference fitting surface; Based on the real-time transformer capacity, the average difference and the seventh reference fitting surface, a fourth harmonic impedance reference value is obtained; An average value among the fourth harmonic impedance reference value, the two first harmonic impedance reference values, the two second harmonic impedance reference values ​​and the two third harmonic impedance reference values ​​is taken as a harmonic impedance detection result.

3. The harmonic impedance detection method of the power system according to claim 1, characterized in that: Get the load distance in the power system; Calculate the average value of the first harmonic impedance, the second harmonic impedance and the third harmonic impedance to obtain the harmonic impedance average value; The load distance is used as a row vector, the average difference is used as a column vector, a matrix is ​​constructed, and the harmonic impedance mean is imported to perform surface fitting to obtain an eighth reference fitting surface; Based on the real-time load distance, the average difference and the eighth reference fitting surface, a fifth harmonic impedance reference value is obtained; An average value among the fifth harmonic impedance reference value, the two first harmonic impedance reference values, the two second harmonic impedance reference values ​​and the two third harmonic impedance reference values ​​is taken as a harmonic impedance detection result.

4. The harmonic impedance detection method of the power system according to claim 1, characterized in that: Get the harmonic number in the power system; Calculate the average value of the first harmonic impedance, the second harmonic impedance and the third harmonic impedance to obtain the harmonic impedance average value; The harmonic order is used as a row vector, the average difference is used as a column vector, a matrix is ​​constructed, and the harmonic impedance mean is imported to perform surface fitting to obtain a ninth reference fitting surface; Based on the real-time harmonic order, average difference and ninth reference fitting surface, a sixth harmonic impedance reference value is obtained; An average value among the sixth harmonic impedance reference value, the two first harmonic impedance reference values, the two second harmonic impedance reference values ​​and the two third harmonic impedance reference values ​​is taken as a harmonic impedance detection result.

5. The harmonic impedance detection method of the power system according to claim 1, characterized in that: Obtain line and equipment impedance in the power system; Calculate the average value of the first harmonic impedance, the second harmonic impedance and the third harmonic impedance to obtain the harmonic impedance average value; The line and equipment impedances are taken as row vectors, the average difference is taken as column vector, a matrix is ​​constructed, and the harmonic impedance mean is imported to perform surface fitting, and the tenth reference fitting surface is obtained; Based on the real-time line and equipment impedance, the average difference and the tenth reference fitting surface, the seventh harmonic impedance reference value is obtained; An average value among the seventh harmonic impedance reference value, the two first harmonic impedance reference values, the two second harmonic impedance reference values ​​and the two third harmonic impedance reference values ​​is taken as a harmonic impedance detection result.

6. The harmonic impedance detection method of the power system according to claim 1, characterized in that: Obtain harmonic frequencies in the power system; Calculate the average value of the first harmonic impedance, the second harmonic impedance and the third harmonic impedance to obtain the harmonic impedance average value; The harmonic frequency is used as a row vector, the average difference is used as a column vector, a matrix is ​​constructed, and the harmonic impedance mean is imported to perform surface fitting, and the eleventh reference fitting surface is obtained; Based on the real-time harmonic frequency, the average difference and the eleventh reference fitting surface, an eighth harmonic impedance reference value is obtained; An average value among the eighth harmonic impedance reference value, the two first harmonic impedance reference values, the two second harmonic impedance reference values ​​and the two third harmonic impedance reference values ​​is taken as a harmonic impedance detection result.

7. The harmonic impedance detection method of the power system according to claim 1, characterized in that: Obtain the distributed capacitance of lines in the power system; Calculate the average value of the first harmonic impedance, the second harmonic impedance and the third harmonic impedance to obtain the harmonic impedance average value; The line distributed capacitance is taken as a row vector, the average difference is taken as a column vector, a matrix is ​​constructed, and the harmonic impedance mean value is imported to perform surface fitting, and a twelfth reference fitting surface is obtained; Based on the real-time line distributed capacitance, the average difference and the twelfth reference fitting surface, a ninth harmonic impedance reference value is obtained; An average value among the ninth harmonic impedance reference value, the two first harmonic impedance reference values, the two second harmonic impedance reference values ​​and the two third harmonic impedance reference values ​​is taken as a harmonic impedance detection result.

8. The harmonic impedance detection method of the power system according to claim 1, characterized in that: Obtain the transformer distributed capacitance in the power system; Calculate the average value of the first harmonic impedance, the second harmonic impedance and the third harmonic impedance to obtain the harmonic impedance average value; The transformer distributed capacitance is used as a row vector, the average difference is used as a column vector, a matrix is ​​constructed, and the harmonic impedance mean is imported to perform surface fitting, and a thirteenth reference fitting surface is obtained; Based on the real-time transformer distributed capacitance, the average difference and the thirteenth reference fitting surface, a tenth harmonic impedance reference value is obtained; An average value among the tenth harmonic impedance reference value, the two first harmonic impedance reference values, the two second harmonic impedance reference values ​​and the two third harmonic impedance reference values ​​is taken as a harmonic impedance detection result.

9. The harmonic impedance detection method of the power system according to claim 1, characterized in that: Inject harmonic current into the power system and gradually increase or decrease the power parameters, measure the resulting harmonic voltage, and calculate the amplitude of harmonic impedance change; Based on the variation amplitude of the injected harmonic current, the variation amplitude of the power parameters and the variation amplitude of the harmonic impedance, a variation amplitude fitting surface is obtained by using a surface fitting method; Based on the real-time injected harmonic current, the real-time adjusted power parameters and the variation amplitude fitting surface, the variation amplitude of the harmonic impedance is obtained, and then the real-time harmonic impedance is calculated; The real-time harmonic impedance, the average of the two first harmonic impedance reference values, the two second harmonic impedance reference values ​​and the two third harmonic impedance reference values ​​are taken as the harmonic impedance detection result; Power parameters include transformer capacity, load distance, harmonic order, line and equipment impedance, harmonic frequency, line distributed capacitance and transformer distributed capacitance.

10. A harmonic impedance detection system for an electric power system, characterized in that: A harmonic impedance detection method for an electric power system according to any one of claims 1 to 9 is implemented, wherein the harmonic impedance detection system of the electric power system comprises: A direct measurement module is used to measure the first harmonic current and the first harmonic voltage generated by the nonlinear load, and calculate the first harmonic impedance; A spectrum analysis module, used for collecting the second harmonic current and the second harmonic voltage in the power system, and determining the second harmonic impedance using a spectrum analysis method; A direct injection module is used to inject the third harmonic current into the power system, measure the third harmonic voltage generated thereby, and calculate the third harmonic impedance; Theoretical harmonic impedance acquisition module is used to establish an equivalent circuit model of the power system, collect harmonic voltage and harmonic current data, and calculate the theoretical harmonic impedance; An average difference acquisition module is used to take the differences between the first harmonic impedance, the second harmonic impedance and the third harmonic impedance and the theoretical harmonic impedance as the first difference, the second difference and the third difference respectively, calculate the average of the first difference, the second difference and the third difference, and obtain the average difference; Surface fitting module for: The first harmonic current is used as a row vector, the average difference is used as a column vector, a matrix is ​​constructed, and the first harmonic impedance is imported to perform surface fitting to obtain a first reference fitting surface; The first harmonic voltage is used as a row vector, the average difference is used as a column vector, a matrix is ​​constructed, and the first harmonic impedance is imported to perform surface fitting to obtain a second reference fitting surface; The second harmonic current is used as a row vector, the average difference is used as a column vector, a matrix is ​​constructed, and the second harmonic impedance is imported to perform surface fitting to obtain a third reference fitting surface; The second harmonic voltage is used as a row vector, the average difference is used as a column vector, a matrix is ​​constructed, and the second harmonic impedance is imported to perform surface fitting to obtain a fourth reference fitting surface; The third harmonic current is used as a row vector, the average difference is used as a column vector, a matrix is ​​constructed, and the third harmonic impedance is imported to perform surface fitting to obtain a fifth reference fitting surface; The third harmonic voltage is used as a row vector, the average difference is used as a column vector, a matrix is ​​constructed, and the third harmonic impedance is imported to perform surface fitting to obtain a sixth reference fitting surface; Detection module for: Based on the real-time first harmonic current, the real-time first harmonic voltage, the average difference, the first reference fitting surface and the second reference fitting surface, two first harmonic impedance reference values ​​are obtained; Based on the real-time second harmonic current, the real-time second harmonic voltage, the average difference, the third reference fitting surface and the fourth reference fitting surface, two second harmonic impedance reference values ​​are obtained; Based on the real-time third harmonic current, the real-time third harmonic voltage, the average difference, the fifth reference fitting surface and the sixth reference fitting surface, two third harmonic impedance reference values ​​are obtained; An average value among the two first harmonic impedance reference values, the two second harmonic impedance reference values ​​and the two third harmonic impedance reference values ​​is taken as a harmonic impedance detection result.

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