A method and device for preventing misoperation of turn-to-turn protection of high-voltage shunt reactor

Abstract

The application relates to a misoperation prevention method and device for high-voltage shunt reactor turn-to-turn protection, which comprises the following steps: analyzing an equivalent loop of a power system; analyzing the equivalent loop based on Kirchhoff's voltage law to obtain a low-frequency component causing misoperation of high-voltage shunt reactor turn-to-turn protection; adopting a digital filter to perform band-pass filtering processing on sampling data of a first end of the high-voltage shunt reactor to obtain filtered sampling data; processing the filtered sampling data by using a fast Fourier algorithm to obtain a zero-sequence power-frequency component; judging the zero-sequence power-frequency component based on a zero-sequence power direction judgment principle; and judging whether to perform high-voltage shunt reactor turn-to-turn protection action based on the judgment result. The method not only avoids misoperation of the high-voltage shunt reactor turn-to-turn protection during recovery of external faults, but also ensures normal action of the high-voltage shunt reactor turn-to-turn protection when a turn-to-turn short-circuit fault occurs, thereby improving the reliability of the high-voltage shunt reactor turn-to-turn protection.

Description

Technical Field

[0001] The present invention relates to the technical field of busbar high-voltage shunt reactor turn-to-turn protection, and in particular to a method and device for preventing malfunction of high-voltage shunt reactor turn-to-turn protection. Background Art

[0002] With the development of the power system, the increase in voltage levels and the extension of transmission lines, the charging power of high-voltage AC lines is large, and the contradiction between reactive power compensation and overvoltage limitation under different load levels is prominent. In addition, intermittent energy sources such as wind power and photovoltaic power generation are characterized by volatility, randomness and uncontrollability. The large-scale centralized access of these new energy sources has made the power and voltage fluctuations on the high-voltage AC transmission channel more severe, thereby increasing the power grid's demand for dynamic reactive power compensation, and even having an adverse impact on the safe and stable operation of the power grid and the quality of power. As a mature means of regulating reactive power, improving system compensation and suppressing system overvoltage, high-voltage shunt reactors (abbreviated as "high-voltage reactors") are widely installed in the busbars and lines of ultra-high and extra-high voltage transmission systems. The correct operation of the high-voltage reactor turn-to-turn protection is crucial to ensuring the stability of AC transmission.

[0003] When a high-voltage reactor is used in a long line with a series compensation device ("series compensation"), in the event of an external fault, the presence of the line series compensation capacitor causes a large low-frequency current or a large non-periodic component current to flow through the reactor, affecting the correct and reliable operation of the high-voltage reactor's inter-turn protection. In severe cases, this protection can cause false tripping of the high-voltage reactor's inter-turn protection. However, current high-voltage reactor inter-turn protection cannot eliminate the effects of these large low-frequency currents or large non-periodic components flowing through the reactor. These factors seriously affect the correct operation of the high-voltage reactor's inter-turn protection. To address the problem of false tripping of the high-voltage reactor's inter-turn protection caused by the low-frequency component generated by the series resonance between the busbar high-voltage reactor and the unremoved line series compensation during external fault recovery, a new anti-false tripping measure for the high-voltage reactor's inter-turn protection is urgently needed. Summary of the Invention

[0004] To overcome the above-mentioned deficiencies of the prior art, the present invention provides a method and device for preventing malfunction of turn-to-turn protection of a high-voltage shunt reactor, which specifically adopts the following technical solutions:

[0005] A method for preventing malfunction of turn-to-turn protection of a high-voltage shunt reactor comprises the following steps:

[0006] Step 1: When the busbar of the power system is recovering from a fault, analyze the equivalent circuit formed by the system-side power supply, the series-compensated line, and the high-voltage shunt reactor in the busbar;

[0007] Step 2: Analyze the equivalent circuit based on Kirchhoff's voltage law to obtain the low-frequency component that causes the malfunction of the high-voltage shunt reactor turn-to-turn protection;

[0008] Step 3: Use a digital filter to perform bandpass filtering on the sampled data at the head end of the high-voltage shunt reactor to filter out the low-frequency components contained in the sampled data and obtain filtered sampled data;

[0009] Step 4: Use the fast Fourier transform algorithm to process the filtered sampled data to obtain the zero-sequence power frequency component;

[0010] Step 5: Determine the zero-sequence power frequency component based on the zero-sequence power direction determination principle to obtain a determination result;

[0011] Step 6: Determine whether to perform the high-voltage shunt reactor turn-to-turn protection action based on the determination result.

[0012] Optional: The step of analyzing the equivalent circuit formed by the system-side power supply, the series-compensated line, and the high-voltage shunt reactor in the busbar in the power system in step 1 includes:

[0013] Analyze the equivalent circuit of the power system during the fault phase and obtain the corresponding RLC differential equation:

[0014]

[0015] where u m sinω0t is the system side power supply voltage, u m is the power supply voltage amplitude, ω0 is the angular frequency of the power frequency component; i L is the current flowing through the bus high-voltage shunt reactor; R1 is the bus resistance; L1 is the bus inductance; L0 is the inductance of the high-voltage shunt reactor; C1 is the bus series compensation capacitor; t is the time variable;

[0016] The current i flowing through the busbar high voltage shunt reactor is obtained by solving the RLC differential equation L , based on the current i L Get the corresponding low-frequency component

[0017]

[0018] where ω c is the angular frequency of the low-frequency component, K1 and K2 are constant parameters of the power system.

[0019] Optionally, the step of obtaining the low-frequency component causing the malfunction of the high-voltage shunt reactor turn-to-turn protection in step 2 includes:

[0020] Based on the characteristics of inductance and capacitance, the line inductance current and series compensation capacitor voltage are analyzed when the power system fault is removed, and the low-frequency components are analyzed. Simplify and obtain the low-frequency component of the current of the busbar high-voltage shunt reactor during the fault recovery process:

[0021]

[0022] wherein is the high current low frequency component amplitude, i k is the short circuit current amplitude; t0 is the fault clearing time; ω c is the low frequency component angular frequency, θ is the low frequency component initial phase angle, θ = arctan(ω0tan(ω0t0) / ω c ); R1 / 2L0 is the low frequency component decay time constant;

[0023] The bus high voltage shunt reactor current contains a current low frequency component based on the expression of the current low frequency component, and the current low frequency component causes the high voltage shunt reactor inter-turn protection misoperation.

[0024] Optionally, the digital filter in the step three adopts a second-order Butterworth filter.

[0025] Optionally, when the parameters of the digital filter in the step three are selected, the following conditions need to be met:

[0026] Based on the characteristic that the digital filter has the minimum attenuation to the signal at the center frequency, the system power frequency is selected as the center frequency of the digital filter;

[0027] The selected digital filter has a theoretical lower limit cutoff frequency f min , which is greater than the maximum frequency f cmax of the low frequency component generated when the non-removed line series compensation and the bus high voltage shunt reactor are in series resonance.

[0028] f min > f cmax .

[0029] Based on the requirement that the digital filter needs to meet the minimum impact on the inter-turn protection speed, the actual lower limit cutoff frequency f min,0 of the actually selected digital filter is greater than the theoretical lower limit cutoff frequency f min .

[0030] Optionally, the step of calculating the maximum frequency of the low frequency component generated when the non-removed line series compensation and the bus high voltage shunt reactor are in series resonance includes:

[0031] Based on the equivalent circuit diagram of the power system, the number of lines between the power generation unit and the bus is obtained;

[0032] When a fault occurs and part of the lines are removed, the resonance frequency f c of the series resonance of the remaining line series compensation capacitor and the bus high voltage shunt reactor is calculated:

[0033]

[0034] According to the calculated resonant frequency f c Get the maximum frequency f of the low-frequency component generated by the corresponding series resonance cmax :

[0035]

[0036] Among them C i is the series compensation capacitor in line i; C min is the minimum value of the series compensation capacitor in all lines; L0 is the inductance of the high-voltage shunt reactor.

[0037] Optionally, the step of processing the filtered sampled data using a fast Fourier transform algorithm in step 4 includes:

[0038] Acquire filtered sampling data, wherein the sampling data at least includes voltage sampling data and current sampling data at the head end of the high-voltage shunt reactor;

[0039] Performing fast Fourier transform on the filtered sampled data to convert the time domain signal of each sampled data into a frequency domain signal;

[0040] Extract the frequency domain signal of each sampled data based on the system power frequency to obtain the spectrum component corresponding to the system power frequency;

[0041] Corresponding amplitude data and phase data are extracted based on the obtained spectral components.

[0042] Optional: The step of determining the zero-sequence power frequency component based on the zero-sequence power direction determination principle in step 5 includes:

[0043] Obtain the corresponding power frequency zero-sequence voltage component and power frequency zero-sequence current component based on the fast Fourier algorithm;

[0044] Determine the phase relationship between the power frequency zero-sequence voltage component and the power frequency zero-sequence current component:

[0045]

[0046] Where U0 is the power frequency zero sequence voltage component; I0 ​​is the power frequency zero sequence current component; k is the inter-turn protection floating parameter; X L0 is the zero-sequence compensation reactance; j is the imaginary unit;

[0047] Based on the phase relationship between the power frequency zero-sequence voltage component and the power frequency zero-sequence current component, the high-voltage shunt reactor turn-to-turn short-circuit fault and the external short-circuit fault are distinguished.

[0048] Optional: The step of distinguishing between a high-voltage shunt reactor turn-to-turn short-circuit fault and an external short-circuit fault based on the phase relationship between the power frequency zero-sequence voltage component and the power frequency zero-sequence current component includes:

[0049] When the phase of the power frequency zero sequence current component lags behind the phase of the power frequency zero sequence voltage component, it is determined that an external short circuit fault has occurred in the high voltage shunt reactor;

[0050] When the phase of the power frequency zero-sequence current component leads the phase of the power frequency zero-sequence voltage component by 90°, it is determined that an inter-turn short circuit fault has occurred in the high-voltage shunt reactor.

[0051] Furthermore, the present invention also discloses a device for preventing malfunction of a high-voltage shunt reactor turn-to-turn protection, which operates as described above in the method for preventing malfunction of a high-voltage shunt reactor turn-to-turn protection. The device comprises:

[0052] The equivalent circuit analysis module is used to analyze the equivalent circuit formed by the system-side power supply, the series-compensated line, and the high-voltage shunt reactor in the busbar during the fault recovery process of the power system;

[0053] A low-frequency component acquisition module is used to analyze the equivalent circuit based on Kirchhoff's voltage law to obtain the low-frequency component that causes the malfunction of the high-voltage shunt reactor inter-turn protection;

[0054] The data filtering module is used to perform bandpass filtering on the sampling data at the head end of the high-voltage shunt reactor using a digital filter to filter out the low-frequency components contained in the sampling data and obtain filtered sampling data;

[0055] A data processing module is used to process the filtered sampled data using a fast Fourier algorithm to obtain a zero-sequence power frequency component;

[0056] A fault determination module is used to determine the zero-sequence power frequency component based on the zero-sequence power direction determination principle to obtain a determination result;

[0057] The action execution module is used to determine whether to perform the high-voltage shunt reactor inter-turn protection action based on the judgment result.

[0058] Beneficial effects

[0059] The technical solution of the present invention achieves the following beneficial effects:

[0060] The method of the present invention analyzes the low-frequency component mechanism generated by the series resonance between the busbar high-voltage reactor and the uncut-off line during the fault recovery process and the original high-voltage reactor turn-to-turn protection judgment criteria, and then uses a Butterworth filter to bandpass filter the sampled signal, and then calculates its zero-sequence component to judge whether the high-voltage reactor has an inter-turn short-circuit fault. This method not only avoids the false operation of the high-voltage reactor turn-to-turn protection during the external fault recovery process, but also ensures the normal operation of the high-voltage reactor turn-to-turn protection when an inter-turn short-circuit fault occurs, which improves the reliability of the high-voltage reactor turn-to-turn protection. In addition, this method overcomes the interference of the low-frequency component generated by the series resonance on the high-voltage reactor turn-to-turn protection, and does not suppress the transient power frequency component during the fault process, does not affect the normal operation of the inter-turn protection, and provides a stable and reliable judgment method for preventing false operation of the high-voltage reactor turn-to-turn protection. BRIEF DESCRIPTION OF THE DRAWINGS

[0061] Figure 1 The figure is a flow chart of a method for preventing false operation of turn-to-turn protection of a high-voltage shunt reactor according to an embodiment of the present invention.

[0062] Figure 2 FIG. 4 is an equivalent circuit diagram of a system with two series compensation lines in an embodiment of the present invention.

[0063] Figure 3 FIG. 4 is an equivalent circuit diagram of a multi-strip series compensation line system in an embodiment of the present invention.

[0064] Figure 4 This is a flow chart of high-voltage inter-turn protection of a Butterworth filter in an embodiment of the present invention.

[0065] Figure 5 : is the amplitude-frequency characteristic curve of the second-order Butterworth bandpass filter in an embodiment of the present invention.

[0066] Figure 6 : is the phase-frequency characteristic curve of the second-order Butterworth bandpass filter in the embodiment of the present invention. DETAILED DESCRIPTION

[0067] The present invention will be further described below with reference to the accompanying drawings. The following examples are only used to more clearly illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. It should be noted that the following detailed description is exemplary and is intended to provide further explanation of the present application.

[0068] Combine Figure 1 As shown, the present invention specifically discloses a method for preventing false operation of a high-voltage shunt reactor turn-to-turn protection, which includes the following steps:

[0069] Step 1: When the busbar of the power system is recovering from a fault, analyze the equivalent circuit formed by the system-side power supply, the series-compensated line, and the high-voltage shunt reactor in the busbar;

[0070] Step 2: Analyze the equivalent circuit based on Kirchhoff's voltage law to obtain the low-frequency component that causes the malfunction of the high-voltage shunt reactor turn-to-turn protection;

[0071] Step 3: Use a digital filter to perform bandpass filtering on the sampled data at the head end of the high-voltage shunt reactor to filter out the low-frequency components contained in the sampled data and obtain filtered sampled data;

[0072] Step 4: Use the fast Fourier transform algorithm to process the filtered sampled data to obtain the zero-sequence power frequency component;

[0073] Step 5: Determine the zero-sequence power frequency component based on the zero-sequence power direction determination principle to obtain a determination result;

[0074] Step 6: Determine whether to perform the high-voltage shunt reactor turn-to-turn protection action based on the determination result.

[0075] Specifically, this embodiment is based on Figure 2 As shown in the structure, it includes two equivalent circuits of series-compensated line systems. Figure 1 Where E1 and E2 are the power supplies at both ends of the system respectively; M and K are the busbars at both sides of the system respectively; R1 and L1 are the resistance and inductance of MN line respectively; R2 and L2 are the resistance and inductance of NK line respectively; C1 is the series compensation capacitor of MN line; C2 is the series compensation capacitor of NK line; L 10 is the high inductance of the MN line; L 20 is the high impedance inductance of NK line; L0 is the high impedance inductance of busbar.

[0076] The step of analyzing the equivalent circuit formed by the system-side power supply, the series-compensated line, and the high-voltage shunt reactor in the busbar in the power system in step 1 includes:

[0077] Since the busbar high-voltage shunt reactor does not have the function of suppressing the backflow current and there is no small reactance at the neutral point, a single-phase reactor can be used to represent the three phases during the analysis process. When a B-phase grounding fault occurs on busbar N, the fault and NK lines are cut off at the same time after a period of time. From the time domain perspective, the fault phase current on the busbar high-voltage reactor L0 during the fault recovery process is analyzed: since the high-voltage reactor inductance value is much larger than the line inductance value, the current amplitude on the MN line during normal operation is much smaller than the current amplitude on the MN line during the fault. Therefore, to simplify the analysis process, the influence of the high-voltage reactor residual magnetism during the recovery process is ignored, that is, the busbar high-voltage reactor is considered to be in a zero state before the fault is restored. Furthermore, during the fault recovery process, the system-side power supply forms a loop with the busbar high-voltage reactor through the belt line and series compensation. The equivalent circuit of the power system fault stage at this time can be analyzed, and the corresponding RLC differential equation can be obtained:

[0078]

[0079] where u msinω0t is the system side power supply voltage, u m is the power supply voltage amplitude, ω0 is the angular frequency of the power frequency component; i L is the current flowing through the bus high-voltage shunt reactor; R1 is the bus resistance; L1 is the bus inductance; L0 is the inductance of the high-voltage shunt reactor; C1 is the bus series compensation capacitor; t is the time variable;

[0080] The current i flowing through the busbar high voltage shunt reactor is obtained by solving the RLC differential equation L , at this time i L Including low frequency components and power frequency components Two parts, based on the current i L Get the corresponding low-frequency component

[0081]

[0082] where ω c is the angular frequency of the low-frequency component, K1 and K2 are constant parameters of the power system.

[0083] Furthermore, in the step 2, due to the characteristics of inductance and capacitance, that is, the inductance current cannot change suddenly and the capacitance voltage cannot change suddenly, the line inductance current and the series compensation capacitor voltage are analyzed when the power system fault is removed, and the low-frequency component is Simplify and obtain the low-frequency component of the current of the busbar high-voltage shunt reactor during the fault recovery process:

[0084]

[0085] in is the amplitude of the low-frequency component of the high-impedance current, i k is the short-circuit current amplitude; t0 is the time when the fault is cleared; ω c is the angular frequency of the low-frequency component, θ is the initial phase angle of the low-frequency component, θ=arctan(ω0tan(ω0t0) / ω c ); R1 / 2L0 is the low-frequency component attenuation time constant;

[0086] In summary, it can be seen that the busbar high-voltage shunt reactor current obtained based on the expression of the current low-frequency component includes a current low-frequency component, and the current low-frequency component causes the high-voltage shunt reactor inter-turn protection to malfunction.

[0087] Typically, high-voltage reactor interturn protection uses a zero-sequence power direction criterion. This method distinguishes interturn short-circuit faults from external faults based on the phase relationship between the zero-sequence voltage and current at the reactor's headend: when a high-voltage reactor experiences an interturn short-circuit fault, the zero-sequence current phase leads the zero-sequence voltage by nearly 90°; when an external fault occurs, the zero-sequence current phase lags the zero-sequence voltage. Practical protection devices all use a Fast Fourier Transformation (FFT) algorithm to extract the power frequency zero-sequence component. However, the presence of low-frequency components leads to large calculation errors when the FFT extracts the power frequency zero-sequence voltage and current components. To prevent the low-frequency components generated during external fault recovery from causing malfunction of the high-voltage reactor interturn protection, the present invention improves the interturn protection criterion based on zero-sequence power direction. A digital filter is used to bandpass filter the voltage and current sampling data at the reactor's headend to remove low-frequency components generated by unremoved line series compensation and busbar high-voltage reactor series resonance. Furthermore, FFT is used to further extract the zero-sequence voltage and current power frequency components before determining interturn short-circuit.

[0088] Among the commonly used digital filters, the Butterworth filter has the characteristics of maximum flatness in the passband, minimum amplitude-frequency response change, and can fully guarantee the accuracy of the sampled data. Therefore, the second-order Butterworth bandpass filter is preferred for filtering the sampled signal, such as Figure 5 and Figure 6 As shown, they are the amplitude-frequency characteristic curve and phase-frequency characteristic curve of the second-order Butterworth bandpass filter respectively.

[0089] It should be noted that when selecting the parameters of the digital filter in step 3 of the method of the present invention, the following principles need to be considered: (1) ensuring that the high-voltage inter-turn protection does not malfunction during the external fault recovery process; (2) ensuring that the high-voltage inter-turn protection operates normally when an inter-turn short-circuit fault occurs. At the same time, it is necessary to ensure that the response speed of the filter is as fast as possible without affecting the speed of the high-voltage inter-turn protection. Based on the above principles, the digital filter parameter selection process of the present invention must meet the following conditions:

[0090] First, the digital filter does not affect the high-voltage inter-turn protection's ability to accurately identify inter-turn short-circuit faults, ensuring that the power frequency signal loss after passing through the filter is as small as possible. Based on the characteristic that the digital filter's center frequency attenuates the signal minimally, for example, the Butterworth bandpass filter's center frequency attenuates the signal almost to zero, the system power frequency is selected as the center frequency of the digital filter, i.e., 50Hz.

[0091] Secondly, it is necessary to avoid the low-frequency components generated by the series resonance of the uncut line and the busbar high-voltage series resistor during the fault recovery process, which will affect the zero-sequence voltage and current calculation and cause the high-voltage series resistor inter-turn protection to malfunction, and ensure that the Butterworth bandpass filter can fully suppress the low-frequency components of all frequencies that may be generated by the series resonance. Therefore, the theoretical lower limit cutoff frequency f of the selected digital filter is min Greater than the maximum frequency f of the low-frequency component generated when the series resonance occurs between the uncut line series compensation and the busbar high-voltage shunt reactor cmax :

[0092] f min >f cmax ;

[0093] Among them combined Figure 3 As shown, the steps for calculating the maximum frequency of the low-frequency component generated when the series compensation of the uncut line and the bus high-voltage shunt reactor resonate in series include:

[0094] Based on the equivalent circuit diagram of the power system, the number of lines SUM between the busbars M and K on both sides and the busbar N is obtained; for example Figure 3 As shown, there are m lines between busbar M and busbar N, and n lines between busbar N and busbar N. Then the number of lines between busbars M and K on both sides and busbar N is SUM=(n+m).

[0095] When a fault occurs and part of the line is cut off, for example, line NKⅠ to line n is cut off, the resonant frequency f of the series resonance between the series compensation capacitors of the remaining m lines and the busbar high-voltage shunt reactor is calculated. c :

[0096]

[0097] According to the calculated resonant frequency f c Get the maximum frequency f of the low-frequency component generated by the corresponding series resonance cmax :

[0098]

[0099] Among them C i is the series compensation capacitor in line i, where i is a positive integer and 1≤i≤SUM; C min is the minimum value of the series compensation capacitor in all lines; L0 is the inductance of the high-voltage shunt reactor.

[0100] In order to effectively suppress the low-frequency components generated by the busbar high impedance and the series compensation resonance of the uncut lines, and taking into account the reservation of a certain margin, the lower limit cutoff frequency f of the Butterworth bandpass filter is min Greater than the maximum frequency f of the low-frequency component that may be generated by series resonance cmax , that is, it satisfies the following relationship:

[0101] f min >f cmax .

[0102] Finally, based on the requirement that the digital filter needs to meet the minimum impact on the turn-to-turn protection speed, the actual lower limit cutoff frequency f of the selected digital filter is set. min,0 Greater than the theoretical lower limit cutoff frequency f min .

[0103] like Figure 4 As shown in Figure 1, it is a high-resistance inter-turn protection process based on Butterworth filter. The process is divided into three stages:

[0104] (1) Signal acquisition and filtering: First, the zero-sequence voltage and current at the high-voltage headend are acquired, and the measured signals are processed using a Butterworth bandpass filter;

[0105] (2) Signal processing: After calculating the zero-sequence power frequency component of the processed signal using FFT, it is substituted into the zero-sequence power direction criterion to calculate the voltage and current phase difference;

[0106] (3) Protection action: Determine whether to issue an action command to the high-voltage inter-turn protection based on the judgment result.

[0107] More specifically, the step of processing the filtered sampled data using the fast Fourier algorithm in step 4 includes:

[0108] Acquire filtered sampling data, wherein the sampling data at least includes voltage sampling data and current sampling data at the head end of the high-voltage shunt reactor;

[0109] Performing fast Fourier transform on the filtered sampled data to convert the time domain signal of each sampled data into a frequency domain signal;

[0110] Extract the frequency domain signal of each sampled data based on the system power frequency to obtain the spectrum component corresponding to the system power frequency;

[0111] Corresponding amplitude data and phase data are extracted based on the obtained spectral components.

[0112] Then, the zero-sequence power frequency component is determined according to the zero-sequence power direction determination principle in step five:

[0113] Obtain the corresponding power frequency zero-sequence voltage component and power frequency zero-sequence current component based on the fast Fourier algorithm;

[0114] Determine the phase relationship between the power frequency zero-sequence voltage component and the power frequency zero-sequence current component:

[0115]

[0116] Where U0 is the power frequency zero sequence voltage component; I0 ​​is the power frequency zero sequence current component; k is the inter-turn protection floating parameter; X L0 is the zero-sequence compensation reactance; j is the imaginary unit;

[0117] Based on the phase relationship between the power frequency zero-sequence voltage component and the power frequency zero-sequence current component, the high-voltage shunt reactor turn-to-turn short-circuit fault and the external short-circuit fault are distinguished: when the phase of the power frequency zero-sequence current component lags behind the phase of the power frequency zero-sequence voltage component, it is determined that an external short-circuit fault has occurred in the high-voltage shunt reactor; when the phase of the power frequency zero-sequence current component leads the phase of the power frequency zero-sequence voltage component by 90°, it is determined that an inter-turn short-circuit fault has occurred in the high-voltage shunt reactor.

[0118] The method of the present invention analyzes the low-frequency component mechanism generated by the series resonance between the bus high-voltage reactor and the uncut-off line during the fault recovery process and the original high-voltage reactor inter-turn protection criterion, and then performs band-pass filtering on the sampled signal through a Butterworth filter, and then calculates its zero-sequence component to determine whether the high-voltage reactor has an inter-turn short-circuit fault. This method not only avoids the interference of the low-frequency component generated by the series resonance on the high-voltage reactor inter-turn protection, but also does not suppress the transient power frequency component during the fault process, and does not affect the normal operation of the inter-turn protection. In this way, the technical problem of the bus high-voltage reactor inter-turn protection misoperation during the fault recovery process in the scenario of a multi-belt series-compensated long-line system is overcome, and a technical method with engineering value is provided for preventing the bus high-voltage reactor inter-turn protection from misoperation, and a theoretical foundation is laid for further analysis of the bus high-voltage reactor inter-turn protection criterion, which has guiding significance for its engineering application and promotion.

[0119] Furthermore, the present invention also discloses a device for preventing malfunction of a high-voltage shunt reactor turn-to-turn protection, which operates as described above in the method for preventing malfunction of a high-voltage shunt reactor turn-to-turn protection. The device comprises:

[0120] The equivalent circuit analysis module is used to analyze the equivalent circuit formed by the system-side power supply, the series-compensated line, and the high-voltage shunt reactor in the busbar during the fault recovery process of the power system;

[0121] A low-frequency component acquisition module is used to analyze the equivalent circuit based on Kirchhoff's voltage law to obtain the low-frequency component that causes the malfunction of the high-voltage shunt reactor inter-turn protection;

[0122] The data filtering module is used to perform bandpass filtering on the sampling data at the head end of the high-voltage shunt reactor using a digital filter to filter out the low-frequency components contained in the sampling data and obtain filtered sampling data;

[0123] A data processing module is used to process the filtered sampled data using a fast Fourier algorithm to obtain a zero-sequence power frequency component;

[0124] A fault determination module is used to determine the zero-sequence power frequency component based on the zero-sequence power direction determination principle to obtain a determination result;

[0125] Action execution module, used to determine whether to perform high-voltage shunt reactor turn-to-turn protection action based on the judgment result

[0126] Furthermore, the present invention also discloses a non-volatile storage medium, which includes a stored program, wherein when the program is running, it controls the device where the non-volatile storage medium is located to execute the above-mentioned anti-false operation method of the high-voltage shunt reactor inter-turn protection.

[0127] In addition, the present invention also discloses a method comprising a processor and a memory; the memory stores computer-readable instructions, and the processor is used to run the computer-readable instructions, wherein the computer-readable instructions execute the above-mentioned method for preventing false operation of the inter-turn protection of the high-voltage shunt reactor when running.

[0128] It will be understood by those skilled in the art that embodiments of the present invention may be provided as methods, systems, or computer program products. Thus, the present invention may take the form of an entirely hardware embodiment, an entirely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present invention may take the form of a computer program product implemented on one or more computer-usable non-transitory storage media (including but not limited to magnetic disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0129] The present invention is described with reference to flowcharts and / or block diagrams of methods, devices, and computer program products according to embodiments of the present invention. It should be understood that each process and / or block in the flowcharts and / or block diagrams, as well as combinations of processes and / or blocks in the flowcharts and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowcharts and / or block diagrams. Figure 1 a process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0130] These computer program instructions may also be stored in a computer readable memory that can direct a computer or other programmable data processing device to work in a specific manner, so that the instructions stored in the computer readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 a process or multiple processes and / or boxes Figure 1 The function specified in one or more boxes.

[0131] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operational steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing the instructions executed on the computer or other programmable device for implementing the process. Figure 1 a process or multiple processes and / or boxes Figure 1 A step that specifies a function in one or more boxes.

[0132] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the technical principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for preventing malfunction of turn-to-turn protection of a high-voltage shunt reactor, characterized in that: The following steps are involved: Step 1: When the busbar of the power system is recovering from a fault, analyze the equivalent circuit formed by the system-side power supply, the series-compensated line, and the high-voltage shunt reactor in the busbar; Step 2: Analyze the equivalent circuit based on Kirchhoff's voltage law to obtain the low-frequency component that causes the malfunction of the high-voltage shunt reactor turn-to-turn protection; Step 3: Use a digital filter to perform bandpass filtering on the sampled data at the head end of the high-voltage shunt reactor to filter out the low-frequency components contained in the sampled data and obtain filtered sampled data; The digital filter adopts a second-order Butterworth filter; When selecting the parameters of the digital filter, the following conditions must be met: Based on the characteristic that the digital filter has the least attenuation on the signal at the center frequency, the system power frequency is selected as the center frequency of the digital filter; The theoretical lower cutoff frequency f of the selected digital filter min Greater than the maximum frequency f of the low-frequency component generated when the series resonance occurs between the uncut line series compensation and the busbar high-voltage shunt reactor cmax : f min >f cmax ; Based on the requirement that the digital filter needs to meet the minimum impact on the turn-to-turn protection speed, the actual lower limit cutoff frequency f of the selected digital filter is set. min,0 Greater than the theoretical lower limit cutoff frequency f min ; Step 4: Use the fast Fourier transform algorithm to process the filtered sampled data to obtain the zero-sequence power frequency component; Step 5: Determine the zero-sequence power frequency component based on the zero-sequence power direction determination principle to obtain a determination result; Step 6: Determine whether to perform the high-voltage shunt reactor turn-to-turn protection action based on the determination result.

2. The method for preventing malfunction of turn-to-turn protection of a high-voltage shunt reactor according to claim 1, characterized in that: The step of analyzing the equivalent circuit formed by the system-side power supply, the series-compensated line, and the high-voltage shunt reactor in the busbar in the power system in step 1 includes: Analyze the equivalent circuit of the power system during the fault phase and obtain the corresponding RLC differential equation: where u m sinω0t is the system side power supply voltage, u m is the power supply voltage amplitude, ω0 is the angular frequency of the power frequency component; i L is the current flowing through the bus high-voltage shunt reactor; R1 is the bus resistance; L1 is the bus inductance; L0 is the inductance of the high-voltage shunt reactor; C1 is the bus series compensation capacitor; t is the time variable; The current i flowing through the busbar high voltage shunt reactor is obtained by solving the RLC differential equation L , based on the current i L Get the corresponding low-frequency component where ω c is the angular frequency of the low-frequency component, K1 and K2 are constant parameters of the power system.

3. The method for preventing malfunction of high-voltage shunt reactor turn-to-turn protection according to claim 2, characterized in that: The step of obtaining the low-frequency component causing the malfunction of the high-voltage shunt reactor turn-to-turn protection in step 2 includes: Based on the characteristics of inductance and capacitance, the line inductance current and series compensation capacitor voltage are analyzed when the power system fault is removed, and the low-frequency components are analyzed. Simplify and obtain the low-frequency component of the current of the busbar high-voltage shunt reactor during the fault recovery process: in is the amplitude of the low-frequency component of the high-impedance current, i k is the short-circuit current amplitude; t0 is the time when the fault is cleared; ω c is the angular frequency of the low-frequency component, θ is the initial phase angle of the low-frequency component, θ=arctan(ω0tan(ω0t0) / ω c ); R1 / 2L0 is the low-frequency component attenuation time constant; Based on the expression of the current low-frequency component, it is obtained that the busbar high-voltage shunt reactor current includes the current low-frequency component, and the current low-frequency component causes the high-voltage shunt reactor inter-turn protection to malfunction.

4. The method for preventing malfunction of turn-to-turn protection of a high-voltage shunt reactor according to claim 1, characterized in that: The step of calculating the maximum frequency of the low-frequency component generated when the series compensation of the uncut-off line and the bus high-voltage shunt reactor resonate in series includes: Based on the equivalent circuit diagram of the power system, obtain the number of lines between the power generation unit and the busbar; When a fault occurs and part of the line is cut off, calculate the resonant frequency f of the series resonance between the remaining line series compensation capacitor and the busbar high-voltage shunt reactor. c : According to the calculated resonant frequency f c Get the maximum frequency f of the low-frequency component generated by the corresponding series resonance cmax : Among them C i is the series compensation capacitor in line i; C min is the minimum value of the series compensation capacitor in all lines; L0 is the inductance of the high-voltage shunt reactor; m is the number of lines between busbar M and busbar N.

5. The method for preventing malfunction of high-voltage shunt reactor turn-to-turn protection according to claim 1, characterized in that: The step of processing the filtered sampled data using the fast Fourier algorithm in step 4 includes: Acquire filtered sampling data, wherein the sampling data at least includes voltage sampling data and current sampling data at the head end of the high-voltage shunt reactor; Performing fast Fourier transform on the filtered sampled data to convert the time domain signal of each sampled data into a frequency domain signal; Extract the frequency domain signal of each sampled data based on the system power frequency to obtain the spectrum component corresponding to the system power frequency; Corresponding amplitude data and phase data are extracted based on the obtained spectral components.

6. The method for preventing malfunction of high-voltage shunt reactor turn-to-turn protection according to claim 5, characterized in that: The step of determining the zero-sequence power frequency component based on the zero-sequence power direction determination principle in step 5 includes: Obtain the corresponding power frequency zero-sequence voltage component and power frequency zero-sequence current component based on the fast Fourier algorithm; Determine the phase relationship between the power frequency zero-sequence voltage component and the power frequency zero-sequence current component: Where U0 is the power frequency zero sequence voltage component; I0 ​​is the power frequency zero sequence current component; k is the inter-turn protection floating parameter; X L0 is the zero-sequence compensation reactance; j is the imaginary unit; Based on the phase relationship between the power frequency zero-sequence voltage component and the power frequency zero-sequence current component, the high-voltage shunt reactor turn-to-turn short-circuit fault and the external short-circuit fault are distinguished.

7. The method for preventing malfunction of high-voltage shunt reactor turn-to-turn protection according to claim 6, characterized in that: The step of determining and distinguishing between a high-voltage shunt reactor turn-to-turn short-circuit fault and an external short-circuit fault based on the phase relationship between the power frequency zero-sequence voltage component and the power frequency zero-sequence current component comprises: When the phase of the power frequency zero sequence current component lags behind the phase of the power frequency zero sequence voltage component, it is determined that an external short circuit fault has occurred in the high voltage shunt reactor; When the phase of the power frequency zero-sequence current component leads the phase of the power frequency zero-sequence voltage component by 90°, it is determined that an inter-turn short circuit fault has occurred in the high-voltage shunt reactor. 8.An anti-malfunction device for turn-to-turn protection of high-voltage shunt reactor, characterized in that: The device operates the method for preventing false operation of the high-voltage shunt reactor turn-to-turn protection according to any one of claims 1 to 7, and the device comprises: The equivalent circuit analysis module is used to analyze the equivalent circuit formed by the system-side power supply, the series-compensated line, and the high-voltage shunt reactor in the busbar during the fault recovery process of the power system; A low-frequency component acquisition module is used to analyze the equivalent circuit based on Kirchhoff's voltage law to obtain the low-frequency component that causes the malfunction of the high-voltage shunt reactor inter-turn protection; The data filtering module is used to perform bandpass filtering on the sampling data at the head end of the high-voltage shunt reactor using a digital filter to filter out the low-frequency components contained in the sampling data and obtain filtered sampling data; A data processing module is used to process the filtered sampled data using a fast Fourier algorithm to obtain a zero-sequence power frequency component; A fault determination module is used to determine the zero-sequence power frequency component based on the zero-sequence power direction determination principle to obtain a determination result; The action execution module is used to determine whether to perform the high-voltage shunt reactor inter-turn protection action based on the judgment result.

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