A method for eliminating harmonic interference from high-voltage switches in coal mines and a filtering monitoring and protection device.

Abstract

A method for eliminating harmonic interference from high-voltage switches in coal mines and a filtering monitoring and protection device are disclosed, relating to the field of measuring electrical variables. In this method, analog signals from the high-voltage switch are acquired via a current transformer and converted into digital signals. The slope of the zero-sequence current mutation is calculated, and the status signals of auxiliary contacts are read to obtain the fundamental frequencies of the three-phase voltage and the zero-sequence voltage. A basic reference vector is constructed based on the fundamental frequency, and the operating scenario is determined according to the switch status and the slope of the zero-sequence current mutation. In transient operating scenarios, an aperiodic DC component is superimposed to obtain the final interference reference vector, using a larger step size coefficient; in non-transient operating scenarios, the basic reference vector is used directly, using a smaller step size coefficient. Finally, an adaptive filtering algorithm is used to process the signal to obtain the purified electrical parameter signal. This application aims to reduce the impact of transient distortion components on signal purification, thereby enhancing the reliability of the high-voltage switch integrated protection device under complex operating conditions.

Description

Technical Field

[0001] This application belongs to the field of measuring electrical variables, and in particular relates to a method for eliminating harmonic interference from high-voltage switches in coal mines and a filtering monitoring and protection device. Background Technology

[0002] Underground power grids in coal mines are characterized by long power supply distances and complex load types. In particular, with the widespread use of nonlinear power electronic devices such as frequency converters and soft starters, a large amount of harmonic current is injected into the grid, causing severe distortion of voltage and current waveforms. High-voltage switches, as key control and protection devices in coal mine power supply systems, rely on precise sampling of electrical parameters to execute protection logic. However, when high-amplitude harmonic interference is mixed into the sampled signal, the microprocessor-based protection device is prone to misjudging the fault type or amplitude, leading to maloperation or failure to operate, threatening the safe and stable operation of the underground power supply system.

[0003] To suppress the impact of harmonic interference on measurement accuracy, related technologies typically employ an adaptive filtering method based on the synthesis of specific harmonics. This method analyzes the characteristic frequencies of the power grid, pre-constructs a basic reference vector composed of sine and cosine functions of the fundamental wave and the main characteristic harmonics, and uses this reference vector as the input of the adaptive filter. The minimum mean square error algorithm is used to dynamically adjust the weight coefficients of each harmonic, thereby canceling out the harmonic components in the original signal in the output signal.

[0004] However, during the transient process of high-voltage switch closing or opening, the circuit state undergoes a drastic change. The resulting electromagnetic transient interference often exhibits non-stationary characteristics and its amplitude changes extremely rapidly. When this non-stationary abrupt interference enters an adaptive filter based on the periodic assumption, it is difficult to fit the abrupt interference using existing orthogonal trigonometric function sequences. This slows down the dynamic response speed of the filter within this critical transient time window, reduces the algorithm's tracking and convergence efficiency for transient distortion signals, and makes it easy for transient distortion components to remain in the output purified signal. This increases the risk of misjudgment by the protection device due to data deviation at the moment of switch action, affecting the overall operational reliability of the coal mine power supply system. Summary of the Invention

[0005] This application provides a method for eliminating harmonic interference from high-voltage switches in coal mines and a filtering monitoring and protection device, which reduces the impact of transient distortion components on signal purification, thereby enhancing the reliability of high-voltage switch integrated protection devices under complex operating conditions.

[0006] Firstly, this application provides a method for eliminating harmonic interference from high-voltage switches in coal mines. The method involves: collecting analog signals from the current transformer of the high-voltage switch and performing analog-to-digital conversion to obtain a sequence of original electrical parameters at the same time; calculating the difference between adjacent sampling points of the zero-sequence current in the original electrical parameter digital signal sequence to obtain the abrupt change slope of the zero-sequence current; real-time reading of the switching status signals of the auxiliary contacts of the high-voltage switch; calculating the fundamental frequencies of the three-phase voltage and the zero-sequence voltage at the current time based on the original electrical parameter digital signal sequence; generating orthogonal function pairs with unit amplitude using trigonometric functions based on the three-phase voltage fundamental frequencies and the zero-sequence voltage fundamental frequencies to construct a basic reference vector; and determining the operating scenario of the high-voltage switch based on the switching status signals and the abrupt change slope of the zero-sequence current. In the case of transient scenarios, a preset aperiodic DC component is superimposed on the basic reference vector to obtain the final interference reference vector. When the operating scenario of the high-voltage switch is determined to be a non-operational transient scenario based on the switching status signal and the abrupt change slope of the zero-sequence current, the basic reference vector is used as the final interference reference vector. The step size coefficient of the preset adaptive filtering algorithm is determined according to the operating scenario of the high-voltage switch, with the step size coefficient for the operational transient scenario being greater than that for the non-operational transient scenario. The original electrical parameter digital signal sequence is used as the desired signal, and the final interference reference vector is used as the input signal. The preset adaptive filtering algorithm is run using the step size coefficient to output the estimated interference signal. The difference between the original electrical parameter digital signal sequence and the estimated interference signal is output as the purified electrical parameter signal.

[0007] By adopting the above technical solution and establishing an operation scenario discrimination mechanism based on switch state and zero-sequence current mutation slope, a non-periodic DC component is specifically superimposed on the basic reference vector in operation transient scenarios. This makes the final interference reference vector more accurately reflect the actual interference characteristics of high-voltage switch operation transients. Simultaneously, by employing differentiated adaptive filtering algorithm step size coefficients for different operation scenarios—using a larger step size in operation transient scenarios to improve the algorithm's convergence speed and a smaller step size in non-operation transient scenarios to ensure filtering accuracy—the adaptive filtering algorithm can better adapt to the changing interference characteristics of high-voltage switches under different operation scenarios. This scenario-based adaptive reference vector construction method and step size adjustment strategy improve the removal effect of harmonic interference in electrical parameter signals and reduce distortion and falsification during signal processing.

[0008] In conjunction with some implementations of the first aspect, in some implementations, after generating orthogonal function pairs with unit amplitudes using trigonometric functions based on the fundamental frequency of the three-phase voltage and the fundamental frequency of the zero-sequence voltage to construct a basic reference vector, the method further includes: real-time monitoring of the on / off state of the auxiliary contacts of the high-voltage switch; if it is determined that the auxiliary contact state has reversed, then it is determined that the current moment is in an operational transient scenario; if it is determined that the auxiliary contact state remains stable, then it is determined whether the slope of the sudden change in the zero-sequence current exceeds a preset grounding sudden change threshold; when the slope of the sudden change in the zero-sequence current is greater than or equal to the grounding sudden change threshold, it is determined that the current moment is in a grounding abnormal scenario, and the grounding abnormal scenario belongs to the non-operational transient scenario; when the slope of the sudden change in the zero-sequence current is less than the grounding sudden change threshold, it is determined that the current moment is in a normal operation scenario, and the normal operation scenario belongs to the non-operational transient scenario.

[0009] By adopting the above technical solution, a complete operational scenario identification mechanism was constructed by real-time monitoring of the on / off state changes of the auxiliary contacts of the high-voltage switch and the abrupt change slope of the zero-sequence current. By comparing the abrupt change slope of the zero-sequence current with a preset grounding abrupt change threshold, grounding anomaly scenarios were identified. This multi-dimensional scenario identification method improves the accuracy of identifying various operational states of the high-voltage switch, enabling subsequent interference elimination strategies to more accurately match actual operational scenarios. By subdividing operational scenarios into transient operational scenarios, grounding anomaly scenarios, and normal operation scenarios, the adaptability to different types of interference is improved, enhancing the targeting and effectiveness of interference elimination.

[0010] In conjunction with some implementation methods of the first aspect, in some implementation methods, the step size coefficient of the preset adaptive filtering algorithm is determined according to the operating scenario of the high-voltage switch. Specifically, this includes: constructing a multi-channel step size vector corresponding to three-phase voltage, two-phase current, zero-sequence voltage, and zero-sequence current; when the scenario is determined to be a transient operation, the elements corresponding to three-phase voltage and two-phase current in the multi-channel step size vector are set to preset first values, and the elements corresponding to zero-sequence voltage and zero-sequence current are set to preset second values; when the scenario is determined to be a grounding anomaly, the elements corresponding to three-phase voltage and two-phase current in the multi-channel step size vector are set to preset third values, and the elements corresponding to zero-sequence voltage and zero-sequence current are set to preset fourth values; when the scenario is determined to be a normal operation, the elements corresponding to three-phase voltage and two-phase current in the multi-channel step size vector are set to preset fifth values, and the elements corresponding to zero-sequence voltage and zero-sequence current are set to preset sixth values, with the preset second value, preset first value, preset fourth value, preset sixth value, preset third value, and preset fifth value decreasing in magnitude.

[0011] By employing the above technical solution, a multi-channel step-size vector is constructed, and different step-size parameters are used for three-phase voltage, two-phase current, zero-sequence voltage, and zero-sequence current. A decreasing step-size sequence is adopted according to different operating scenarios. Larger step-size values ​​are used in transient operating scenarios to improve the algorithm's convergence speed, while step-size values ​​are gradually reduced in grounding anomaly and normal operating scenarios to ensure steady-state accuracy. This multi-dimensional step-size adjustment strategy based on signal type and operating scenario improves the flexibility of the adaptive filtering algorithm in handling different types of electrical parameters, enhances the algorithm's adaptability in various operating scenarios, and improves the overall interference removal effect.

[0012] In conjunction with some implementation methods of the first aspect, in some implementation methods, a preset aperiodic DC component is superimposed on the basic reference vector to obtain the final interference reference vector. Specifically, this includes: calling a preset arc decay time constant and a preset arc interference center frequency; calculating the arc amplitude envelope using a preset exponential decay function based on the time corresponding to the current sampling moment, where the exponential part of the preset exponential decay function is composed of the negative of the ratio of time to the preset arc decay time constant; calculating the arc oscillation component using a sine function, where the frequency of the sine function is the preset arc interference center frequency; multiplying the arc amplitude envelope by the arc oscillation component and multiplying by a preset arc interference amplitude coefficient to obtain the arc interference reference component during the operation transient period; and superimposing the arc interference reference component onto the basic reference vector to obtain the final interference reference vector in the operation transient scenario.

[0013] By adopting the above technical solution, a time-domain model of arc interference was constructed using an exponential decay function and a sine function by introducing a preset arc decay time constant and a preset arc interference center frequency. By multiplying the arc amplitude envelope by the arc oscillation component and superimposing a preset arc interference amplitude coefficient, an interference reference component that more closely resembles the actual arc characteristics was obtained. This interference modeling method, which considers both arc decay and oscillation characteristics, improves the accuracy of characterizing arc interference during transient high-voltage switch operation, enhances the ability of the interference reference vector to represent transient switch operation characteristics, and improves the interference removal effect in transient operation scenarios.

[0014] In some implementations of the first aspect, the original electrical parameter digital signal sequence is used as the desired signal and the final interference reference vector is used as the input signal. A preset adaptive filtering algorithm is run using a step size coefficient to output an estimated interference signal. Specifically, this includes: obtaining the adaptive filter weight vector at the current moment; calculating the inner product of the adaptive filter weight vector at the current moment and the final interference reference vector to obtain the estimated interference signal and outputting it; calculating the difference between the original electrical parameter digital signal sequence and the estimated interference signal to obtain the prediction error; and correcting the adaptive filter weight vector at the current moment using the step size coefficient, the prediction error, and the final interference reference vector to obtain the adaptive filter weight vector at the next moment, which is used for the calculation and output of the estimated interference signal at the next moment.

[0015] By employing the above technical solution, the estimated interference signal is obtained by calculating the inner product of the adaptive filter weight vector and the final interference reference vector. The prediction error is then calculated using the difference between the original digital signal sequence of electrical parameters and the estimated interference signal. Based on this prediction error, the filter weight vector is corrected in real time. This allows the filter to continuously track and adapt to the dynamic changes in various interference components in the power system, improving the filter's accuracy in identifying sudden and gradually changing interferences and enhancing its ability to separate different types of interference. By using inner product operations and error feedback to update the filter parameters, computational complexity is reduced, and the real-time performance of the algorithm is improved, enabling the filter to respond more quickly to various interference changes in the system.

[0016] In conjunction with some implementations of the first aspect, in some implementations, after outputting the difference between the original electrical parameter digital signal sequence and the estimated interference signal as the purified electrical parameter signal, the method further includes: based on the purified electrical parameter signal, accumulating the sum of squares and averaging them within one fundamental period, and then performing a square root operation to calculate the effective values ​​of the three-phase voltage, the effective values ​​of the three-phase current, the effective value of the zero-sequence voltage, and the effective value of the zero-sequence current; extracting the fundamental amplitude and the harmonic amplitudes of a preset first order to a preset second order from the purified electrical parameter signal, wherein the preset first order is less than the preset second order; calculating the ratio of the sum of squares of all harmonic amplitudes to the square of the fundamental amplitude, and performing a square root operation on the ratio to obtain the total harmonic distortion rate.

[0017] By employing the above technical solution, effective value calculation and harmonic analysis are performed on the purified electrical parameter signals. The effective values ​​of each phase voltage and current are obtained by averaging and then taking the square root of the sum of squares within one fundamental period. The amplitudes of the fundamental wave and each harmonic are extracted to calculate the total harmonic distortion rate, thus improving the accuracy of power quality assessment indicators. Because purified electrical parameter signals are used for analysis and calculation, the impact of various interferences on power quality assessment is reduced, improving the reliability of the effective value calculation and harmonic analysis results. The periodic accumulation calculation method reduces the impact of sampling noise on the assessment results, enhancing the anti-interference capability of power quality assessment.

[0018] In conjunction with some implementations of the first aspect, in some implementations, after obtaining the total harmonic distortion rate, the method further includes: calculating the basic operating time using an inverse time characteristic formula when the effective value of the three-phase current is determined to be greater than or equal to a preset multiple of the rated current; extending the basic operating time by a preset proportion to obtain the final operating time when the total harmonic distortion rate is determined to be greater than or equal to a preset distortion rate; issuing an overcurrent protection command based on the final operating time; and issuing a grounding protection command within a preset duration when the effective value of the zero-sequence current is determined to be greater than or equal to a preset current value and the effective value of the zero-sequence voltage is determined to be greater than or equal to a preset voltage value.

[0019] By adopting the above technical solution, the total harmonic distortion rate (THD) is used as the delay criterion for overcurrent protection. When a large current with high harmonic content is detected, the protection action time is appropriately extended. Through the combination of inverse time characteristics and preset proportional delay, the risk of protection maloperation caused by harmonic interference is reduced. In zero-sequence protection, the effective values ​​of zero-sequence current and zero-sequence voltage are monitored simultaneously, and a preset time is set as the criterion delay, improving the reliability of ground fault detection. The combined criterion of harmonic distortion rate and preset proportional delay enhances the protection function's immunity to interference and improves the accuracy of the protection device in complex electromagnetic environments.

[0020] In a second aspect, embodiments of this application provide a filtering monitoring and protection device, which includes: one or more processors and a memory; the memory is coupled to one or more processors, and the memory is used to store computer program code, the computer program code including computer instructions, and the one or more processors call the computer instructions to cause the filtering monitoring and protection device to perform the method described in the first aspect and any possible implementation thereof.

[0021] Thirdly, embodiments of this application provide a computer-readable storage medium including instructions that, when executed on a filter monitoring and protection device, cause the filter monitoring and protection device to perform the method described in the first aspect and any possible implementation thereof.

[0022] Fourthly, embodiments of this application provide a computer program product that, when running on a filter monitoring and protection device, causes the filter monitoring and protection device to execute the method described in any possible implementation of the first aspect.

[0023] One or more technical solutions provided in the embodiments of this application have at least the following technical effects or advantages:

[0024] 1. This application provides a method for eliminating harmonic interference from high-voltage switches in coal mines. By establishing an operating scenario discrimination mechanism based on switch state and the slope of zero-sequence current abrupt change, a non-periodic DC component is specifically superimposed on the basic reference vector under transient operating scenarios. This makes the final interference reference vector more accurately reflect the actual interference characteristics of the high-voltage switch under transient operating conditions. Simultaneously, by employing differentiated adaptive filtering algorithm step size coefficients for different operating scenarios—using a larger step size in transient operating scenarios to improve the algorithm's convergence speed and a smaller step size in non-transient operating scenarios to ensure filtering accuracy—the adaptive filtering algorithm can better adapt to the changing interference characteristics of high-voltage switches under different operating scenarios. This scenario-based adaptive reference vector construction method and step size adjustment strategy improve the elimination effect of harmonic interference in electrical parameter signals and reduce distortion and falsification during signal processing.

[0025] 2. This application provides a method for eliminating harmonic interference from high-voltage switches in coal mines. By real-time monitoring of the on / off state changes of auxiliary contacts and the abrupt change slope of zero-sequence current, a complete operational scenario identification mechanism is constructed. By comparing the abrupt change slope of zero-sequence current with a preset grounding abrupt change threshold, grounding anomaly scenarios are identified. This multi-dimensional scenario identification method improves the accuracy of identifying various operational states of high-voltage switches, enabling subsequent interference elimination strategies to more accurately match actual operational scenarios. By subdividing operational scenarios into transient operational scenarios, grounding anomaly scenarios, and normal operation scenarios, the adaptability to different types of interference is improved, enhancing the targeting and effectiveness of interference elimination. Attached Figure Description

[0026] Figure 1 This is a flowchart illustrating a method for eliminating harmonic interference from a high-voltage switch in a coal mine, as described in this application.

[0027] Figure 2 This is another schematic diagram of a method for eliminating harmonic interference from a high-voltage switch in a coal mine, as described in this application.

[0028] Figure 3 This is another flowchart illustrating a method for eliminating harmonic interference from a high-voltage switch in a coal mine, as described in this application.

[0029] Figure 4This is a schematic diagram of the physical structure of a coal mine high-voltage switch harmonic interference elimination and filtering monitoring and protection device provided in the embodiments of this application. Detailed Implementation

[0030] The terminology used in the following embodiments of this application is for the purpose of describing particular embodiments only and is not intended to be limiting of this application. As used in the specification and appended claims of this application, the singular expressions “a,” “an,” “the,” “the,” “the,” and “this” are intended to include the plural expressions as well, unless the context clearly indicates otherwise. It should also be understood that the term “and / or” as used in this application refers to any or all possible combinations including one or more of the listed items.

[0031] Hereinafter, the terms "first" and "second" are used for descriptive purposes only and should not be construed as implying or suggesting relative importance or implicitly indicating the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature, and in the description of the embodiments of this application, unless otherwise stated, "multiple" means two or more.

[0032] First, let me describe the filtering monitoring and protection device provided in this application: This filtering monitoring and protection device is a high-voltage switch built-in monitoring and protection device with a sheet metal housing. The device adopts an integrated design with a sheet metal housing and can be directly embedded into the secondary chamber of the high-voltage switch. There is no need to add additional explosion-proof components. It directly relies on the explosion-proof structure of the high-voltage switch itself to achieve explosion protection. The overall hardware structure design is as follows:

[0033] 1. Sheet metal protective housing

[0034] Made of 304 stainless steel, with external dimensions of 150mm×120mm×50mm, and the surface is coated with insulating paint.

[0035] Functions: ① Mechanical protection; ② Internal compartment design to avoid electromagnetic interference between modules; ③ Reserved interface for current transformers.

[0036] 2. Multi-channel signal acquisition module

[0037] Three three-phase voltage transformers are installed on the secondary side terminal block of the switch PT and connected to the device via a 1m shielded cable.

[0038] Two phase current transformers are installed on the secondary side of the switch CT.

[0039] One zero-sequence voltage transformer is connected in parallel to the three-phase voltage neutral point.

[0040] One zero-sequence current transformer is installed on the neutral line of the switch.

[0041] Signal conditioning circuit: 7 independent conditioning channels, each containing: ① low-pass filter; ② instrumentation amplifier; ③ opto-isolator, to uniformly condition the signal to 0-5V for the processing unit.

[0042] 3. Adaptive Filtering and Protection Processing Module

[0043] (1) Core processor: STM32H747 microprocessor with a main frequency of 480MHz, supports 7-channel parallel data processing, integrates hardware floating-point unit, and the time for processing 7 signals in a single cycle is ≤0.5ms, providing hardware support for the rapid response of protection actions.

[0044] (2) Storage unit: Equipped with a 128MB Flash storage chip for stable storage of key data required for algorithm operation and protection judgment:

[0045] A pre-stored multi-channel harmonic feature library, containing model parameters for three-phase steady-state harmonics and zero-sequence interference, provides a data foundation for real-time interference sensing and reference signal generation.

[0046] Store protection setting parameters, such as overcurrent protection threshold, grounding resistance threshold, and harmonic distortion rate judgment threshold, to ensure the consistency and adjustability of protection logic judgment.

[0047] 4. The protection execution module is equipped with four JQX-10F relays, with a contact capacity of DC 24V / 5A and an operating time of ≤5ms, which can meet the requirements of "fast response + stable load" for the execution elements of high-voltage switches in coal mines. The four relays have clearly defined functions, respectively used to drive the high-voltage switch to trip, provide fault alarms, and lock out trips. Furthermore, the relays and the core processor adopt an optocoupler isolation design, effectively avoiding malfunctions caused by external electromagnetic interference, and further improving the reliability of protection execution.

[0048] The following example is used in conjunction with Figure 1 The following describes a method for eliminating harmonic interference from a high-voltage switch in a coal mine, as described in the embodiments of this application: Please refer to... Figure 1 This is a flowchart illustrating a method for eliminating harmonic interference from a high-voltage switch in a coal mine, as described in this application.

[0049] S101. The analog signal collected by the current transformer through the high-voltage switch is converted from analog to digital to obtain the original electrical parameter digital signal sequence at the same moment;

[0050] High-voltage switches are electrical devices used in power systems to connect or disconnect high-voltage circuits. Their rated voltage is typically above 1kV. Instrument transformers, including voltage transformers and current transformers, are used to convert the large voltage and current in high-voltage circuits into low-voltage and low-current analog signals suitable for instrumentation and relay measurement. Analog signals are signals that change continuously in both time and value. Analog-to-digital conversion (ADC) is the process of converting a time-continuous, amplitude-continuous analog signal into a time-discrete, amplitude-discrete digital signal. The original electrical parameter digital signal sequence refers to the set of voltage or current values ​​arranged in chronological order after analog-to-digital conversion, without any filtering. "Simultaneous moment" refers to data points acquired synchronously by all channels under the same sampling pulse trigger. The core of this step lies in using high-precision acquisition equipment to convert the physical electrical quantities in the coal mine underground power supply system into a discrete data stream that can be processed by a computer or microprocessor, laying the data foundation for subsequent harmonic analysis and interference removal.

[0051] One specific approach to this step is to employ multi-channel synchronous acquisition technology based on FPGA (Field-Programmable Gate Array). This technology utilizes the high-speed parallel processing capabilities of the FPGA to control multiple high-precision ADC chips to simultaneously sample the output signals of voltage and current transformers. The FPGA incorporates state machine logic to generate precise sampling clock signals, ensuring strict synchronization of sampling times across channels. The converted digital values ​​are then read into the FPGA's internal FIFO (First-In, First-Out) buffer via a parallel bus or LVDS interface. Another implementation method is to use a high-performance DSP (Digital Signal Processor) system with integrated multi-channel ADCs. Utilizing the DSP's integrated sample-and-hold circuitry and analog-to-digital converter module, and configuring a DMA (Direct Memory Access) controller, the conversion of multi-channel analog signals is automatically completed under timer interrupt triggering, and the results are directly transferred to a designated buffer in memory, reducing CPU intervention and achieving efficient data acquisition.

[0052] S102. Calculate the difference between adjacent sampling points of the zero-sequence current in the original electrical parameter digital signal sequence to obtain the abrupt change slope of the zero-sequence current.

[0053] Zero-sequence current refers to the phasor sum of the three-phase currents in a three-phase four-wire or three-phase three-wire circuit, and is commonly used to detect ground faults. The difference between adjacent sampling points refers to the numerical difference between the current sampled value and the previous sampled value in a discrete-time series; this difference reflects the amount of signal change within a unit sampling interval. The abrupt change slope is a measure of the rate of change of the signal; in this step, it specifically refers to the degree of rapid change of the zero-sequence current within a very short time. The calculation process involves performing first-order difference operations on the discrete data. This step aims to capture the high-frequency abrupt change characteristics in the zero-sequence current signal, because the zero-sequence current often exhibits drastic transient changes during high-voltage switch operation or when a fault occurs. Calculating the slope quantifies these transient characteristics, serving as an important basis for subsequent judgment of the high-voltage switch's operating scenario.

[0054] S103. Real-time reading of the switching status signal of the auxiliary contact of the high-voltage switch;

[0055] High-voltage switch auxiliary contacts refer to auxiliary contacts mechanically connected to the main contact shaft of a high-voltage circuit breaker or disconnector, whose opening and closing states maintain a strict logical correspondence with the main contacts. Switch status signals are digital signals with only two logical states, "0" and "1," representing the "open" and "closed" positions of the switch, respectively. Real-time reading refers to the control system continuously polling or acquiring this status signal at a very high frequency, or through interruption, to ensure that the state learned by the system maintains minimal time delay with the actual action of the physical switch. The purpose of this step is to introduce prior information at the physical level; the state reversal of the auxiliary contacts directly corresponds to the occurrence of a switching operation event, providing the most direct evidence to distinguish whether electromagnetic interference originates from switching operation or an external fault.

[0056] This step can be implemented using an opto-isolated input circuit combined with GPIO (General Purpose Input / Output) scanning technology. The auxiliary contacts of the high-voltage switch are connected in series in a 24V or 110V control circuit, which is connected to the input of an optocoupler. When the contacts are closed, the optocoupler conducts, outputting a low level; when the contacts are open, the optocoupler is cut off, outputting a high level. The microcontroller's GPIO pins are configured in input mode, and the pin level is periodically read using a timer interrupt to obtain the switch status. Another implementation method is to use industrial fieldbus communication for reading. If the high-voltage switch is equipped with an intelligent protection device, this device encodes the auxiliary contact status into a Modbus TCP or IEC 61850 message. The main control system uses an Ethernet or RS485 interface to parse the received message using a protocol stack, extracting the status bit information representing the switch position.

[0057] S104. Based on the original electrical parameter digital signal sequence, calculate the fundamental frequency of the three-phase voltage and the fundamental frequency of the zero-sequence voltage at the current moment.

[0058] The fundamental frequency of three-phase voltage refers to the frequency of the main components of the three-phase AC voltage in a power system, typically 50Hz or 60Hz for standard power frequencies. The fundamental frequency of zero-sequence voltage refers to the fundamental frequency of the zero-sequence voltage component that occurs during ground faults or unbalanced operation. The original digital signal sequence of electrical parameters contains the fundamental frequency as well as various higher harmonics and noise. Calculating the fundamental frequency involves extracting the periodic characteristics of the main energy components from the broadband signal. This step is crucial for the subsequent construction of the reference vector, as the construction of the reference vector depends on accurate phase and frequency information. If the frequency calculation is inaccurate, the generated orthogonal function pair will not be synchronized with the actual signal, resulting in a significant decrease in filtering effectiveness.

[0059] One specific method to implement this step is a frequency measurement algorithm based on zero-crossing detection. After applying a digital low-pass filter to the original digital voltage signal sequence to remove high-frequency interference, the moment the signal waveform crosses the zero axis from the negative half-cycle to the positive half-cycle is detected. The time interval between two consecutive rising edges crossing the zero point is recorded; the reciprocal of this interval is the current fundamental frequency. To improve accuracy, a moving average can be applied to the measured values ​​over multiple cycles. Another implementation method is to use digital phase-locked loop (NCO) technology. A closed-loop feedback system is constructed, including a phase detector, loop filter, and digitally controlled oscillator (NCO). The original voltage signal is compared in phase with the reference signal output by the NCO. The resulting error signal is filtered and used to control the frequency of the NCO, ensuring that the NCO's output frequency is tightly locked to the fundamental frequency of the input signal. The NCO's frequency control word represents the current fundamental frequency.

[0060] S105. Based on the fundamental frequency of the three-phase voltage and the fundamental frequency of the zero-sequence voltage, use trigonometric functions to generate orthogonal function pairs with unit amplitude to construct a basic reference vector.

[0061] Unit amplitude refers to the generated signal amplitude being normalized to 1. An orthogonal function pair refers to two mathematically orthogonal functions, typically a sine and a cosine function, which are 90 degrees out of phase. The fundamental reference vector is a vector sequence composed of these orthogonal function pairs, forming the input basis of the adaptive filter. Using the frequency calculated by S104 and the current sampling time, the phase angle can be calculated. The process of constructing the fundamental reference vector is essentially synthesizing a set of standard, clean signals with the same frequency as the grid voltage. This step is crucial for the adaptive harmonic detection algorithm because the adaptive filter needs a reference input correlated with the desired signal at its fundamental frequency to extract or cancel specific frequency components by adjusting the weights.

[0062] One way to implement this step is by combining a lookup table with linear interpolation. A high-resolution sine function table is pre-built in memory. Based on the calculated real-time phase angle, it is mapped to an index address in the table, and the corresponding sine and cosine values ​​are read. If the phase angle lies between two indices, linear interpolation is used to calculate the accurate function value, thus generating orthogonal function pairs. Another implementation method is to use the CORDIC (Coordinate Rotation Numerical Calculation) algorithm. This is an iterative algorithm that calculates trigonometric function values ​​using only shift and addition / subtraction operations. In FPGAs or microcontrollers that do not support hardware floating-point operations, the CORDIC algorithm core is used to directly output high-precision sine and cosine values ​​after a fixed number of iterative rotations based on the input phase angle parameters, forming a basic reference vector.

[0063] S106. When the operating scenario of the high-voltage switch is determined to be an operational transient scenario based on the switching status signal and the abrupt change slope of the zero-sequence current, a preset non-periodic DC component is superimposed on the basic reference vector to obtain the final interference reference vector; when the operating scenario of the high-voltage switch is determined to be a non-operation transient scenario based on the switching status signal and the abrupt change slope of the zero-sequence current, the basic reference vector is used as the final interference reference vector.

[0064] When the high-voltage switch is determined to be operating in a transient scenario based on the switching status signal and the abrupt change slope of the zero-sequence current, a preset aperiodic DC component is superimposed on the basic reference vector to obtain the final interference reference vector. Specifically, this involves: calling a preset arc decay time constant and a preset arc interference center frequency; calculating the arc amplitude envelope using a preset exponential decay function based on the time corresponding to the current sampling moment, where the exponent of the preset exponential decay function is composed of the negative of the ratio of time to the preset arc decay time constant; calculating the arc oscillation component using a sine function, where the frequency of the sine function is the preset arc interference center frequency; multiplying the arc amplitude envelope by the arc oscillation component and then by a preset arc interference amplitude coefficient to obtain the arc interference reference component during the transient operation period; and superimposing the arc interference reference component onto the basic reference vector to obtain the final interference reference vector under the transient operation scenario.

[0065] When the operating scenario of the high-voltage switch is determined to be a non-operational transient scenario based on the switching status signal and the abrupt change slope of the zero-sequence current, the basic reference vector is used as the final disturbance reference vector.

[0066] High-voltage switch operation scenarios are divided into operational transient scenarios and non-operational transient scenarios. Operational transient scenarios refer to the period when the switch performs opening and closing actions, resulting in an electric arc between the contacts and accompanied by a severe electromagnetic transient process; non-operational transient scenarios include normal stable operation or fault states not caused by switch operation. The preset aperiodic DC component refers to the combination of the attenuated DC component simulating arc characteristics and the high-frequency oscillation component. The core logic of this step is "scenario-driven reference vector reconstruction". In non-operational transients, the interference mainly comes from the background harmonics of the power grid, which the basic reference vector is sufficient to handle; however, in operational transients, the electric arc introduces nonlinear and aperiodic complex interference. At this time, it is necessary to artificially inject the arc model into the reference vector so that the adaptive filter can learn and eliminate this specific arc interference.

[0067] The specific implementation of the superimposed components in the transient operation scenario includes the following process: First, a preset arc decay time constant and a preset arc interference center frequency are called. Based on the current sampling time, the arc amplitude envelope is calculated using a preset exponential decay function, which describes the process of arc energy dissipation over time. Simultaneously, the arc oscillation component is calculated using a sine function. Then, the two are multiplied and multiplied by a preset amplitude coefficient to obtain the arc interference reference component during the transient operation. Finally, this component is superimposed onto the base reference vector generated in S105. For non-transient operation scenarios, the base reference vector in S105 is directly used as the final interference reference vector without any superposition.

[0068] One specific approach to this step is to employ a piecewise function generation technique based on a state machine. A state machine is defined in the software, and when an operational transient is detected, it enters the "arc generation" state. In this state, the floating-point unit of the DSP is used to approximate the exponential and sine functions through Taylor series expansion, or by calling standard mathematical library functions, to calculate the arc component value at each sampling point in real time and add it to the corresponding element of the base vector. Another implementation method is to use pre-stored waveform data playback technology. Arc interference waveform data during typical high-voltage switch operations is pre-acquired through offline simulation or actual measurement recording, normalized, and stored in Flash memory. When an operational transient is detected, this pre-stored data is read according to the current sampling rate, scaled proportionally according to the actual measured current amplitude, and then superimposed onto the base reference vector. This method has a low computational load and a fast response speed.

[0069] S107. Determine the step size coefficient of the preset adaptive filtering algorithm according to the operating scenario of the high-voltage switch;

[0070] The step size coefficient of the preset adaptive filtering algorithm is determined based on the operating scenario of the high-voltage switch. Specifically, this includes: constructing a multi-channel step size vector corresponding to three-phase voltage, two-phase current, zero-sequence voltage, and zero-sequence current; when the scenario is determined to be a transient operation, the elements corresponding to three-phase voltage and two-phase current in the multi-channel step size vector are set to preset first values, and the elements corresponding to zero-sequence voltage and zero-sequence current are set to preset second values; when the scenario is determined to be a grounding anomaly, the elements corresponding to three-phase voltage and two-phase current in the multi-channel step size vector are set to preset third values, and the elements corresponding to zero-sequence voltage and zero-sequence current are set to preset fourth values; when the scenario is determined to be a normal operation, the elements corresponding to three-phase voltage and two-phase current in the multi-channel step size vector are set to preset fifth values, and the elements corresponding to zero-sequence voltage and zero-sequence current are set to preset sixth values, with the preset second value, preset first value, preset fourth value, preset sixth value, preset third value, and preset fifth value decreasing in magnitude.

[0071] The step size coefficient is a key parameter in adaptive filtering algorithms, determining the magnitude and speed of filter weight vector updates. A larger step size results in faster convergence and stronger tracking capability, but also a larger steady-state error; a smaller step size leads to higher steady-state accuracy, but slower convergence. Multi-channel step size vectors refer to setting independent step size values ​​for different signal channels, such as three-phase voltage, two-phase current, zero-sequence voltage, and zero-sequence current. This step dynamically adjusts the step size of each channel based on the operating scenario determined in S106 to achieve the optimal balance between convergence speed and filtering accuracy. The zero-sequence component changes most drastically during operational transients, requiring the largest step size for rapid tracking; while the three-phase voltage is most stable during normal operation, using the smallest step size to ensure accuracy.

[0072] One way to implement this step is by using a lookup table index assignment method. A two-dimensional array or structure array is defined in the program's memory, with row indices corresponding to the three running scenarios and column indices corresponding to different signal channel groups. After the scenario determination logic outputs its result, the corresponding preset step size value is read directly from the array using the scenario ID as the index and assigned to the step size control variable of the adaptive filter. Another implementation method is using conditional branch logic assignment. A switch-case or if-else statement structure is used in the code to judge and execute the corresponding assignment operation one by one according to the current scenario flag. For example, if(scene==TRANSIENT){mu_zero=VAL2;mu_phase=VAL1;}. This method is logically intuitive, facilitates code maintenance, and allows for fine-tuning for specific conditions.

[0073] S108. Using the original electrical parameter digital signal sequence as the desired signal and the final interference reference vector as the input signal, the preset adaptive filtering algorithm is run using the step size coefficient to output the estimated interference signal.

[0074] Using the original digital signal sequence of electrical parameters as the desired signal and the final interference reference vector as the input signal, a preset adaptive filtering algorithm is run using a step size coefficient to output an estimated interference signal. Specifically, this includes: obtaining the adaptive filter weight vector at the current moment; calculating the inner product of the adaptive filter weight vector at the current moment and the final interference reference vector to obtain the estimated interference signal and outputting it; calculating the difference between the original digital signal sequence of electrical parameters and the estimated interference signal to obtain the prediction error; and correcting the adaptive filter weight vector at the current moment using the step size coefficient, the prediction error, and the final interference reference vector to obtain the adaptive filter weight vector at the next moment, which is used for the calculation and output of the estimated interference signal at the next moment.

[0075] The desired signal refers to the observed signal containing the information to be extracted and interference noise, i.e., the original digital signal sequence of electrical parameters acquired in S101. The input signal refers to the reference signal related to the interference source, i.e., the final interference reference vector constructed in S106. The adaptive filter weight vector is a set of adjustable coefficients used to perform a weighted summation of the input signal. The estimated interference signal is the output of the filter, which attempts to simulate the interference components in the original signal. The prediction error is the difference between the desired signal and the estimated interference signal. This step is the core computational link of the entire interference removal method, and its specific process includes: first, obtaining the current weight vector W(n); calculating the inner product y(n) = W^T(n)X(n) of the weight vector and the input vector X(n) to obtain the estimated interference signal y(n); calculating the error e(n) = d(n) - y(n), where d(n) is the original signal; finally, using the update formula of the LMS (Least Mean Square) algorithm, the weights are corrected using the step size coefficient and error information to prepare for the calculation at the next time step.

[0076] This step can be implemented using the standard LMS adaptive filtering algorithm. In the multiply-accumulate unit of the DSP or FPGA, vector dot product, error subtraction, and vector update operations are performed strictly according to the LMS algorithm formula. This method is simple in structure, has low computational complexity, and is easy to implement in hardware. Another implementation method is to use the normalized LMS algorithm. The standard LMS algorithm is sensitive to changes in the power of the input signal, which may lead to stability issues.

[0077] S109. The difference between the original electrical parameter digital signal sequence and the estimated interference signal is used as the output of the purified electrical parameter signal.

[0078] The purified electrical parameter signal refers to a signal that has been processed to remove harmonic interference and transient operational interference, primarily retaining the fundamental component and true fault characteristic information. The difference operation is the final step in the adaptive interference cancellation principle. In S108, the adaptive filter has adjusted its weights to make the output estimated interference signal as close as possible to the interference components in the original signal. Therefore, subtracting this estimated interference signal from the original signal, the remaining residual is theoretically the pure signal we need. The output of this step will be directly provided to subsequent relay protection logic, metering modules, or fault diagnosis systems.

[0079] In the above embodiments, by establishing an operation scenario discrimination mechanism based on switch state and zero-sequence current abrupt change slope, a non-periodic DC component is specifically superimposed on the basic reference vector in the transient operation scenario, making the final interference reference vector more accurately reflect the actual interference characteristics of the high-voltage switch under the transient operation. Simultaneously, by employing differentiated adaptive filtering algorithm step size coefficients for different operation scenarios—using a larger step size in the transient operation scenario to improve the algorithm's convergence speed, and a smaller step size in the non-transient operation scenario to ensure filtering accuracy—the adaptive filtering algorithm can better adapt to the changing interference characteristics of the high-voltage switch under different operation scenarios. This scenario-based adaptive reference vector construction method and step size adjustment strategy improve the elimination effect of harmonic interference in electrical parameter signals and reduce the degree of distortion and falsification during signal processing.

[0080] Based on the operational scenario discrimination mechanism of the above embodiments, the specific implementation process of this application in scenario recognition is further described below. By refining the technical solution for scenario recognition, the operating status of high-voltage switches can be classified more accurately, thereby providing a more precise scenario basis for subsequent interference elimination. The following section combines... Figure 2 Another method for eliminating harmonic interference from high-voltage switches in coal mines, as described in the embodiments of this application, is as follows: Please refer to... Figure 2 This is another flowchart illustrating a method for eliminating harmonic interference from a high-voltage switch in a coal mine, as described in this application.

[0081] S201. Real-time monitoring of the on / off status of auxiliary contacts of high-voltage switch;

[0082] Real-time monitoring refers to the continuous observation and recording of a target object with extremely high temporal resolution and continuity. This monitoring is typically at the millisecond or even microsecond level to ensure that no instantaneous changes are missed. High-voltage switch auxiliary contacts are auxiliary electrical contacts in high-voltage switchgear used to reflect the position and state of the main contacts. They typically include normally open and normally closed contacts, and their mechanical linkage mechanism ensures that their state changes are strictly synchronized with the actions of the main contacts. On / off state refers to the conduction or disconnection of a contact in a circuit, corresponding to "1" or "0" in binary logic, or "closed" or "open" in physical states. In this step, real-time monitoring of the on / off state of the high-voltage switch auxiliary contacts means continuously acquiring the electrical signals of the auxiliary contacts through hardware interfaces or sensor networks and converting them into digital signals for processor analysis. This process not only includes reading the current state but also implicitly involves accurately capturing the moments of state changes. The monitoring system needs to have high anti-interference capabilities to adapt to the complex electromagnetic environment of underground coal mines.

[0083] S202. If it is determined that the auxiliary contact has been detected to have a state flip, then it is determined that the current moment is in an operation transient scenario.

[0084] Detection refers to the process of confirming whether an input signal meets specific conditions through a specific algorithm or logical judgment. Auxiliary contact state reversal refers to the instantaneous process of the auxiliary contact's logical state changing from "on" to "off," or from "off" to "on," which typically corresponds to the main contacts of a high-voltage switch performing a closing or opening action. Judgment refers to the process of drawing conclusions based on the detection results and preset logical rules. The current moment refers to the point in time when the system detects the state change and the subsequent extremely short time window. An operational transient scenario refers to a specific time period during which the circuit parameters undergo drastic nonlinear changes due to physical phenomena such as arc reignition and contact bounce during the mechanical operation of a high-voltage switch. In this step, once the system detects a 0-to-1 or 1-to-0 transition in the auxiliary contact signal, the system immediately marks the current operating state as an operational transient scenario. This logic is based on the fact that the reversal of the auxiliary contact is a direct physical result of the high-voltage switch's action, with extremely high temporal synchronization, thus serving as an absolute trigger condition for judging the occurrence of an operational transient. Defining this moment as an operational transient scenario is to enable subsequent specialized handling measures for the unique high-frequency transient interference in this scenario, and to avoid misjudging it as a fault signal.

[0085] There are two main methods for detecting auxiliary contact state reversals and determining transient operation scenarios. The first method is based on an edge-triggered detection algorithm. In the microprocessor's software logic, a variable is set to store the contact state of the previous sampling period. In each new sampling period, the current contact state is read and XORed with the stored previous state. If the XOR result is 1, it indicates that the state has reversed. At this time, the system records the current timestamp and sets a flag bit, indicating entry into "transient operation mode." This mode lasts for a preset time window, the width of which is set according to the mechanical characteristic parameters of the high-voltage switch, covering the entire opening and closing transient process. The second method is a state machine-based detection method. A finite state machine is constructed, containing states such as "steady-state opening," "steady-state closing," "opening in progress," and "closing in progress." The system drives the state machine to transition states based on the input auxiliary contact signal. When the input signal changes, the state machine transitions from the steady state to the corresponding in-process state, at which point the system outputs a determination of the transient operation scenario. The state machine can contain a timer to automatically return to a steady state after an action is completed, or to return to a steady state after detecting current and voltage.

[0086] S203. If it is determined that the auxiliary contact state remains stable, then determine whether the slope of the zero-sequence current change exceeds the preset ground change threshold.

[0087] The auxiliary contact state remaining stable means that the logic state of the auxiliary contact remains consistent across multiple consecutive sampling periods, without any flipping or jittering. This indicates that the high-voltage switch is in a static closed-operation or open-standby state, without any mechanical operation. Zero-sequence current refers to the vector sum of the three-phase currents, which should be zero in an ideal balanced system. However, it can exhibit a non-zero value when a ground fault occurs or when current is present due to three-phase parameter imbalance. The abrupt change slope refers to the rate of change of a signal per unit time, usually obtained by dividing the difference between the current sampled value and the previous sampled value by the sampling time interval. It reflects the drastic degree of signal change. The preset ground fault threshold is a numerical limit derived through theoretical calculation or empirical statistics, used to distinguish between normal signal fluctuations and signal abrupt changes caused by faults. This threshold is not fixed and can be adjusted based on parameters such as the grid voltage level and system capacitance current. In this step, the system first eliminates the possibility of operational transients, confirming that the switch is in a steady state. Under this premise, the system then focuses on changes in electrical quantities, especially the characteristics of zero-sequence current changes.

[0088] S204. When the slope of the sudden change of the zero-sequence current is greater than or equal to the grounding sudden change threshold, it is determined that the current moment is in a grounding abnormal scenario, and the grounding abnormal scenario belongs to the non-operational transient scenario.

[0089] A ground fault threshold greater than or equal to the ground fault change threshold means that the calculated rate of change of the zero-sequence current is mathematically not less than a pre-set critical value, which logically constitutes a sufficient condition for triggering an anomaly determination. A ground fault scenario refers to a specific operating state in a power system where a single-phase ground fault or similar insulation breakdown event causes a large jump in the zero-sequence current within a very short time. This scenario differs from normal load fluctuations, characterized by the suddenness and non-periodicity of the current change. Classifying it as a non-operational transient scenario is a classification logic that clarifies that although a ground fault is also a "transient" change, it is not caused by switching operations. Therefore, in subsequent signal processing, it cannot be simply filtered out as operational interference but should be retained as a fault characteristic or subject to special fault handling. In this step, the system formally establishes the current system state based on the comparison results from the previous step. Once the slope exceeds the threshold, the system logic immediately locks the "ground fault" status flag.

[0090] S205. When the slope of the zero-sequence current change is less than the ground change threshold, it is determined that the current moment is in the normal operation scenario, and the normal operation scenario belongs to the non-operational transient scenario.

[0091] A value below the ground fault threshold refers to a low rate of change in the zero-sequence current. Such minor fluctuations are typically caused by normal load adjustments in the power grid, slight drift due to three-phase imbalance, or inherent noise in the measurement system. Normal operation refers to a state where high-voltage switches are either closed or open, and grid parameters are stable, with no switching operations or electrical faults occurring. This is the state the power system is in most of the time. Classifying the scenario as non-operational transient is also part of the classification logic, distinguishing normal operation from operational transients and ground faults. In this step, as the final branch of the logical judgment, after ruling out operational transients and ground faults, the remaining situation naturally falls under normal operation.

[0092] In the above embodiments, a complete operational scenario identification mechanism was constructed by real-time monitoring of the on / off state changes of the auxiliary contacts of the high-voltage switch and the abrupt change slope of the zero-sequence current. By comparing the abrupt change slope of the zero-sequence current with a preset grounding abrupt change threshold, grounding anomaly scenarios were identified. This multi-dimensional scenario identification method improves the accuracy of identifying various operational states of the high-voltage switch, enabling subsequent interference elimination strategies to more accurately match actual operational scenarios. By subdividing operational scenarios into transient operational scenarios, grounding anomaly scenarios, and normal operation scenarios, the adaptability to different types of interference is improved, enhancing the targeting and effectiveness of interference elimination.

[0093] Based on the aforementioned scene recognition mechanism, this application also provides another method for eliminating harmonic interference from high-voltage switches in coal mines. By further analyzing and processing the purified electrical parameter signals, real-time monitoring and protection control of the system's operating status are achieved, making the entire technical solution a complete closed loop from signal acquisition and interference elimination to protection control.

[0094] The following is combined Figure 3 This application describes another method for eliminating harmonic interference from high-voltage switches in coal mines: Please refer to [link to relevant documentation]. Figure 3 This is another flowchart illustrating a method for eliminating harmonic interference from a high-voltage switch in a coal mine, as described in this application.

[0095] S301. Based on the purified electrical parameter signal, the sum of squares is accumulated and averaged within one fundamental frequency period, and then the square root operation is performed to calculate the effective values ​​of three-phase voltage, three-phase current, zero-sequence voltage, and zero-sequence current.

[0096] Purified electrical parameter signals refer to pure digital signal sequences that have undergone preliminary processing to remove high-frequency noise, random interference, and harmonic components of specific frequency bands. They contain the fundamental frequency and main characteristic components reflecting the true operating state of the power grid. The fundamental period refers to the time required for one complete cycle of change in the AC power grid's voltage or current. In my country's standard power grid frequency of 50Hz, the theoretical fundamental period is 20 milliseconds. Sum of squares refers to the mathematical process of squaring the values ​​of discrete sampling points and then summing all the results; this is a fundamental step in calculating energy or power. Averaging involves dividing the accumulated sum by the number of sampling points to obtain the average energy density per unit time. Square root calculation involves calculating the arithmetic square root of the average value to obtain the effective value (RMS). The RMS value is the equivalent DC value that measures the AC electrothermal effect and is the most critical parameter in power system protection and metering. The RMS values ​​of three-phase voltage and three-phase current correspond to the voltage and current amplitude characteristics of phases A, B, and C, respectively. The RMS values ​​of zero-sequence voltage and zero-sequence current are key indicators reflecting system grounding faults or imbalances. In this step, the system utilizes digital signal processing technology to calculate the voltage, current, and zero-sequence component of each phase point by point. This process not only involves data statistics but also transforms the discrete waveform in the time domain into steady-state values ​​that can be used for logical judgment. Since the input signal has been purified to eliminate glitches and atypical interference, the calculated effective values ​​more accurately reflect the load level and insulation status of the primary equipment, avoiding artificially high effective values ​​caused by high-frequency noise. This provides accurate data support for subsequent overcurrent and grounding protection.

[0097] S302. Extract the fundamental amplitude and the preset first to second harmonic amplitudes from the purified electrical parameter signal;

[0098] The fundamental frequency amplitude and the harmonic amplitudes of preset first to second orders are extracted from the purified electrical parameter signal. The preset first order is smaller than the preset second order. Extraction refers to the process of separating specific frequency components from a complex, mixed signal and quantifying their intensity. The fundamental frequency amplitude is the maximum value of the sinusoidal component in the signal with the same frequency as the power grid frequency; it is the main carrier of electrical energy. The harmonic amplitude is the maximum value of the sinusoidal component whose frequency is an integer multiple of the fundamental frequency. The preset first and second orders are two positive integer thresholds used to define the harmonic frequency range to be analyzed, with the first order being smaller than the second order. For example, the first order can be set to 2, and the second order to 21, meaning the range from the 2nd to the 21st harmonic can be analyzed. This range is usually determined based on the spectral characteristics of the main interference sources at the coal mine site. In this step, the system analyzes the spectral structure of the purified electrical parameter signal in depth. Although the signal has undergone preliminary purification, certain harmonics of specific orders may be retained because they have fault indication significance or are difficult to remove by simple filtering. By extracting the harmonic amplitudes of these specific frequency bands, the system can distinguish between normal load currents and nonlinear load currents containing abundant harmonics, or identify specific fault characteristics. This step is a prerequisite for calculating the total harmonic distortion rate and also forms the data foundation for achieving refined protection and control.

[0099] There are two main methods for extracting the fundamental frequency and specified harmonic amplitudes. The first method utilizes the Fast Fourier Transform (FFT) algorithm. After windowing the purified signal data for one or more fundamental frequency periods, an FFT operation is performed to convert the time-domain signal into a frequency-domain spectrum. The magnitude of the spectral line corresponding to the fundamental frequency is directly read as the fundamental amplitude, and the magnitudes of each spectral line corresponding to the first to second harmonic orders are read according to the frequency index as harmonic amplitudes. This method can obtain the amplitude information of all frequencies of interest at once. The second method uses a digital bandpass filter bank or a generalized discrete Fourier transform (DFT). If the harmonic orders of interest are few and discrete, a set of infinite impulse response (IR) or finite impulse response (FIR) bandpass filters with center frequencies of the fundamental frequency and each harmonic frequency can be designed. The purified signal is passed through these filters in parallel, and the peak value of the output signal is the amplitude of the corresponding frequency.

[0100] S303. Calculate the ratio of the sum of squares of all harmonic amplitudes to the square of the fundamental amplitude, and then perform a square root operation on the ratio to obtain the total harmonic distortion rate.

[0101] Total Harmonic Distortion (THD) is a dimensionless physical quantity used to quantitatively describe the degree of distortion of a waveform relative to a pure sine wave. It is the ratio of the root of the square of the effective values ​​of all harmonic components to the effective value of the fundamental component, usually expressed as a percentage. The sum of squares of all harmonic amplitudes is calculated by squaring each of the preset first to second order harmonic amplitudes extracted in step S302 and then summing these squared values. The square of the fundamental amplitude is calculated by multiplying the fundamental amplitude by itself. The ratio operation divides the sum of the squares of the harmonics by the square of the fundamental amplitude. The square root operation takes the arithmetic square root of the ratio result. In this step, the system rigorously calculates the THD value according to the mathematical definition. This indicator directly reflects the quality of the current power grid and the degree of pollution to the system by nonlinear loads. In high-voltage power supply systems in coal mines, excessively high THD can not only lead to equipment overheating and insulation aging but may also cause malfunctions in relay protection devices. By calculating THD in real time, the system can determine whether the current increase is caused by a pure short-circuit fault or by harmonic sources such as inverter startup, thus providing a basis for subsequent protection logic to make decisions on "harmonic blocking" or "time extension".

[0102] S304. When the effective value of the three-phase current is determined to be greater than or equal to a preset multiple of the rated current, the basic operating time is calculated using the inverse time characteristic formula.

[0103] The effective value of the three-phase current refers to the RMS value of the three-phase currents A, B, and C calculated in step S301. The preset multiple of the rated current is the threshold value for initiating overcurrent protection, typically set to 1.1 times, 1.2 times, etc., of the rated current, used to distinguish between normal overload and fault current. The inverse-time characteristic means that the operating time of the protection device is inversely proportional to the magnitude of the current flowing through it; that is, the larger the current, the shorter the operating time, and the smaller the current, the longer the operating time. This characteristic simulates the thermal accumulation process of electrical equipment, aiming to allow short-term initiation or overload current to pass through while protecting the equipment from thermal damage. The basic operating time is the theoretical tripping delay calculated according to the standard inverse-time curve formula. In this step, the system first compares the real-time current with the setting value; once an overcurrent is confirmed, the inverse-time algorithm is immediately invoked. This step reflects the selectivity and sensitivity of the protection, ensuring rapid disconnection in the event of a severe short circuit, while allowing sufficient time for the fault to disappear on its own or for operators to handle minor overloads; it is the core component of the high-voltage switch protection logic in coal mines.

[0104] There are two main methods for calculating the basic operating time using the inverse-time characteristic formula. The first method is the lookup table interpolation method. An inverse-time characteristic curve table is pre-stored in the microcontroller's non-volatile memory. This table uses the current multiple as an index and the corresponding operating time as the value. When an overcurrent is detected, the current multiple is calculated, the two nearest nodes are found in the table, and the accurate basic operating time is calculated through linear interpolation. This method is extremely fast and avoids complex exponential calculations. The second method is the real-time analytical calculation method. Standard inverse-time equations conforming to IEC60255 or IEEE standards are directly written into the program. Utilizing the high-performance floating-point arithmetic capabilities of the microcontroller, the current effective current value and preset time multiples and curve constants are input in real-time for calculation.

[0105] S305. If the total harmonic distortion rate is greater than or equal to the preset distortion rate, the basic motion time is extended by a preset ratio and then used as the final motion time.

[0106] The preset distortion rate is a threshold used to determine whether the current waveform is severely polluted by harmonics. The preset ratio is a coefficient greater than 0 used to determine the degree of delay. Extending the basic operating time by the preset ratio means multiplying the time calculated by S304 by a coefficient greater than 1, thereby delaying the occurrence of the protection action. The final operating time is the actual execution delay after correction. In this step, the system introduces the concept of harmonic blocking or harmonic braking. In coal mine environments, operations such as starting large motors and closing transformers under no-load conditions are often accompanied by large inrush currents and high harmonic distortion rates. If inverse-time protection is performed solely based on the current amplitude, false tripping is very likely. However, although the current in these operating conditions is large, the duration is short and the fault is not permanent. By detecting THD, if severe current distortion is found, the system infers that this may not be a pure metallic short circuit, but rather caused by some kind of operational transient or nonlinear load.

[0107] S306. Issue an overcurrent protection command based on the final action time;

[0108] The final action time is the protection delay value after harmonic correction. The overcurrent protection command is an electrical control signal issued by the microcontroller to the operating mechanism of the high-voltage switch, typically manifested as driving a relay to close or outputting a high-level pulse. Issuing the command signifies the end of the protection logic flow and the beginning of the actuator's action. In this step, the system enters a countdown or comparison state. The system continuously monitors whether the fault conditions are still met. If the fault disappears before the final action time arrives, the timer is reset, and no command is issued; if the fault persists until the time expires, the system decisively issues a trip signal to disconnect the faulty circuit. This step is the interface between the protection algorithm and the physical action, requiring extremely high reliability and real-time performance; any delay or jitter may affect the protection effect.

[0109] S307. When it is determined that the effective value of the zero-sequence current is greater than or equal to the preset current value and the effective value of the zero-sequence voltage is greater than or equal to the preset voltage value, a grounding protection command shall be issued within a preset time period.

[0110] The effective values ​​of zero-sequence current and zero-sequence voltage are characteristic quantities reflecting ground faults calculated in step S301. The preset current and voltage values ​​are the setting thresholds for activating ground fault protection. The preset duration is the operating delay of the ground fault protection, usually short, used to avoid instantaneous electromagnetic interference. Issuing a ground fault protection command means driving the switch to trip or issuing a ground fault alarm signal. In this step, a dual criterion of "zero-sequence voltage" and "zero-sequence current" is used. In coal mine systems where the neutral point is ungrounded or grounded via an arc suppression coil, a single-phase ground fault will cause a rise in zero-sequence voltage, and capacitive current will also flow through non-faulty lines. It is often difficult to accurately determine the faulty line based solely on zero-sequence current or zero-sequence voltage. This step requires both to exceed the limits simultaneously, essentially forming the prototype of directional ground fault protection or high-sensitivity ground fault protection. Protection is only activated when the system exhibits a significant zero-sequence voltage and a large zero-sequence current flows through the line. This dual criterion significantly improves the accuracy of ground fault location and reduces false alarms.

[0111] In the above embodiments, the effective value of the purified electrical parameter signal is calculated and harmonic analysis is performed. The effective values ​​of each phase voltage and current are obtained by averaging and then taking the square root of the sum of squares within one fundamental period. The amplitudes of the fundamental wave and each harmonic are extracted to calculate the total harmonic distortion rate, thus improving the accuracy of the power quality assessment indicators. Because the purified electrical parameter signal is used for analysis and calculation, the impact of various interferences on power quality assessment is reduced, improving the reliability of the effective value calculation and harmonic analysis results. The periodic accumulation calculation method reduces the impact of sampling noise on the assessment results, enhancing the anti-interference capability of the power quality assessment.

[0112] The filtering monitoring and protection device in the embodiments of this invention is described below from the perspective of hardware processing. Please refer to [link / reference needed]. Figure 4 This is a schematic diagram of the physical structure of a coal mine high-voltage switch harmonic interference elimination and filtering monitoring and protection device provided in the embodiments of this application.

[0113] It should be noted that, Figure 4 The structure of the filter monitoring and protection device shown is merely an example and should not impose any limitations on the functionality and scope of use of the embodiments of the present invention.

[0114] like Figure 4As shown, the filtering monitoring and protection device includes a Central Processing Unit (CPU) 401, which can perform various appropriate actions and processes according to a program stored in Read-Only Memory (ROM) 402 or a program loaded from storage section 408 into Random Access Memory (RAM) 403, such as executing the method described in the above embodiment. The RAM 403 also stores various programs and data required for the operation of the filtering monitoring and protection device. The CPU 401, ROM 402, and RAM 403 are interconnected via a bus 404. An input / output (I / O) interface 405 is also connected to the bus 404.

[0115] The following components are connected to I / O interface 405: input section 406 including a camera, infrared sensor, etc.; output section 407 including a liquid crystal display (LCD) and speakers, etc.; storage section 408 including a hard disk, etc.; and communication section 409 including a network interface card such as a LAN (Local Area Network) card and a modem, etc. Communication section 409 performs communication processing via a network such as the Internet. Drive 410 is also connected to I / O interface 405 as needed. Removable media 411, such as a disk, optical disk, magneto-optical disk, semiconductor memory, etc., are installed on drive 410 as needed so that computer programs read from it can be installed into storage section 408 as needed.

[0116] In particular, according to embodiments of the present invention, the processes described above with reference to the flowcharts can be implemented as computer software programs. For example, embodiments of the present invention include a computer program product comprising a computer program carried on a computer-readable medium, the computer program containing computer programs for performing the methods shown in the flowcharts. In such embodiments, the computer program can be downloaded and installed from a network via communication section 409, and / or installed from removable medium 411. When the computer program is executed by central processing unit (CPU) 401, it performs the various functions defined in the present invention.

[0117] It should be noted that the computer-readable medium shown in the embodiments of the present invention can be a computer-readable signal medium or a computer-readable storage medium, or any combination thereof. A computer-readable storage medium can be, for example,—but not limited to—an electrical, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or any combination thereof. More specific examples of a computer-readable storage medium may include, but are not limited to: an electrical connection having one or more wires, a portable computer disk, a hard disk, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM), flash memory, optical fiber, portable compact disc read-only memory (CD-ROM), optical storage device, magnetic storage device, or any suitable combination thereof. In the present invention, a computer-readable storage medium can be any tangible medium containing or storing a program that can be used by or in conjunction with an instruction execution system, apparatus, or device. In the present invention, a computer-readable signal medium can include a data signal propagated in baseband or as part of a carrier wave, wherein a computer-readable computer program is carried. The transmitted data signal can take many forms, including but not limited to electromagnetic signals, optical signals, or any suitable combination thereof.

[0118] The flowcharts and block diagrams in the accompanying drawings illustrate the architecture, functions, and operations of possible implementations of filtering monitoring and protection devices, methods, and computer program products according to various embodiments of the present invention. Each block in a flowchart or block diagram may represent a module, program segment, or portion of code, which contains one or more executable instructions for implementing a specified logical function. It should also be noted that in some alternative implementations, the functions indicated in the blocks may occur in a different order than those indicated in the drawings. For example, two consecutively indicated blocks may actually be executed substantially in parallel, or they may sometimes be executed in reverse order, depending on the functions involved. It should also be noted that each block in a block diagram or flowchart, and combinations of blocks in a block diagram or flowchart, can be implemented using a dedicated hardware-based filtering monitoring and protection device that performs the specified function or operation, or using a combination of dedicated hardware and computer instructions.

[0119] In another aspect, the present invention also provides a computer-readable storage medium, which may be included in the filtering monitoring and protection device described in the above embodiments; or it may exist independently and not assembled into the filtering monitoring and protection device. The storage medium carries one or more computer programs that, when executed by a processor of a filtering monitoring and protection device, cause the filtering monitoring and protection device to implement the methods provided in the above embodiments.

[0120] The above-described embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit it. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

[0121] As used in the above embodiments, depending on the context, the term "when..." can be interpreted as "if...", "after...", "in response to determining...", or "in response to detecting...". Similarly, depending on the context, the phrase "when determining..." or "if (the stated condition or event) is interpreted as "if determining...", "in response to determining...", "when (the stated condition or event) is detected", or "in response to detecting (the stated condition or event)".

[0122] In the above embodiments, implementation can be achieved entirely or partially through software, hardware, firmware, or any combination thereof. When implemented using software, it can be implemented entirely or partially in the form of a computer program product. The computer program product includes one or more computer instructions. When the computer program instructions are loaded and executed on a computer, all or part of the processes or functions described in the embodiments of this application are generated. The computer can be a general-purpose computer, a special-purpose computer, a computer network, or other programmable device. The computer instructions can be stored in a computer-readable storage medium or transmitted from one computer-readable storage medium to another. For example, the computer instructions can be transmitted from one website, computer, server, or data center to another website, computer, server, or data center via wired (e.g., coaxial cable, fiber optic, digital subscriber line) or wireless (e.g., infrared, wireless, microwave, etc.) means. The computer-readable storage medium can be any available medium that a computer can access or a data storage device such as a server or data center that integrates one or more available media. The available medium can be a magnetic medium (e.g., floppy disk, hard disk, magnetic tape), an optical medium (e.g., DVD), or a semiconductor medium (e.g., solid-state drive), etc.

[0123] Those skilled in the art will understand that all or part of the processes in the methods of the above embodiments can be implemented by a computer program instructing related hardware. This program can be stored in a computer-readable storage medium, and when executed, it can include the processes described in the above method embodiments. The aforementioned storage medium includes various media capable of storing program code, such as ROM or random access memory (RAM), magnetic disks, or optical disks.

Claims

1. A method for eliminating harmonic interference of a high-voltage switch in a coal mine, characterized in that, The method comprises the following steps: analog signals collected by a mutual inductor of a high-voltage switch are converted into digital signals to obtain a sequence of original electric parameter digital signals at the same time; a difference between adjacent sampling points of zero sequence current in the sequence of original electric parameter digital signals is calculated to obtain a mutation slope of the zero sequence current; a switching quantity state signal of an auxiliary contact of the high-voltage switch is read in real time; a fundamental frequency of three-phase voltage and a fundamental frequency of zero sequence voltage at the current time are calculated based on the sequence of original electric parameter digital signals; a basic reference vector is constructed by using a set of orthogonal functions with unit amplitude generated by a trigonometric function based on the fundamental frequency of three-phase voltage and the fundamental frequency of zero sequence voltage; in a case where it is determined according to the switching quantity state signal and the mutation slope of the zero sequence current that an operation scene of the high-voltage switch is an operating transient scene, a preset non-periodic direct current component is superimposed in the basic reference vector to obtain a final interference reference vector; in a case where it is determined according to the switching quantity state signal and the mutation slope of the zero sequence current that the operation scene of the high-voltage switch is a non-operating transient scene, the basic reference vector is taken as the final interference reference vector; a step coefficient of a preset adaptive filtering algorithm is determined according to the operation scene of the high-voltage switch, and the step coefficient in the operating transient scene is greater than the step coefficient in the non-operating transient scene; the sequence of original electric parameter digital signals is taken as an expected signal, the final interference reference vector is taken as an input signal, and the preset adaptive filtering algorithm is run by using the step coefficient to output an estimated interference signal; a difference between the sequence of original electric parameter digital signals and the estimated interference signal is taken as a purified electric parameter signal and output.

2. The method of claim 1, wherein, After the step of constructing the basic reference vector by using the set of orthogonal functions with unit amplitude generated by the trigonometric function based on the fundamental frequency of three-phase voltage and the fundamental frequency of zero sequence voltage, the method further comprises the following steps: a state of the auxiliary contact of the high-voltage switch is monitored in real time; in a case where it is determined that the state of the auxiliary contact is detected to be reversed, it is determined that the current time is in the operating transient scene; in a case where it is determined that the state of the auxiliary contact is detected to be stable, it is determined whether the mutation slope of the zero sequence current exceeds a preset ground fault mutation threshold; in a case where the mutation slope of the zero sequence current is greater than or equal to the ground fault mutation threshold, it is determined that the current time is in a ground fault scene, and the ground fault scene belongs to the non-operating transient scene; in a case where the mutation slope of the zero sequence current is less than the ground fault mutation threshold, it is determined that the current time is in a normal operation scene, and the normal operation scene belongs to the non-operating transient scene.

3. The method according to claim 1 or 2, characterized in that, The step of determining the step coefficient of the preset adaptive filtering algorithm according to the operation scene of the high-voltage switch specifically comprises the following steps: a multi-channel step vector corresponding to three-phase voltage, two-phase current, zero sequence voltage and zero sequence current is constructed; in a case where it is determined that the operating transient scene, elements corresponding to the three-phase voltage and the two-phase current in the multi-channel step vector are set to a preset first value, and elements corresponding to the zero sequence voltage and the zero sequence current are set to a preset second value. When it is determined that the ground fault scene, the elements corresponding to the three-phase voltage and the two-phase current in the multi-channel step vector are set to a preset third value, and the elements corresponding to the zero sequence voltage and the zero sequence current are set to a preset fourth value; When it is determined that the normal operation scene, the elements corresponding to the three-phase voltage and the two-phase current in the multi-channel step vector are set to a preset fifth value, and the elements corresponding to the zero sequence voltage and the zero sequence current are set to a preset sixth value, the preset second value, the preset first value, the preset fourth value, the preset sixth value, the preset third value and the preset fifth value decrease in size.

4. The method of claim 1, wherein, The preset non-periodic direct current component is superimposed in the basic reference vector to obtain a final interference reference vector, and the method specifically comprises: a preset arc decay time constant and a preset arc interference center frequency are called; an arc amplitude envelope is calculated based on the time corresponding to the current sampling time, and an exponential part of a preset exponential decay function is composed of a negative number of a ratio of the time to the preset arc decay time constant; an arc oscillation component is calculated by using a sine function, and a frequency of the sine function is the preset arc interference center frequency; the arc amplitude envelope and the arc oscillation component are multiplied, and multiplied by a preset arc interference amplitude coefficient to obtain an arc interference reference component in an operating transient period; the arc interference reference component is superimposed into the basic reference vector to obtain the final interference reference vector in the operating transient scene.

5. The method of claim 1, wherein, The original electric parameter digital signal sequence is taken as an expected signal, the final interference reference vector is taken as an input signal, the preset adaptive filtering algorithm is run by using the step coefficient, and an estimated interference signal is outputted, and the method specifically comprises: an adaptive filter weight vector of the current time is obtained; an inner product of the adaptive filter weight vector of the current time and the final interference reference vector is calculated to obtain the estimated interference signal and output the estimated interference signal; a difference between the original electric parameter digital signal sequence and the estimated interference signal is calculated to obtain a prediction error; the adaptive filter weight vector of the current time is corrected by using the step coefficient, the prediction error and the final interference reference vector to obtain an adaptive filter weight vector of a next time, so as to be used for calculation and output of an estimated interference signal of the next time.

6. The method of claim 1, wherein, After the difference between the original electric parameter digital signal sequence and the estimated interference signal is taken as a purified electric parameter signal and outputted, the method further comprises: based on the purified electric parameter signal, a square sum is accumulated and averaged in one fundamental period, and then square root operation is performed to calculate three-phase voltage effective values, three-phase current effective values, zero sequence voltage effective values and zero sequence current effective values; fundamental amplitudes in the purified electric parameter signal and harmonic amplitudes of preset first times to preset second times are extracted, and the preset first times are less than the preset second times; a ratio of a square sum of all the harmonic amplitudes to a square of the fundamental amplitude is calculated, and square root operation is performed on the ratio to obtain a total harmonic distortion rate.

7. The method of claim 6, wherein, After the total harmonic distortion rate is obtained, the method further comprises: In a case where the three-phase current effective value is greater than or equal to a preset multiple of the rated current, calculating a basic action time by using an inverse time limit characteristic formula; In a case where the total harmonic distortion rate is greater than or equal to a preset distortion rate, extending the basic action time by a preset proportion to obtain a final action time; Issuing an overcurrent protection instruction according to the final action time; In a case where the zero sequence current effective value is greater than or equal to a preset current value and the zero sequence voltage effective value is greater than or equal to a preset voltage value, issuing a ground protection instruction within a preset time length.

8. A filter monitoring protection device, characterized by The filter monitoring protection device comprises: One or more processors and a memory; the memory is coupled to the one or more processors, the memory is used to store computer program code, the computer program code comprises computer instructions, and the one or more processors invoke the computer instructions to enable the filter monitoring protection device to perform the method in any one of claims 1-7.

9. A computer-readable storage medium comprising instructions, characterized in that, When the instructions run on the filter monitoring protection device, the filter monitoring protection device performs the method in any one of claims 1-7.

10. A computer program product, characterised in that, When the computer program product runs on the filter monitoring protection device, the filter monitoring protection device performs the method in any one of claims 1-7.

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