An electric energy metering fault intelligent diagnosis method and system

Abstract

This invention discloses an intelligent diagnostic method and system for electricity metering faults, belonging to the field of data processing. The intelligent diagnostic method for electricity metering faults includes the following steps: collecting instantaneous values ​​of three-phase voltage and three-phase current at the metering point, obtaining voltage sampling sequences and current sampling sequences, and extracting the fundamental voltage amplitude and phase. Compared with the prior art, the beneficial effects of this invention are: by extracting fundamental voltage and fundamental current parameters and calculating the total active power and total reactive power of the three phases, this invention uses the active power symbol and reactive power symbol to jointly determine the overall polarity state of the three-phase current transformer, effectively distinguishing between normal reverse power flow and true polarity reverse connection faults; at the same time, it monitors the correlation characteristics between the negative sequence current imbalance and the photovoltaic active power output change rate, accurately identifying the polarity reverse connection state of single-phase current transformers; while maintaining the normal passage of reverse power flow, it accurately detects polarity anomalies, avoiding the risk of under-metering of electricity and malfunction of protection.

Description

Technical Field

[0001] This invention belongs to the field of data processing, and in particular relates to an intelligent diagnostic method and system for power metering faults. Background Technology

[0002] Intelligent diagnostic methods for electricity metering automatically determine whether there are wiring errors, equipment malfunctions, or human interference in the metering circuit by collecting electrical parameters such as voltage, current, and phase in real time and based on preset logic rules. This method can replace traditional manual inspections, improve the timeliness of fault detection, and has become a core supporting technology for intelligent electricity management and line loss control.

[0003] In low-voltage areas with distributed photovoltaic grid connection, when the power generated by the user-side solar power generation equipment exceeds its own power consumption, the excess energy is fed back to the grid. In this case, the power flow direction is from the user side to the grid side, and the total three-phase active power is negative. Conventional intelligent energy metering diagnostic methods have a built-in fixed rule that "negative active power indicates reverse polarity of the current transformer." This rule is effective in pure load areas, but in the above reverse power flow scenario, it will misidentify normal reverse power as a current transformer reverse polarity fault. To avoid a large number of false alarms, on-site maintenance personnel usually adjust the diagnostic threshold to a very lenient state or directly disable this alarm item.

[0004] The above-mentioned handling methods prevent the diagnostic system from detecting actual current transformer reverse connection faults. If current transformer reverse connection faults persist for a long time, they will cause problems such as continuous under-counting of metered electricity, distortion of three-phase power imbalance records, and consequently lead to disputes over electricity billing. They may also cause malfunctions due to sampling deviations of protection devices.

[0005] In summary, conventional intelligent diagnostic methods for electricity metering face a dilemma at distributed photovoltaic grid-connected points: if the diagnostic rules remain in effect, a large number of false alarms will occur during reverse power flow periods; if the diagnostic rules are relaxed, actual current transformer polarity reverse connection faults will be missed. Existing methods lack effective means to distinguish the nature of reverse active power under bidirectional power flow conditions, and improvements are needed. Summary of the Invention

[0006] Therefore, it is necessary to provide an intelligent diagnostic method and system for power metering faults to address the above-mentioned problems.

[0007] The present invention is implemented as follows: an intelligent diagnostic method for power metering faults includes the following steps: Collect the instantaneous values ​​of three-phase voltage and three-phase current at the metering point, obtain the voltage sampling sequence and current sampling sequence, and extract the fundamental voltage amplitude, fundamental voltage phase, fundamental current amplitude, and fundamental current phase; Based on the fundamental voltage amplitude, fundamental voltage phase, fundamental current amplitude, and fundamental current phase, the fundamental active power and fundamental reactive power are calculated separately for each phase. The three-phase fundamental active power is obtained by summing the three-phase fundamental active power, and the three-phase fundamental reactive power is obtained by summing the three-phase fundamental reactive power. Obtain the symbols for the total active power and total reactive power of the three phases, and determine the overall polarity state of the three-phase current transformer based on the two power symbols. Monitor the negative sequence current imbalance and the photovoltaic active power output change rate, and determine the polarity reverse connection status of the single-phase current transformer based on the combined changes in negative sequence current imbalance and photovoltaic active power output change rate.

[0008] In one embodiment, the present invention provides an intelligent diagnostic method for power metering faults. The steps of collecting instantaneous values ​​of three-phase voltage and three-phase current at the metering point, obtaining voltage sampling sequences and current sampling sequences, and extracting the fundamental voltage amplitude, fundamental voltage phase, fundamental current amplitude, and fundamental current phase specifically include: The instantaneous values ​​of three-phase voltage and three-phase current at the metering point are synchronously collected at a fixed sampling frequency to construct a three-phase voltage sampling sequence and a three-phase current sampling sequence with a time window length of a preset number of cycles; Adaptive notch filtering is applied to the three-phase voltage sampling sequence and the three-phase current sampling sequence to filter out the high-frequency switching ripple and interharmonic interference introduced by the distributed photovoltaic grid-connected inverter, resulting in the filtered three-phase voltage sampling sequence and the filtered three-phase current sampling sequence. Perform Discrete Fourier Transform on the filtered phase voltage sampling sequence and the corresponding filtered phase current sampling sequence to extract the fundamental voltage amplitude, fundamental voltage phase, fundamental current amplitude, and fundamental current phase.

[0009] In one embodiment, the present invention provides an intelligent diagnosis method for power metering faults. The step of obtaining the three-phase total active power symbol and the three-phase total reactive power symbol, and determining the overall polarity state of the three-phase current transformer based on the two power symbols, specifically includes: Obtain the symbols for the total three-phase active power and the total three-phase reactive power; If the sign of the total active power of the three phases is negative and the sign of the total reactive power of the three phases is negative, then the overall polarity of the three-phase current transformer is determined to be reversed, and a reverse connection alarm of the three-phase current transformer is output. If the sign of the total three-phase active power is negative and the sign of the total three-phase reactive power is positive, then it is further determined whether the absolute value of the total three-phase reactive power is less than the preset first threshold (minimum reactive power threshold): if the absolute value of the total three-phase reactive power is greater than or equal to the preset first threshold, then the current operating condition is determined to be normal reverse power flow, and the three-phase current transformer reverse connection alarm output is suppressed; if the absolute value of the total three-phase reactive power is less than the preset first threshold, then the current direction judgment conclusion is suspended, and the judgment is re-evaluated after the data accumulation of the next calculation cycle. If the number of consecutive suspensions exceeds the preset seventh threshold (cumulative suspension number threshold), then the current operating condition cannot be confirmed, and the three-phase current transformer reverse connection alarm is output.

[0010] In one embodiment, the present invention provides an intelligent diagnostic method for power metering faults. The step of monitoring the negative sequence current imbalance and the rate of change of photovoltaic active power output, and jointly determining the reverse polarity state of the single-phase current transformer based on the changes in negative sequence current imbalance and the rate of change of photovoltaic active power output, specifically includes: Continuously monitor the negative sequence current imbalance and the rate of change of photovoltaic active power output at distributed photovoltaic grid-connected points; When the rate of change of photovoltaic active power output exceeds the preset second threshold (rate of change threshold), the ratio of the negative sequence current imbalance at the current moment to the steady-state negative sequence current imbalance before the change of photovoltaic active power output is calculated as the first ratio. At the same time, the correlation coefficient between the change in negative sequence current imbalance and the change in photovoltaic active power output is calculated. If the first ratio exceeds the preset third threshold (mutation multiple threshold) and the correlation coefficient is greater than the preset fourth threshold (correlation coefficient threshold), then it is determined that there is a single-phase current transformer polarity reverse connection fault, and a single-phase current transformer reverse connection alarm is output.

[0011] In one embodiment, the present invention provides an intelligent diagnostic method for power metering faults, wherein before the step of continuously monitoring the negative sequence current imbalance and the rate of change of photovoltaic active power output at the distributed photovoltaic grid-connected point, the method further includes: When the negative sequence current imbalance changes, the current three-phase voltage imbalance is obtained, and the ratio of the change in three-phase voltage imbalance to the change in negative sequence current imbalance is calculated as the second ratio. If the second ratio falls within the preset fifth threshold (voltage imbalance change ratio threshold) range, it is determined to be a voltage imbalance disturbance on the grid side, and the current current transformer polarity reverse connection state diagnosis process is terminated; if the second ratio exceeds the preset fifth threshold range, the current current transformer polarity reverse connection state diagnosis process continues.

[0012] In one embodiment, the present invention provides an intelligent diagnosis method for power metering faults. After the step of determining that a single-phase current transformer polarity reverse connection fault exists and outputting a single-phase current transformer reverse connection alarm if the first ratio exceeds a preset third threshold and the correlation coefficient is greater than a preset fourth threshold, the method further includes: During the dynamic period when the rate of change of photovoltaic active power output exceeds the preset second threshold, the normalized change of the three-phase current amplitudes of A, B, and C relative to the change of photovoltaic active power output is calculated respectively. The consistency of the change of the three-phase current amplitude is compared. If the deviation of the change of the current amplitude of one phase from the change of the current amplitude of the other two phases exceeds the preset sixth threshold (consistency deviation threshold), it is determined that there is a poor contact fault in the secondary circuit of the current transformer of that phase, and an abnormal alarm of the secondary circuit of the corresponding current transformer is output.

[0013] In one embodiment, the present invention provides an intelligent diagnostic system for power metering faults, comprising: The power data acquisition module is used to collect the instantaneous values ​​of the three-phase voltage and the three-phase current at the metering point, obtain the voltage sampling sequence and the current sampling sequence, and extract the fundamental voltage amplitude, fundamental voltage phase, fundamental current amplitude, and fundamental current phase. The total power summation module is used to calculate the fundamental active power and fundamental reactive power of each phase based on the fundamental voltage amplitude, fundamental voltage phase, fundamental current amplitude, and fundamental current phase. It sums the three-phase fundamental active power to obtain the total three-phase active power and sums the three-phase fundamental reactive power to obtain the total three-phase reactive power. The three-phase current transformer judgment module is used to obtain the three-phase total active power symbol and the three-phase total reactive power symbol, and to determine the overall polarity state of the three-phase current transformer based on the two power symbols. The single-phase current transformer judgment module is used to monitor the negative sequence current imbalance and the photovoltaic active power output change rate, and to jointly determine the polarity reverse connection status of the single-phase current transformer based on the change in negative sequence current imbalance and the change rate of photovoltaic active power output.

[0014] In one embodiment, the present invention provides an intelligent diagnostic system for power metering faults, wherein the power data acquisition module includes: The sampling sequence acquisition unit is used to synchronously acquire the instantaneous values ​​of the three-phase voltage and the three-phase current at a fixed sampling frequency, and to construct a three-phase voltage sampling sequence and a three-phase current sampling sequence with a time window length of a preset number of cycles. The interference filtering unit is used to perform adaptive notch filtering on the three-phase voltage sampling sequence and the three-phase current sampling sequence to filter out the high-frequency switching ripple and interharmonic interference introduced by the distributed photovoltaic grid-connected inverter, and obtain the filtered three-phase voltage sampling sequence and the filtered three-phase current sampling sequence. The voltage and current data acquisition unit is used to perform discrete Fourier transform on the filtered voltage sampling sequence of each phase and the filtered current sampling sequence of the corresponding phase, respectively, to extract the fundamental voltage amplitude, fundamental voltage phase, fundamental current amplitude, and fundamental current phase.

[0015] In one embodiment, the present invention provides an intelligent diagnostic system for power metering faults, wherein the three-phase current transformer judgment module includes: The positive / negative determination unit is used to obtain the sign of the total three-phase active power and the sign of the total three-phase reactive power. The reverse connection judgment unit is used to determine the overall polarity reverse connection fault of the three-phase current transformer if the sign of the total active power of the three phases is negative and the sign of the total reactive power of the three phases is negative, and outputs a reverse connection alarm for the three-phase current transformer. The normal identification unit is used to determine whether the absolute value of the total three-phase reactive power is less than a preset first threshold (minimum reactive power threshold) if the sign of the total three-phase active power is negative and the sign of the total three-phase reactive power is positive. If the absolute value of the total three-phase reactive power is greater than or equal to the preset first threshold, the current operating condition is determined to be normal reverse power flow, and the three-phase current transformer reverse connection alarm output is suppressed. If the absolute value of the total three-phase reactive power is less than the preset first threshold, the current judgment conclusion is suspended, and the judgment is re-evaluated after the data accumulation of the next calculation cycle. If the number of consecutive suspensions exceeds the preset seventh threshold (cumulative suspension number threshold), the current operating condition cannot be confirmed, and a three-phase current transformer reverse connection alarm is output.

[0016] In one embodiment, the present invention provides an intelligent diagnostic system for power metering faults, wherein the single-phase current transformer judgment module includes: The data monitoring unit is used to continuously monitor the negative sequence current imbalance and the rate of change of photovoltaic active power output at the distributed photovoltaic grid-connected point. The data calculation unit is used to calculate the ratio of the negative sequence current imbalance to the steady-state negative sequence current imbalance before the change in photovoltaic active power output when the rate of change of photovoltaic active power output exceeds the preset second threshold (rate of change threshold), and use it as the first ratio. At the same time, it calculates the correlation coefficient between the change in negative sequence current imbalance and the change in photovoltaic active power output. The result determination unit is used to determine that there is a single-phase current transformer polarity reverse connection fault if the first ratio exceeds the preset third threshold (mutation multiple threshold) and the correlation coefficient is greater than the preset fourth threshold (correlation coefficient threshold), and outputs a single-phase current transformer reverse connection alarm.

[0017] In one embodiment, the present invention provides an intelligent diagnostic system for power metering faults, wherein the single-phase current transformer judgment module further includes: The execution identification unit is used to obtain the current three-phase voltage imbalance when the negative sequence current imbalance changes, calculate the ratio of the change in three-phase voltage imbalance to the change in negative sequence current imbalance as the second ratio. If the second ratio falls within the preset fifth threshold (voltage imbalance change ratio threshold) range, it is determined to be a voltage imbalance disturbance on the grid side, and the current current transformer polarity reverse connection state diagnosis process is terminated; if the second ratio exceeds the preset fifth threshold range, the current current transformer polarity reverse connection state diagnosis process continues.

[0018] In one embodiment, the present invention provides an intelligent diagnostic system for power metering faults, wherein the single-phase current transformer judgment module further includes: The fault transformer determination unit is used to calculate the normalized change of the three-phase current amplitudes of A, B, and C relative to the change in photovoltaic active power output during a dynamic period when the rate of change of photovoltaic active power output exceeds a preset second threshold. It compares the consistency of the change in the three-phase current amplitudes. If the deviation of the change in the current amplitude of one phase from the change in the current amplitude of the other two phases exceeds a preset sixth threshold (consistency deviation threshold), it determines that there is a poor contact fault in the secondary circuit of the current transformer of that phase and outputs an abnormal alarm for the secondary circuit of the corresponding current transformer.

[0019] Compared with the prior art, the beneficial effects of the present invention are as follows: The present invention extracts the fundamental voltage and fundamental current parameters and calculates the total active power and total reactive power of the three phases. It uses the active power symbol and reactive power symbol to jointly determine the overall polarity state of the three-phase current transformer, effectively distinguishing between normal reverse power flow and true polarity reverse connection faults. At the same time, it monitors the correlation characteristics between the negative sequence current imbalance and the photovoltaic active power output change rate, accurately identifying the polarity reverse connection state of the single-phase current transformer. This solves the dilemma of false alarms and missed judgments in the conventional rules for distributed photovoltaic grid-connected points under bidirectional power flow conditions. While maintaining the normal passage of reverse power flow, it accurately detects polarity abnormalities, avoiding the risk of under-counting of electricity and false tripping of protection. Attached Figure Description

[0020] Figure 1 This is a flowchart illustrating an intelligent diagnostic method for power metering faults provided in an embodiment of the present invention.

[0021] Figure 2 This is a schematic diagram of the process for collecting and processing electrical energy data provided in an embodiment of the present invention.

[0022] Figure 3 This is a schematic diagram of the process for determining whether a three-phase current transformer is faulty, provided in an embodiment of the present invention.

[0023] Figure 4 This is a schematic diagram of the process for determining whether a single-phase current transformer is faulty, provided in an embodiment of the present invention.

[0024] Figure 5 This is a schematic diagram of an intelligent diagnostic system for power metering faults provided in an embodiment of the present invention.

[0025] Figure 6 This is a schematic diagram of an electrical energy data acquisition module provided in an embodiment of the present invention.

[0026] Figure 7 This is a schematic diagram of a three-phase current transformer judgment module provided in an embodiment of the present invention.

[0027] Figure 8 This is a schematic diagram of a single-phase current transformer judgment module provided in an embodiment of the present invention. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0029] It is understood that the terms "first," "second," etc., used in this application may be used herein to describe various elements, but unless otherwise specified, these elements are not limited by these terms. These terms are used only to distinguish one element from another. For example, without departing from the scope of this application, a first script may be referred to as a second script, and similarly, a second script may be referred to as a first script.

[0030] In one embodiment, such as Figure 1 As shown, an intelligent diagnostic method for power metering faults includes the following steps: Step S1: Collect the instantaneous values ​​of the three-phase voltage and the three-phase current at the metering point, obtain the voltage sampling sequence and the current sampling sequence, and extract the fundamental voltage amplitude, fundamental voltage phase, fundamental current amplitude, and fundamental current phase. Step S2: Based on the fundamental voltage amplitude, fundamental voltage phase, fundamental current amplitude, and fundamental current phase, calculate the fundamental active power and fundamental reactive power for each phase, sum the three-phase fundamental active power to obtain the total three-phase active power, and sum the three-phase fundamental reactive power to obtain the total three-phase reactive power. Step S3: Obtain the symbol of the total active power and the symbol of the total reactive power of the three phases, and determine the overall polarity state of the three-phase current transformer based on the two power symbols. Step S4: Monitor the negative sequence current imbalance and the photovoltaic active power output change rate, and determine the polarity reverse connection status of the single-phase current transformer based on the change in negative sequence current imbalance and the change rate of photovoltaic active power output.

[0031] Step S1 collects the instantaneous values ​​of three-phase voltage and current and extracts the fundamental voltage amplitude, fundamental voltage phase, fundamental current amplitude, and fundamental current phase to provide basic parameters for power calculation. Step S2 calculates the total three-phase active power and total three-phase reactive power based on the above fundamental parameters. Step S3 obtains the active power sign and reactive power sign, and determines the overall polarity state of the three-phase current transformers based on the two signs: when both active and reactive power are negative, it is determined to be a reverse polarity connection; when active power is negative and reactive power is positive, it is determined to be a normal reverse power flow, thus solving the false alarm problem of conventional rules under bidirectional power flow conditions. Step S4 monitors the negative sequence current imbalance and the rate of change of photovoltaic active power output. When the photovoltaic active power output changes rapidly, the abrupt change characteristics of the negative sequence current imbalance determine the polarity reversal of the single-phase current transformers, solving the problem of missed detection caused by shielded alarms in conventional rules. These four steps work together to accurately detect polarity anomalies while maintaining normal reverse power flow.

[0032] In one embodiment, such as Figure 2 As shown, an intelligent fault diagnosis method for electricity metering, in step S1, which involves collecting the instantaneous values ​​of the three-phase voltage and the three-phase current at the metering point, obtaining the voltage sampling sequence and the current sampling sequence, and extracting the fundamental voltage amplitude, fundamental voltage phase, fundamental current amplitude, and fundamental current phase, specifically includes: Step S11: Synchronously collect the instantaneous values ​​of three-phase voltage and three-phase current at a fixed sampling frequency to construct a three-phase voltage sampling sequence and a three-phase current sampling sequence with a time window length of a preset number of cycles; Step S12: Perform adaptive notch filtering on the three-phase voltage sampling sequence and the three-phase current sampling sequence to filter out the high-frequency switching ripple and interharmonic interference introduced by the distributed photovoltaic grid-connected inverter, and obtain the filtered three-phase voltage sampling sequence and the filtered three-phase current sampling sequence. Step S13: Perform Discrete Fourier Transform on the filtered voltage sampling sequence of each phase and the filtered current sampling sequence of the corresponding phase to extract the fundamental voltage amplitude, fundamental voltage phase, fundamental current amplitude, and fundamental current phase.

[0033] Steps S11 and S13 together complete the sampling sequence construction and fundamental parameter extraction functions required by step S1: Step S11 synchronously collects the instantaneous values ​​of the three-phase voltage and three-phase current at a fixed sampling frequency to construct a three-phase voltage sampling sequence and a three-phase current sampling sequence with a time window length of a preset number of cycles; Step S13 performs a discrete Fourier transform on the filtered sequences to extract the fundamental voltage amplitude, fundamental voltage phase, fundamental current amplitude, and fundamental current phase. Based on this, an additional step S12 is designed to perform adaptive notch filtering on the three-phase voltage sampling sequence and the three-phase current sampling sequence to filter out high-frequency switching ripple and interharmonic interference introduced by the distributed photovoltaic grid-connected inverter. This design avoids zero-crossing jitter caused by high-frequency noise during fundamental phase extraction, ensuring that the fundamental parameters used for subsequent active power symbol and reactive power symbol calculations are not contaminated by power electronic equipment.

[0034] In one embodiment, such as Figure 3 As shown, in an intelligent fault diagnosis method for electricity metering, step S3, which involves obtaining the three-phase total active power symbol and the three-phase total reactive power symbol, and determining the overall polarity state of the three-phase current transformer based on the joint determination of the two power symbols, specifically includes: Step S31: Obtain the symbols for the total three-phase active power and the total three-phase reactive power; Step S32: If the sign of the total active power of the three phases is negative and the sign of the total reactive power of the three phases is negative, then it is determined that the polarity of the three-phase current transformer is reversed and a three-phase current transformer reverse connection alarm is output. Step S33: If the sign of the total three-phase active power is negative and the sign of the total three-phase reactive power is positive, then further determine whether the absolute value of the total three-phase reactive power is less than the preset first threshold (minimum reactive power threshold): If the absolute value of the total three-phase reactive power is greater than or equal to the preset first threshold, then determine that the current operating condition is normal reverse power flow and suppress the reverse connection alarm output of the three-phase current transformer; if the absolute value of the total three-phase reactive power is less than the preset first threshold, then suspend the current judgment conclusion and wait for the data accumulation of the next calculation cycle to re-judge. If the number of consecutive suspensions exceeds the preset seventh threshold (cumulative suspension number threshold), then determine that the current operating condition cannot be confirmed and output the reverse connection alarm of the three-phase current transformer.

[0035] Steps S31 and S32 together complete the basic function of joint direction determination required by step S3: Step S31 obtains the signs of the three-phase total active power and the three-phase total reactive power; Step S32 determines that the overall polarity of the three-phase current transformer is reversed when both the signs of the three-phase total active power and the three-phase total reactive power are negative and outputs an alarm. Based on this, an additional reactive power amplitude threshold check is designed in step S33: when the sign of the three-phase total active power is negative and the sign of the three-phase total reactive power is positive, it further determines whether the absolute value of the three-phase total reactive power is less than a preset first threshold. If the absolute value of the total reactive power of the three phases is lower than the preset first threshold (e.g., 1% of the rated power), even if the sign is positive, it may be due to measurement noise or line no-load, which is insufficient as a reliable criterion. The current directional judgment should be suspended and the judgment should be made after the data is accumulated in the next calculation cycle to avoid misreading the sign due to the low reactive power. If the number of consecutive suspensions exceeds the preset seventh threshold, the current operating condition is determined to be unconfirmable, and a three-phase current transformer reverse connection alarm is output to prevent the diagnostic process from getting stuck in an infinite wait.

[0036] In one embodiment, such as Figure 4 As shown, in an intelligent fault diagnosis method for electricity metering, step S4, which involves monitoring the negative sequence current imbalance and the rate of change of photovoltaic active power output, and jointly determining the reverse polarity state of the single-phase current transformer based on the changes in negative sequence current imbalance and the rate of change of photovoltaic active power output, specifically includes: Step S42: Continuously monitor the negative sequence current imbalance and the rate of change of photovoltaic active power output at the distributed photovoltaic grid connection point; Step S43: When the rate of change of photovoltaic active power output exceeds the preset second threshold (rate of change threshold), calculate the ratio of the negative sequence current imbalance at the current moment to the steady-state negative sequence current imbalance before the change of photovoltaic active power output, and use it as the first ratio. At the same time, calculate the correlation coefficient between the change in negative sequence current imbalance and the change in photovoltaic active power output. Step S44: If the first ratio exceeds the preset third threshold (mutation multiple threshold) and the correlation coefficient is greater than the preset fourth threshold (correlation coefficient threshold), it is determined that there is a single-phase current transformer polarity reverse connection fault, and a single-phase current transformer reverse connection alarm is output.

[0037] The calculation of the first ratio in steps S42 and S43 together completes the basic function required in step S4 for determining the polarity reversal of the single-phase current transformer based on the sudden change in negative sequence current imbalance: Step S42 continuously monitors the negative sequence current imbalance and the rate of change of photovoltaic active power output at the distributed photovoltaic grid-connected point; Step S43 calculates the ratio of the current negative sequence current imbalance to the steady-state negative sequence current imbalance before the change in photovoltaic active power output when the rate of change in photovoltaic active power output exceeds the preset second threshold, using this as the first ratio. Based on this, the calculation of the correlation coefficient in step S43 and the verification of the correlation coefficient in step S44 are additionally designed: when detecting whether the negative sequence current imbalance suddenly increases due to the change in photovoltaic active power output, the correlation coefficient between the change in negative sequence current imbalance and the change in photovoltaic active power output is further calculated. A single-phase current transformer reversal alarm is only output when the two are strongly positively correlated (correlation coefficient greater than the preset fourth threshold) and the first ratio exceeds the preset third threshold. This approach can eliminate occasional negative sequence fluctuations caused by grid background voltage asymmetry or load switching, and pinpoint the diagnosis to single-phase polarity anomalies directly related to photovoltaic active power output.

[0038] In one embodiment, such as Figure 4 As shown, an intelligent diagnostic method for power metering faults, prior to step S42, which involves continuously monitoring the negative sequence current imbalance and the rate of change of photovoltaic active power output at the distributed photovoltaic grid-connected point, further includes: Step S41: When the negative sequence current imbalance changes, obtain the current three-phase voltage imbalance, calculate the ratio of the change in three-phase voltage imbalance to the change in negative sequence current imbalance, and use it as the second ratio. If the second ratio falls within the preset fifth threshold (voltage imbalance change ratio threshold) range, it is determined to be a grid-side voltage imbalance disturbance, and the current current transformer polarity reverse connection state diagnosis process is terminated; if the second ratio exceeds the preset fifth threshold range, the current current transformer polarity reverse connection state diagnosis process continues.

[0039] Step S41 is an additional pre-interference identification step added to step S4, which monitors the negative sequence current imbalance and the rate of change of photovoltaic active power output. The low-voltage distribution network where the distributed photovoltaic grid connection point is located may experience three-phase voltage imbalance due to uneven load distribution or faults in the upstream lines. This grid-side voltage imbalance will naturally lead to three-phase current imbalance, a phenomenon superficially similar to the current imbalance caused by reverse polarity of a single-phase current transformer or abnormal secondary circuits. Without differentiation, the diagnostic system may easily misjudge grid background voltage imbalance as a metering circuit fault, resulting in ineffective maintenance. Step S41 acquires the three-phase voltage imbalance when the negative sequence current imbalance changes, calculates the second ratio, and determines whether it falls within the preset fifth threshold range. If it does, it is determined to be a grid-side voltage imbalance disturbance, and the current current transformer reverse polarity state diagnostic process is terminated, thereby effectively separating the grid background disturbance from the actual fault in the metering circuit.

[0040] In one embodiment, such as Figure 4 As shown, in a smart diagnostic method for electricity metering faults, step S44, if the first ratio exceeds a preset third threshold and the correlation coefficient is greater than a preset fourth threshold, determines that a single-phase current transformer polarity reverse connection fault exists, and outputs a single-phase current transformer reverse connection alarm, further includes: Step S45: During the dynamic period when the rate of change of photovoltaic active power output exceeds the preset second threshold, calculate the normalized change of the three-phase current amplitudes of A, B, and C relative to the change in photovoltaic active power output; compare the consistency of the change in the three-phase current amplitudes; if the deviation of the change in the current amplitude of one phase from the change in the current amplitude of the other two phases exceeds the preset sixth threshold (consistency deviation threshold), it is determined that there is a poor contact fault in the secondary circuit of the current transformer of that phase, and output an abnormal alarm for the secondary circuit of the corresponding current transformer.

[0041] Step S45 is an additional step in the secondary circuit contact failure diagnosis process added to the framework of step S4, which monitors the rate of change of photovoltaic active power output. Secondary circuit contact failures in current transformers are intermittent and susceptible to vibration. They may not show obvious abnormalities during periods of stable photovoltaic active power output. However, when rapid changes in photovoltaic active power output cause fluctuations in line current, the nonlinear change in resistance at the point of contact failure will lead to a discrepancy between the corresponding phase current amplitude change and the other two phases. Conventional steady-state diagnostic methods struggle to detect such hidden faults. Step S45 calculates the normalized change in the three-phase current amplitude relative to the value before the photovoltaic active power output change during the dynamic period when the rate of change of photovoltaic active power output exceeds a preset second threshold. By comparing the consistency of the three-phase current amplitude changes, phases with deviations exceeding a preset sixth threshold are identified as having secondary circuit contact failures, thus achieving dynamic detection and phase-specific location of intermittent contact failures.

[0042] In one embodiment, such as Figure 5 As shown, an intelligent fault diagnosis system for electricity metering includes: The power data acquisition module 1 is used to acquire the instantaneous values ​​of the three-phase voltage and the three-phase current at the metering point, obtain the voltage sampling sequence and the current sampling sequence, and extract the fundamental voltage amplitude, fundamental voltage phase, fundamental current amplitude, and fundamental current phase. The total power summation module 2 is used to calculate the fundamental active power and fundamental reactive power of each phase based on the fundamental voltage amplitude, fundamental voltage phase, fundamental current amplitude, and fundamental current phase, and to sum the three-phase fundamental active power to obtain the three-phase total active power and sum the three-phase fundamental reactive power to obtain the three-phase total reactive power. The three-phase current transformer judgment module 3 is used to obtain the three-phase total active power symbol and the three-phase total reactive power symbol, and to determine the overall polarity state of the three-phase current transformer based on the two power symbols. The single-phase current transformer judgment module 4 is used to monitor the negative sequence current imbalance and the photovoltaic active power output change rate, and to jointly determine the polarity reverse connection status of the single-phase current transformer based on the change in negative sequence current imbalance and the change rate of photovoltaic active power output.

[0043] Negative sequence current imbalance refers to the ratio of the magnitude of the negative sequence component to the magnitude of the positive sequence component in the three-phase current, and is used to quantify the degree of asymmetry in the three-phase current.

[0044] The photovoltaic active power output variation rate refers to the ratio of the change in active power output at the photovoltaic grid-connected point per unit time to the rated power, and is used to characterize the degree of fluctuation in photovoltaic output.

[0045] In one embodiment, such as Figure 6 As shown, an intelligent diagnostic system for power metering faults includes a power data acquisition module 1 comprising: The sampling sequence acquisition unit 11 is used to synchronously acquire the instantaneous values ​​of the three-phase voltage and the three-phase current at a fixed sampling frequency, and to construct a three-phase voltage sampling sequence and a three-phase current sampling sequence with a time window length of a preset number of cycles. Interference filtering unit 12 is used to perform adaptive notch filtering on the three-phase voltage sampling sequence and the three-phase current sampling sequence to filter out the high-frequency switching ripple and interharmonic interference introduced by the distributed photovoltaic grid-connected inverter, and obtain the filtered three-phase voltage sampling sequence and the filtered three-phase current sampling sequence. The voltage and current data acquisition unit 13 is used to perform discrete Fourier transform on the filtered voltage sampling sequence of each phase and the filtered current sampling sequence of the corresponding phase, respectively, to extract the fundamental voltage amplitude, fundamental voltage phase, fundamental current amplitude, and fundamental current phase.

[0046] Adaptive notch filtering is implemented by performing a Fast Fourier Transform on the three-phase voltage and current sampling sequences to identify the high-frequency components with prominent amplitudes in the spectrum as the inverter switching frequency. A notch filter is then positioned around this frequency, dynamically adjusting its bandwidth and attenuation depth to filter out switching ripple and interharmonics in real time, outputting the filtered sequence.

[0047] In one embodiment, such as Figure 7 As shown, an intelligent fault diagnosis system for electricity metering includes a three-phase current transformer judgment module 3 comprising: The positive / negative judgment unit 31 is used to obtain the sign of the total active power and the sign of the total reactive power of the three phases; The reverse connection judgment unit 32 is used to determine the overall polarity reverse connection fault of the three-phase current transformer if the sign of the total active power of the three phases is negative and the sign of the total reactive power of the three phases is negative, and output the reverse connection alarm of the three-phase current transformer. The normal identification unit 33 is used to further determine whether the absolute value of the total three-phase reactive power is less than a preset first threshold (minimum reactive power threshold) if the sign of the total three-phase active power is negative and the sign of the total three-phase reactive power is positive. If the absolute value of the total three-phase reactive power is greater than or equal to the preset first threshold, the current operating condition is determined to be normal reverse power flow, and the three-phase current transformer reverse connection alarm output is suppressed. If the absolute value of the total three-phase reactive power is less than the preset first threshold, the current judgment conclusion is suspended, and the judgment is re-evaluated after the data accumulation of the next calculation cycle. If the number of consecutive suspensions exceeds the preset seventh threshold (cumulative suspension number threshold), the current operating condition cannot be confirmed, and the three-phase current transformer reverse connection alarm is output.

[0048] The first threshold (minimum reactive power threshold) can be set at 1% of the rated power to distinguish between effective reactive power and noise; the seventh threshold (cumulative suspension times threshold) can be set to 3 to 5 times to prevent infinite waiting due to continuous low reactive power.

[0049] In one embodiment, such as Figure 8 As shown, an intelligent fault diagnosis system for electricity metering includes a single-phase current transformer judgment module 4 comprising: Data monitoring unit 42 is used to continuously monitor the negative sequence current imbalance and the rate of change of photovoltaic active power output at the distributed photovoltaic grid connection point; The data calculation unit 43 is used to calculate the ratio of the negative sequence current imbalance to the steady-state negative sequence current imbalance before the change in photovoltaic active power output when the rate of change of photovoltaic active power output exceeds the preset second threshold (rate of change threshold), and use it as the first ratio. At the same time, it calculates the correlation coefficient between the change in negative sequence current imbalance and the change in photovoltaic active power output. The result determination unit 44 is used to determine that there is a single-phase current transformer polarity reverse connection fault if the first ratio exceeds the preset third threshold (mutation multiple threshold) and the correlation coefficient is greater than the preset fourth threshold (correlation coefficient threshold), and output a single-phase current transformer reverse connection alarm.

[0050] The second threshold (rate of change threshold) can be set to 30% / second of the rated power, corresponding to rapid fluctuations in photovoltaic output. The third threshold (mutation multiple threshold) can be set to 3, indicating that a sudden increase in negative sequence current to more than 3 times the steady-state value is considered abnormal. The fourth threshold (correlation coefficient threshold) can be set to 0.8 to ensure a strong positive correlation between the negative sequence increment and the change in output.

[0051] In one embodiment, such as Figure 8 As shown, in an intelligent fault diagnosis system for electricity metering, the single-phase current transformer judgment module 4 further includes: The identification unit 41 is used to obtain the current three-phase voltage imbalance when the negative sequence current imbalance changes, calculate the ratio of the change in three-phase voltage imbalance to the change in negative sequence current imbalance as the second ratio. If the second ratio falls within the preset fifth threshold (voltage imbalance change ratio threshold) range, it is determined to be a voltage imbalance disturbance on the grid side, and the current current transformer polarity reverse connection state diagnosis process is terminated; if the second ratio exceeds the preset fifth threshold range, the current current transformer polarity reverse connection state diagnosis process continues.

[0052] The fifth threshold (voltage imbalance change ratio threshold) can be set between 0.8 and 1.2. When the second ratio (the ratio of voltage imbalance change to negative sequence current imbalance change) falls within this range, it indicates that the current imbalance is entirely caused by the linear voltage imbalance and is judged as a grid-side disturbance.

[0053] The change in three-phase voltage unbalance refers to the difference between the current three-phase voltage unbalance and the previous steady-state three-phase voltage unbalance. The three-phase voltage unbalance is the ratio of the amplitude of the negative sequence component to the amplitude of the positive sequence component in the three-phase voltage.

[0054] In one embodiment, such as Figure 8 As shown, in an intelligent fault diagnosis system for electricity metering, the single-phase current transformer judgment module 4 further includes: The fault transformer determination unit 45 is used to calculate the normalized change of the three-phase current amplitudes of A, B, and C relative to the change in photovoltaic active power output during the dynamic period when the rate of change of photovoltaic active power output exceeds the preset second threshold; compare the consistency of the change in the three-phase current amplitudes; if the deviation of the change in the current amplitude of one phase from the change in the current amplitude of the other two phases exceeds the preset sixth threshold (consistency deviation threshold), it is determined that there is a poor contact fault in the secondary circuit of the current transformer of that phase, and outputs an abnormal alarm for the secondary circuit of the corresponding current transformer.

[0055] The sixth threshold (consistency deviation threshold) can be set to 15%. When the normalized change in the current amplitude of a certain phase deviates from the average change in the other two phases by more than 15%, the change in that phase is judged to be inconsistent and identified as a secondary circuit contact failure.

[0056] It should be understood that although the steps in the flowcharts of the various embodiments of the present invention are shown sequentially according to the arrows, these steps are not necessarily executed in the order indicated by the arrows. Unless explicitly stated herein, there is no strict order restriction on the execution of these steps, and they can be executed in other orders. Moreover, at least some steps in the various embodiments may include multiple sub-steps or multiple stages. These sub-steps or stages are not necessarily completed at the same time, but can be executed at different times. The execution order of these sub-steps or stages is not necessarily sequential, but can be performed alternately or in turn with other steps or at least a portion of the sub-steps or stages of other steps. Those skilled in the art will understand that all or part of the processes in the systems described in the above embodiments can be implemented by a computer program instructing related hardware. The program can be stored in a non-volatile computer-readable storage medium, and when executed, it can include the processes of the embodiments described above. Any references to memory, storage, databases, or other media used in the embodiments provided in this application can include non-volatile and / or volatile memory. Non-volatile memory can include read-only memory (ROM), programmable ROM (PROM), electrically programmable ROM (EPROM), electrically erasable programmable ROM (EEPROM), or flash memory. Volatile memory can include random access memory (RAM) or external cache memory. By way of illustration and not limitation, RAM is available in various forms, such as static RAM (SRAM), dynamic RAM (DRAM), synchronous DRAM (SDRAM), dual data rate SDRAM (DDRSDRAM), enhanced SDRAM (ESDRAM), synchronous link DRAM (SLDRAM), Rambus direct RAM (RDRAM), direct memory bus dynamic RAM (DRDRAM), and memory bus dynamic RAM (RDRAM), etc.

[0057] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0058] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

[0059] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

[0060] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A method for intelligent diagnosis of power metering faults, characterized in that, The intelligent diagnosis method for power metering faults includes the following steps: Collect the instantaneous values ​​of three-phase voltage and three-phase current at the metering point, obtain the voltage sampling sequence and current sampling sequence, and extract the fundamental voltage amplitude, fundamental voltage phase, fundamental current amplitude, and fundamental current phase; Based on the fundamental voltage amplitude, fundamental voltage phase, fundamental current amplitude, and fundamental current phase, the fundamental active power and fundamental reactive power are calculated separately for each phase. The three-phase fundamental active power is obtained by summing the three-phase fundamental active power, and the three-phase fundamental reactive power is obtained by summing the three-phase fundamental reactive power. Obtain the symbols for the total active power and total reactive power of the three phases, and determine the overall polarity state of the three-phase current transformer based on the two power symbols. Monitor the negative sequence current imbalance and the photovoltaic active power output change rate, and determine the polarity reverse connection status of the single-phase current transformer based on the combined changes in negative sequence current imbalance and photovoltaic active power output change rate.

2. The intelligent fault diagnosis method for electricity metering according to claim 1, characterized in that, The steps of acquiring the instantaneous values ​​of the three-phase voltage and the instantaneous values ​​of the three-phase current at the metering point, obtaining the voltage sampling sequence and the current sampling sequence, and extracting the fundamental voltage amplitude, fundamental voltage phase, fundamental current amplitude, and fundamental current phase specifically include: The instantaneous values ​​of three-phase voltage and three-phase current at the metering point are synchronously collected at a fixed sampling frequency to construct a three-phase voltage sampling sequence and a three-phase current sampling sequence with a time window length of a preset number of cycles; Adaptive notch filtering is applied to the three-phase voltage sampling sequence and the three-phase current sampling sequence to filter out the high-frequency switching ripple and interharmonic interference introduced by the distributed photovoltaic grid-connected inverter, resulting in the filtered three-phase voltage sampling sequence and the filtered three-phase current sampling sequence. Perform Discrete Fourier Transform on the filtered phase voltage sampling sequence and the corresponding filtered phase current sampling sequence to extract the fundamental voltage amplitude, fundamental voltage phase, fundamental current amplitude, and fundamental current phase.

3. The intelligent fault diagnosis method for electricity metering according to claim 1, characterized in that, The step of obtaining the symbols for the total three-phase active power and the total three-phase reactive power, and determining the overall polarity state of the three-phase current transformer based on the two power symbols, specifically includes: Obtain the symbols for the total three-phase active power and the total three-phase reactive power; If the sign of the total active power of the three phases is negative and the sign of the total reactive power of the three phases is negative, then the overall polarity of the three-phase current transformer is determined to be reversed, and a reverse connection alarm of the three-phase current transformer is output. If the sign of the total three-phase active power is negative and the sign of the total three-phase reactive power is positive, then it is further determined whether the absolute value of the total three-phase reactive power is less than a preset first threshold. If the absolute value of the total three-phase reactive power is greater than or equal to the preset first threshold, then the current operating condition is determined to be normal reverse power flow, and the three-phase current transformer reverse connection alarm output is suppressed. If the absolute value of the total three-phase reactive power is less than the preset first threshold, then the current direction judgment conclusion is suspended, and the judgment is re-evaluated after the data accumulation of the next calculation cycle. If the number of consecutive suspensions exceeds the preset seventh threshold, then the current operating condition cannot be confirmed, and the three-phase current transformer reverse connection alarm is output.

4. The intelligent fault diagnosis method for electricity metering according to claim 1, characterized in that, The step of monitoring the negative sequence current imbalance and the rate of change of photovoltaic active power output, and jointly determining the polarity reversal status of the single-phase current transformer based on the changes in negative sequence current imbalance and the rate of change of photovoltaic active power output, specifically includes: Continuously monitor the negative sequence current imbalance and the rate of change of photovoltaic active power output at distributed photovoltaic grid-connected points; When the rate of change of photovoltaic active power output exceeds the preset second threshold, the ratio of the negative sequence current imbalance at the current moment to the steady-state negative sequence current imbalance before the change of photovoltaic active power output is calculated as the first ratio. At the same time, the correlation coefficient between the change in negative sequence current imbalance and the change in photovoltaic active power output is calculated. If the first ratio exceeds the preset third threshold and the correlation coefficient is greater than the preset fourth threshold, it is determined that there is a single-phase current transformer polarity reverse connection fault, and a single-phase current transformer reverse connection alarm is output.

5. The intelligent fault diagnosis method for electricity metering according to claim 4, characterized in that, Before the step of continuously monitoring the negative sequence current imbalance and the rate of change of photovoltaic active power output at the distributed photovoltaic grid-connected point, the following is also included: When the negative sequence current imbalance changes, the current three-phase voltage imbalance is obtained, and the ratio of the change in three-phase voltage imbalance to the change in negative sequence current imbalance is calculated as the second ratio. If the second ratio falls within the preset fifth threshold range, it is determined to be a voltage imbalance disturbance on the grid side, and the current current transformer polarity reverse connection state diagnosis process is terminated. If the second ratio exceeds the preset fifth threshold range, the current current transformer polarity reverse connection state diagnosis process continues.

6. The intelligent diagnostic method for power metering faults according to claim 4 or 5, characterized in that, Also includes: After the step of determining that a single-phase current transformer polarity reverse connection fault exists and outputting a single-phase current transformer reverse connection alarm if the first ratio exceeds a preset third threshold and the correlation coefficient is greater than a preset fourth threshold, the method further includes: During the dynamic period when the rate of change of photovoltaic active power output exceeds the preset second threshold, the normalized change of the current amplitude of the three phases A, B, and C relative to the change of photovoltaic active power output is calculated respectively. The consistency of the change of the current amplitude of the three phases is compared. If the deviation of the change of the current amplitude of one phase from the change of the current amplitude of the other two phases exceeds the preset sixth threshold, it is determined that there is a poor contact fault in the secondary circuit of the current transformer of that phase, and an abnormal alarm of the secondary circuit of the current transformer of the corresponding phase is output.

7. An intelligent diagnostic system for power metering faults, characterized in that, include: The power data acquisition module is used to collect the instantaneous values ​​of the three-phase voltage and the three-phase current at the metering point, obtain the voltage sampling sequence and the current sampling sequence, and extract the fundamental voltage amplitude, fundamental voltage phase, fundamental current amplitude, and fundamental current phase. The total power summation module is used to calculate the fundamental active power and fundamental reactive power of each phase based on the fundamental voltage amplitude, fundamental voltage phase, fundamental current amplitude, and fundamental current phase. It sums the three-phase fundamental active power to obtain the total three-phase active power and sums the three-phase fundamental reactive power to obtain the total three-phase reactive power. The three-phase current transformer judgment module is used to obtain the three-phase total active power symbol and the three-phase total reactive power symbol, and to determine the overall polarity state of the three-phase current transformer based on the two power symbols. The single-phase current transformer judgment module is used to monitor the negative sequence current imbalance and the photovoltaic active power output change rate, and to jointly determine the polarity reverse connection status of the single-phase current transformer based on the change in negative sequence current imbalance and the change rate of photovoltaic active power output.

8. The intelligent fault diagnosis system for electricity metering according to claim 6, characterized in that, The power data acquisition module includes: The sampling sequence acquisition unit is used to synchronously acquire the instantaneous values ​​of the three-phase voltage and the three-phase current at a fixed sampling frequency, and to construct a three-phase voltage sampling sequence and a three-phase current sampling sequence with a time window length of a preset number of cycles. The interference filtering unit is used to perform adaptive notch filtering on the three-phase voltage sampling sequence and the three-phase current sampling sequence to filter out the high-frequency switching ripple and interharmonic interference introduced by the distributed photovoltaic grid-connected inverter, and obtain the filtered three-phase voltage sampling sequence and the filtered three-phase current sampling sequence. The voltage and current data acquisition unit is used to perform discrete Fourier transform on the filtered voltage sampling sequence of each phase and the filtered current sampling sequence of the corresponding phase, respectively, to extract the fundamental voltage amplitude, fundamental voltage phase, fundamental current amplitude, and fundamental current phase.

9. The intelligent fault diagnosis system for electricity metering according to claim 6, characterized in that, The three-phase current transformer judgment module includes: The positive / negative determination unit is used to obtain the sign of the total three-phase active power and the sign of the total three-phase reactive power. The reverse connection judgment unit is used to determine the overall polarity reverse connection fault of the three-phase current transformer if the sign of the total active power of the three phases is negative and the sign of the total reactive power of the three phases is negative, and outputs a reverse connection alarm for the three-phase current transformer. The normal identification unit is used to determine whether the absolute value of the total three-phase reactive power is less than a preset first threshold if the sign of the total three-phase active power is negative and the sign of the total three-phase reactive power is positive. If the absolute value of the total three-phase reactive power is greater than or equal to the preset first threshold, the current operating condition is determined to be normal reverse power flow, and the three-phase current transformer reverse connection alarm output is suppressed. If the absolute value of the total three-phase reactive power is less than the preset first threshold, the current direction judgment conclusion is suspended, and the judgment is re-evaluated after the data accumulation of the next calculation cycle. If the number of consecutive suspensions exceeds the preset seventh threshold, the current operating condition cannot be confirmed, and the three-phase current transformer reverse connection alarm is output.

10. The intelligent fault diagnosis system for electricity metering according to claim 6, characterized in that, The single-phase current transformer judgment module includes: The data monitoring unit is used to continuously monitor the negative sequence current imbalance and the rate of change of photovoltaic active power output at the distributed photovoltaic grid-connected point. The data calculation unit is used to calculate the ratio of the negative sequence current imbalance to the steady-state negative sequence current imbalance before the change in photovoltaic active power output when the rate of change of photovoltaic active power output exceeds the preset second threshold. This ratio is used as the first ratio. At the same time, the correlation coefficient between the change in negative sequence current imbalance and the change in photovoltaic active power output is calculated. The result determination unit is used to determine that there is a single-phase current transformer polarity reversal fault if the first ratio exceeds the preset third threshold and the correlation coefficient is greater than the preset fourth threshold, and outputs a single-phase current transformer reversal alarm.

Images