Electric energy metering method under power grid waveform distortion

Abstract

The invention discloses an electric energy metering method under power grid waveform distortion, and particularly relates to the technical field of electric energy metering. The problems of false triggering of an energy compensation mechanism, metering deviation and electricity price settlement risks caused by zero-sequence current or false phase drift easily generated in a multipoint grounding or grounding fault power system in the prior art are solved. According to the anomaly identification and control method integrating zero-sequence current frequency domain characteristic analysis and three-phase phase deviation trend consistency judgment, the false phase deviation state is accurately identified through synchronous sampling, frequency domain analysis and trend consistency evaluation of three-phase voltage, three-phase current and neutral line current, and the false phase deviation state is accurately identified. The error compensation behavior is shielded in real time, the fundamental wave power metering mode is switched to, the electric energy metering accuracy is guaranteed through an error backtracking correction mechanism after recovery, and the anti-interference capability and metering reliability of the electric meter under complex working conditions are effectively improved.

Description

Technical Field

[0001] The present invention relates to the technical field of electric energy metering, and particularly to an electric energy metering method under power grid waveform distortion. Background Art

[0002] Electric energy metering under power grid waveform distortion refers to the process of accurately measuring electric energy when the power grid voltage or current waveform is distorted (i.e., deviates from the ideal sine waveform) due to factors such as non-linear loads. Since waveform distortion can cause phenomena such as harmonics and voltage flicker, traditional electric energy meters may have metering errors. Therefore, electric energy metering technologies with anti-interference and harmonic identification capabilities are required to ensure high-precision electric energy metering in complex power grid environments.

[0003] The existing technologies have the following deficiencies: In a power system with multi-point grounding or grounding faults (such as a subway traction system, a long-distance transmission line), zero-sequence current or false phase drift may occur in the current loop, which is easily misjudged as a real load phase shift by the phase shift identification algorithm. In addition, this misjudgment will trigger an incorrect energy compensation mechanism, resulting in improper decomposition of active and reactive power, and further causing a significant overestimation of apparent power metering and distortion of power factor calculation, which may lead to contract execution errors or punitive electricity price settlement problems. Summary of the Invention

[0004] The purpose of the present invention is to provide an electric energy metering method under power grid waveform distortion to solve the deficiencies in the background art.

[0005] To achieve the above purpose, the present invention provides the following technical solution: An electric energy metering method under power grid waveform distortion, including: Collect three-phase voltage and three-phase current signals to obtain synchronous sampling data including voltage signals, current signals, and neutral line current signals; Perform frequency-domain analysis on the sampling data to obtain the total harmonic distortion rate of each phase and the phase angle between voltage and current; Based on the calculation result of the phase angle, identify whether there is a phase shift and trigger a compensation algorithm; Simultaneously calculate the three-phase zero-sequence current, and judge whether there is a grounding fault or non-linear loop interference based on the amplitude and spectral characteristics of the zero-sequence current; In the case of judging the existence of a grounding fault or non-linear loop interference, further analyze the consistency of the phase shift trends of each phase to identify the false phase shift state; When the false phase shift state is identified, shield the current phase compensation operation and adopt an alternative metering algorithm based on fundamental wave power calculation; Continuously monitor the zero-sequence current and phase changes. If the detection result returns to the normal range, restore the phase compensation mechanism and correct the error.

[0006] Preferably, the frequency-domain analysis includes: Apply a window function to the sampled signal; Perform a fast Fourier transform on each phase signal; Extract the fundamental and high-order harmonic frequency components for calculating the total harmonic distortion rate and the fundamental phase angle.

[0007] Preferably, determining whether the phase shift is abnormal includes: Compare the phase angles of each phase in the current cycle with the set normal range of phase angles; If any phase angle deviates from the interval and exceeds the tolerance threshold within several consecutive cycles, it is determined that there is an abnormal phase shift.

[0008] Preferably, after analyzing the spectral characteristics, a zero-sequence current frequency-domain anomaly index is generated. The generation method is: Extract the time-domain signal through the zero-sequence current calculation formula , perform FFT spectral analysis on the zero-sequence current, and Apply a window function and perform a fast Fourier transform within a complete cycle to obtain the spectrum: ; where is the amplitude component of the nth harmonic, represents the fundamental wave (50Hz) amplitude, represents the highest harmonic component; set the weighting coefficient , calculate the zero-sequence current frequency-domain anomaly index, and the expression is: ; is the zero-sequence current frequency-domain anomaly index.

[0009] Preferably, after analyzing the consistency of the phase shift trends of each phase, a phase shift trend consistency index is generated. The generation method is: Set a sliding time window T, and record the phase difference between the three-phase voltage and current in each sampling cycle: ; where: ; n is the number of sampling points within the time window; is the phase drift time series of phase X, is the phase drift time series of phase Y, is the phase drift time series of phase Z; Calculate the cosine similarity for each pair of phase drift vectors , and the expression is: ; is the drift angle trend included angle between phase X and Y, and calculate three groups of cosine similarities: ; Calculate the Phase Deviation Trend Consistency Index (PDCI), that is, average and normalize the three-phase cosine similarity. The expression is: .

[0010] Preferably, normalize the zero-sequence current frequency-domain anomaly index and the phase deviation trend consistency index so that they are both in the range of [0, 1]. After weighted averaging the normalized zero-sequence current frequency-domain anomaly index and the phase deviation trend consistency index, the phase deviation state anomaly score value is obtained.

[0011] Preferably, set a preset judgment threshold Sth ∈ [0, 1]. If the phase deviation state anomaly score value is greater than or equal to the preset judgment threshold, it is determined as a false phase deviation state, and the compensation algorithm trigger should be blocked or switched to the fundamental wave dominant model; otherwise, it is regarded as a real load change, and power compensation processing can be carried out normally.

[0012] Preferably, the error correction includes: recording the start and end times during the compensation shielding period and the alternative metered electrical energy; after the abnormal state is lifted, estimating the real electrical energy based on the historical power factor or the load characteristic model; performing error backfilling on the cumulative electrical energy value through interpolation or a unified correction factor, and marking the corrected section.

[0013] In the above technical solution, the technical effects and advantages provided by the present invention are: 1. The electrical energy metering method under power grid waveform distortion proposed by the present invention can effectively solve the problem of misjudgment of phase drift caused by grounding faults or non-linear interference in the prior art. By collecting synchronous data of three-phase voltage, current and neutral line current, and performing frequency-domain analysis and trend consistency calculation on the signals, accurate identification of false phase deviation states is achieved, avoiding power decomposition distortion and electrical energy metering deviation caused by mis-triggering the compensation mechanism, and effectively improving the anti-interference ability and robustness of the system in multi-point grounding and complex load scenarios.

[0014] 2. By introducing the fundamental wave power substitution metering mechanism and the error correction mechanism, the continuity and credibility of metering data are ensured even in the misjudgment state. After the abnormal state is lifted, the system can automatically switch to the normal compensation mode and backtrack to correct the error, constructing a complete metering adaptive closed loop. This method is especially suitable for complex power quality scenarios such as subway traction power supply systems, long-distance transmission lines and industrial distribution networks, and has wide engineering applicability and significant economic value. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments recorded in the present invention. For those of ordinary skill in the art, other drawings can also be obtained based on these drawings.

[0016] Figure 1 This is the method mind map of the present invention. Detailed implementation manners

[0017] To make the objectives, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are some but not all of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0018] For the embodiments, please refer to Figure 1 As shown, the power metering method under power grid waveform distortion in this embodiment includes: Collect three-phase voltage and three-phase current signals to obtain synchronous sampling data including voltage signals, current signals and neutral line current signals; Perform frequency-domain analysis on the sampling data to obtain the total harmonic distortion rate of each phase and the phase angle between voltage and current; Based on the calculation result of the phase angle, identify whether there is a phase shift and trigger a compensation algorithm; At the same time, calculate the three-phase zero-sequence current, and judge whether there is a ground fault or non-linear loop interference based on the amplitude and frequency spectrum characteristics of the zero-sequence current; In the case of judging that there is a ground fault or non-linear loop interference, further analyze the consistency of the phase shift trends of each phase to identify false phase shift states; When it is identified as a false phase shift state, shield the current phase compensation operation and adopt an alternative metering algorithm based on fundamental power calculation; Continuously monitor the zero-sequence current and phase change. If the detection result returns to the normal range, restore the phase compensation mechanism and correct the error.

[0019] In the embodiments of the present invention, aiming at the power metering requirements under power grid waveform distortion conditions, a set of synchronous sampling module is first designed and implemented to collect multi-channel electrical signals including three-phase voltage (Ua, Ub, Uc), three-phase current (Ia, Ib, Ic) and neutral line current (In) as the input data basis for subsequent distortion identification and metering calculation.

[0020] Specifically, in this embodiment, a high-precision analog-to-digital converter (ADC) is configured in the electric energy metering device. The ADC has at least 7 synchronous sampling channels, which respectively collect three-phase voltage, three-phase current, and neutral line current signals. The sampling frequency of the analog-to-digital converter is preferably set to not less than 10 kHz to ensure that common high-order harmonic components (such as the 15th to 40th harmonics) and non-periodic interference characteristics can be accurately captured.

[0021] To achieve consistent sampling of the amplitudes and phases of voltage and current signals, this embodiment uses a unified reference clock source to trigger the ADC channel sampling and uniformly controls the sampling starting point through a synchronization controller, so as to maintain a strict time correspondence relationship between the voltage and current waveforms and ensure the accuracy of subsequent phase angle analysis.

[0022] In addition, to enhance the detection ability of zero-sequence components, the sampling channel of the neutral line current In is isolated and coupled by a dedicated current transformer, and its sensitivity is set to 0.1 A / bit to ensure that even weak zero-sequence current fluctuations can be captured and identified. The collected neutral line current signal will be synthesized and analyzed with each phase current to determine whether there are multiple grounding points, grounding faults, or three-phase unbalance conditions in the system.

[0023] All sampled voltage and current signals will be temporarily stored in the buffer unit with an FIFO structure, and read by the embedded processor at a set period and subjected to preliminary signal preprocessing, including operations such as low-pass filtering, amplitude normalization, and abnormal spike removal, and further used for steps such as spectrum analysis, phase identification, and distortion determination.

[0024] Through the above implementation structure and method, the present invention can achieve accurate synchronous acquisition and subsequent analysis of various electric energy parameters in a severely distorted or non-ideal power supply environment, providing accurate and reliable basic data support for subsequent phase shift correction and compensation strategies.

[0025] After completing the synchronous sampling of three-phase voltage, current, and neutral line current, the present invention further performs frequency-domain analysis and processing on the obtained sampling data to extract the main frequency characteristic parameters required for electric energy metering, including the total harmonic distortion (Total Harmonic Distortion, abbreviated as THD) of each phase voltage and current signals and the phase angle between the voltage and current.

[0026] Specifically, this embodiment uses the Fast Fourier Transform (FFT) algorithm to perform discrete spectrum analysis on each phase voltage and current signal within a fixed time window. The time window is preferably set to an integer multiple of a complete power frequency cycle, such as 20 ms, 40 ms, or 80 ms, which not only ensures the frequency resolution but also avoids spectrum leakage caused by boundary truncation.

[0027] During the frequency-domain transformation process, in this embodiment, a window function is first applied to the input signal, preferably using a Hanning window, to reduce the interference of sidelobe leakage on the calculation of high-order harmonics. Then, the FFT is performed on each phase voltage Ua, Ub, Uc and current Ia, Ib, Ic respectively to extract the fundamental frequency (usually 50 Hz or 60 Hz) and the amplitude components of several harmonics.

[0028] The calculation formula for the total harmonic distortion rate THD is: ; where represents the fundamental amplitude, represents the amplitude of the nth harmonic component, and N is the harmonic order of the analysis upper limit, preferably 25 or higher.

[0029] At the same time, to obtain the phase angle relationship between each phase voltage and current, the present invention extracts the phase angle θ of the fundamental component in the corresponding spectrum and calculates the phase difference through the formula: ; where is the fundamental voltage phase angle, is the fundamental current phase angle, and ϕ represents the phase voltage-current phase shift.

[0030] In actual implementation, all frequency-domain analysis operations are performed by an embedded processor or a supporting digital signal processor (DSP) to ensure real-time requirements on the embedded platform. The frequency-domain analysis results will be temporarily stored and sent to the subsequent distortion discrimination and compensation determination logic.

[0031] Through this implementation method, the present invention can not only comprehensively identify and quantify the harmonic distortion levels of each phase, but also accurately calculate the phase angle change trend, thereby providing data support for whether to enable the phase compensation mechanism in the subsequent stage and effectively avoiding the problem of power misdecomposition caused by inaccurate frequency component identification.

[0032] After calculating the phase angles between each phase voltage and current, the present invention further implements a trigger mechanism for the phase shift identification and compensation algorithm to determine whether there is a risk of electric energy measurement error under the current working conditions and accordingly decide whether to adjust and compensate the power calculation model.

[0033] Specifically, this embodiment sets a group of reference phase angle intervals to represent the normal phase angle ranges corresponding to typical load types (such as resistive, inductive, capacitive) in an ideal sinusoidal grid environment. The reference intervals can be preset according to the system type or established through a self-learning method. Usually, the following interval references are set for the 50 Hz fundamental frequency environment: Resistive load: ų≈ 0°±5°; Inductive load: ų∈ [+10°, +45°]; Capacitive load: ų ∈ [−10°, −45°]; During actual operation, the phase angles ų calculated by the system in real time are compared with the above reference interval. If the phase angle of any phase deviates from its typical interval threshold within a continuous number of cycles (such as 3 to 5 cycles), and the deviation amplitude exceeds the set error tolerance (for example, ±10°), then an abnormal phase shift is identified currently.

[0034] Once an abnormal phase shift is identified, the present invention will start a compensation algorithm. The compensation algorithm switches to a "phase compensation enhancement mode" according to the current distortion level and the phase change trend. In this mode: A phase correction factor Δų is introduced to adjust the calculation expressions of the active power P and the reactive power Q; The phase synchronization of the original voltage and current signals is corrected to calibrate the calculation of the power factor cosų; Depending on the specific scenario, a fundamental wave dominant model or a harmonic rejection model is enabled to ensure that the compensation result is only based on the effective energy components.

[0035] In addition, to avoid false triggering caused by short-term disturbances, this embodiment adopts a time window consistency judgment method. Only when the abnormal phase shift continuously exists and is consistent with the change trend of the zero-sequence current, the compensation trigger is finally confirmed, ensuring that the system has good anti-interference ability and misjudgment suppression ability.

[0036] Through this implementation method, the electric energy metering system can effectively sense the abnormal phase drift situation, dynamically adjust the power calculation path under waveform distortion or system abnormal state, and ensure the accuracy and reliability of the metering result.

[0037] To improve the recognition ability of abnormal grid conditions, especially the recognition accuracy of grounding faults and nonlinear circuit interferences, after completing the frequency-domain analysis of the three-phase voltage and current, the present invention further introduces the calculation and spectral feature analysis steps of the zero-sequence current.

[0038] Specifically, the zero-sequence current is obtained by real-time calculation through the following formula: ; where , , are the three-phase current sampling signals respectively. This calculation can be performed in an embedded processor or a digital signal processor (DSP), and is updated once per sampling period to maintain dynamic monitoring of the neutral unbalance state of the system.

[0039] To further identify the abnormal source of the zero-sequence current, the present invention conducts a frequency-domain analysis on , extracts its spectral features, and generates a zero-sequence current frequency-domain anomaly index after analyzing the spectral features. The generation method is: Extract the time-domain signal through the zero-sequence current calculation formula , perform FFT spectrum analysis on the zero-sequence current. Apply a window function (such as the Hanning window) and perform fast Fourier transform (FFT) within a complete cycle (such as 40 ms) to obtain the spectrum: ; where ; is the amplitude component of the nth harmonic, represents the fundamental wave (50 Hz) amplitude, represents the highest harmonic component (such as the 25th harmonic, i.e., 1250 Hz).

[0040] Set the weighting coefficient to emphasize the importance of high-frequency components. The commonly used weighting methods are linear increase or exponential weighting. Calculate the zero-sequence current frequency-domain anomaly index, and the expression is: ; is the zero-sequence current frequency-domain anomaly index.

[0041] FDAI < 0.05: The spectral energy is mainly concentrated in the fundamental wave, and the zero-sequence current is normal unbalance; FDAI≈0.1 - 0.3: There is a certain non-linear disturbance, which may be grounding stray current; FDAI > 0.3: The spectral energy is significantly biased towards high frequencies, suspected of having a grounding fault, harmonic injection or high-frequency coupling interference.

[0042] In the case of judging the existence of a grounding fault or non-linear loop interference, analyze the consistency of the phase shift trend of each phase and generate the phase shift trend consistency index. The generation method is: Set a sliding time window T (for example, 200 ms, corresponding to 10 power frequency cycles of 20 ms), and record the phase difference between the three-phase voltage and current in each sampling period: ; where: ; n is the number of sampling points within the time window (for example, n = 10); is the phase drift time series of phase X, is the phase drift time series of phase Y, is the phase drift time series of phase Z; Calculate the cosine similarity for each pair of phase drift vectors , and the expression is: ; is the included angle of the drift angle trend between phase X and Y. Calculate three groups of cosine similarities: ; Calculate the phase shift trend consistency index PDCI, that is, average and normalize the three-phase cosine similarities, and the expression is: .

[0043] PDCI ≈ 1: The three-phase trends are highly consistent, which may be due to systematic load changes; PDCI ∈ [0.5, 0.9]: There are differences in the phase drifts of some phases, and the zero-sequence current needs to be combined for judgment; PDCI < 0.5: The three-phase trends are seriously inconsistent, suspected of grounding faults, local interference or sampling anomalies, and the compensation mechanism needs to be blocked.

[0044] Normalize the zero-sequence current frequency-domain anomaly index and the phase shift trend consistency index so that they are both within [0, 1]. After weighted average calculation of the normalized zero-sequence current frequency-domain anomaly index and the phase shift trend consistency index, the phase shift state anomaly score value is obtained.

[0045] Set a preset judgment threshold Sth ∈ [0, 1] (for example, 0.5 - 0.7) to distinguish between real load phase shifts and false phase shifts caused by non-power anomalies. If the phase shift state anomaly score value is greater than or equal to the preset judgment threshold, it is determined as a false phase shift state, and the compensation algorithm trigger should be blocked or switched to the fundamental wave dominant model; otherwise, it is regarded as a real load change, and power compensation processing can be carried out normally.

[0046] After determining the abnormal state, the system automatically prohibits the execution of the phase compensation logic in the current cycle, specifically including: Suspend the operation path for correcting the active power and reactive power decomposition according to the phase angle; Do not update the compensation control register or the power correction coefficient; Mark this cycle as a compensation shielding cycle and write it into the event record buffer for later traceability and statistics.

[0047] This measure can effectively prevent the system from wrongly adjusting the power components under non-power distortion conditions and avoid miscalculation or overcorrection in electricity bill settlement.

[0048] While shielding the compensation operation, the present invention adopts a simplified power measurement method based on fundamental wave components as an alternative path to ensure stable and reliable power measurement values can still be provided under false phase drift conditions.

[0049] The specific implementation of the fundamental wave power measurement method includes the following steps: Use Fourier transform or band-pass filter to extract the fundamental wave part (50Hz or 60Hz) from the voltage and current signals, denoted as 、 。

[0050] Calculate the instantaneous fundamental wave active power ,The expression is: ;Among them, It is the phase angle between the fundamental voltage and current. If the phase information cannot be obtained stably, a default power factor (such as 0.95) can be set for estimation.

[0051] The fundamental active power obtained is integrated over time to obtain the periodic electric energy. , the expression is: ; , Indicates a time period, and in the final electric energy data, indicates that this period of data comes from the fundamental wave alternative metering mode, so that the back-end billing system can independently identify it or apply the subsidy mechanism.

[0052] The system continuously monitors the abnormal score value of the phase offset state. Once the score value is lower than the threshold for a number of cycles (for example, 3 consecutive cycles), the system automatically switches back to the normal phase compensation mode; If switching occurs, the system performs error compensation or interpolation correction to maintain the continuity and accuracy of long-term power statistics results.

[0053] Continuously monitor the zero-sequence current and phase changes. If the detection results return to the normal range, the phase compensation mechanism is restored and the error is corrected. Specifically: Read all compensation mask cycle data from the event record buffer to obtain the start and end times , the fundamental wave replacement measurement mode is adopted during this period.

[0054] Extract the integral value of fundamental power during this period of time ; Compensate for system conditions during blanking (temperature, load type, THD level, etc.); After the system is freed from the anomaly, the phase compensation model is restored. At this time, the actual power value that should have occurred during the shielding period is estimated based on the restored grid phase state and harmonic level. .

[0055] Common methods include: comparing the current load power factor, harmonic power rate and other characteristics with the historical database; finding the most similar power mode and predicting the true value ; Calculate the total error value , the expression is: ; Execution error compensation strategy: Adjust the accumulated electric energy value: interpolate ΔE back to The segment can be added back uniformly in the subsequent settlement: the total power value is adjusted directly through the correction factor. The segment is marked as corrected; the original and corrected values ​​are archived for audit and verification; if the system supports remote communication, the power data correction event can be reported to the backend platform.

[0056] The above formulas are all dimensionless and take their numerical values for calculation. The formulas are obtained by collecting a large amount of data for software simulation to get a formula closest to the actual situation. The preset parameters in the formulas are set by those skilled in the art according to the actual situation.

[0057] The above embodiments can be implemented in whole or in part by software, hardware, firmware, or any combination thereof. When implemented using software, the above embodiments can be implemented in whole or in part in the form of a computer program product. The computer program product includes one or more computer instructions or computer programs. When the computer instructions or computer programs are loaded or executed on a computer, the processes or functions described in the embodiments of the present application are generated in whole or in part. The computer can be a general-purpose computer, a special-purpose computer, a computer network, or other programmable devices. 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 in a wired or wireless (such as infrared, wireless, microwave, etc.) manner. The computer-readable storage medium can be any available medium that can be accessed by a computer, or a data storage device such as a server or data center that contains one or more collections of available media. The available media can be magnetic media (such as floppy disks, hard disks, magnetic tapes), optical media (such as DVDs), or semiconductor media. The semiconductor media can be a solid-state drive.

[0058] It should be understood that the term "and / or" in this article is only a description of the association relationship between associated objects, indicating that three relationships can exist. For example, A and / or B can represent: A exists alone, A and B exist simultaneously, and B exists alone. Here, A and B can be singular or plural. In addition, the character " / " in this article generally represents an "or" relationship between the associated objects before and after, but it may also represent an "and / or" relationship, which can be specifically understood by referring to the context. Those of ordinary skill in the art can realize that the units and algorithm steps of each example described in combination with the embodiments disclosed in this article can be implemented by electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are executed in a hardware or software manner depends on the specific application and design constraints of the technical solution. Professional technicians can use different methods to implement the described functions for each specific application, but such implementation should not be considered to exceed the scope of this application.

[0059] As described above, the above is only the specific implementation manner of this application, but the protection scope of this application is not limited thereto. Any person skilled in the art within the technical scope disclosed in this application can easily think of changes or substitutions, which should all be covered by the protection scope of this application.

Claims

1. A method for measuring electric energy under power grid waveform distortion, characterized in that: Including: Collect three-phase voltage and three-phase current signals to obtain synchronous sampling data including voltage signals, current signals, and neutral line current signals; Perform frequency-domain analysis on the sampling data to obtain the total harmonic distortion rate of each phase and the phase angle between voltage and current; Based on the calculation result of the phase angle, identify whether there is a phase shift and trigger a compensation algorithm; Simultaneously calculate the three-phase zero-sequence current, and judge whether there is a ground fault or non-linear loop interference based on the amplitude and frequency spectrum characteristics of the zero-sequence current; In the case of judging that there is a ground fault or non-linear loop interference, further analyze the consistency of the phase shift trends of each phase to identify false phase shift states; When identifying a false phase shift state, shield the current phase compensation operation and adopt an alternative metering algorithm based on fundamental power calculation; Continuously monitor the zero-sequence current and phase change. If the detection result returns to the normal range, restore the phase compensation mechanism and correct the error.

2. The power metering method under power grid waveform distortion according to claim 1, wherein: The frequency-domain analysis includes: Apply a window function to the sampling signal; Perform a fast Fourier transform on each phase signal; Extract the fundamental and higher harmonic frequency components for calculating the total harmonic distortion rate and the fundamental phase angle.

3. The power metering method under power grid waveform distortion according to claim 1, characterized in that: Judging whether the phase shift is abnormal includes: Compare the phase angles of each phase in the current cycle with the set normal phase angle range; If any phase angle deviates from the range and exceeds the tolerance threshold within several consecutive cycles, it is determined that there is an abnormal phase shift.

4. The power metering method under power grid waveform distortion according to claim 1, characterized in that: After analyzing the frequency spectrum characteristics, generate a zero-sequence current frequency-domain anomaly index. The generation method is: Extract the time-domain signal through the zero-sequence current calculation formula , perform FFT spectrum analysis on the zero-sequence current, and apply a window function, and perform a fast Fourier transform within a complete cycle to obtain the spectrum: ; where is the amplitude component of the nth harmonic,[[]] represents the fundamental wave (50Hz) amplitude,[[]] represents the highest harmonic component; set the weighting coefficient , and calculate the zero-sequence current frequency-domain anomaly index, and the expression is: ; is the zero-sequence current frequency-domain anomaly index.

5. The power metering method under power grid waveform distortion according to claim 4, characterized in that: After analyzing the consistency of the phase shift trends of each phase, generate a phase shift trend consistency index. The generation method is: Set a sliding time window T, and record the phase difference between the three-phase voltage and current within each sampling period: ; where: ; n is the number of sampling points within the time window; is the phase drift time series of phase X, is the phase drift time series of phase Y, is the phase drift time series of phase Z; Calculate the cosine similarity for each pair of phase drift vectors , the expression is: ; is the included angle of the drift angle trend between phases X and Y, calculate three groups of cosine similarities: ; Calculate the phase deviation trend consistency index PDCI, that is, average and normalize the three-phase cosine similarities, and the expression is: .

6. The power metering method under power grid waveform distortion according to claim 5, characterized in that: Normalize the zero-sequence current frequency-domain anomaly index and the phase shift trend consistency index so that they are both between [0, 1]. After weighted average calculation of the normalized zero-sequence current frequency-domain anomaly index and the phase shift trend consistency index, obtain the abnormal score value of the phase shift state.

7. The method for measuring electric energy under power grid waveform distortion according to claim 6, characterized in that: Set a preset judgment threshold Sth ∈ [0, 1]. If the abnormal score value of the phase shift state is greater than or equal to the preset judgment threshold, it is determined as a false phase shift state, and the compensation algorithm trigger should be blocked or switched to the fundamental wave dominant model; otherwise, it is regarded as a real load change, and power compensation processing can be carried out normally.

8. The power metering method under power grid waveform distortion according to claim 7, characterized in that: The error correction includes: recording the start and end times during the compensation shielding period and the alternative metering electric energy; after the abnormal state is lifted, estimating the real electric energy based on the historical power factor or load characteristic model; performing error backfilling on the cumulative electric energy value through interpolation or a unified correction factor, and marking the correction section.

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