Error correction method and system for electric energy metering and electric energy metering device

Abstract

The invention relates to an error correction method and system for electric energy metering and an electric energy metering device, and belongs to the technical field of electric power system measurement. According to the voltage phasor and the current phasor of the pre-selected specific subharmonic, calculating to obtain the current fundamental wave impedance, and taking the current fundamental wave impedance as the current power grid impedance; correcting the current power supply voltage by using the current power grid impedance to obtain corrected virtual power supply voltage; the current electric energy metering operation is executed by using the current current and the corrected virtual power supply voltage, the technical prejudice and practice convention of a traditional metering method are broken through, a brand new and feed-forward correction dimension is introduced, the problem of too fast or too slow is particularly avoided in a weak power grid environment, and the precision is remarkably improved.

Description

Technical Field

[0001] This invention relates to an error correction method and system for electricity metering, and an electricity metering device, belonging to the field of power system measurement technology. Background Technology

[0002] With the large-scale integration of distributed photovoltaic (PV) power into distribution networks, the operating characteristics of the power grid have changed. Traditional electricity metering technology is based on the assumption of an "ideal power grid" (i.e., zero grid impedance and an ideal voltage source). However, real power grids, especially rural distribution networks (weak grids) with long power lines, have non-negligible line impedance. This impedance leads to two key problems: 1. The load current generates a voltage drop across the grid impedance, causing the voltage amplitude and phase at the metering point to deviate from the actual power supply voltage; 2. Harmonic currents generated by nonlinear loads (including photovoltaic inverters) produce harmonic voltages across the grid impedance, causing distortion of the voltage waveform at the metering point.

[0003] Existing electricity metering devices only measure at the grid connection point, resulting in the direct use of the already disturbed voltage at the grid connection point for calculations, which inherently introduces a source of measurement error. Chinese invention patent application CN109061259A discloses a method for analyzing metering errors in smart electricity meters, a metering device, and a smart electricity meter. This method utilizes a sampling circuit to obtain voltage and current sample values ​​from the power grid line; obtains influence parameters after the sampling circuit; corrects the voltage and / or current sample values ​​based on at least one influence parameter; and generates a metering value based on the corrected voltage and current sample values. The influence parameters include harmonic parameters of the sampled signal in the sampling circuit and / or the temperature parameter corresponding to the sampling circuit. It is evident that in this patent application (CN109061259A), the correction of voltage and / or current is used to address the impact of harmonic current on the metering accuracy under temperature variations, but it fails to consider and compensate for the influence of grid impedance on metering accuracy.

[0004] In scenarios with high grid impedance, even with highly accurate metering devices, the measurement results cannot accurately reflect the active power injected into the grid by the photovoltaic system, leading to inaccurate metering. Therefore, there is an urgent need for a new metering method that can sense grid characteristics and automatically correct the errors caused by them. Summary of the Invention

[0005] The purpose of this invention is to provide an error correction method and system for electricity metering, as well as an electricity metering device, to solve the problem of metering errors caused by line impedance voltage drop, realize active identification and real-time correction, and improve the metering accuracy of distributed photovoltaic and other scenarios under weak grid conditions.

[0006] To achieve the above objectives, the present invention proposes an error correction method for electricity metering, comprising the following steps: 1) Extract the pre-selected specific harmonic from the current spectrum and voltage spectrum corresponding to the current preset time window of the grid connection point, and calculate the current fundamental impedance based on the voltage phasor and current phasor of the pre-selected specific harmonic, and use the current fundamental impedance as the current grid impedance. 2) Correct the current power supply voltage using the current grid impedance to obtain the corrected virtual power supply voltage; 3) Perform the current energy metering operation using the current current and the corrected virtual power supply voltage.

[0007] Furthermore, based on the voltage and current phasors of a pre-selected specific harmonic, the current fundamental impedance is calculated using the following method: By dividing the voltage phasor by the current phasor, the frequency impedance of a pre-selected specific harmonic is obtained; The current fundamental impedance is obtained based on the frequency impedance of a pre-selected specific subharmonic and the frequency ratio between the pre-selected specific subharmonic and the fundamental frequency.

[0008] Furthermore, the pre-selected specific subharmonics include two types of harmonics; the method further includes: The frequency impedance of a class of harmonics is calculated using one class of harmonics; the frequency impedance is then verified using another class of harmonics.

[0009] Furthermore, the corrected virtual power supply voltage is obtained using the following formula: u_s(t)=u_m(t)+i(t) Z_grid; Where u_s(t) is the corrected virtual power supply voltage; u_m(t) is the measured voltage; i(t) is the measured current; and Z_grid is the equivalent impedance of the power grid.

[0010] Furthermore, the corrected virtual power supply voltage is obtained by the following method: in the frequency domain, the current spectrum and the voltage spectrum are corrected using the current grid impedance; the corrected current spectrum and voltage spectrum are used to obtain the corrected virtual power supply voltage spectrum; the corrected virtual power supply voltage spectrum is transformed to the time domain to obtain the corrected virtual power supply voltage.

[0011] Furthermore, the current spectrum and voltage spectrum corresponding to the current preset time window of the grid connection point are obtained by the following method: The voltage and current signals at the grid connection point are collected, and anti-aliasing filtering is applied to the voltage and current signals; the anti-aliasing filtered voltage and current signals are then cached in the current preset time window. Both the buffered voltage and current signals are subjected to Fast Fourier Transform to obtain the current spectrum and voltage spectrum corresponding to the current preset time window of the grid connection point.

[0012] Furthermore, the current electricity metering operation includes calculating active power and electrical energy respectively.

[0013] Furthermore, it also includes: periodically calculating the current grid impedance; or, In response to detecting a change in grid current that reaches a preset threshold for triggering the calculation of the current grid impedance, the current grid impedance is calculated.

[0014] On the other hand, the present invention also proposes an error correction system for electricity metering, including a processor, the processor being configured to perform the following method steps: 1) Extract the pre-selected specific harmonic from the current spectrum and voltage spectrum corresponding to the current preset time window of the grid connection point, and calculate the current fundamental impedance based on the voltage phasor and current phasor of the pre-selected specific harmonic, and use the current fundamental impedance as the current grid impedance. 2) Correct the current power supply voltage using the current grid impedance to obtain the corrected virtual power supply voltage; 3) Perform the current energy metering operation using the current current and the corrected virtual power supply voltage.

[0015] Furthermore, based on the voltage and current phasors of a pre-selected specific harmonic, the current fundamental impedance is calculated using the following method: By dividing the voltage phasor by the current phasor, the frequency impedance of a pre-selected specific harmonic is obtained; The current fundamental impedance is obtained based on the frequency impedance of a pre-selected specific subharmonic and the frequency ratio between the pre-selected specific subharmonic and the fundamental frequency.

[0016] Furthermore, the pre-selected specific subharmonics include two types of harmonics; the method further includes: The frequency impedance of a class of harmonics is calculated using one class of harmonics; the frequency impedance is then verified using another class of harmonics.

[0017] Furthermore, the corrected virtual power supply voltage is obtained using the following formula: u_s(t)=u_m(t)+i(t) Z_grid; Where u_s(t) is the corrected virtual power supply voltage; u_m(t) is the measured voltage; i(t) is the measured current; and Z_grid is the equivalent impedance of the power grid.

[0018] Furthermore, the corrected virtual power supply voltage is obtained by the following method: in the frequency domain, the current spectrum and the voltage spectrum are corrected using the current grid impedance; the corrected current spectrum and voltage spectrum are used to obtain the corrected virtual power supply voltage spectrum; the corrected virtual power supply voltage spectrum is transformed to the time domain to obtain the corrected virtual power supply voltage.

[0019] Furthermore, the current spectrum and voltage spectrum corresponding to the current preset time window of the grid connection point are obtained by the following method: The voltage and current signals at the grid connection point are collected, and anti-aliasing filtering is applied to the voltage and current signals; the anti-aliasing filtered voltage and current signals are then cached in the current preset time window. Both the buffered voltage and current signals are subjected to Fast Fourier Transform to obtain the current spectrum and voltage spectrum corresponding to the current preset time window of the grid connection point.

[0020] Furthermore, the current electricity metering operation includes calculating active power and electrical energy respectively.

[0021] Furthermore, it also includes: periodically calculating the current grid impedance; or, In response to detecting a change in grid current that reaches a preset threshold for triggering the calculation of the current grid impedance, the current grid impedance is calculated.

[0022] On the other hand, the present invention also proposes an energy metering device, including a processor, the processor being used to integrate the energy metering error correction system to perform the following method steps: 1) Extract the pre-selected specific harmonic from the current spectrum and voltage spectrum corresponding to the current preset time window of the grid connection point, and calculate the current fundamental impedance based on the voltage phasor and current phasor of the pre-selected specific harmonic, and use the current fundamental impedance as the current grid impedance. 2) Correct the current power supply voltage using the current grid impedance to obtain the corrected virtual power supply voltage; 3) Perform the current energy metering operation using the current current and the corrected virtual power supply voltage.

[0023] Furthermore, based on the voltage and current phasors of a pre-selected specific harmonic, the current fundamental impedance is calculated using the following method: By dividing the voltage phasor by the current phasor, the frequency impedance of a pre-selected specific harmonic is obtained; The current fundamental impedance is obtained based on the frequency impedance of a pre-selected specific subharmonic and the frequency ratio between the pre-selected specific subharmonic and the fundamental frequency.

[0024] Furthermore, the pre-selected specific subharmonics include two types of harmonics; the method further includes: The frequency impedance of a class of harmonics is calculated using one class of harmonics; the frequency impedance is then verified using another class of harmonics.

[0025] Furthermore, the corrected virtual power supply voltage is obtained using the following formula: u_s(t)=u_m(t)+i(t) Z_grid; Where u_s(t) is the corrected virtual power supply voltage; u_m(t) is the measured voltage; i(t) is the measured current; and Z_grid is the equivalent impedance of the power grid.

[0026] Furthermore, the corrected virtual power supply voltage is obtained by the following method: in the frequency domain, the current spectrum and the voltage spectrum are corrected using the current grid impedance; the corrected current spectrum and voltage spectrum are used to obtain the corrected virtual power supply voltage spectrum; the corrected virtual power supply voltage spectrum is transformed to the time domain to obtain the corrected virtual power supply voltage.

[0027] Furthermore, the current spectrum and voltage spectrum corresponding to the current preset time window of the grid connection point are obtained by the following method: The voltage and current signals at the grid connection point are collected, and anti-aliasing filtering is applied to the voltage and current signals; the anti-aliasing filtered voltage and current signals are then cached in the current preset time window. Both the buffered voltage and current signals are subjected to Fast Fourier Transform to obtain the current spectrum and voltage spectrum corresponding to the current preset time window of the grid connection point.

[0028] Furthermore, the current electricity metering operation includes calculating active power and electrical energy respectively.

[0029] Furthermore, it also includes: periodically calculating the current grid impedance; or, In response to detecting a change in grid current that reaches a preset threshold for triggering the calculation of the current grid impedance, the current grid impedance is calculated.

[0030] The beneficial effects of this invention are as follows: A pre-selected specific harmonic is extracted from the current spectrum and voltage spectrum corresponding to the current preset time window at the grid connection point. Based on the voltage phasor and current phasor of the pre-selected specific harmonic, the current fundamental impedance is calculated and used as the current grid impedance. The current power supply voltage is corrected using the current grid impedance to obtain the corrected virtual power supply voltage. The current energy metering operation is performed using the current current and the corrected virtual power supply voltage. This breaks through the technical biases and practical conventions of traditional metering methods, introducing a new, feedforward correction dimension. In particular, it avoids the problem of being too fast or too slow in a weak grid environment, significantly improving accuracy. Attached Figure Description

[0031] Figure 1 This is a flowchart of an error correction method for electricity metering proposed in this invention in practical application scenario 1; Figure 2 This is a flowchart of the online identification of power grid impedance in practical application scenario 2, based on the error correction method for power metering proposed in this invention. Figure 3 This is a system structure diagram of an error correction system for electricity metering proposed in this invention in a practical application scenario; Figure 4 This is a flowchart of the metering application of an electricity metering device proposed in this invention in actual application scenario 3. Detailed Implementation

[0032] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0033] The inventive concept of this invention is as follows: In order to solve the problem of voltage waveform distortion at metering points caused by grid impedance in actual power grids, this invention performs "virtual calibration" on voltage measurement values ​​by identifying grid impedance online, thereby fundamentally eliminating the metering system error introduced by grid impedance and achieving truly high-precision metering.

[0034] Detailed implementation method 1: The present invention proposes an error correction method for electricity metering, comprising steps S11, S12, and S13, specifically: It should be noted that before step S11, the voltage and current signals at the grid connection point are acquired and subjected to anti-aliasing filtering. The anti-aliasing filtered voltage and current signals are then buffered into a current preset time window; in this application, the preset time window is preferably 2 seconds. Fast Fourier Transform is performed on both the buffered voltage and current signals to obtain the current spectrum and voltage spectrum corresponding to the current preset time window at the grid connection point in step S11.

[0035] To promptly detect grid impedance generated in the power grid, the step of calculating the current grid impedance can be performed periodically; alternatively, the calculation can be triggered by events, including but not limited to responding to a preset threshold value for detecting a change in grid current that triggers the calculation of the current grid impedance. Specifically: Step S11: Extract the pre-selected specific harmonic from the current spectrum and voltage spectrum corresponding to the current preset time window of the grid connection point, and calculate the current fundamental impedance based on the voltage phasor and current phasor of the pre-selected specific harmonic, and use the current fundamental impedance as the current grid impedance.

[0036] Step S12: Correct the current power supply voltage using the current grid impedance to obtain the corrected virtual power supply voltage. The virtual power supply voltage can be calculated in either the frequency domain or the time domain. When calculated in the frequency domain, the current spectrum and voltage spectrum from step S11 are corrected to obtain the corrected virtual power supply voltage spectrum, which is then transformed back to the time domain to obtain the corrected virtual power supply voltage. When calculated in the time domain, it is directly calculated using the following formula: u_s(t)=u_m(t)+i(t) Z_grid; Where u_s(t) is the corrected virtual power supply voltage; u_m(t) is the measured voltage; i(t) is the measured current; and Z_grid is the equivalent impedance of the power grid.

[0037] Step S13 performs the current energy metering operation using the current current and the corrected virtual power supply voltage; here, the current energy metering operation includes calculating active power and energy respectively.

[0038] Through steps S11-S13, the systematic metering error caused by line impedance voltage drop is fundamentally eliminated by active identification and real-time correction, significantly improving the metering accuracy of distributed photovoltaic and other scenarios under weak grid conditions.

[0039] Method Detailed Implementation 2: The following explanation, in conjunction with a practical application scenario, details the error correction method for electricity metering proposed in this invention, which includes steps 1-4, specifically: Step 1: Synchronously collect the measured voltage u_m(t) and measured current i(t) at the grid connection point.

[0040] Step 2: Based on the measured voltage u_m(t) and measured current i(t), identify the equivalent impedance Z_grid of the power grid online.

[0041] Step 3: Using the equivalent impedance Z_grid of the power grid and the measured current i(t), the measured voltage u_m(t) is corrected to obtain the corrected virtual power supply voltage u_s(t).

[0042] Step 4: Use the corrected virtual power supply voltage u_s(t) and the measured current i(t) to perform power metering.

[0043] Method Detailed Implementation 3: Following the specific embodiments described above, in step 1, after acquiring the measured voltage u_m(t) and measured current i(t) at the grid connection point, the acquired measured voltage u_m(t) and measured current i(t) are further preprocessed and subjected to Fast Fourier Transform. Specifically: Preprocessing refers to performing anti-aliasing filtering on the measured voltage u_m(t) and measured current i(t) respectively, and caching the data for a preset time window (preferably, the preset time window is 2 seconds); Fast Fourier Transform is to perform FFT on the voltage and current data included in the preset time window cached during preprocessing to obtain the spectrum U_m(w) and i(w).

[0044] In step 2, specifically: based on the spectrum U_m(w) and i(w), specific harmonic vectors are extracted; based on the extracted different harmonic vectors, the grid impedance at each harmonic frequency is calculated; the fundamental impedance is derived from the grid impedance at all harmonic frequencies, and the fundamental impedance is determined as the grid equivalent impedance Z_grid.

[0045] In step 3, the corrected virtual power supply voltage is calculated using the following formula: u_s(t)=u_m(t)+i(t) Z_grid; Where u_s(t) is the corrected virtual power supply voltage; u_m(t) is the measured voltage; i(t) is the measured current; and Z_grid is the equivalent impedance of the power grid.

[0046] In step 4, the use of the corrected virtual power supply voltage u_s(t) and the measured current i(t) for energy metering refers to the use of the corrected virtual power supply voltage and the measured current for energy calculation, which includes active power calculation, energy calculation, etc.

[0047] Method Detailed Implementation 4: like Figure 1The diagram shows a flowchart of an error correction method for electricity metering proposed in this invention in practical application scenario 1. First, the voltage signal u_m(t) and current signal i(t) of the grid connection point are collected and measured synchronously. Then, the identification of grid impedance is performed periodically or by event triggering, that is, whether there is valid grid impedance Z_grid data. If not, it indicates that the grid impedance is zero and the grid is in the state of "ideal grid". At this time, the collected voltage and current signals are used directly for electricity calculation.

[0048] If it exists, then initiate / execute the online grid impedance identification process to obtain the current grid impedance Z_grid data; according to the formula u_s(t) = u_m(t) + i(t) Z_grid calculates the virtual power supply voltage u_s(t); uses the virtual power supply voltage u_s(t) and current signal i(t) to perform electrical energy calculations (including the calculation of active power P and electrical energy W), and finally outputs the metering results.

[0049] like Figure 2 The diagram shows a flowchart of the online identification of grid impedance in practical application scenario 2 of the error correction method for electricity metering proposed in this invention. First, the inputs are: the acquired voltage signal u_m(t) and current signal i(t) (from the signal acquisition unit); preprocessing: anti-aliasing filtering is performed on u_m(t) and i(t), and data for a time window (e.g., 2 seconds) is buffered; fast Fourier transform (FFT): FFT is performed on the buffered voltage and current data to obtain the spectra U_m(w) and i(w); extraction of specific harmonic phasors: from the spectrum, the voltage phasor U_5 and current phasor I_5 of the 5th harmonic (250Hz) are extracted. Optionally, the 7th harmonics U_7 and I_7 can be extracted simultaneously for verification. The 5th harmonic (250Hz) is chosen because it has a high content and good signal-to-noise ratio in the distribution network, which helps improve the accuracy of impedance identification. The 7th harmonic is used for verification because it has a different frequency but the same impedance characteristics as the 5th harmonic, which can improve the reliability of the identification results. The verification includes: calculating the impedance at the corresponding frequency using the 5th and 7th harmonics respectively, and then estimating the fundamental impedance according to the frequency ratio. If the two results are consistent within the preset error range, it is considered valid; otherwise, it is considered invalid or triggers an abnormal processing procedure.

[0050] Calculate the harmonic frequency impedance: Z_5 = U_5 / I_5 (complex division); Estimate the fundamental frequency (50Hz) impedance: Assuming the impedance characteristic is mainly inductive, estimate according to the frequency ratio: Z_grid ≈ (50 / 250) Z_5; Finally, output: The calculated fundamental equivalent impedance Z_grid (resistance component R_g and inductance component L_g) is output to the error correction calculation unit; This result will be stored in the register and remain valid until the next identification is completed.

[0051] Method Detailed Implementation 4: For example, the measured voltage u_m(t) and current i(t) at the grid connection point are collected synchronously. Based on u_m(t) and i(t), the equivalent impedance Z_grid of the power grid is identified online. To reduce computational load, the identification of impedance Z_grid can be performed periodically (e.g., every 5 minutes) or triggered when a change in grid current exceeds a certain threshold. In specific calculations, the background harmonic method can be preferred: FFT analysis is performed on the collected voltage and current signals to extract the voltage phasor U_5 and current phasor I_5 of the 5th harmonic. Then, the impedance Z_5 at this frequency is Z_5 = U_5 / I_5, and the fundamental impedance Z_grid at the power frequency can be calculated. No additional signal injection is required, and there is no impact on the power grid.

[0052] According to the formula u_s(t) = u_m(t) + i(t) Z_grid is used to calculate the corrected virtual power supply voltage u_s(t); using the virtual power supply voltage u_s(t) and the collected current i(t), the accurate active power P and electrical energy W are calculated.

[0053] System Specific Implementation Method 1: On the other hand, the present invention also proposes an error correction system for electricity metering, wherein the system includes a processor for executing the steps of the above-described error correction method for electricity metering.

[0054] In practical applications, the correction system preferably includes: a signal acquisition unit for synchronously measuring the voltage and current signals at the grid connection point; an online grid impedance identification unit for calculating the equivalent impedance (i.e., grid impedance) on the grid side in real time based on the voltage and current signals; an error correction calculation unit for correcting the measured voltage signal according to the equivalent impedance and the current signal to obtain a corrected virtual power supply voltage signal; and a core metering unit for calculating electrical energy using the corrected virtual power supply voltage signal and the current signal.

[0055] In the online power grid impedance identification unit, impedance identification is achieved by monitoring the background harmonics of the power grid or by injecting specific current disturbances into the power grid (background harmonics: impedance is calculated using inherent harmonics in the power grid without external injection; disturbance injection: signals are actively injected, suitable for scenarios with weak harmonics); it is configured to perform impedance identification periodically or event-triggered (periodic: executed at fixed time intervals; event-triggered: triggered when the current change exceeds a threshold; the two are parallel and can be selected or combined according to actual needs); it is also configured to extract the phasors of specific harmonics (preferably 5th or 7th) in the voltage and current signals through fast Fourier transform, and calculate the power grid impedance at the corresponding frequency based on the phasors of the specific harmonics.

[0056] In the error correction calculation unit, the voltage is corrected by performing the following calculations: u_s(t)=u_m(t)+i(t) Z_grid; Where u_s(t) is the corrected virtual power supply voltage; u_m(t) is the measured voltage; i(t) is the measured current; and Z_grid is the equivalent impedance of the power grid.

[0057] System Specific Implementation Method 2: like Figure 3 The diagram shown illustrates the system architecture of an error correction system for electricity metering proposed in this invention in a practical application scenario. The system can be integrated into a standalone electricity metering device, with its core processor (such as a DSP) configured to perform impedance identification, error correction, and electricity calculation tasks. The system includes: a signal acquisition unit, an online grid impedance identification unit, an error correction calculation unit, and a core calculation unit. Specifically: The signal acquisition unit is used to synchronously measure the voltage signal u_m(t) and current signal i(t) at the grid connection point.

[0058] An online grid impedance identification unit, connected to the signal acquisition unit, is used to calculate the equivalent grid impedance Z_grid in real time based on the voltage signal u_m(t) and the current signal i(t). Impedance identification is achieved by monitoring grid background harmonics or injecting specific current disturbances into the grid. Preferably, the impedance is calculated by analyzing specific harmonic components (such as the 5th and 7th harmonics) in the voltage and current signals.

[0059] An error correction calculation unit, connected to the online impedance identification unit and the signal acquisition unit, is used to calculate the voltage error caused by impedance voltage drop based on the impedance Z_grid and the current signal i(t), and to correct the measured voltage u_m(t) based on this error to obtain the corrected virtual power supply voltage u_s(t). This is achieved according to circuit theory using the following formula: u_s(t) = u_m(t) + i(t). Z_grid corrects the measured voltage, where u_s(t) is the corrected virtual power supply voltage.

[0060] The core metering unit, connected to the error correction calculation unit and the signal acquisition unit, is used to calculate the active power P and electrical energy W using the corrected virtual power supply voltage u_s(t) and the acquired current signal i(t).

[0061] Specific implementation method 1 of the device: On the other hand, the present invention also proposes an energy metering device, including a processor for integrating an error correction system for energy metering as described above.

[0062] like Figure 4 The diagram shows a flowchart of the metering application of the electricity metering device proposed in this invention in practical application scenario 3. Based on traditional electricity metering technology, the grid side obtains an ideal voltage source U_s based on an ideal source. Combining grid impedance identification and error correction calculation, the current grid impedance is obtained as Z_grid (the complex form of the grid equivalent impedance: R + JwL, where R is the resistive component; JwL is the inductive reactance component, J is the imaginary unit, w is the angular frequency, and L is the inductance). Based on the current grid impedance, the metering device measures active power and electrical energy, and the obtained active power and electrical energy are used for the photovoltaic power station load.

[0063] Furthermore, the specific implementation methods, system implementation methods, and device implementation methods can be referred to each other, and will not be repeated here.

[0064] In summary, this invention discloses an error correction method and system for electricity metering, as well as an electricity metering device. The method includes: synchronously acquiring grid connection point voltage and current; online identification of the grid's equivalent impedance; correcting the measured voltage using the identified impedance and measured current to obtain a virtual power supply voltage; and performing electricity metering based on the corrected voltage. The system includes: a signal acquisition unit, an online grid impedance identification unit, an error correction calculation unit, and a core metering unit, used to implement the steps of the method. The electricity metering device further incorporates a novel metering method. Both methods overcome the technical bias of traditional metering ignoring the influence of grid impedance. Through active identification and real-time correction, they fundamentally eliminate systematic metering errors caused by line impedance voltage drop, significantly improving the metering accuracy of distributed photovoltaic and other scenarios under weak grid conditions.

[0065] The beneficial effects are as follows: 1. For the first time, a systematic approach has been taken to identify and resolve the root cause of error: This invention breaks the long-standing technical bias and practice in the industry that "the voltage at the metering point is the ideal power supply voltage," and for the first time clearly points out that "grid impedance" is an inherent source of error affecting metering accuracy, and provides a systematic solution. This is not obvious to those skilled in the art.

[0066] 2. A revolutionary change in metering paradigm: upgrading the metering device from a passive "signal recorder" to an active "system state sensor and corrector." This invention is not a patching of existing metering methods, but rather introduces a completely new, feedforward-oriented correction dimension, changing the design paradigm of electricity metering devices.

[0067] 3. Significantly improves metering accuracy under weak power grid conditions: Especially for rural power grids or end lines with high impedance, this invention can effectively correct voltage deviation caused by impedance voltage drop, making the metering results closer to the actual power exchange. It solves the problem of traditional devices being systematically too slow or too fast in weak power grid environments, and achieves unexpected accuracy improvement.

[0068] 4. High cost-effectiveness through hardware and software integration: It is mainly achieved through algorithm upgrades. An impedance identification and correction algorithm module can be added to the existing high-precision metering device without the need for expensive new hardware, which has extremely high promotional value.

Claims

1. A method of error correction for electric energy metering, characterized in that, The method comprises the following steps: 1) extracting pre-selected specific harmonics from the current spectrum and voltage spectrum corresponding to the current preset time window of the grid connection point, and calculating the current fundamental impedance according to the voltage phase and current phase of the pre-selected specific harmonics, and taking the current fundamental impedance as the current grid impedance; 2) correcting the current power supply voltage using the current grid impedance to obtain the corrected virtual power supply voltage; 3) performing the current electric energy metering operation using the current and the corrected virtual power supply voltage.

2. The error correction method of electrical energy metering according to claim 1, characterized in that, The current fundamental impedance is calculated according to the voltage phase and current phase of the pre-selected specific harmonics by the following method: The frequency impedance of the pre-selected specific harmonics is obtained by dividing the voltage phase by the current phase; The current fundamental impedance is obtained according to the frequency impedance of the pre-selected specific harmonics and the frequency ratio between the pre-selected specific harmonics and the fundamental.

3. The error correction method of electrical energy metering according to claim 2, characterized in that, The pre-selected specific harmonics include two types of harmonics; the method further comprises: The frequency impedance of one type of harmonics is calculated, and the other type of harmonics is used to verify the frequency impedance.

4. The error correction method of electrical energy metering according to claim 1, characterized in that, The corrected virtual power supply voltage is obtained by the following formula: u_s(t) = u_m(t) + i(t) Z_grid; Where u_s(t) is the corrected virtual power supply voltage; u_m(t) is the measured voltage; i(t) is the measured current; Z_grid is the equivalent impedance of the grid.

5. The error correction method of electrical energy metering according to claim 1, characterized in that, The corrected virtual power supply voltage is also obtained by the following method: in the frequency domain, the current spectrum and the voltage spectrum are corrected using the current grid impedance; the corrected current spectrum and voltage spectrum are used to obtain the corrected virtual power supply voltage spectrum; the corrected virtual power supply voltage spectrum is transformed to the time domain to obtain the corrected virtual power supply voltage.

6. The error correction method of electrical energy metering according to claim 1, characterized in that, The current spectrum and voltage spectrum corresponding to the current preset time window of the grid connection point are obtained by the following method: The voltage signal and current signal of the grid connection point are collected, and the voltage signal and current signal are subjected to anti-aliasing filtering; the voltage signal and current signal subjected to anti-aliasing filtering are cached to the current preset time window; The cached voltage signal and current signal are subjected to fast Fourier transform to obtain the current spectrum and voltage spectrum corresponding to the current preset time window of the grid connection point.

7. The error correction method of electrical energy metering according to claim 1, characterized in that, The current electric energy metering operation includes calculating active power and electric energy respectively.

8. The error correction method of electrical energy metering according to claim 1, characterized in that, Further comprising: periodically calculating the current grid impedance; or, calculating the current grid impedance in response to detecting that the grid current change reaches a preset change threshold for triggering calculation of the current grid impedance.

9. A system for error correction of electrical energy metering, characterized by It comprises a processor for executing the method steps of any one of claims 1-8.

10. An electrical energy metering device, characterized by It comprises a processor for integrating the system of claim 9.

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