Electric energy metering compensation method based on photovoltaic grid connection, electric energy metering device and computer readable storage medium

Abstract

The invention relates to a photovoltaic grid-connected-based electric energy metering compensation method, an electric energy metering device and a computer readable storage medium, and belongs to the technical field of electric power system metering, and the method comprises the steps: carrying out the fast Fourier transform of a current signal in response to the condition that each operation parameter of a grid-connected point of a power grid at the current moment is smaller than a corresponding preset parameter threshold value; obtaining the phase of each harmonic wave including the fundamental wave; according to the phases of all the harmonic waves, dividing all the harmonic waves according to a positive sequence component, a negative sequence component and a zero sequence component; calling a pre-established model about the relationship between the harmonic phase sequence and the power error contribution weight to obtain the power error contribution weight of each harmonic in each phase sequence component; based on the current and power error contribution weight of each harmonic wave in each phase sequence component, calculating to obtain a current total error compensation amount; and adding the fundamental wave active power and the current total error compensation amount to obtain target active power, thereby realizing high-precision electric energy metering in a full working condition range.

Description

Technical Field

[0001] This invention relates to a photovoltaic grid-connected power metering and compensation method, power metering device, and computer-readable storage medium, belonging to the field of power system metering technology. Background Technology

[0002] Electricity metering is the cornerstone of fair electricity trading. With the high penetration rate of distributed photovoltaic (PV) systems at the end of distribution networks, their output characteristics pose a severe challenge to traditional metering methods. PV systems output very little current under weak sunlight, and traditional current transformers operate in the nonlinear region of the magnetization curve, leading to a significant increase in metering errors. Furthermore, PV inverters, as power electronic devices, have high harmonic content in their output current, and their power factor (the ratio of active power to apparent power, reflecting the utilization efficiency of effective power in AC circuits) is low under light loads, resulting in significant phase errors in traditional metering algorithms based on the sine wave assumption.

[0003] Therefore, although existing technologies improve accuracy by modifying hardware or performing harmonic filtering, this results in high costs and poor adaptability. For example, Chinese invention patent application CN115754886A discloses a method for compensating electricity meter readings, a storage medium, and an electricity meter. Under half-wave conditions, boundary condition parameters and metering current values ​​are obtained. The boundary condition parameters include at least one of the following: the proportion of the second harmonic to the fundamental frequency or the power factor. When the proportion of the second harmonic to the fundamental frequency and / or the power factor meets preset half-wave compensation conditions, a compensation value corresponding to the metering current value is obtained, and the electricity meter readings are corrected based on the compensation value. The preset half-wave compensation conditions include at least one of the following: the proportion of the second harmonic to the fundamental frequency is between a preset maximum and a preset minimum value; the power factor is between a preset maximum and a preset minimum value. It is evident that this method (i.e., CN115754886A) only uses the proportion of the second harmonic to the fundamental wave and the power factor as parameters for half-wave compensation conditions, resulting in fewer coupling parameters and inability to guarantee accuracy under complex operating conditions. Summary of the Invention

[0004] The purpose of this invention is to provide a photovoltaic grid-connected power metering compensation method, power metering device, and computer-readable storage medium to solve the problem of large metering errors. By utilizing multi-parameter collaborative criteria and refined harmonic phase sequence compensation, high-precision adaptive metering under all operating conditions can be achieved.

[0005] To achieve the above objectives, this invention proposes a power metering and compensation method based on photovoltaic grid connection, comprising the following steps:

[0006] 1) In response to the fact that all operating parameters of the grid connection point at the current moment are less than the corresponding preset parameter thresholds, a fast Fourier transform is performed on the current signal to obtain the phase of each harmonic, including the fundamental wave.

[0007] 2) Based on the phase of all harmonics, classify all harmonics into positive-sequence components, negative-sequence components, and zero-sequence components;

[0008] 3) Call the pre-established model of the relationship between harmonic phase sequence and power error contribution weight to obtain the power error contribution weight of each harmonic sequence; based on the current and power error contribution weight of each harmonic sequence, calculate the current total error compensation amount;

[0009] 4) Add the fundamental active power to the current total error compensation to obtain the target active power;

[0010] The operating parameters include the effective value of the current, the power factor, and the rate of change of the current.

[0011] Furthermore, the following method is used to determine that all operating parameters at the grid connection point at the current time are less than the corresponding preset parameter thresholds:

[0012] The voltage and current signals at the grid connection point are acquired and preprocessed. Based on the preprocessed voltage and current signals, the effective value of the current, the power factor, and the rate of change of the current at the current moment are calculated.

[0013] The effective value of current, power factor, and rate of change of current are compared with the corresponding preset effective current threshold, preset power factor threshold, and preset rate of change of current threshold, respectively. If they are the same, it is determined that all operating parameters of the grid connection point at the current moment are less than the corresponding preset parameter thresholds.

[0014] Furthermore, the preset effective current threshold value ranges from 0.5%I_b to 2%I_b;

[0015] The preset power factor threshold value ranges from 0.4 to 0.6;

[0016] The preset current change rate threshold ranges from 0.05I_b / s to 0.2I_b / s;

[0017] Among them, I _ b represents the rated current of the current transformer.

[0018] Furthermore, in the pre-established model relating harmonic phase sequence to power error contribution weight, the power error contribution weight of negative-sequence harmonics and zero-sequence harmonics is greater than that of positive-sequence harmonics.

[0019] Furthermore, the harmonics include the fundamental frequency up to the 13th harmonic.

[0020] Furthermore, when calculating the fundamental active power, digital lock-in amplification technology is used to enhance the fundamental current signal.

[0021] Furthermore, it also includes the following: if at the current moment, there are one, two, or more operating parameters of the grid connection point that are not less than the corresponding preset parameter threshold, then the fundamental active power is taken as the target active power.

[0022] On the other hand, the present invention also proposes an energy metering device, including a processor, the processor being configured to perform the following method, comprising the following steps:

[0023] 1) In response to the fact that all operating parameters of the grid connection point at the current moment are less than the corresponding preset parameter thresholds, a fast Fourier transform is performed on the current signal to obtain the phase of each harmonic, including the fundamental wave.

[0024] 2) Based on the phase of all harmonics, classify all harmonics into positive-sequence components, negative-sequence components, and zero-sequence components;

[0025] 3) Call the pre-established model of the relationship between harmonic phase sequence and power error contribution weight to obtain the power error contribution weight of each harmonic sequence; based on the current and power error contribution weight of each harmonic sequence, calculate the current total error compensation amount;

[0026] 4) Add the fundamental active power to the current total error compensation to obtain the target active power;

[0027] The operating parameters include the effective value of the current, the power factor, and the rate of change of the current.

[0028] Furthermore, the following method is used to determine that all operating parameters at the grid connection point at the current time are less than the corresponding preset parameter thresholds:

[0029] The voltage and current signals at the grid connection point are acquired and preprocessed. Based on the preprocessed voltage and current signals, the effective value of the current, the power factor, and the rate of change of the current at the current moment are calculated.

[0030] The effective value of current, power factor, and rate of change of current are compared with the corresponding preset effective current threshold, preset power factor threshold, and preset rate of change of current threshold, respectively. If they are the same, it is determined that all operating parameters of the grid connection point at the current moment are less than the corresponding preset parameter thresholds.

[0031] Furthermore, the preset effective current threshold value ranges from 0.5%I_b to 2%I_b;

[0032] The preset power factor threshold value ranges from 0.4 to 0.6;

[0033] The preset current change rate threshold ranges from 0.05I_b / s to 0.2I_b / s;

[0034] Where I_b is the rated current of the current transformer.

[0035] Furthermore, in the pre-established model relating harmonic phase sequence to power error contribution weight, the power error contribution weight of negative-sequence harmonics and zero-sequence harmonics is greater than that of positive-sequence harmonics.

[0036] Furthermore, the harmonics include the fundamental frequency up to the 13th harmonic.

[0037] Furthermore, when calculating the fundamental active power, digital lock-in amplification technology is used to enhance the fundamental current signal.

[0038] Furthermore, it also includes the following: if at the current moment, there are one, two, or more operating parameters of the grid connection point that are not less than the corresponding preset parameter threshold, then the fundamental active power is taken as the target active power.

[0039] On the other hand, the present invention also proposes a computer-readable storage medium storing a computer program / instructions thereon, which is executed by a processor to describe the following method, including the following steps:

[0040] 1) In response to the fact that all operating parameters of the grid connection point at the current moment are less than the corresponding preset parameter thresholds, a fast Fourier transform is performed on the current signal to obtain the phase of each harmonic, including the fundamental wave.

[0041] 2) Based on the phase of all harmonics, classify all harmonics into positive-sequence components, negative-sequence components, and zero-sequence components;

[0042] 3) Call the pre-established model of the relationship between harmonic phase sequence and power error contribution weight to obtain the power error contribution weight of each harmonic sequence; based on the current and power error contribution weight of each harmonic sequence, calculate the current total error compensation amount;

[0043] 4) Add the fundamental active power to the current total error compensation to obtain the target active power;

[0044] The operating parameters include the effective value of the current, the power factor, and the rate of change of the current.

[0045] Furthermore, the following method is used to determine that all operating parameters at the grid connection point at the current time are less than the corresponding preset parameter thresholds:

[0046] The voltage and current signals at the grid connection point are acquired and preprocessed. Based on the preprocessed voltage and current signals, the effective value of the current, the power factor, and the rate of change of the current at the current moment are calculated.

[0047] The effective value of current, power factor, and rate of change of current are compared with the corresponding preset effective current threshold, preset power factor threshold, and preset rate of change of current threshold, respectively. If they are the same, it is determined that all operating parameters of the grid connection point at the current moment are less than the corresponding preset parameter thresholds.

[0048] Furthermore, the preset effective current threshold value ranges from 0.5%I_b to 2%I_b;

[0049] The preset power factor threshold value ranges from 0.4 to 0.6;

[0050] The preset current change rate threshold ranges from 0.05I_b / s to 0.2I_b / s;

[0051] Where I_b is the rated current of the current transformer.

[0052] Furthermore, in the pre-established model relating harmonic phase sequence to power error contribution weight, the power error contribution weight of negative-sequence harmonics and zero-sequence harmonics is greater than that of positive-sequence harmonics.

[0053] Furthermore, the harmonics include the fundamental frequency up to the 13th harmonic.

[0054] Furthermore, when calculating the fundamental active power, digital lock-in amplification technology is used to enhance the fundamental current signal.

[0055] Furthermore, it also includes the following: if at the current moment, there are one, two, or more operating parameters of the grid connection point that are not less than the corresponding preset parameter threshold, then the fundamental active power is taken as the target active power.

[0056] The beneficial effects of this invention are as follows: In response to the fact that all operating parameters of the grid connection point at the current moment are less than the corresponding preset parameter thresholds, a fast Fourier transform is performed on the current signal to obtain the phase of each harmonic, including the fundamental wave; based on the phase of all harmonics, all harmonics are divided into positive sequence components, negative sequence components, and zero sequence components; a pre-established model on the relationship between harmonic phase sequence and power error contribution weight is called to obtain the power error contribution weight of each harmonic in each phase sequence component; based on the current and power error contribution weights of each harmonic in each phase sequence component, the current total error compensation amount is calculated; the fundamental active power is added to the current total error compensation amount to obtain the target active power; through multi-parameter collaborative judgment, typical photovoltaic grid-connected operating conditions are accurately identified, and fine compensation is performed based on the harmonic phase sequence characteristics, thereby achieving high-precision power metering across the entire operating condition range. Attached Figure Description

[0057] Figure 1 This is a flowchart of a photovoltaic grid-connected power metering and compensation method proposed in this invention;

[0058] Figure 2 This is a flowchart of the logical judgment of multi-parameter coupling criteria and mode switching in a practical application scenario of the photovoltaic grid-connected power metering and compensation method proposed in this invention.

[0059] Figure 3 This is a flowchart of a photovoltaic grid-connected power metering and compensation method proposed in this invention in a practical application scenario;

[0060] Figure 4 This is a schematic diagram illustrating the impact of harmonic phase sequence on error in existing technologies;

[0061] Figure 5 This is a schematic diagram illustrating the effect of using the photovoltaic grid-connected power metering compensation method proposed in this invention in a practical application scenario. Detailed Implementation

[0062] 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.

[0063] The inventive concept of this invention lies in: real-time acquisition of voltage and current signals at the grid connection point, and calculation of the effective current value I, power factor PF, and rate of change. / By judging I, PF, | / The system accurately identifies complex operating conditions of photovoltaic grid-connected systems, such as low current, low power factor, and quasi-steady state, by simultaneously checking whether the current is below the corresponding set threshold. When the conditions are met, a high-precision adaptive metering mode is activated. This mode performs harmonic analysis on the current and calculates the current total error compensation based on the phase sequence (positive, negative, and zero sequence) of each harmonic component, according to a preset model relating harmonic phase sequence to power error contribution weights. This corrects the fundamental active power. This effectively overcomes the shortcomings of traditional methods in terms of large metering errors under complex photovoltaic operating conditions. Through multi-parameter collaborative criteria and refined harmonic phase sequence compensation, high-precision adaptive metering is achieved across all operating conditions.

[0064] Detailed implementation method 1:

[0065] like Figure 1 The diagram shows a flowchart of a photovoltaic grid-connected power metering compensation method proposed in this invention, which includes steps S11, S12, S13, and S14, specifically:

[0066] Step S11: In response to the fact that all operating parameters of the grid connection point at the current moment are less than the corresponding preset parameter thresholds, a fast Fourier transform is performed on the current signal to obtain the phase of each harmonic, including the fundamental wave. Here, the operating parameters include the effective value of the current, the power factor, and the rate of change of the current. The rate of change of the current is obtained by calculating the difference between the effective value of the current in the current power frequency cycle and the previous power frequency cycle, and then dividing it by the duration of the power frequency cycle. The fast Fourier transform of the current signal to obtain the phase of each harmonic, including the fundamental wave, refers to performing a spectrum analysis on the current signal. The analysis is performed up to the 13th harmonic to obtain the phase information of at least the fundamental wave, the 5th harmonic, and the 7th harmonic.

[0067] Before step S11, voltage and current signals at the grid connection point are acquired synchronously in real time; the voltage and current signals are processed to calculate the current RMS value I, power factor PF, and current change rate at the current moment. / Determine whether the effective value of the current I is less than a first set threshold I_set, whether the power factor PF is less than a second set threshold PF_set, and whether the rate of change of the current... / Check if the absolute value is less than the third preset threshold D_set; if all operating parameters are less than the corresponding preset parameter thresholds, then execute step S11. At this time, it indicates that the system is in a typical complex photovoltaic grid-connected operating condition and high-precision adaptive metering needs to be started; otherwise, execute the conventional metering mode (see [link to relevant documentation]). Figure 2 ).

[0068] Step S12: Based on the phase of all harmonics, divide all harmonics into positive sequence components, negative sequence components, and zero sequence components.

[0069] Step S13: A pre-established model relating harmonic phase sequence and power error contribution weights is invoked to obtain the power error contribution weights of each harmonic in each phase sequence component. Based on the current and power error contribution weights of each harmonic in each phase sequence component, the current total error compensation is calculated. Here, the current of each harmonic is obtained through the amplitude of each harmonic. The total error compensation can be expressed by the following formula:

[0070] ;

[0071] Where n is the total number of harmonics; A weighting coefficient is contributed to the power error corresponding to the i-th harmonic. This coefficient is usually determined by factors such as harmonic frequency, voltage distortion characteristics, and metering device characteristics. Let i be the current of the i-th harmonic. The formula uses the square term i. 2 This is because the additional losses caused by harmonics are proportional to the square of the current, which conforms to the power loss model in electrical engineering theory (such as resistive loss P=I). 2 R).

[0072] Step S14: Add the fundamental active power to the current total error compensation to obtain the target active power.

[0073] Through steps S11-S14, the collaborative judgment of multiple parameters (effective current value, power factor and current change rate) is used as the criterion for identifying typical photovoltaic grid-connected operating conditions. This enables the formulation of a collaborative processing mechanism for the coupled influence of multiple factors such as "small current", "low power factor" and "dynamic change". It is found that the system is in a typical complex photovoltaic grid-connected operating condition, and high-precision adaptive metering needs to be activated to achieve accurate metering even under complex operating conditions.

[0074] Method Detailed Implementation 2:

[0075] Following the specific embodiments described above, in step S11, the determination of whether the photovoltaic grid-connected system is under typical complex operating conditions is achieved through various operating parameters and their corresponding preset parameter thresholds (i.e., when all operating parameters of the grid connection point are less than the corresponding preset parameter thresholds at the current moment, it indicates that the photovoltaic grid-connected system is under typical complex operating conditions). Therefore, in order to effectively distinguish between normal load fluctuations and abnormal operating conditions caused by harmonics in the power system and avoid false triggering of the compensation mechanism under normal small fluctuations, the preset effective current threshold corresponding to the effective current value is preferably set in the range of 0.5%I_b to 2%I_b; the preset power factor threshold corresponding to the power factor is set in the range of 0.4 to 0.6; and the preset current change rate threshold corresponding to the current change rate is set in the range of 0.05I_b / s to 0.2I_b / s; where I_b is the rated current of the current transformer. By setting reasonable "thresholds" for each operating parameter, unnecessary harmonic analysis and compensation calculations are reduced, the computational load of the processor is reduced, and the overall response speed and operational stability of the power metering system are improved.

[0076] In addition, the preset parameter thresholds are based on typical engineering experience. When the preset effective current threshold is 1% I_b, the preferred preset power factor threshold is 0.5, and the preferred preset current change rate threshold is 0.1 I_b / s, the present invention can be applied to a wider range of application scenarios and has both sensitivity and anti-interference capability.

[0077] like Figure 3 The diagram shows a flowchart of a photovoltaic grid-connected power metering and compensation method proposed in this invention in a practical application scenario. The method involves real-time synchronous acquisition of the voltage signal V(t) and current signal I(t) at the grid connection point; preprocessing of the voltage signal V(t) and current signal I(t) to calculate the current effective value I, power factor PF, and current change rate at the current moment. / Perform multi-parameter coupling criteria: determine whether the effective value of the current I is less than I_set, whether the power factor PF is less than PF_set, and whether the absolute value of the current change rate ΔI / Δt is less than D_set.

[0078] If all conditions are met simultaneously, a high-precision adaptive metering mode is executed. The high-precision adaptive metering mode includes: performing spectral analysis on the current signal to obtain amplitude and phase information of at least the fundamental wave, the 5th harmonic, and the 7th harmonic; dividing each harmonic into positive-sequence, negative-sequence, or zero-sequence components based on the phase information; and calculating the error compensation amount of each harmonic on the total active power based on a pre-established model relating harmonic phase sequence to power error contribution weights. P, where the model assigns different error contribution weights (i.e., power error contribution weights) to harmonic components of different phase sequences. When assigning different error contribution weights, the error contribution weights of negative-sequence harmonics and zero-sequence harmonics are greater than those of positive-sequence harmonics. The fundamental active power is calculated, and the fundamental active power is compared with the error compensation amount. Adding P together yields the final active power value.

[0079] Otherwise, the conventional metering mode is executed, that is, the fundamental active power is used as the target active power.

[0080] In the model establishment process, since negative-sequence and zero-sequence harmonics cause additional heating and torque pulsation in three-phase power systems, their impact on metering equipment errors is usually more significant than that of positive-sequence harmonics. Therefore, negative-sequence and zero-sequence harmonics are given greater weights to make the error model closer to the real physical process. The weight allocation strategy based on the pre-trained model enables the compensation algorithm to more effectively suppress the harmonic components that contribute the most to the metering error. Especially in scenarios with three-phase imbalance in the power grid or with a large number of single-phase nonlinear loads, it can significantly improve the accuracy of the final power metering. With limited compensation resources, priority is given to compensating the harmonic components with greater impact, achieving an optimal balance between compensation effect and computational cost.

[0081] Method Detailed Implementation 3:

[0082] The following section will explain the proposed photovoltaic grid-connected power metering and compensation method in conjunction with practical application scenarios.

[0083] Step 1: Real-time synchronous acquisition of voltage signal u(t) and current signal i(t) at the grid connection point.

[0084] Step 2: Preprocess and analyze the acquired signals to calculate the current operating parameters; wherein, the operating parameters include the effective value of the current I, the power factor PF, and the rate of change of the current per unit time. / .

[0085] Step 3: Multi-parameter coupling criterion and mode switching: Compare each operating parameter with its corresponding preset threshold. If and only if each operating parameter reaches its corresponding preset threshold, it is determined that the current system is under typical complex conditions of photovoltaic grid connection. At this time, it is necessary to avoid the error in metering accuracy caused by traditional metering algorithms. Therefore, proceed to step 4, i.e., high-precision adaptive metering mode. If any operating parameter does not reach its corresponding preset threshold, it indicates that the current system is not under typical complex conditions of photovoltaic grid connection. At this time, the conventional metering mode is used.

[0086] The conditions for determining whether a photovoltaic grid-connected system is in a typical complex operating condition are as follows:

[0087] Condition a: The effective value of the current I is less than the first set threshold I_set; Condition b: The power factor PF is less than the second set threshold PF_set; Condition c: The rate of change of the current | / | Less than the third set threshold D_set.

[0088] Step 4: High-precision adaptive metrology: The high-precision adaptive metrology mode includes the following steps:

[0089] 4.1: Perform a Fast Fourier Transform on the current signal i(t) to analyze its harmonic spectrum and obtain the amplitude and phase information of each harmonic. Here, the amplitude is the direct basis for quantifying the magnitude of the harmonics and thus assessing their influence. The phase is used for phase sequence division. Specifically, the amplitude of each harmonic is used to calculate the effective value of each harmonic current and its related values ​​(such as the square value). Based on the effective value calculation results of the amplitude, subsequent steps include harmonic energy assessment, error contribution weight allocation, and final calculation of error compensation (such as...). P = K I 2 The core input data (in the form of).

[0090] 4.2: Error Compensation Based on Harmonic Phase Sequence: Based on the phase relationship of each harmonic, they are divided into positive sequence, negative sequence, and zero sequence components. Based on a pre-established model of the mapping relationship between harmonic phase sequence and power error, the error compensation amount generated by each harmonic sequence on the total active power is calculated. P; wherein the model includes the contribution weights of harmonics of different phase sequences to the measurement error under low power factor conditions.

[0091] 4.3: Digital phase-locked amplification technology is used to enhance the fundamental current signal in order to improve the signal-to-noise ratio and accurately extract the fundamental component; here, the digital phase-locked amplification technology is an amplification technology that can separate a specific carrier frequency signal from an environment with extremely high interference.

[0092] 4.4: Calculate the fundamental active power P_fundamental, and compare the fundamental active power P_fundamental with the error compensation amount. Adding P together yields the final precise real-time active power P, i.e., P = P_fundamental + P.

[0093] Method Detailed Implementation 4:

[0094] Following the specific embodiments described above, in steps 1 and 2, during signal acquisition and processing, a high-precision ADC chip (e.g., ADS131A04 chip) is preferably used to synchronously acquire the voltage signal u(t) and the current signal i(t) at a sampling rate of 10kHz or higher. After digital filtering (e.g., a low-pass filter), the effective value of the current I and the power factor PF are calculated, and the rate of change of the current is obtained by calculating the difference in the effective value of the current between adjacent power frequency cycles (e.g., 20ms). / .

[0095] When switching modes in step 3, the preferred preset thresholds for each operating parameter are as follows: the preset threshold for the effective current value parameter is set to I_set = 0.01 I_b (where I_b is the rated current); the preset threshold for the power factor parameter is set to PF_set = 0.5; and the preset threshold for the current change rate parameter is set to D_set = 0.1 I_b / s. It is particularly important to emphasize that only when all three operating parameters simultaneously reach their corresponding preset thresholds is it determined to be a typical complex photovoltaic operating condition requiring the activation of the high-precision mode.

[0096] In step 4, during high-precision measurement, the FFT (Fractional Fourier Transform) algorithm is applied to the current signal i(t) to analyze up to the 13th harmonic. This yields amplitude and phase information for at least the fundamental, 5th, and 7th harmonics. The application of the FFT algorithm to analyze the 13th harmonic covers most typical low-order harmonics of interest in international standards (such as the IEC 61000 series), ensuring full coverage of common harmonic pollution sources and making the current signal analysis more comprehensive. Specifically, the 5th and 7th harmonics are extracted because they are abundant and frequently occur in a large number of industrial and civilian power electronic devices (such as frequency converters and rectifiers), and their contribution to measurement errors is particularly significant. Based on this comprehensive analysis, focused processing is performed, optimizing computational resources and improving the real-time performance and engineering applicability of the method while maintaining accuracy. The pre-established model relating harmonic phase sequence and power error is preferably a lookup table or a linear combination formula.

[0097] For example, a preferred approach is to apply the FFT algorithm to the current signal i(t) to extract the amplitude and phase information of the fundamental, 5th, and 7th harmonics; then, by calling a pre-established model relating the harmonic phase sequence to the power error contribution weights, the weight coefficients for the 5th and 7th negative harmonics are obtained as K_5_neg and K_7_neg, respectively, and the weight for the zero-sequence harmonic (e.g., the 3rd) is K_3_zero. The error compensation amount is then calculated. The coefficients were determined by fitting previous experimental data.

[0098] Ultimately, the active power P = P_fundamental + P.

[0099] It should be noted that in actual power grids, the phase sequence of harmonics is complex due to factors such as load asymmetry, transformer magnetic circuit imbalance, and nonlinearity of power electronic equipment. The results of actual analysis using FFT to extract harmonic phase information differ from those obtained solely based on ideal theory. For example, in an ideal symmetrical three-phase sinusoidal system, the 7th harmonic typically exhibits positive-sequence characteristics, while in actual measurements, the 7th harmonic component will contain significant negative-sequence components. Therefore, a specific weighting coefficient (K_7_neg) is assigned to the 7th harmonic according to its negative-sequence component, enabling the design of compensation strategies based on its actual impact on metering errors under specific practical operating conditions. This reflects the invention's optimization philosophy of starting from practical engineering problems rather than adhering to ideal theory, making the compensation model more adaptable and accurate.

[0100] Method Detailed Implementation 5:

[0101] like Figure 4 The diagram illustrates the impact of harmonic phase sequence on error in existing technologies. It qualitatively demonstrates the influence curves of different harmonic types (positive sequence, negative sequence, and zero sequence) on power metering error as the harmonic content increases. It is clearly shown that, at the same content, the increase in metering error caused by negative sequence and zero sequence harmonics is much greater than that caused by positive sequence harmonics. This directly verifies the theoretical basis and necessity of assigning a greater error contribution weight to negative sequence / zero sequence harmonics in this invention.

[0102] like Figure 5 The diagram illustrates the effect of using the proposed photovoltaic grid-connected power metering compensation method in a practical application scenario. It demonstrates the significant suppression of power metering errors after applying the harmonic phase sequence division and weight compensation method. Compared to uncompensated or traditional compensation methods, the error curve using the proposed method is closer to the zero error line, directly demonstrating the effectiveness and superiority of the proposed technical solution.

[0103] Combination Figure 4 and Figure 5 , Figure 4 This reveals the significant differences in the impact of harmonics with different phase sequences. Figure 5 This demonstrates the solution provided by the present invention (a targeted compensation method that effectively solves the problem). Together, these elements constitute a complete illustrated explanation of the problem-solving logic of the present invention.

[0104] On the other hand, the present invention also proposes an energy metering device, including a processor, which is used to execute an energy metering compensation method based on photovoltaic grid connection as described above. Here, the specific implementation of the device can be referred to the specific implementation methods 1-5 above. The energy metering device realizes flexible switching between conventional metering mode and high-precision adaptive metering mode based on multi-parameter coupling criteria, so as to meet the requirements of adaptive high-precision metering under all working conditions.

[0105] On the other hand, the present invention also proposes a computer-readable storage medium storing a computer program / instruction thereon. When the computer program / instruction is executed by a processor, it implements the above-described photovoltaic grid-connected power metering compensation method. Here, the computer program / instruction can be implemented by embedded system (such as DSP, ARM) or FPGA programming and integrated into the power metering device. For specific implementation of the computer storage, please refer to the specific implementation methods 1-5 above. Through soft algorithm upgrade, the accuracy of the existing metering device is improved at a lower cost. It can effectively cope with the challenges brought by photovoltaic grid connection, such as low current, low power factor and rich harmonics, and ensure the metering accuracy and fairness under various operating conditions, from abundant to weak sunlight and from full load to light load.

[0106] In summary, the beneficial effects of this invention are as follows: 1. It breaks through the limitations of traditional single-parameter judgment: by using a three-parameter coupled criterion of effective current value, power factor, and current change rate, it achieves accurate and reliable identification of complex photovoltaic grid-connected operating conditions, effectively avoiding misjudgments and omissions, and solving the problem of poor adaptability of conventional methods. This multi-parameter collaborative judgment mechanism is not a simple superposition, but is based on a deep understanding of the dynamic characteristics of photovoltaic output, which is not obvious to those skilled in the art.

[0107] 2. A revolutionary compensation approach was proposed: For the first time, the concept of "harmonic phase sequence" from power system analysis was introduced into power metering error compensation, and a "harmonic phase sequence-power error mapping model" was established. This method recognizes that harmonics of different phase sequences have different impact mechanisms on power metering, thus achieving a leap from "coarse amplitude compensation" to "refined mechanism compensation," achieving unexpectedly high-precision compensation results, especially with significant advantages in low power factor scenarios.

[0108] 3. Achieved high precision under all operating conditions: Through software algorithm upgrades, this invention improves the accuracy of existing metering devices at a lower cost, effectively addressing challenges such as low current, low power factor, and abundant harmonics brought about by photovoltaic grid connection, and ensuring metering accuracy and fairness under various operating conditions, from abundant to weak sunlight and from full load to light load.

Claims

1. A method for electricity metering and compensation based on photovoltaic grid connection, characterized in that, Includes the following steps: 1) In response to the fact that all operating parameters of the grid connection point at the current moment are less than the corresponding preset parameter thresholds, a fast Fourier transform is performed on the current signal to obtain the phase of each harmonic, including the fundamental wave. 2) Based on the phase of all harmonics, classify all harmonics into positive-sequence components, negative-sequence components, and zero-sequence components; 3) Call the pre-established model of the relationship between harmonic phase sequence and power error contribution weight to obtain the power error contribution weight of each harmonic sequence; The current total error compensation amount is calculated based on the current and power error contribution weights of each sequence harmonic. 4) Add the fundamental active power to the current total error compensation to obtain the target active power; The operating parameters include the effective value of the current, the power factor, and the rate of change of the current.

2. The power metering and compensation method based on photovoltaic grid connection according to claim 1, characterized in that, The following method is used to determine that all operating parameters of the power grid connection point are less than the corresponding preset parameter thresholds at the current moment: The voltage and current signals at the grid connection point are acquired, and the voltage and current signals are preprocessed. Based on the preprocessed voltage and current signals, calculate the effective value of the current, the power factor, and the rate of change of the current at the current moment; The effective value of current, power factor, and rate of change of current are compared with the corresponding preset effective current threshold, preset power factor threshold, and preset rate of change of current threshold, respectively. If they are the same, it is determined that all operating parameters of the grid connection point at the current moment are less than the corresponding preset parameter thresholds.

3. The power metering and compensation method based on photovoltaic grid connection according to claim 2, characterized in that, The preset effective current threshold value ranges from 0.5%I_b to 2%I_b; The preset power factor threshold value ranges from 0.4 to 0.6; The preset current change rate threshold ranges from 0.05I_b / s to 0.2I_b / s; Where I_b is the rated current of the current transformer.

4. The power metering and compensation method based on photovoltaic grid connection according to claim 1, characterized in that, In the pre-established model relating harmonic phase sequence to power error contribution weight, the power error contribution weight of negative-sequence harmonics and zero-sequence harmonics is greater than that of positive-sequence harmonics.

5. The power metering and compensation method based on photovoltaic grid connection according to claim 1, characterized in that, The harmonics include the fundamental frequency up to the 13th harmonic.

6. The power metering and compensation method based on photovoltaic grid connection according to claim 1, characterized in that, When calculating the fundamental active power, digital lock-in amplification technology is used to enhance the fundamental current signal.

7. The power metering and compensation method based on photovoltaic grid connection according to claim 1, characterized in that, It also includes the following: if at the current moment, there is one or two or more operating parameters of the grid connection point that are not less than the corresponding preset parameter threshold, then the fundamental active power will be used as the target active power.

8. An electricity metering device, characterized in that, Includes a processor for performing the method as described in any one of claims 1-7.

9. A computer-readable storage medium having a computer program / instructions stored thereon, characterized in that, When the computer program / instructions are executed by the processor, they implement the steps of the method described in any one of claims 1-7.

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