A method and system for identifying and calibrating metering errors of half-wave signals of an electric energy meter

Abstract

The application discloses a kind of electric energy meter half-wave signal identification and metering error calibration method, comprising the following steps: obtaining the sampling data of current signal continuous cycle;By analyzing the frequency domain characteristics and time domain characteristics of the current signal, a double criterion is constructed to determine whether the current signal is a half-wave signal;When the current signal is identified as a half-wave signal, the electric energy meter calls the pre-stored half-wave basic compensation coefficient and half-wave segmented compensation coefficient, generates a half-wave metering error compensation curve, and determines the corresponding half-wave compensation value according to the real-time measured current value, and calibrates the metering error of the half-wave signal based on the half-wave compensation value.The application also discloses an electric energy meter half-wave signal identification and metering error calibration system.The application solves the technical problem of how to accurately and quickly identify half-wave signals and calibrate the metering error of electric energy meters under half-wave conditions with high precision.

Description

Technical Field

[0001] This invention relates to the field of electricity metering technology, and in particular to a method and system for identifying half-wave signals of electricity meters and calibrating metering errors. Background Technology

[0002] With the rapid development of power electronics technology, the proportion of nonlinear loads in the power grid (such as thyristor voltage regulating equipment, electric arc furnaces, welding machines, charging piles and various AC / DC converters) is increasing day by day. These loads generate a large number of harmonics during operation, which causes distortion of the power grid current waveform and seriously affects the metering accuracy of electricity meters.

[0003] Currently, traditional three-phase electricity meters generally use electromagnetic current transformers (CTs) for current sampling. However, due to the physical characteristics of the CT core material, their resistance to DC saturation is relatively weak. Under typical harmonic conditions like half-wave, the DC component in the current causes the core to rapidly saturate, resulting in severe distortion of the secondary output waveform of the transformer. This makes it impossible to accurately reproduce the primary current signal, leading to a significant increase in the metering error, sometimes far exceeding the error limits allowed by national standards. Therefore, there is an urgent need to propose a method and system for half-wave signal identification and metering error calibration in electricity meters, addressing the technical problem of accurately and quickly identifying half-wave signals and performing high-precision calibration of metering errors under half-wave conditions. Summary of the Invention

[0004] The main objective of this invention is to propose a method and system for identifying half-wave signals and calibrating metering errors in electricity meters. This aims to solve the technical problem of how to accurately and quickly identify half-wave signals and perform high-precision calibration of metering errors under half-wave conditions.

[0005] To achieve the above objectives, the present invention provides a method for identifying and calibrating half-wave signals of an electricity meter, wherein the method includes the following steps:

[0006] S1. Acquire sampling data of continuous cycles of the current signal;

[0007] S2. By analyzing the frequency domain and time domain characteristics of the current signal, a dual criterion is constructed to determine whether the current signal is a half-wave signal;

[0008] S3. When the current signal is identified as a half-wave signal, the energy meter calls the pre-stored half-wave basic compensation coefficient and half-wave segmented compensation coefficient to generate a half-wave metering error compensation curve, and determines the corresponding half-wave compensation value based on the real-time measured current value, and calibrates the metering error of the half-wave signal based on the half-wave compensation value.

[0009] In one preferred embodiment, step S2 involves analyzing the frequency domain characteristics of the current signal, including:

[0010] Read the sampled data of the first cycle and save it to the data buffer Buffer0;

[0011] The second harmonic content of the first cycle is calculated using the FFT algorithm with a lookup table method, specifically as follows:

[0012] A table of sine and cosine component constants for the fundamental wave and the second harmonic; the table of sine and cosine component constants includes a table of fundamental wave cosine, a table of fundamental wave sine, a table of second harmonic cosine, and a table of second harmonic sine.

[0013] The sampled data in Buffer0 are sequentially multiplied by the sine and cosine component constant tables and then summed to obtain the sum of the fundamental cosine components, the sum of the fundamental sine components, the sum of the second harmonic cosine components, and the sum of the second harmonic sine components, respectively.

[0014] Calculate the square of the fundamental amplitude and the square of the second harmonic amplitude, and calculate the second harmonic content based on the square of the fundamental amplitude and the square of the second harmonic amplitude;

[0015] A first threshold range is set, and it is determined whether the second harmonic content of the first cycle is within the first threshold range. If not, the first cycle is determined to be a non-half-wave signal.

[0016] One preferred embodiment is that the calculation of the square of the fundamental amplitude and the square of the second harmonic amplitude specifically involves:

[0017] The square of the fundamental amplitude is:

[0018]

[0019] The square of the second harmonic amplitude is:

[0020]

[0021] in, The square of the fundamental amplitude, The square of the second harmonic amplitude, The sum of the fundamental cosine components. This is the sum of the second harmonic cosine components. The sum of the fundamental sinusoidal components. It is the sum of the sinusoidal components of the second harmonic.

[0022] In one preferred embodiment, the second harmonic content is:

[0023]

[0024] in, This represents the second harmonic content rate.

[0025] In one preferred embodiment, step S2 involves analyzing the time-domain characteristics of the current signal, including:

[0026] Set a second threshold interval; if the second harmonic content of the first cycle is within the first threshold interval, calculate the ratio of the first absolute value of the maximum and minimum values ​​of the first cycle sampling data, and determine whether the first absolute value ratio is within the second threshold interval. If not, determine that the first cycle is a non-half-wave signal; if so, determine that the first cycle is a half-wave signal.

[0027] In one preferred embodiment, step S2, by analyzing the frequency domain and time domain characteristics of the current signal, further includes:

[0028] Read the sampled data from the second cycle and save it to the data buffer Buffer1;

[0029] The second harmonic content of the second cycle is calculated using the FFT algorithm with a lookup table method; specifically:

[0030] Table of sine and cosine component constants for the preset fundamental and second harmonic frequencies;

[0031] The sampled data in Buffer1 are sequentially multiplied by the sine and cosine component constant tables and then summed to obtain the sum of the fundamental cosine components, the sum of the fundamental sine components, the sum of the second harmonic cosine components, and the sum of the second harmonic sine components, respectively.

[0032] Calculate the square of the fundamental amplitude and the square of the second harmonic amplitude, and calculate the second harmonic content of the second cycle based on the square of the fundamental amplitude and the square of the second harmonic amplitude;

[0033] Determine whether the second harmonic content of the second cycle is within the first threshold range; if not, determine that the second cycle is a non-half-wave signal.

[0034] If it is, then calculate the ratio of the second absolute value of the maximum and minimum values ​​of the second cycle sampling data, and determine whether the second absolute value ratio is within the second threshold range. If it is not, then determine that the second cycle is a non-half-wave signal; if it is, then determine that the second cycle is a half-wave signal.

[0035] If both the first and second cycles are half-wave signals, then the current signal is determined to be a half-wave signal.

[0036] In one preferred embodiment, the half-wave base compensation coefficient includes the half-wave ratio difference base compensation coefficient and the half-wave angle difference base compensation coefficient.

[0037] In one preferred embodiment, the half-wave segmented compensation coefficient includes the half-wave ratio difference segmented compensation coefficient and the half-wave angle difference segmented compensation coefficient.

[0038] In one preferred embodiment, the half-wave measurement error compensation curve includes a half-wave ratio difference compensation curve and a half-wave angle difference compensation curve;

[0039] The formula for the half-wave ratio difference compensation curve is:

[0040]

[0041] The formula for the half-wave angle difference compensation curve is:

[0042]

[0043] in, This is the half-wave ratio difference compensation value. This is the half-wave angle difference compensation value. The half-wave ratio difference basic compensation coefficient is obtained through the first half-wave basic calibration point. The half-wave angle difference basic compensation coefficient is obtained through the second half-wave basic calibration point. The half-wave ratio differential piecewise compensation coefficient function varies with the current value. The half-wave angle difference piecewise compensation coefficient function varies with the current value.

[0044] A half-wave signal identification and metering error calibration system for an energy meter, including the aforementioned method for half-wave signal identification and metering error calibration, comprises:

[0045] A half-wave signal identification module and a half-wave measurement error calibration module; the half-wave signal identification module is connected to the half-wave measurement error calibration module;

[0046] The half-wave signal identification module is used to identify whether the current signal is a half-wave signal;

[0047] The half-wave measurement error calibration module is used to call the pre-stored half-wave compensation coefficients, generate a half-wave measurement error compensation curve, determine the corresponding half-wave compensation value based on the real-time measured current value, and calibrate the measurement error of the half-wave signal based on the half-wave compensation value.

[0048] In the above technical solution of the present invention, the method for half-wave signal identification and metering error calibration of an energy meter includes the following steps: acquiring sampling data of continuous cycles of a current signal; constructing dual criteria by analyzing the frequency domain characteristics and time domain characteristics of the current signal to determine whether the current signal is a half-wave signal; when the current signal is identified as a half-wave signal, the energy meter calls the pre-stored half-wave basic compensation coefficient and half-wave segmented compensation coefficient to generate a half-wave metering error compensation curve, and determines the corresponding half-wave compensation value based on the real-time measured current value, and calibrates the metering error of the half-wave signal based on the half-wave compensation value. The present invention solves the technical problem of how to accurately and quickly identify half-wave signals and perform high-precision calibration of the metering error of an energy meter under half-wave operating conditions. Attached Figure Description

[0049] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0050] Figure 1 This is a schematic diagram of a method for identifying half-wave signals and calibrating metering errors in an energy meter according to an embodiment of the present invention.

[0051] The realization of the objective, functional characteristics and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0052] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0053] Furthermore, in this invention, descriptions involving "first," "second," etc., are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined with "first" or "second" may explicitly or implicitly include at least one of that feature.

[0054] Furthermore, the technical solutions of the various embodiments of the present invention can be combined with each other, but only if they are based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such combination of technical solutions does not exist and is not within the scope of protection claimed by the present invention.

[0055] See Figure 1 According to one aspect of the present invention, the present invention provides a method for identifying and calibrating the half-wave signal of an electricity meter, wherein the method includes the following steps:

[0056] S1. Acquire sampling data of continuous cycles of the current signal;

[0057] S2. By analyzing the frequency domain and time domain characteristics of the current signal, a dual criterion is constructed to determine whether the current signal is a half-wave signal;

[0058] S3. When the current signal is identified as a half-wave signal, the energy meter calls the pre-stored half-wave basic compensation coefficient and half-wave segmented compensation coefficient to generate a half-wave metering error compensation curve, and determines the corresponding half-wave compensation value based on the real-time measured current value, and calibrates the metering error of the half-wave signal based on the half-wave compensation value.

[0059] Specifically, in this embodiment, step S2 involves analyzing the frequency domain characteristics of the current signal, including:

[0060] Read the sampled data of the first cycle and save it to the data buffer Buffer0;

[0061] The second harmonic content of the first cycle is calculated using the FFT algorithm with a lookup table method, specifically as follows:

[0062] A table of sine and cosine component constants for the fundamental wave and the second harmonic; the table of sine and cosine component constants includes a table of fundamental wave cosine, a table of fundamental wave sine, a table of second harmonic cosine, and a table of second harmonic sine.

[0063] The sampled data in Buffer0 are sequentially multiplied by the sine and cosine component constant tables and then summed to obtain the sum of the fundamental cosine components, the sum of the fundamental sine components, the sum of the second harmonic cosine components, and the sum of the second harmonic sine components, respectively.

[0064] Calculate the square of the fundamental amplitude and the square of the second harmonic amplitude, and calculate the second harmonic content based on the square of the fundamental amplitude and the square of the second harmonic amplitude;

[0065] A first threshold range is set, and it is determined whether the second harmonic content of the first cycle is within the first threshold range. If not, the first cycle is determined to be a non-half-wave signal.

[0066] Specifically, in this embodiment, the calculation of the square of the fundamental amplitude and the square of the second harmonic amplitude is as follows:

[0067] The square of the fundamental amplitude is:

[0068]

[0069] The square of the second harmonic amplitude is:

[0070]

[0071] in, The square of the fundamental amplitude, The square of the second harmonic amplitude, The sum of the fundamental cosine components. This is the sum of the second harmonic cosine components. The sum of the fundamental sinusoidal components. It is the sum of the sinusoidal components of the second harmonic.

[0072] Specifically, in this embodiment, the second harmonic content is:

[0073]

[0074] in, This represents the second harmonic content rate.

[0075] In one preferred embodiment, step S2 involves analyzing the time-domain characteristics of the current signal, including:

[0076] Set a second threshold interval; if the second harmonic content of the first cycle is within the first threshold interval, calculate the ratio of the first absolute value of the maximum and minimum values ​​of the first cycle sampling data, and determine whether the first absolute value ratio is within the second threshold interval. If not, determine that the first cycle is a non-half-wave signal; if so, determine that the first cycle is a half-wave signal.

[0077] Specifically, in this embodiment, step S2, by analyzing the frequency domain characteristics and time domain characteristics of the current signal, further includes:

[0078] Read the sampled data from the second cycle and save it to the data buffer Buffer1;

[0079] The second harmonic content of the second cycle is calculated using the FFT algorithm with a lookup table method; specifically:

[0080] Table of sine and cosine component constants for the preset fundamental and second harmonic frequencies;

[0081] The sampled data in Buffer1 are sequentially multiplied by the sine and cosine component constant tables and then summed to obtain the sum of the fundamental cosine components, the sum of the fundamental sine components, the sum of the second harmonic cosine components, and the sum of the second harmonic sine components, respectively.

[0082] Calculate the square of the fundamental amplitude and the square of the second harmonic amplitude, and calculate the second harmonic content of the second cycle based on the square of the fundamental amplitude and the square of the second harmonic amplitude;

[0083] Determine whether the second harmonic content of the second cycle is within the first threshold range; if not, determine that the second cycle is a non-half-wave signal.

[0084] If it is, then calculate the ratio of the second absolute value of the maximum and minimum values ​​of the second cycle sampling data, and determine whether the second absolute value ratio is within the second threshold range. If it is not, then determine that the second cycle is a non-half-wave signal; if it is, then determine that the second cycle is a half-wave signal.

[0085] If both the first and second cycles are half-wave signals, then the current signal is determined to be a half-wave signal.

[0086] Specifically, in this embodiment, the half-wave base compensation coefficient includes the half-wave ratio difference base compensation coefficient and the half-wave angle difference base compensation coefficient.

[0087] Specifically, in this embodiment, based on the operating current range of the energy meter and the characteristics of the half-wave metering error curve, a first half-wave basic calibration point is selected. The calibration device is controlled to output the half-wave signal corresponding to the first half-wave basic calibration point, and the first half-wave metering error value of the energy meter at the first half-wave basic calibration point is obtained. The first power gain of the first half-wave basic calibration point is calculated. The first power gain is:

[0088]

[0089] in, For the first power gain, This represents the measurement error value for the first half-wave.

[0090] If the first power gain is greater than or equal to 0, then the half-wave ratio difference basic compensation coefficient is:

[0091]

[0092] Conversely, the half-wave ratio difference basic compensation coefficient is:

[0093]

[0094] in, This is the basic compensation coefficient for half-wave ratio difference;

[0095] Write the half-wave ratio difference basic compensation coefficient into the electricity meter.

[0096] Specifically, in this embodiment, based on the operating current range of the energy meter and the characteristics of the half-wave metering error curve, a second half-wave basic calibration point is selected. The calibration device is controlled to output the half-wave signal corresponding to the second half-wave basic calibration point, and the second half-wave metering error value of the energy meter at the second half-wave basic calibration point is obtained. The first phase compensation of the second half-wave basic calibration point is calculated. The first phase compensation is:

[0097]

[0098] in, For the first phase compensation, This is the measurement error value for the second half-wave.

[0099] If the first phase compensation is greater than or equal to 0, then the basic compensation coefficient for half-wave angle difference is:

[0100]

[0101] Conversely, the basic compensation coefficient for half-wave angle difference is:

[0102]

[0103] in, This is the basic compensation coefficient for half-wave angle difference;

[0104] Write the half-wave angle difference basic compensation coefficient into the electricity meter.

[0105] Specifically, in this embodiment, the half-wave segmented compensation coefficient includes the half-wave ratio difference segmented compensation coefficient and the half-wave angle difference segmented compensation coefficient.

[0106] Specifically, in this embodiment, the half-wave measurement error compensation curve includes a half-wave ratio difference compensation curve and a half-wave angle difference compensation curve;

[0107] The formula for the half-wave ratio difference compensation curve is:

[0108]

[0109] The formula for the half-wave angle difference compensation curve is:

[0110]

[0111] in, This is the half-wave ratio difference compensation value. This is the half-wave angle difference compensation value. The half-wave ratio difference basic compensation coefficient is obtained through the first half-wave basic calibration point. The half-wave angle difference basic compensation coefficient is obtained through the second half-wave basic calibration point. The half-wave ratio differential piecewise compensation coefficient function varies with the current value. The half-wave angle difference piecewise compensation coefficient function varies with the current value.

[0112] Specifically, in this embodiment, the data cache and variables of the A-phase half-wave signal identification module are initialized, the synchronous sampling unit of the metering chip is configured, and the sampling data of at least two consecutive cycles (144 points) of the A-phase current signal are cached. The sampling data of 72 points of the first cycle are read from the metering chip and saved to the data cache Buffer0. The second harmonic content of the first cycle is calculated using the FFT algorithm with a lookup table.

[0113] A pre-set table of sine and cosine component constants for the fundamental and second harmonic waves is provided in the storage area. This table includes a fundamental cosine table, a fundamental sine table, a second harmonic cosine table, and a second harmonic sine table. The 72 sampled data points in Buffer0 are sequentially multiplied by the above four constant tables and summed to obtain the sum of the fundamental cosine components, the fundamental sine components, the second harmonic cosine components, and the second harmonic sine components, respectively. The squared amplitude of the fundamental wave and the squared amplitude of the second harmonic wave are calculated. The squared amplitude of the fundamental wave is:

[0114]

[0115] The square of the second harmonic amplitude is:

[0116]

[0117] in, The square of the fundamental amplitude, The square of the second harmonic amplitude, The sum of the fundamental cosine components. This is the sum of the second harmonic cosine components. The sum of the fundamental sinusoidal components. This is the sum of the sinusoidal components of the second harmonic;

[0118] The second harmonic content is calculated based on the square of the fundamental amplitude and the square of the second harmonic amplitude; the second harmonic content is:

[0119]

[0120] in, The second harmonic content;

[0121] A first threshold range and a second threshold range are set; in this invention, the first threshold range is 40%-65%, and the second threshold range is 87%-115%. This invention does not impose specific limitations, and the range can be set as needed. It is determined whether the second harmonic content of the first cycle is within the 40%-65% range. If it is not within this range, the cycle is determined to be a non-half-wave signal, and half-wave signal identification for phases B and C is performed. If it is within this range, the first absolute value ratio of the maximum to minimum value of the first cycle sampling data is calculated. The first absolute value ratio is:

[0122]

[0123] If the first absolute value ratio is not within the range of 87%-115%, the first cycle is determined to be a non-half-wave signal, and half-wave signal identification of phases B and C is performed. If it is within the range, the first cycle is determined to be a half-wave signal.

[0124] The sampling data of 72 points for the second cycle is read from the metering chip and saved to the data buffer Buffer1. The second harmonic content of the second cycle is calculated using the FFT algorithm with a lookup table. The specific calculation process is the same as that for the first cycle and will not be elaborated further. It is determined whether the second harmonic content of the second cycle is within the range of 40%-65%. If it is not within this range, the second cycle is determined to be a non-half-wave signal, and half-wave signal identification of phases B and C is performed. If it is within this range, the second absolute value ratio of the maximum and minimum values ​​of the second cycle sampling data is calculated. The second absolute value ratio is:

[0125]

[0126] If the second absolute value ratio is not within the range of 87%-115%, the second cycle is determined to be a non-half-wave signal, and half-wave signal identification of phases B and C is performed. If it is within the range, the second cycle is determined to be a half-wave signal.

[0127] When both the first and second cycles are half-wave signals, the current signal of phase A is determined to be a half-wave signal. Repeat the above steps to complete the half-wave signal identification of phases B and C.

[0128] Specifically, in this embodiment, based on the operating current range of the energy meter and the characteristics of the half-wave metering error curve, a current value is selected. The first half-wave baseline calibration point with a power factor of 1.0 and a current value of The second half-wave baseline calibration point has a power factor of 0.5L. A power factor of 1.0 indicates resistive operation, and a power factor of 0.5L indicates inductive operation. The host computer sends a command to the calibration device, controlling the device to output the half-wave signal corresponding to the first half-wave baseline calibration point. The computer waits for the output of the calibration device to stabilize, obtains the first half-wave metering error value of the energy meter at the first half-wave baseline calibration point, and calculates the first power gain at the first half-wave baseline calibration point. The first power gain is:

[0129]

[0130] in, For the first power gain, This represents the measurement error value for the first half-wave.

[0131] If the first power gain is greater than or equal to 0, then the half-wave ratio difference basic compensation coefficient is:

[0132]

[0133] Conversely, the half-wave ratio difference basic compensation coefficient is:

[0134]

[0135] in, This is the basic compensation coefficient for half-wave ratio difference;

[0136] Write the half-wave ratio difference basic compensation coefficient into the electricity meter;

[0137] The control and verification device outputs the half-wave signal corresponding to the second half-wave basic calibration point, and obtains the second half-wave metering error value of the energy meter at the second half-wave basic calibration point, and calculates the first phase compensation of the second half-wave basic calibration point; the first phase compensation is:

[0138]

[0139] in, For the first phase compensation, This is the measurement error value for the second half-wave.

[0140] If the first phase compensation is greater than or equal to 0, then the basic compensation coefficient for half-wave angle difference is:

[0141]

[0142] Conversely, the basic compensation coefficient for half-wave angle difference is:

[0143]

[0144] in, This is the basic compensation coefficient for half-wave angle difference;

[0145] Write the half-wave angle difference basic compensation coefficient into the electricity meter;

[0146] After the half-wave basic calibration point is calibrated, select a current value of 1.2. The power factor is 1.0 and the current value is The power factor is 1.0 and the current value is 0.3. The power factor is 1.0 and the current value is 10. Four half-wave ratio differential calibration points with a power factor of 1.0 were selected, with a current value of 1.2. The power factor is 0.5L and the current value is The power factor is 0.5L and the current value is 0.3. The power factor is 0.5L and the current value is 10. The four half-wave angle difference segment calibration points with a power factor of 0.5L are used to adjust the output of the calibration device in the order of the four half-wave ratio difference segment calibration points. After the output of the calibration device stabilizes, the half-wave measurement error of the energy meter is obtained from the calibration device in sequence. Based on the power gain calculation formula, the half-wave ratio differential piecewise compensation coefficient is calculated. The data is then written into the electricity meter. Following the sequence of the four half-wave angle difference segment calibration points, the output of the control verification device is adjusted. Once the output of the verification device stabilizes, the half-wave measurement error values ​​of the electricity meter are sequentially obtained from the verification device. Based on the phase compensation calculation formula, the half-wave angle difference piecewise compensation coefficient is calculated. The data is then written into the energy meter. At this point, both the half-wave basic calibration point and the half-wave segment calibration point have been calibrated. The energy meter's software program generates a half-wave metering error compensation curve based on the half-wave ratio difference basic compensation coefficient, the half-wave angle difference basic compensation coefficient, the half-wave ratio difference segment compensation coefficient, and the half-wave angle difference segment compensation coefficient. The half-wave metering error compensation curve includes the half-wave ratio difference compensation curve and the half-wave angle difference compensation curve.

[0147] The formula for the half-wave ratio difference compensation curve is:

[0148]

[0149] The formula for the half-wave angle difference compensation curve is:

[0150]

[0151] in, This is the half-wave ratio difference compensation value. This is the half-wave angle difference compensation value. The half-wave ratio difference basic compensation coefficient is obtained through the first half-wave basic calibration point. The half-wave angle difference basic compensation coefficient is obtained through the second half-wave basic calibration point. The half-wave ratio differential piecewise compensation coefficient function varies with the current value. The half-wave angle difference piecewise compensation coefficient function varies with the current value.

[0152] Specifically, in this embodiment, the present invention constructs dual criteria in both the frequency and time domains by analyzing the second harmonic content rate and the ratio of the maximum to minimum value of the time domain waveform of at least two consecutive cycles of the current signal, and performs consistency verification on at least two consecutive cycles, thereby achieving accurate and reliable identification of half-wave signals and improving the accuracy and anti-interference capability of half-wave signal identification.

[0153] Specifically, in this embodiment, only 72 sampling data points are needed for each cycle. The second harmonic content rate is calculated using the FFT algorithm with a lookup table. There is no need to calculate harmonics of other orders. It does not require a large number of multiplications and trigonometric function operations. The entire harmonic analysis process has significant advantages such as low computational load, fast execution speed, and low MCU resource consumption.

[0154] Specifically, in this embodiment, the present invention adopts a two-level compensation strategy combining "half-wave basic compensation and half-wave segmented compensation" to construct a high-precision half-wave metering error compensation system. This method sets a half-wave basic calibration point and multiple half-wave segmented calibration points. The generated half-wave metering error compensation curve can highly fit the actual error characteristics, realizing accurate calibration of active and reactive power metering errors under full-range current and different power factors (including but not limited to 1.0 and 0.5L) under half-wave operating conditions. Without upgrading the hardware, it solves the metering error problem caused by CT saturation under half-wave operating conditions, achieving a high precision of less than ±0.6% half-wave metering error. The half-wave metering accuracy is improved by 80% compared with the existing standard.

[0155] According to another aspect of the present invention, a half-wave signal identification and metering error calibration system for an electricity meter includes: a half-wave signal identification module and a half-wave metering error calibration module; the half-wave signal identification module is connected to the half-wave metering error calibration module.

[0156] The half-wave signal identification module is used to identify whether the current signal is a half-wave signal;

[0157] The half-wave measurement error calibration module is used to call the pre-stored half-wave compensation coefficients, generate a half-wave measurement error compensation curve, determine the corresponding half-wave compensation value based on the real-time measured current value, and calibrate the measurement error of the half-wave signal based on the half-wave compensation value.

[0158] The above are merely preferred embodiments of the present invention and do not limit the patent scope of the present invention. All equivalent structural transformations made using the contents of the present invention's specification and drawings under the inventive concept of the present invention, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present invention.

Claims

1. A method for identifying half-wave signals and calibrating metering errors in an energy meter, characterized in that, Includes the following steps: S1. Acquire sampling data of continuous cycles of the current signal; S2. By analyzing the frequency domain and time domain characteristics of the current signal, a dual criterion is constructed to determine whether the current signal is a half-wave signal; Step S2 involves analyzing the frequency domain characteristics of the current signal, including: Read the sampled data of the first cycle and save it to the data buffer Buffer0; The second harmonic content of the first cycle is calculated using the FFT algorithm with a lookup table method, specifically as follows: A table of sine and cosine component constants for the fundamental wave and the second harmonic; the table of sine and cosine component constants includes a table of fundamental wave cosine, a table of fundamental wave sine, a table of second harmonic cosine, and a table of second harmonic sine. The sampled data in Buffer0 are sequentially multiplied by the sine and cosine component constant tables and then summed to obtain the sum of the fundamental cosine components, the sum of the fundamental sine components, the sum of the second harmonic cosine components, and the sum of the second harmonic sine components, respectively. Calculate the square of the fundamental amplitude and the square of the second harmonic amplitude, and calculate the second harmonic content based on the square of the fundamental amplitude and the square of the second harmonic amplitude; Set a first threshold range and determine whether the second harmonic content of the first cycle is within the first threshold range. If not, determine that the first cycle is a non-half-wave signal. Step S2 involves analyzing the time-domain characteristics of the current signal, including: Set a second threshold interval; if the second harmonic content of the first cycle is within the first threshold interval, calculate the ratio of the first absolute value of the maximum and minimum values ​​of the first cycle sampling data, and determine whether the first absolute value ratio is within the second threshold interval. If not, determine that the first cycle is a non-half-wave signal; if so, determine that the first cycle is a half-wave signal. S3. When the current signal is identified as a half-wave signal, the energy meter calls the pre-stored half-wave basic compensation coefficient and half-wave segmented compensation coefficient to generate a half-wave metering error compensation curve, and determines the corresponding half-wave compensation value based on the real-time measured current value, and calibrates the metering error of the half-wave signal based on the half-wave compensation value.

2. The method for identifying half-wave signals and calibrating metering errors in an energy meter according to claim 1, characterized in that, The calculation of the square of the fundamental amplitude and the square of the second harmonic amplitude is specifically as follows: The square of the fundamental amplitude is: The square of the second harmonic amplitude is: in, The square of the fundamental amplitude, The square of the second harmonic amplitude, The sum of the fundamental cosine components. This is the sum of the second harmonic cosine components. The sum of the fundamental sinusoidal components. It is the sum of the sinusoidal components of the second harmonic.

3. The method for identifying half-wave signals and calibrating metering errors in an energy meter according to claim 2, characterized in that, The second harmonic content is: in, This represents the second harmonic content rate.

4. The method for identifying half-wave signals and calibrating metering errors in an energy meter according to claim 3, characterized in that, Step S2, by analyzing the frequency domain and time domain characteristics of the current signal, further includes: Read the sampled data from the second cycle and save it to the data buffer Buffer1; The second harmonic content of the second cycle is calculated using the FFT algorithm with a lookup table method; specifically: Table of sine and cosine component constants for the preset fundamental and second harmonic frequencies; The sampled data in Buffer1 are sequentially multiplied by the sine and cosine component constant tables and then summed to obtain the sum of the fundamental cosine components, the sum of the fundamental sine components, the sum of the second harmonic cosine components, and the sum of the second harmonic sine components, respectively. Calculate the square of the fundamental amplitude and the square of the second harmonic amplitude, and calculate the second harmonic content of the second cycle based on the square of the fundamental amplitude and the square of the second harmonic amplitude; Determine whether the second harmonic content of the second cycle is within the first threshold range. If not, determine that the second cycle is a non-half-wave signal. If it is, then calculate the ratio of the second absolute value of the maximum and minimum values ​​of the second cycle sampling data, and determine whether the second absolute value ratio is within the second threshold range. If it is not, then determine that the second cycle is a non-half-wave signal; if it is, then determine that the second cycle is a half-wave signal. If both the first and second cycles are half-wave signals, then the current signal is determined to be a half-wave signal.

5. A method for identifying half-wave signals and calibrating metering errors in an energy meter according to any one of claims 1-4, characterized in that, The half-wave base compensation coefficient includes the half-wave ratio difference base compensation coefficient and the half-wave angle difference base compensation coefficient.

6. A method for identifying half-wave signals and calibrating metering errors in an energy meter according to any one of claims 1-4, characterized in that, The half-wave segment compensation coefficient includes the half-wave ratio difference segment compensation coefficient and the half-wave angle difference segment compensation coefficient.

7. A method for identifying half-wave signals and calibrating metering errors in an energy meter according to any one of claims 1-4, characterized in that, The half-wave measurement error compensation curve includes the half-wave ratio difference compensation curve and the half-wave angle difference compensation curve; The formula for the half-wave ratio difference compensation curve is: The formula for the half-wave angle difference compensation curve is: in, This is the half-wave ratio difference compensation value. This is the half-wave angle difference compensation value. The half-wave ratio difference basic compensation coefficient is obtained through the first half-wave basic calibration point. The half-wave angle difference basic compensation coefficient is obtained through the second half-wave basic calibration point. The half-wave ratio differential piecewise compensation coefficient function varies with the current value. The half-wave angle difference piecewise compensation coefficient function varies with the current value.

8. A half-wave signal identification and metering error calibration system for an energy meter, comprising the half-wave signal identification and metering error calibration method according to any one of claims 1-7, characterized in that, include: Half-wave signal identification module and half-wave measurement error calibration module; The half-wave signal identification module is connected to the half-wave measurement error calibration module; The half-wave signal identification module is used to identify whether the current signal is a half-wave signal; The half-wave measurement error calibration module is used to call the pre-stored half-wave compensation coefficients, generate a half-wave measurement error compensation curve, determine the corresponding half-wave compensation value based on the real-time measured current value, and calibrate the measurement error of the half-wave signal based on the half-wave compensation value.

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