CN116718832B - High-precision electric energy metering method and system - Google Patents
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Abstract
The application provides a high-precision electric energy metering method and a high-precision electric energy metering system, which belong to the technical field of electric energy metering, collect current signals and voltage signals, and align phases of the current signals and the voltage signals through a phase shifting algorithm; and (5) respectively calculating A, B, C three-phase active power based on the metering device, then calculating the total active power of the combined phases, and finally calculating the electric energy through time integration. The application realizes the phase self-adaptive compensation of a wide current-voltage range based on the segmented self-adaptive current-voltage phase compensation model of the FIR filter. The application supports the development of the full-domestic high-precision electric energy meter and improves the electric energy metering precision.
Description
Technical Field
The application belongs to the technical field of electric energy metering, and particularly relates to a high-precision electric energy metering method and system.
Background
In the prior art, the electric energy metering is to obtain voltage and current waveform data through a current and voltage sensor, and the generated instantaneous current and voltage waveform can be used for metering parameter calculation. For example, the voltage and current effective value calculating process is that current or voltage analog signals pass through an AD chip, synchronous timing sampling analysis is carried out by an acquisition controller, and the average value of the signals can be obtained through a series of operations such as squaring, digital filtering and the like on current sampling values. Similarly, the voltage effective value measurement is the same flow.
The calculation of the active power and the reactive power is based on the active power of each phase and is obtained by performing a series of digital signal processing such as multiplication, addition, digital filtering and the like on the current and voltage signals after the direct current components are removed. The total active power is typically used for billing purposes and includes both fundamental and harmonic power. The reactive power metering algorithm is similar to the active power except that the voltage signal is shifted by 90 degrees, and the phase shifting mode adopts a Hilbert filter.
In the prior art, the calculation of the electric energy is realized by a real-time accumulator, and the electric energy is obtained by real-time accumulation of active power or reactive power. In the metering design of the electric energy meter, the above basic method is generally adopted for analysis metering.
For the prior art, as the application number 202211088000.2 discloses an electric energy metering compensation algorithm and system for a medium-low voltage alternating current-direct current power distribution network, the file comprises a sampling module for acquiring line direct current and direct current voltage and carrying out sampling measurement; the processing module is used for optimizing the sampling data by using an anti-pulse interference moving average method so as to reduce sampling errors; the compensation module is used for carrying out interpolation algorithm compensation and delay algorithm compensation on the data transmitted by the processing module; and the electric energy metering module is used for obtaining accumulated electric energy at any moment through the compensated instantaneous power. The method can be used for carrying out phase compensation on the current and voltage channels according to the characteristics of wide current range and dynamic change of the direct-current electric energy meter, so that current and voltage synchronous sampling is realized, and the electric energy metering precision is improved. However, the document does not consider the influence of the phase, and does not relate to the influence of the current and voltage change on the amplitude, the phase and other factors of the device, so that the electric energy metering precision is low, and the metering requirement cannot be met.
Disclosure of Invention
According to the high-precision electric energy metering method provided by the application, the influence of the phase is considered, the influence of the current and voltage change on the amplitude, the phase and other factors of the device is also considered, and the electric energy metering precision is improved by designing a multidimensional compensation model.
The method comprises the following steps:
s1: collecting a current signal and a voltage signal, and aligning the phases of the current signal and the voltage signal through a phase shifting algorithm;
s2: and (5) respectively calculating A, B, C three-phase active power based on the metering device, then calculating the total active power of the combined phases, and finally calculating the electric energy through time integration.
In the method, it is further noted thatRepresenting the instantaneous values of voltage and current respectively, then in the segmented analog signal acquisition it is denoted +.>N and m represent the simulation of voltage and currentThe number of signal segments;
the active power is calculated by the instantaneous value product of current and voltage in a single period, wherein the phase a active power is calculated as:
。
it should be further noted that, the phase-combining instantaneous active power calculation mode is as follows:
reactive power calculation introduces Hilbert transformation, deflects the current phase by 90 degrees, and then calculates the instantaneous value product with the voltage;
the active electric energy of the A phase is expressed as:
。
it should be further noted that, the step S2 further includes a current-voltage phase compensation method, which specifically includes the following steps:
the phase shifting of the phase is realized through the FIR filter, the influence on the phase under different current and voltage is calculated, the phase difference value under different voltage and current values is obtained, and the self-adaptive phase value is selected according to the current and voltage values.
It should be further noted that the form of the FIR filter is as follows:
selecting a point in the acquisition signal at which the voltage changes from negative to positive, and setting the point asThe point is followed by a collection point +.>By means of wiresThe difference value calculates the accurate zero crossing point of the voltage signal, and the position isObtaining a zero crossing point of the voltage signal;
similarly, the zero crossing point of the current at the corresponding position is obtained asAnd obtaining a difference value between the current and the voltage signal, wherein the difference value is a target of voltage and current signal compensation, and a FIR filter is utilized to obtain design parameters.
It should be further noted that step S2 further includes an electric energy metering compensation model, where the electric energy metering compensation model is based on an electric energy metering algorithm, and compensates for electric energy metering errors caused by the device itself under the variation of different current, voltage, power factor, temperature, humidity and frequency factors of the chip;
the electric energy metering compensation model defines the variation range of current, voltage, power factor, frequency, temperature and humidity which influence the calculation of active and reactive power, determines the upper and lower limit values, selects n points according to the upper and lower limit values and the range of currentSelecting a current input point value of +.>Covering the upper and lower limit range of the current, and selecting the number of the preset number of points.
It should be further noted that, according to the current selection mode, the input value of the electric energy metering compensation model is voltageAnd Power factor->；
Based on the current change, the active power calculation value is obtained,
the active power output corresponding to the read power source is,
selecting A phase active power values under different current values, and forming a numerical pair to be expressed asAnd constructing an error compensation model of the A-phase power under the influence of different current values by using a cubic spline polynomial method.
It should be further noted that the calculated value and the ideal value of the a-phase active power value under the current change are expressed asA cubic spline polynomial model is built in each interval as follows:
cubic function corresponding to n intervalsThe mathematical expression of (2) is as follows:
wherein->；
Solving the various typesConstructing a multi-spline interpolation model to obtain the following modes:
(1) All points meet the interpolation condition, i.eIn addition to two endpoints, other points satisfyThe front and rear segments have 2 (n-1) equations, and the two end point equations are added, so that 2n equations are added;
(2) The points in the interval are all continuous in the first derivative, and the first derivatives of the end point of the current interval and the start point of the next interval are equal, namelyThen there are n-1 equations;
(3) The second derivative of points within the interval being continuous, i.eThen there are n-1 equations;
the above constructs 4n-2 equations altogether, solvesIs set to 4n parameters:
assuming that the second derivative of the i-th point isI.e. +.>And let->The product is obtained by the method,constructing a system of equations with m as an unknown quantity, which is obtained by m, < >>The solution of (2) is expressed as:
finally, two boundary conditions are added to construct 2 equations, thereby solving。
It should be further noted that the method further includes:
(11) Configuring a free boundary: the second derivative of the boundary endpoint is 0,obtain->Then a system of linear equations is constructed as:
(12) Constructing a fixed boundary: the first derivatives of the specified endpoints are defined as A and B, respectively, i.e，Obtain->，/>Then a system of linear equations is constructed as:
(13) Constructing a non-node boundary: the third derivative value of the first interpolation point is equal to the third derivative value of the second point, and finally the third derivative value of the first point is equal to the third derivative value of the penultimate point, i.e，Obtain (I)>Then a system of linear equations is constructed as:
solving for a linear equation setIs calculated by Gaussian elimination>Further obtain the in-sectionIs a cubic spline interpolation polynomial of (c):
。
the application also provides a high-precision electric energy metering system, which comprises: the device comprises a current acquisition processing module, a voltage acquisition processing module, a current-voltage phase compensation module and a metering device;
the current-voltage phase compensation module is connected with the current acquisition processing module to acquire current signals in real time, is also connected with the voltage acquisition processing module to acquire voltage signals in real time, and is used for realizing phase shifting of phases through the FIR filter, calculating influences on the phases under different current and voltages to obtain phase difference values under different voltage and current values, carrying out sectional compensation based on the phase difference values under the voltage and current values, taking the phase difference value at a certain point in a section as a compensation value in the section, determining a sectional section according to the current or voltage at each time, and then carrying out self-adaptive selection compensation on the compensation value of a corresponding section so as to realize the voltage-current phase compensation;
the metering device is connected with the current-voltage phase compensation module, acquires the voltage-current value after the current-voltage phase compensation module outputs compensation, calculates A, B, C three-phase active power respectively, calculates total active power of the phase combination, and finally calculates electric energy through time integration.
From the above technical scheme, the application has the following advantages:
the high-precision electric energy metering method provided by the application is based on a segmented self-adaptive current-voltage phase compensation model of the FIR filter, so that the phase self-adaptive compensation of a wide current-voltage range is realized. And an electric energy metering error compensation model based on multidimensional cubic spline interpolation is also constructed, an LSTM model is introduced to optimize errors, the electric energy metering precision is improved, high-precision electric energy metering is realized, and the metering precision is improved.
In addition, the high-precision electric energy metering method provided by the application not only considers the influence of the phase, but also considers the influence of the current and voltage change on the amplitude, the phase and other factors of the device, and improves the electric energy metering precision by designing a multidimensional compensation model. The application also adopts a lightweight artificial intelligence technology, and compensates the electric energy metering precision based on the hardware analysis of the changes of factors such as current, voltage, power factor and the like, thereby improving the metering precision.
Drawings
In order to more clearly illustrate the technical solutions of the present application, the drawings that are needed in the description will be briefly introduced below, it being obvious that the drawings in the following description are only some embodiments of the present application, and that other drawings can be obtained according to these drawings without inventive effort for a person skilled in the art.
FIG. 1 is a flow chart of a high-precision electrical energy metering method;
FIG. 2 is a schematic diagram of an active and reactive power compensation model;
FIG. 3 is a schematic view of LSTM structure;
fig. 4 is a schematic diagram of the electric energy metering error model metering.
Detailed Description
The high-precision electric energy metering provided by the application is simultaneously oriented to the characteristics of fundamental frequency fluctuation, widening current range and the like caused by high-proportion new energy and power electronic equipment connected to a power grid, and the application constructs an electric energy metering error compensation model based on multi-dimensional cubic spline interpolation, introduces an LSTM model to optimize errors and improves electric energy metering precision.
The high-precision electric energy metering method can acquire and process the associated data based on the artificial intelligence technology. The high-precision electric energy metering method utilizes a digital computer to control a machine to simulate, extend and expand human intelligence, sense environment, acquire knowledge and acquire a theory, a method, a technology and an application device of an optimal result by using the knowledge.
The high-precision electric energy metering method of the application has the technology of both hardware level and software level. The application can include technologies such as transformers, dedicated artificial intelligence chips, cloud computing, distributed storage, big data processing technologies, operation/interaction systems, electromechanical integration, and the like. Techniques for software may include natural language processing techniques, machine learning/deep learning, artificial neural networks, belief networks, reinforcement learning, transfer learning, induction learning, programming language, and the like. Programming languages include, but are not limited to, object-oriented programming languages such as Java, smalltalk, C ++, and conventional procedural programming languages such as the "C" language or similar programming languages.
The high-precision electric energy metering method provided by the application introduces an LSTM model to optimize errors, divides the wide current and voltage analog signal range into a plurality of sections based on the hardware design of the multi-section analog signal acquisition circuit, and is used as input signals of different AD chips, thereby realizing high-precision acquisition of the wide current and voltage analog signals, and improving the calculation precision of active and reactive power based on a multi-layer LSTM power compensation model influenced by multi-dimensional factor coupling, and further improving the electric energy metering accuracy.
The following description of the embodiments of the present application will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present application, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the application without making any inventive effort, are intended to be within the scope of the application.
Referring to fig. 1 to 4, a flowchart and a model diagram of a method for high-precision electric energy metering in an embodiment are shown, the method includes:
s1: collecting a current signal and a voltage signal, and aligning the phases of the current signal and the voltage signal through a phase shifting algorithm;
in one exemplary embodiment, based on a hardware design of the multi-section analog signal acquisition circuit, the wide current and voltage analog signal range is divided into multiple sections and used as input signals of different AD chips, so that high-precision acquisition of the wide current and voltage analog signals is realized. In the aspect of data processing, sampling signals are simultaneously output to different AD chips through a processor, synchronous sampling of the different AD chips is realized, data is sent to the processor after sampling is received, and then unified data processing is carried out.
In the present embodiment, definitionRepresenting the instantaneous values of voltage and current respectively, it can be expressed as +.>N and m represent the number of segments of the voltage and current analog signal. Because of the influence of the inductance-capacitance device factors of circuit hardware, the phase deviation exists between the sampled voltage signal and the current signal, and the alignment of the current and the voltage phase is realized through a phase shifting algorithm.
S2: and (5) respectively calculating A, B, C three-phase active power based on the metering device, then calculating the total active power of the combined phases, and finally calculating the electric energy through time integration.
Specifically, the active power is calculated by multiplying instantaneous values of current and voltage in a single period, and taking an a-phase active power calculation as an example, calculating phases B and C are the same as calculating phase a, and an a-phase active power calculation is exemplified below, where the a-phase active power can be expressed as:
the phase-closing instantaneous active power can be expressed as:
reactive power calculation introduces a hilbert transformation, first deflecting the current phase by 90 degrees, and then calculating the instantaneous value product with the voltage.
The active electric energy of the A phase is expressed as:
the accuracy of the electrical energy metering is directly related to the value of the electrical energy, which is determined by the integration of power over time, so that the accuracy of the active power of A, B, C three phases is directly the accuracy of the active electrical energy.
The embodiment aims at the electric energy metering device, designs a method suitable for high-precision electric energy compensation, and compensates for the performance deficiency of hardware devices through innovation in algorithm, so that high-precision electric energy metering is realized.
Aiming at the influence of factors such as current, voltage, power factor, temperature and the like on the electric energy metering precision, firstly, the influence condition of the changes of the factors on the active power and the reactive power is obtained, ideal active power and reactive power are obtained by means of a high-precision power source, and meanwhile, the actual active power and the actual reactive power are obtained through calculation. And constructing an electric energy metering error model by using the actual active power value, the actual reactive power value and the ideal value, wherein the whole execution flow and the relation are shown in the following figure 4.
According to the embodiment of the application, the metering process is divided into two stages, namely a current-voltage phase compensation stage and an electric energy metering compensation model construction stage.
(1) A current-voltage phase compensation stage;
the phase shifting of the phase is realized through the FIR filter, the influence on the phase under different current and voltage is calculated, the phase difference value under different voltage and current values is obtained, and the self-adaptive phase value is selected according to the current and voltage values.
The FIR filter has faster time domain response and higher precision, and the output of the FIR filter with length N corresponds to the input time sequenceThe relationship of (2) is given in the form of a finite convolution, the specific form is as follows:
in the aspect of selecting the N value, taking a certain voltage current signal as an example, a high-precision power source is utilized to input sinusoidal voltage and current analog signals with the same phase, voltage current conversion signals are collected at high frequency, the frequency of the adoption of a high-precision electric energy metering algorithm is generally about 12kHz, the frequency of the adoption of 15kHz is adopted in the phase compensation process of the voltage current signal, and synchronously collected signals are processed. The point in the acquired signal at which the voltage changes from negative to positive is selected, and the point is considered to be a zero-crossing point of the voltage signalThe point after this point isAt the zero crossing point where the voltage signal is precisely calculated by using the linear difference, the position isAnd obtaining the accurate zero crossing point of the voltage signal.
Similarly, the zero crossing point of the current at the corresponding position is obtained asThus, a difference between the current and voltage signals can be obtained. When the difference value is the target of voltage and current signals to be compensated, the design parameters of the FIR filter are obtained by utilizing the FIR filter design module.
In this embodiment, since different current and voltage amplitudes will correspond to different phase differences, the phase differences are nonlinear, the difference between different values is smaller, if the phase compensation is performed for each voltage and current value, the phase compensation model is too complex, and a high requirement is put forward for the processor, so that the phase differences are subjected to segment compensation according to the current and voltage segment values, the phase differences at a certain point in a segment are used as compensation values in the segment, the segment is determined each time according to the current or voltage, and then adaptive selection compensation is performed for selecting the compensation value in the corresponding segment, thereby realizing the phase compensation for the voltage and current.
(2) An electric energy metering compensation model;
the adaptively selected FIR filter of the embodiment can compensate the voltage-current phase difference value, plays a certain role in improving the precision of the electric energy metering compensation model, and simultaneously introduces amplitude errors. The electric energy metering compensation model is based on an electric energy metering algorithm, and compensates electric energy metering errors caused by the device under the change of factors such as different currents, voltages, power factors, temperature, humidity, frequency and the like.
Firstly, the variation ranges of multiple factors such as current, voltage, power factor, frequency, temperature, humidity and the like which influence active power and reactive power calculation are defined, the upper limit value and the lower limit value are determined, and n points are selected according to the upper limit value and the lower limit value.
Illustratively, in terms of the range of currentSelecting a current input point value of +.>The upper and lower limit ranges of the current are covered, and the number of points can be selected as much as possible to ensure the accuracy of the model. According to the current selection mode, selecting the input point value of other factors as voltage +.>Power factor->Etc.
When the model sample is obtained, the high-precision power source respectively inputs the selected fingers according to the selected points of the multidimensional factors, only one value is changed each time, and the calculated value of each item of active power and reactive power at A, B, C and the actual value of the power source output are recorded.
Taking the current change as an example, the calculated active power value is:
the active power output corresponding to the high-precision power source is read as follows:
selecting A phase active power values under different current values, and forming numerical value pairs to be expressed asAnd then, constructing an error compensation model of the A-phase power under the influence of different current values by using a cubic spline polynomial method.
For the convenience of calculation, the calculated value and ideal value of the A-phase active power value under the current change can be expressed asBuild three times per intervalA spline polynomial model as follows:
cubic function corresponding to n intervalsThe mathematical expression of (2) is as follows:
wherein->。
Solving the various typesConstructing various interpolation models, and knowing:
1) All points must meet interpolation conditions, i.eIn addition to two endpoints, other points satisfyThere are 2 (n-1) equations for the front and back segments, and 2n equations for the two end point equations.
2) The points in the interval are all continuous in the first derivative, so that the first derivatives of the end point of the current interval and the start point of the next interval should be equal, i.eThere are n-1 equations.
3) The second derivative of points within the interval being continuous, i.eThere are n-1 equations.
The above constructs 4n-2 equations altogether, solvesAlso two equations are needed for the 4n parameters of (c).
Assuming that the second derivative of the i-th point isI.e. +.>And let->By deriving the time, it is possible, by deriving,an equation set with m as an unknown quantity is constructed, from which m is known,/is>The solution of (c) can be expressed as:
finally, two boundary conditions are added to construct 2 equations, thereby solving。
Embodiments of the present application also relate to the resolution of free boundaries, wherein the boundary endpoint second derivative is 0,can get->Then a system of linear equations is constructed as:
for a fixed boundary: the first derivatives of the specified endpoints are defined as A and B, respectively, i.e，Can get->，/>Then a system of linear equations is constructed as: />
For non-node boundaries, the third derivative value of the first interpolation point is equal to the third derivative value of the second point, and the third derivative value of the last first point is equal to the third derivative value of the penultimate point, i.e，Available (Lee Suo)>Then a system of linear equations is constructed as:
can be solved for the above matrixThe corresponding ++is calculated by Gaussian elimination and the like>Further, the interval +.>Is a cubic spline interpolation polynomial of (c):
。
from the above, a phase a active power cubic spline polynomial model was constructed from the current variation.
Similarly, a cubic spline polynomial compensation model of the A, B, C three-phase active and reactive power of the voltage, the power factor, the frequency, the temperature, the humidity and other factor changes is respectively constructed, so that a multidimensional cubic spline polynomial active and reactive power compensation model influenced by multidimensional factors is built. In the practical application process, corresponding working intervals are selected by judging the current, voltage, power factor, frequency, temperature and other multidimensional factorsThe value is further used for realizing active power compensation and reactive power compensation, and the calculation accuracy of the active power and the reactive power is improved. />
The multi-dimensional cubic spline polynomial compensation method can compensate the influence of the change of multi-dimensional factors on the calculation precision of the active power and the reactive power, but some factors have coupling influence, the compensation of the deviation can not be shown in a multi-dimensional cubic spline compensation model, and the analysis difficulty of the part is high, so that a multi-layer long-short-term memory (LSTM) model is introduced, and the factors such as the active power, the reactive power, the current, the voltage, the power factor, the frequency and the like passing through the multi-dimensional cubic spline interpolation model are taken as input values, and the input values are output as the active power value and the reactive power value.
In embodiments of the present application, a multi-dimensional cubic spline compensation model+multilayer LSTM is employedIn the method, in the construction process of the multilayer LSTM model, the current, voltage, power factor, frequency, temperature and other multidimensional factors and the active and reactive power output by a multidimensional cubic spline compensation model are used as the input vector of the LSTMThe output value is active power and reactive power, and meanwhile, high-precision power source data are read to serve as comparison values, so that the difference between the output value and the comparison values is calculated, the multilayer LSTM model parameters are calculated with the minimum difference, and the multilayer LSTM compensation model is further constructed.
LSTM is a special cyclic neural network (Recurrent Neural Network, RNN) and introduces selective mechanisms of 'gating' based on the RNN, namely a forgetting gate, an input gate and an output gate, as shown in figure 3, so that information is selectively reserved or deleted to better learn long-term dependency.
For the multilayer LSTM compensation model, as described by the following equation,
wherein,output information for forgetting gate,/->、/>Weight and bias parameters for forgetting gate, +.>For inputting the output information of the gate, +.>、/>For the weight and bias parameters of the input gates,/>、/>for the weight and bias function of the tanh layer, +.>For the cellular state->Is an activation function, the output range is 0-1, < >>For outputting the output information of the gate, +.>、/>For outputting the weight and bias parameters of the gate, +.>Representing the output of the previous cell, +.>For the output of the unit, +.>Representing the current input.
Taking the multilayer LSTM model of a-phase active power as an example, the input vector is expressed as:
output is +.>Output value and high-precision power source data form digital pairUsing adaptive momentsAnd (3) an estimation optimization (Adam) tool, namely recording the output value and the power source value pair by changing the multi-dimensional factor change one by one, so as to calculate the parameters of the multilayer LSTM model.
It can be seen that the application builds the electric energy metering error compensation model based on multidimensional cubic spline interpolation based on the high-precision electric energy metering device, introduces the LSTM model to optimize the error, improves the electric energy metering precision, realizes high-precision electric energy metering, and improves the metering precision.
It should be understood that the sequence number of each step in the foregoing embodiment does not mean that the execution sequence of each process should be determined by the function and the internal logic, and should not limit the implementation process of the embodiment of the present application.
The following are embodiments of a high-precision electric energy metering system provided by the embodiments of the present disclosure, which belong to the same inventive concept as the high-precision electric energy metering method of the above embodiments, and details of the embodiments of the high-precision electric energy metering system, which are not described in detail, may refer to the embodiments of the high-precision electric energy metering method.
The system comprises: the device comprises a current acquisition processing module, a voltage acquisition processing module, a current-voltage phase compensation module and a metering device;
the current-voltage phase compensation module is connected with the current acquisition processing module to acquire current signals in real time, is also connected with the voltage acquisition processing module to acquire voltage signals in real time, and is used for realizing phase shifting of phases through the FIR filter, calculating influences on the phases under different current and voltages to obtain phase difference values under different voltage and current values, carrying out sectional compensation based on the phase difference values under the voltage and current values, taking the phase difference value at a certain point in a section as a compensation value in the section, determining a sectional section according to the current or voltage at each time, and then carrying out self-adaptive selection compensation on the compensation value of a corresponding section so as to realize the voltage-current phase compensation;
the metering device is connected with the current-voltage phase compensation module, acquires the voltage-current value after the current-voltage phase compensation module outputs compensation, calculates A, B, C three-phase active power respectively, calculates total active power of the phase combination, and finally calculates electric energy through time integration.
The embodiment of the disclosure provides a high-precision electric energy metering system, which aims at the problems of insufficient precision, insufficient consistency and the like of devices, designs a high-precision electric energy metering model influenced by multidimensional factors, has a simple model structure, can be applied to hardware such as a common MCU and the like, and improves electric energy metering precision.
The units and algorithm steps of each example described in the embodiments disclosed in the high-precision electric energy metering method provided by the application can be implemented in electronic hardware, computer software or a combination of the two, and in order to clearly illustrate the interchangeability of hardware and software, the components and steps of each example have been generally described in terms of functions in the above description. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the solution. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present application.
The high-precision electrical energy metering system provided by the application is the units and algorithm steps of each example described in connection with the embodiments disclosed herein, and can be implemented as electronic hardware, computer software, or a combination of both, and to clearly illustrate the interchangeability of hardware and software, the components and steps of each example have been described generally in terms of functionality in the foregoing description. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the solution. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present application.
The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the application. Thus, the present application is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
Claims (6)
1. A method for high precision electrical energy metering, the method comprising:
s1: collecting a current signal and a voltage signal, and aligning the phases of the current signal and the voltage signal through a phase shifting algorithm;
s2: calculating A, B, C three-phase active power based on the metering device respectively, calculating total active power of the combined phases, and finally calculating electric energy through time integration;
the electric energy metering compensation model is based on an electric energy metering algorithm, and compensates electric energy metering errors caused by the device under the condition that different current, voltage, power factors, temperature, humidity and frequency factors change;
the electric energy metering compensation model defines the variation range of current, voltage, power factor, frequency, temperature and humidity which influence the calculation of active and reactive power, determines the upper and lower limit values, selects n points according to the upper and lower limit values and the range of currentSelecting a current input point value of +.>Covering the upper and lower limit ranges of the current, and selecting the number of points with preset number;
according to the current selection mode, the input value of the electric energy metering compensation model is voltageAnd power factor；
Based on the current change, the active power calculation value is obtained,
the active power output corresponding to the read power source is,
selecting A phase active power values under different current values, and forming a numerical pair to be expressed asThen, constructing an error compensation model of the A-phase power under the influence of different current values by using a cubic spline polynomial method;
the calculated value and ideal value of the A phase active power value under the current change are expressed asA cubic spline polynomial model is built in each interval as follows:
cubic function corresponding to n intervalsThe mathematical expression of (2) is as follows:
wherein->；
Solving the various typesConstructing a multi-spline interpolation model to obtain the following modes:
(1) All points meet the interpolation condition, i.eIn addition to two endpoints, other points satisfyThe front and rear segments have 2 (n-1) equations, and the two end point equations are added, so that 2n equations are added;
(2) The points in the interval are all continuous in the first derivative, and the first derivatives of the end point of the current interval and the start point of the next interval are equal, namelyThen there are n-1 equations;
(3) The second derivative of points within the interval being continuous, i.eThen there are n-1 equations;
the above constructs 4n-2 equations altogether, solvesIs set to 4n parameters:
assuming that the second derivative of the i-th point isI.e. +.>And let->The product is obtained by the method,constructing a system of equations with m as an unknown quantity, which is obtained by m, < >>The solution of (2) is expressed as:
finally, two boundary conditions are added to construct 2 equations, thereby solving；
The method further comprises the steps of:
(11) Configuring a free boundary: the second derivative of the boundary endpoint is 0,obtain->Then a system of linear equations is constructed as:
(12) Constructing a fixed boundary: the first derivatives of the specified endpoints are defined as A and B, respectively, i.e，/>Obtain->，/>Then a system of linear equations is constructed as:
(13) Constructing a non-node boundary: the third derivative value of the first interpolation point is equal to the third derivative value of the second point, and finally the third derivative value of the first point is equal to the third derivative value of the penultimate point, i.e，Obtain (I)>Then a system of linear equations is constructed as:
solving for a linear equation setIs calculated by Gaussian elimination>Further obtain the in-sectionIs a cubic spline interpolation polynomial of (c):
。
2. the method for measuring electric energy with high precision according to claim 1, wherein,
in the method, set upRepresenting instantaneous values of voltage and current respectively, then in the segmented analog signal acquisition it is represented asN and m represent the number of segments of the voltage and current analog signals;
the active power is calculated by the instantaneous value product of current and voltage in a single period, wherein the phase a active power is calculated as:
。
3. the method for measuring electric energy with high precision according to claim 1 or 2, wherein,
the phase-combining instantaneous active power calculation mode is as follows:
reactive power calculation introduces Hilbert transformation, deflects the current phase by 90 degrees, and then calculates the instantaneous value product with the voltage;
phase a active electrical energy is expressed as
。
4. The method of high-precision electric energy metering according to claim 1 or 2, wherein step S2 further comprises a current-voltage phase compensation method, specifically comprising the steps of:
the phase shifting of the phase is realized through the FIR filter, the influence on the phase under different current and voltage is calculated, the phase difference value under different voltage and current values is obtained, and the self-adaptive phase value is selected according to the current and voltage values.
5. The method for high-precision power metering according to claim 4, wherein,
the form of the FIR filter is as follows:
selecting a point in the acquisition signal at which the voltage changes from negative to positive, and setting the point asThe point is followed by a collection point +.>Calculating accurate zero crossing point of voltage signal by using linear difference value, wherein the position is +.>Obtaining a zero crossing point of the voltage signal;
similarly, the zero crossing point of the current at the corresponding position is obtained asAnd obtaining a difference value between the current and the voltage signal, wherein the difference value is a target of voltage and current signal compensation, and a FIR filter is utilized to obtain design parameters.
6. A high-precision electric energy metering system, characterized in that the system adopts the high-precision electric energy metering method according to any one of claims 1 to 5;
the system comprises: the device comprises a current acquisition processing module, a voltage acquisition processing module, a current-voltage phase compensation module and a metering device;
the current-voltage phase compensation module is connected with the current acquisition processing module to acquire current signals in real time, is also connected with the voltage acquisition processing module to acquire voltage signals in real time, and is used for realizing phase shifting of phases through the FIR filter, calculating influences on the phases under different current and voltages to obtain phase difference values under different voltage and current values, carrying out sectional compensation based on the phase difference values under the voltage and current values, taking the phase difference value at a certain point in a section as a compensation value in the section, determining a sectional section according to the current or voltage at each time, and then carrying out self-adaptive selection compensation on the compensation value of a corresponding section so as to realize the voltage-current phase compensation;
the metering device is connected with the current-voltage phase compensation module, acquires the voltage-current value after the current-voltage phase compensation module outputs compensation, calculates A, B, C three-phase active power respectively, calculates total active power of the phase combination, and finally calculates electric energy through time integration.
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