CN101915872A - Nonlinear-load electric energy measuring method - Google Patents
Nonlinear-load electric energy measuring method Download PDFInfo
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- CN101915872A CN101915872A CN 201010273234 CN201010273234A CN101915872A CN 101915872 A CN101915872 A CN 101915872A CN 201010273234 CN201010273234 CN 201010273234 CN 201010273234 A CN201010273234 A CN 201010273234A CN 101915872 A CN101915872 A CN 101915872A
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Abstract
The invention discloses a nonlinear-load measuring method having a high integral algebraic accuracy grade. Aiming at the traditional dot product measuring algorithm, the invention points out the algorithm accuracy deficiency under the condition of calculating nonlinear loads based on the analysis of algorithm characteristics, thereby providing a scheme to improve the accuracy and the adaptability of an electric energy meter on the modern nonlinear-load electric energy measurement by using a complex Newton-Cotes integral algorithm having a high-order measuring algebraic accuracy grade. Based on the theoretical analysis of the algorithm and the real-time operation characteristics of the current measuring system, the invention designs and provides a method for the real-time operation of the algorithm. Simulation and experiment results prove that the invention can effectively improve the accuracy of an electric meter in the electric energy measuring field, thereby improving the adaptability of the electric meter on wider nonlinear-load measurement.
Description
Technical field
The invention belongs to electric system electric energy metrical field.
Background technology
Electric energy metrical is the basic basis that carries out economic balance between electricity power enterprise, power transmission and transformation enterprise and the electricity consumption client, and its accuracy directly influences three's interests.In the process of the industrial develop rapidly of modernization, electric system has inserted a large amount of nonlinear-loads, and consequent a large amount of harmonic currents, harmonic voltage have not only had a strong impact on power transmission efficiency, and the accuracy of electric energy metrical produced seriously influences.
For effectively solving the influence of mains by harmonics to the electric energy metrical accuracy, each experts and scholars has launched the research to the nonlinear load electric energy metrical one after another.At present, industry is generally by research part throttle characteristics, electrical network modeling and the problems such as accuracy, rationality that solve the nonlinear-load metering based on the methods such as frequency analysis of FFT.
At present, industry generally adopts dot-product operation to calculate to be had, capacity of idle power, has, reactive power and parameters such as voltage, current effective value.Wherein concrete active energy computing formula is as follows:
In the formula
Be instantaneous power,
Be electric flux in the signal period,
Be maximum sub-range length,
Be the signal period,
Be the signal sampling time interval.As seen, dot-product operation directly prolongs the basic definition formula of having used integral operation.But in calculating process, how many formulas need count to participate in calculating could be satisfied the accuracy of calculating, and formula does not provide guidance.So, when being input as standard pure sinusoid signal, some integration method accuracy difference under the unlike signal sampling rate.
Be calculated as example with active energy, establish input voltage, current signal is:
,
, in the formula
,
Be input signal cycle, can get:
(2)
Substitution formula (1), then the electric energy theoretical value is in the signal period:
Substitution formula (1) then with dot product mode signal calculated electric energy in the cycle, can get formula (5).
(5)
Contrast formula (5) and Theoretical Calculation be formula (3) result of calculation as a result, can be as drawing a conclusion:
(1) for the pure sinusoid periodic signal, be parameters such as the electric weight of accurate signal calculated, power, effective value, the signals sampling rate must guarantee that weekly the phase samples more than 3 at least;
(2) the highest for containing
The signal of subharmonic is wanted the parameters such as electric weight, power, effective value of accurate signal calculated, and then the signals sampling rate must guarantee per primitive period signal sampling
More than the point;
Notice that conclusion (2) is the inference of conclusion (1), it is a non-adequate condition of necessity.For example, for a sine signal source that contains 21 subharmonic, if will accurately calculate their electric weight, then signal sampling rate must guarantee fundamental signal ripple sampling more than 63 weekly.
As can be known above-mentioned, the basic definition formula of having used the definite integral computing is just directly prolonged in the dot product of industry-wide adoption and computing.When sampling number was determined, the class of accuracy of the right integrating meter formula was then determined thereupon.Numerical analysis in modern times theory is pointed out: if quadrature formula is to all number of times
The polynomial expression quadrature accurately set up, but for
Order polynomial is inaccurate, then claims this integral algorithm to have
Inferior algebraically accuracy.Obviously, the some integration method is a Riemann's ladder integral algorithm that has only 0 rank algebraically accuracy, and it is only accurately set up the integration of direct current measurement (0 order polynomial).With reference to formula (4) and Fig. 1 as can be known, standard sine input signal instantaneous power is divided into constant component and positive string section, because the odd symmetry of sinusoidal signal, make in the sinusoidal signal cycle more than 3 that evenly distribution each point sum is zero, therefore the electric flux that the integral algorithm of 0 rank algebraically accuracy just can accurate Calculation two sinusoidal signals more than 3.But when input signal no longer be thereby that the standard sine signal is when having destroyed this symmetry, the error of calculation of algorithm will produce thereupon, this asymmetric non-standard sinusoidal input signal is very general in the nonlinear-load metering, causes existing ammeter error in dipping bigger.How could nonlinear-load accurately be measured, especially under asymmetric non-standard sinusoidal signal input condition, accurately to measure nonlinear-load, become present problem demanding prompt solution.
Summary of the invention
The object of the present invention is to provide and a kind ofly can improve the especially nonlinear-load electric energy measuring method of real time measure accuracy of the ammeter accuracy of measuring.
This nonlinear-load electric energy measuring method provided by the invention is at one-period
Sampling
Point is gathered current instantaneous voltage and momentary current, calculate current instantaneous power [
], based on the principle of high-order newton-Ke Tesi Numerical Integral Formulas to current sampling instant electric weight carry out real-time integration obtain the integral and calculating value (
), and to the real-time integration of electric weight carry out the cycle accumulation obtain cycle electric weight accumulating value (
), with this accumulating value multiply by a coefficient and multiply by the cycle electric flux that a factor obtains nonlinear-load (
), the described factor is a periodic quantity
With sampling number
Ratio.
Obtain above-mentioned electric weight accumulating value (
) after, when definite current input signal zero passage, calculate nonlinear-load electric weight (
), described integral and calculating value (
) suitable following two kinds of formula:
In the above-mentioned formula
Following formula
Crossing electric weight accumulating value in null cycle for signal, is with the instantaneous electric weight of current calculating gained
With electric weight accumulating value before this
After adding up, deposit back
The middle preservation.
Be current sampling instant electric weight to be carried out real-time integration obtain real-time integral and calculating value;
Be periodic quantity,
Be sampling number,
Be the periodic signal electric energy value after the execution cycle computing.
The inventive method utilizes the Newton-Cotes integral algorithm to have the characteristics of high-order accuracy of measuring grade, current sampling instant electric weight is carried out real-time integration, and the real-time integration of electric weight carried out the cycle accumulation, this method has the accuracy of high-order numerical integration algebraically, therefore it has higher algorithm accuracy than industry conventional point integration method, can be adapted to nonlinear-load metering widely, effectively improve electric energy meter the accuracy of Modern Nonlinear load electric energy metering and the adaptability that all kinds of nonlinear-loads are measured.The inventor shows that by emulation and experiment show this method provided by the invention is highly effective to improving ammeter accuracy aspect.
Description of drawings
Fig. 1 is the synoptic diagram of prior art metering.
Fig. 2 is the process flow diagram of a kind of embodiment of the inventive method.
Fig. 3 is the process flow diagram of the another kind of embodiment of the inventive method.
The figure as a result that Fig. 4 experimentizes with the inventive method.
Embodiment
Embodiment one: this is an embodiment with 3 rank accuracy metering grades, referring to Fig. 2.
The one-period of input signal (
) some points of sampling (
), signal time in the cycle is divided into
Individual interval
, according to current instantaneous voltage and momentary current, calculate current instantaneous power [
] maybe can be abbreviated as
, utilize the Simpson integral algorithm to by stages such as per 2
Active power carry out electric weight and calculate, be shown below:
In the formula,,, adopted and former integral formula index for explaining conveniently because the complexification integral formula is the single interval integral formula that adopts two adjacent sectors integrations and substitute the initial point integration method
Different indexs
Represent that each computation interval originates in the even number index.Simultaneously, please note the difference of following formula and hot Pu's physiology opinion quadrature formula, because algorithm is the continuous integrated value of calculating two intervals, so aforementioned calculation formula coefficient is 2 times of the theoretical calculation formula coefficient.Then, following formula in the summation that adds up of the interval upper integral value of each equal portions, can be got:
(2)
T: the signal period value
N: sampling number, i.e. signals sampling rate in the signal period
Above-mentioned formula (7) is a theoretical calculation formula, can not satisfy the real-time operation requirement of modern real-time digital signal processing system.In order to utilize the Xin Fusheng algorithm to calculate in real time in actual applications, need make suitable modification to following formula.Observe calculating formula (7), and launch and can get:
Formula (8) is real-time computing formula, promptly in actual applications, when whenever obtaining a sampled point, then according to the current sampling point index data is accumulated: when index is even number, data are directly accumulated; When index is odd number, then data are taken advantage of 2 accumulations.If
For current sampling instant integral and calculating value, above-mentioned formulate is become algorithm, the formula of employing is:
In the formula
, be the instantaneous power value of current voltage, current sample;
In the formula,
The address offset amount in internal memory for current sampling index or data,
Be to index
Carry out mould 2 complementation computings, symbol
Be the fixed-point data shift left operation.
Above-mentioned real-time integration type is carried out the cycle accumulation
, the electric weight that obtains at last is multiplied by coefficient more respectively and multiply by the factor
, running up to then in total electric weight, computing method are applicable to following formula:
(10)
In the formula
The cycle electric weight that obtains at last when being the input signal zero passage.
The electric weight that formula (5) is calculated is accumulated in total electric weight, make ammeter accurately measure the electric weight that nonlinear load uses, and in this way, the signal of no matter importing is that the sinusoidal waveform or the asymmetrical waveform of symmetry can both accurately measure, and has effectively improved the accuracy of ammeter to the nonlinear-load metering.
Embodiment two: this is an embodiment with 5 rank accuracy metering grades, referring to Fig. 3.
The one-period of input signal (
) some points of sampling (
), signal time in the cycle is divided into
Individual interval
, according to current instantaneous voltage and momentary current, calculate current instantaneous power [
], utilize quadravalence newton-Ke Tesi integral formula to whenever
4Deng the by stages
Active power carry out electric weight and calculate, be shown below:
In like manner, note the following formula index
With aforementioned index
Between relation, and the formula coefficient is 4 times of these difference of theoretical calculation formula coefficient.Then, following formula in the summation that adds up of the interval upper integral value of each equal portions, can be got:
: current period electric energy metrical value
In like manner, above-mentioned formula (12) need suitably to be revised the aforementioned calculation formula and be convenient to the engineering real-time operation in order to utilize in actual applications.Observe calculating formula (12), expansion can get:
Formula (13) is the real-time computing formula of 4 rank newton-Ke Tesi, promptly in actual applications, when whenever obtaining a sampled point, then data are accumulated:, be added to the electric weight totalizer after current sampled data product enlarged 7 times when sampled voltage, when current data indicator memory mould 4 residual values are 0 according to the current sampling point index; When datarams desired value mould 4 residual values are 1, be added to the electric weight totalizer after then current sampled data product value being enlarged 16 times; When datarams desired value mould 4 residual values are 2, be added to the electric weight totalizer after then current sampled data product value being enlarged 6 times; When datarams desired value mould 4 residual values are 3, be added to the electric weight totalizer after then current sampled data product value being enlarged 16 times.So go round and begin again, back and forth calculate, establish
For current sampling instant integral and calculating value, above-mentioned formulate is become algorithm, the formula of employing is:
In the formula
Calculate the signal period electric weight of gained when being the input signal zero passage.Present embodiment can obtain 5 grades of integration algebraically class of accuracies, can carry out more accurate metering to nonlinear-load.
In order to confirm that the inventive method possesses the higher accuracy of measuring than prior art, the inventor has done following experiment:
If the input voltage and input current signal is respectively
V,
A, for realizing the asymmetry of input signal, current signal adopts nonsinusoidal signal here.Order
, its waveform can be referring to Fig. 4.Calculate this signal period electric flux theoretical value, can get:
Use the trapezoidal quadrature of dot product, complexification of prior art and the above-mentioned two kinds of embodiments of the present invention respectively under the different mining sampling point, right
The cycle of carrying out active energy calculates.The error of calculation is listed in the table under each algorithm, and is as shown in table 1.
Table 1
In the table as can be known, when sampling number increases, the also corresponding increase of the accuracy in computation of each integral formula.But under identical sampling number, high-order Newton-Cotes integral algorithm exceeds 2 orders of magnitude than the dot product accuracy.As seen, the inventive method can further improve the class of accuracy of integral and calculating for asymmetric load under identical sampling number situation.
Below be the inventive method to be applied to ammeter (the ammeter specifications and models are DTSD341-MA1,3 * 57.7V/100V, 3 * 1.5 (6) A, 20000imp/kWh, 50Hz, 0.1s level (the mark Q/OKRW 013-2010 of enterprise)), enumerate the meritorious three-phase and four-line Measuring and testing accuracy data of forward, as shown in table 2.
Test result: uncertainty/accuracy is 0.01% (k=2).
Table 2
As can be seen from Table 2, the ammeter under the inventive method is used, its accuracy of measuring be lower than the highest domestic measurement standard GB/T17215.322-2008 regulation the accuracy index 20%, from minute having embodied the superiority of the inventive method.
Claims (2)
1. the electric energy gauging method of a nonlinear-load, its feature is being at one-period
Sampling
Point is gathered current instantaneous voltage and momentary current, calculate current instantaneous power [
P(
k)], based on the principle of high-order newton-Ke Tesi Numerical Integral Formulas to current sampling instant electric weight carry out real-time integration obtain instantaneous integral and calculating value (
I k ), and to the real-time integration of electric weight carry out the cycle accumulation obtain the electric weight accumulating value (
I), with this accumulating value multiply by a coefficient and multiply by the cycle electric flux that a factor obtains nonlinear-load (
E), the described factor is a periodic quantity
TWith sampling number
NRatio.
2. nonlinear-load electric energy measuring method according to claim 1, it is characterized in that obtaining the electric weight accumulating value (
I) after, when definite current input signal zero passage, calculate nonlinear-load electric weight (
E), described integral and calculating value (
I k ) suitable following two kinds of formula:
Formula two: based on quadravalence Ke Tesi formula
I k For:
The electric weight of described nonlinear-load (
E) suitable following two kinds of formula:
In the above-mentioned formula
I=I+I
k
Following formula
Crossing electric weight accumulating value in null cycle for signal, is with the instantaneous electric weight of current calculating gained
With electric weight accumulating value before this
After adding up, deposit back
The middle preservation.
Be current sampling instant electric weight to be carried out real-time integration obtain real-time integral and calculating value;
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Cited By (6)
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CN103344824A (en) * | 2013-07-08 | 2013-10-09 | 国家电网公司 | Electric energy integration method based on time mark measurement |
CN104316894A (en) * | 2014-10-16 | 2015-01-28 | 国家电网公司 | Simulation and calibration method for practical running environment of electric energy meter |
CN104989381A (en) * | 2015-06-15 | 2015-10-21 | 西安华瑞网电设备有限公司 | Soft measuring method and device for stroke period of beam-pumping unit |
CN106033098A (en) * | 2015-03-19 | 2016-10-19 | 上海机电工程研究所 | AC power measuring method and device based on data collection |
CN110687348A (en) * | 2019-10-29 | 2020-01-14 | 四川长虹电器股份有限公司 | Electric energy metering device and electric energy metering method |
CN113257638A (en) * | 2021-06-23 | 2021-08-13 | 江苏能电科技有限公司 | Universal type plastic shell circuit breaker |
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Cited By (10)
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CN103344824A (en) * | 2013-07-08 | 2013-10-09 | 国家电网公司 | Electric energy integration method based on time mark measurement |
CN103344824B (en) * | 2013-07-08 | 2016-05-04 | 国家电网公司 | The electric flux integration method measuring based on markers |
CN104316894A (en) * | 2014-10-16 | 2015-01-28 | 国家电网公司 | Simulation and calibration method for practical running environment of electric energy meter |
CN104316894B (en) * | 2014-10-16 | 2017-10-17 | 国家电网公司 | A kind of realistically displayed method of electric energy meter actual motion environment |
CN106033098A (en) * | 2015-03-19 | 2016-10-19 | 上海机电工程研究所 | AC power measuring method and device based on data collection |
CN104989381A (en) * | 2015-06-15 | 2015-10-21 | 西安华瑞网电设备有限公司 | Soft measuring method and device for stroke period of beam-pumping unit |
CN104989381B (en) * | 2015-06-15 | 2017-12-05 | 西安华瑞网电设备有限公司 | A kind of flexible measurement method and device of beam pumping unit stroke cycle |
CN110687348A (en) * | 2019-10-29 | 2020-01-14 | 四川长虹电器股份有限公司 | Electric energy metering device and electric energy metering method |
CN110687348B (en) * | 2019-10-29 | 2021-04-27 | 四川长虹电器股份有限公司 | Electric energy metering device and electric energy metering method |
CN113257638A (en) * | 2021-06-23 | 2021-08-13 | 江苏能电科技有限公司 | Universal type plastic shell circuit breaker |
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Application publication date: 20101215 Assignee: Shenzhen Wismei Technology Co.,Ltd. Assignor: Wasion Group Co., Ltd. Contract record no.: 2013440020316 Denomination of invention: Nonlinear-load electric energy measuring method Granted publication date: 20120829 License type: Exclusive License Record date: 20131112 |
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