CN105067881A - Harmonic detection-based electrical safety monitoring method - Google Patents
Harmonic detection-based electrical safety monitoring method Download PDFInfo
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- CN105067881A CN105067881A CN201510440355.7A CN201510440355A CN105067881A CN 105067881 A CN105067881 A CN 105067881A CN 201510440355 A CN201510440355 A CN 201510440355A CN 105067881 A CN105067881 A CN 105067881A
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Abstract
The invention provides a harmonic detection-based electrical safety monitoring method, which comprises the steps of firstly, sampling a to-be-measured signal and conducting the frequency tracking method at the same time to ensure the synchronization of the sampling period with the signal period; secondly, figuring out the signal period through the digital low-pass filtering process, and uniformly extracting data points within one period; thirdly, figuring out all harmonic parameters through the synchronous sampling SRFFT process; and finally simulating the curve of the to-be-measured signal and then displaying the curve in combination with the obtained harmonic parameters. According to the technical scheme of the invention, based on the synchronous sampling SRFFT process, all harmonic parameters can be figured out. The method is high in calculation accuracy and convenient in monitoring operation, wherein the all the harmonic parameters can be intuitively displayed.
Description
Technical field
The present invention relates to a kind of Electrical Safety method for supervising based on harmonic detecting.
Background technology
The develop rapidly of modern power electronics technology, various power electronic equipment is used widely in various fields such as electric system, industry, traffic, but because power electronic equipment is a kind of nonlinear time-varying topology load, its harmonic wave produced and idle injection electrical network, place capacity and line loss can be made to increase, cause the decline of being transported to electric plant factor, affect power supply quality, potential threat is formed to the safe and stable operation of electric system.At present, harmonic pollution, electromagnetic interference (EMI) and power factor reduce by the three large public hazards having become electric system, therefore, research and analysis harmonic wave Producing reason, for the detection method suppressing the humorous wave interference of electric system to provide, raising operation of power networks quality is met consumers' demand there is important practical significance.And now, the protective device of the motor used in commercial production, can monitor the line current in motor operation course and voltage, and trip protection and warning early warning can be given when there is unusual condition.But not real time modelling does not go out electric current in operational process and voltage curve, thus can not observe in operating loop the harmonic wave of the quality of power supply that whether has an impact intuitively.
Harmonic analysis in power system is all realized by fast fourier transform (FFT) usually, but there is fence effect and spectrum leakage in this method, make the harmonic parameters that calculates and frequency, amplitude and phase place inaccurate, especially phase error is very large, cannot meet harmonic measure requirement accurately.
Summary of the invention
For solving above technical deficiency, the invention provides a kind of Electrical Safety method for supervising based on harmonic detecting, harmonic parameters computational accuracy is high, and security monitoring is intuitively accurate.
The present invention is achieved by the following measures:
A kind of Electrical Safety method for supervising based on harmonic detecting of the present invention, comprises the following steps:
Step 1, samples to measured signal, adopts frequency-tracking simultaneously, ensure the sampling period and the signal period synchronous;
Step 2, adopts the method for digital low-pass filtering to ask for the signal period, then one-period time
In evenly extract 2*N data point, wherein N-1 is most higher hamonic wave exponent number;
Step 3, adopts synchronized sampling SRFFT to obtain each harmonic parameters;
Step 4, the harmonic parameters that integrating step 3 draws, simulates the curve of measured signal, and shows.
In step 1, over-sampling is carried out to measured signal, sample frequency=F*2*N*K, wherein F is the fundamental frequency of signal, N-1 is most higher hamonic wave exponent number, K is sampling multiplying power, and K is greater than 9, adopt ask intermediate value by the method for fitting a straight line at adjacent 2, often organize data sampling and will ensure to be greater than two signal primitive periods.
Digital low-pass filtering adopts iir filter, carries out Computer Aided Design with MATLAB language to iir filter, obtains the filter coefficient of specifying index, adopts elliptic filter modelling iir digital filter.
Filtering asks the cycle to refer to, and the waveform periodic method to only remaining first-harmonic composition asks for the primitive period.
Even extraction 2*N point refers to the value evenly asking for 2*N data point in the time of a complete cycle by the method for fitting a straight line interpolation, and N-1 is most higher hamonic wave exponent number.
The invention has the beneficial effects as follows: the present invention adopts SRFFT to obtain each harmonic parameters, has very high computational accuracy, even if also its parameters can be obtained exactly for the even-order harmonic that amplitude is less, especially more obvious for the precision improving phase calculation.And can show intuitively, convenient monitoring.
Embodiment
A kind of Electrical Safety method for supervising based on harmonic detecting of the present invention, first samples to measured signal, adopts frequency-tracking simultaneously, ensure the sampling period and the signal period synchronous.Carry out over-sampling sample frequency=F*2*N*K to measured signal, wherein F is the fundamental frequency of signal, and N-1 is most higher hamonic wave exponent number, K is sampling multiplying power, and K is greater than 9, adopt ask intermediate value by the method for fitting a straight line at adjacent 2, often organize data sampling and will ensure to be greater than two signal primitive periods.Then and carry out analog to digital conversion, the maximum cycle value estimated by measured signal, ensures often to organize the data that data can sample two signal periods.Design iir digital filter carries out filtering to data, by whole for the harmonic components beyond first-harmonic filtering.Before filtering is carried out to data, first by the sample frequency of digital filter, resampling is carried out to raw data, use a fixing frequency carry out resampling be in order to make wave filter easily obtain stability factor when designing and in filtering time can settle out in the short period of time.Owing to carrying out filtering to data just in order to ask the primitive period, so just there is no too high requirement, as long as base is constant just passable for wave period after filtering to the amplitude versus frequency characte of wave filter and phase-frequency characteristic.The most classical digital filter is FIR filter and iir filter, but under identical performance index, the exponent number of FIR filter is more much higher than iir filter, in order to reduce calculated amount, selects iir filter here.With MATLAB language, Computer Aided Design is carried out to iir filter, obtain the filter coefficient of specifying index.Here elliptic filter modelling iir digital filter is used, because its exponent number is minimum and easily obtain stable filtering system.When designing filter, under being operated in more stable state to make wave filter always, here not carry out filtering separately to often organizing data, but using the initial value that M (M the is filter length) data before and after upper one group of data filtering are organized as next, just more stable filtering being carried out to the data of a group very long with regard to being equivalent to like this, avoiding the transitional period often organized data and all need wait one longer.
By periodic method, primitive period value is asked for filtered data.In order to reduce the impact of upper one group of data on next group data, selecting to deduct second zero crossing with the 4th zero crossing here and asking for the cycle.Time before second zero crossing is transit time, ensures the transitional period of certain hour, makes this
Fundamental frequency acquiring method has stronger adaptability.
Within the time of a primitive period, evenly extract 2*N point to raw data, N-1 is most higher hamonic wave exponent number.Starting point is not specially required, as long as it is just passable to ensure there are thereafter the data of a complete cycle.When the point that will extract is not in raw data, just by the method for fitting a straight line, matching is carried out to adjacent 2 of raw data.Because the sample frequency of raw data is very high, still very high precision can be obtained so ask for by the method for fitting a straight line.Ask for 2*N data point by this method, when avoiding synchronous sampling by software, truncation error causes circular error, reduces final spectrum leakage.
The value of each harmonic components is asked for by the SRFFT method of synchronized sampling method.Utilize complex sequence cosin-window interpolation split-radix fast fourier transform (SRFFT).This algorithm greatly can improve the precision that FFT calculates, thus meets the accuracy requirement to harmonic parameters in harmonic measure.For the requirement of power system harmonic measurement, design data Acquisition Circuit.In order to eliminate the error that frequency alias brings, specialized designs has low-pass filter and the digital filter of better performance; Due to system frequency undulatory property, be designed with hardware circuit composition frequency-tracking link, finally realize the sampling period and the signal period synchronous.And write A/D conversion driver, control program and arithmetic subroutine, they are applied to harmonic measurement unit, thus complete harmonic analysis in power system.
Because the data of 2*N above point evenly ask in the time of a complete cycle, it almost reaches desirable synchronized sampling, therefore asks for by synchronized sampling method the spectrum leakage that harmonic parameters causes just very little.Compared with quasi-synchronuous sampling method, this method is while meeting higher accuracy requirement, and real-time doubles left and right compared with quasi synchronous three to five signal periods.This method can accomplish that every two signal periods upgrade a secondary data, and very accurately can measure base wave period.Finally combine the harmonic parameters drawn, simulate the curve of measured signal, and show.Result can be made so more directly perceived, and convenient operation person observes.
The above is only the preferred implementation of this patent; it should be pointed out that for those skilled in the art, under the prerequisite not departing from the art of this patent principle; can also make some improvement and replacement, these improve and replace the protection domain that also should be considered as this patent.
Claims (5)
1., based on an Electrical Safety method for supervising for harmonic detecting, it is characterized in that, comprise the following steps:
Step 1, samples to measured signal, adopts frequency-tracking simultaneously, ensure the sampling period and the signal period synchronous;
Step 2, adopts the method for digital low-pass filtering to ask for the signal period, then within the time of one-period, evenly extracts 2*N data point, and wherein N-1 is most higher hamonic wave exponent number;
Step 3, adopts synchronized sampling SRFFT to obtain each harmonic parameters;
Step 4, the harmonic parameters that integrating step 3 draws, simulates the curve of measured signal, and shows.
2. the Electrical Safety method for supervising based on harmonic detecting according to claim 1, it is characterized in that: in step 1, over-sampling is carried out to measured signal, sample frequency=F*2*N*K, wherein F is the fundamental frequency of signal, N-1 is most higher hamonic wave exponent number, and K is sampling multiplying power, and K is greater than 9, adopt ask intermediate value by the method for fitting a straight line at adjacent 2, often organize data sampling and will ensure to be greater than two signal primitive periods.
3. the Electrical Safety method for supervising based on harmonic detecting according to claim 1, it is characterized in that: digital low-pass filtering adopts iir filter, with MATLAB language, Computer Aided Design is carried out to iir filter, obtain the filter coefficient of specifying index, adopt elliptic filter modelling iir digital filter.
4. the Electrical Safety method for supervising based on harmonic detecting according to claim 1, is characterized in that: filtering is asked the cycle to refer to and asked for the primitive period to the waveform periodic method of only surplus first-harmonic composition.
5. the Electrical Safety method for supervising based on harmonic detecting according to claim 1, it is characterized in that: evenly extract 2*N and put and refer to the value evenly asking for 2*N data point in the time of a complete cycle by the method for fitting a straight line interpolation, N-1 is most higher hamonic wave exponent number.
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| CN106168651A (en) * | 2016-07-06 | 2016-11-30 | 重庆理工大学 | Based on the exciting power unit on-line fault diagnosis method and system of window when synchronizing |
| CN113533846A (en) * | 2021-07-13 | 2021-10-22 | 国网江苏省电力有限公司营销服务中心 | High-speed synchronous acquisition and calculation method and device for electrical load data |
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