Research On Power System Phasor Measurement Methods

Fast and accurate measurement of electrical phasor is a basis in power systemmonitoring, protection and control. With rapid development of national economy andimprovement of smart grid construction, an increasing demand of estimated accuracyin steady state of phasor measurements and speed of dynamic response in modernpower system arise. Based on digital signal processing technology, computertechnology and power system automation technology, this paper made a briefdescription of phasor measurement definitions and classifications, and analysis andcomparison of phasor measurements in common algorithm and performance. On thebasis, three improved algorithm were put forward in phasor measurements.1) To get power system frequency fast and accurately, frequency measurementalgorithm was proposed based on first derivative in the paper. According to basiccharacteristics of power signal, it used system fundamental frequency by firstderivative of signa, and fixed sampling frequency through the previous measurementfrequency of the system signal. The results show that this algorithm can effectivelyreduce estimated amount of computation and response time of the frequency. Then itcan enhance fast speed, accuracy and robustness in the phasor measurements.2) In the paper, it advanced a phase measurement algorithm based on flat-topwindows Double Line. Firstly, analysis in characteristics of common window function,and choice of flat-top window for power phasor were present. Secondly, the electricalsignal was sampled to get N-point. Then by extracting N/2odd number of samplingpoints and N/2even serial sampling point DFT was transformed. And maximum linesand maximum spectrum phase was respectively get. Lastly, by phase weighted it getfrequency, amplitude and phase. The simulation results show that the method iseffective to reduce and suppress mutual interference between the fundamental andharmonic spectrum, and significantly to improve the phase measurement accuracy.3) According to characteristics in spectrum of harmonics, inter-harmonics, andthe window function, with a problem of non-synchronous sampling under the spectrumleakage and fence effect, the paper proposed estimation algorithm. It is based onpolynomial approximation in extreme value of fundamental wave, integer harmonicsand inter-harmonics parameters. The algorithm significantly reduced computationalcomplexity to strike frequency correction factor. An impact of spectral leakage of neighboring harmonics and inter-harmonics was taking into account. Then use ofmatrix inversion method was to revise amplitude and phase of the harmonic spectrumphase. The simulation results show that the method is easy to implement. And it caneffectively improve the accuracy in parameters detection of the fundamental wave,harmonics and inter-harmonic.