Voltage Flicker Testing Algorithm Of Power Quality

Voltage flicker is one of the most important factors of electric power quality. Aiming to meet the requirements of advanced metering infrastructure of smart grid construction, and perfect power quality testing, the algorithm to calculate voltage flicker was investigated.In the first part, power quality monitoring flow and software construction were presented to make clear the importance of voltage flicker in power quality. Then the conception, causes and harm of voltage flicker were introduced. After transforming IEC analogue filter into digital filter, statistical calculation of instantaneous flicker sensation was introduced.In the second part, based on existing algorithms, two comparisons were made with help of Matlab simulation. The first comparison is about envelope testing, including square method, Hilbert transform method, Teager method and instantaneous reactive power method. The second comparison is about the calculation of flicker sensation, including IEC method, FFT method, and HHT(Hilbert Huang Transform)method.In the third part, a research of inter-harmonic flicker was conducted and the IEC flicker testing method was improved. After analyzing inter-harmonic effect on voltage root-mean-square value and peak value quantitatively, the inter-harmonic flicker frequency-fluctuation curve was created. In the end of this part a inter-harmonic flicker testing method based on extremum value searching and spline interpolation was brought up in the end of this part.The result of the analysis indicates that:in the section of voltage envelope testing, Hilbert transform method and instantaneous reactive power method can give relative accurate result in the whole frequency range, the square method has big error in the low frequency range while Tegear method has big error in the high frequency range. In the section of flicker sensation calculation, the experimental result of IEC flicker testing method is different from real result in the very low frequency range, and the front output data of filter are unstable. FFT method has small quantities of outputs of flicker sensation per second. HHT method can provide time-varying information of amplitude and frequency, but the calculation is complex compared with the other two methods. In the section of inter-harmonic flicker testing, the method based on extremum value searching and spline interpolation can give correct result.