Research On Power Quality Detection Algorithm And Its Application

With the development of science and the improvement of people's quality of life,people's demand for power quality is getting higher and higher.At present,the problem of power quality has aroused the widespread interest and research of the research institutions all over the world.But the accurate detection of power quality is the primary task to improve the power quality.Therefore,the research and application of power quality detection algorithm has certain theoretical significance and practical value.Based on the research of power quality detection algorithm,according to the harmonic/ inter-harmonic signal,7 kinds of typical single disturbance signal and 3 kinds of composite disturbance signal in mathematical models,and the signal characteristics are researched on harmonic/inter harmonics and power quality disturbance detection and location problem.Focus on the following 3 points of research,and achieved some results,these results can provide a reference for the analysis and control of power quality problems.(1)In order to solve the problems of low accuracy of the inter harmonic detection and the difficulty of locating the transient harmonic signals,a new method of inter-harmonics detection is discussed.First,the signal is decomposed by wavelet packet and FFT transform,calculate the relative wavelet packet energy,then apply spectrum characteristics and the relative wavelet packet energy determine the signal containing components,finally,wavelet packet reconstruction and apFFT algorithm are used to detect and locate the signal,and calculate amplitude and frequency of inter-harmonics.The detection method is simulated by using the model of transient and harmonic signals,and the simulation results are compared with the results in the literature.The results show that the proposed method can detect inter harmonics more effectively and has higher accuracy and precision.(2)Aiming at the problems such as low accuracy of EEMD and CEEMD harmonic detection algorithm,incomplete completeness and difficult detection of harmonic signal,a harmonic detection method is discussed.First,the signal is decomposed by CEEMD,calculated PE of each order IMF component,then selected IMF component from the signal,after screening the remainder of the EMD decomposition to obtain the harmonic signal.Finally this method is compared with EEMD,CEEMD method,the harmonic detection method has higher accuracy and resolution.(3)Aiming at the problem that the Hilbert transform can not detect the complex disturbance signal,the improved CEEMD can not estimate the parameters of the disturbance and the start / stop time,a detection method of power quality disturbance signal is discussed.Firstly,an improved CEEMD algorithm is used to decompose the original signal to obtain the corresponding single disturbance signal,then the instantaneous frequency and instantaneous amplitude information are obtained by Hilbert transform.Finally,the frequency and amplitude of the disturbance and the start and stop time are estimated by the method of maximum and mean fitting.The mathematical model of 7 kinds of single disturbance signal and voltage rise superimposed harmonic signal is used to simulate the algorithm.The simulation results show that the proposed method has good detection and localization effect,and can realize the detection and localization of single / complex disturbance signal.