Research On Power Quality Detection Algorithm Based On All-phase Fourier Transform

With the increasing of nonlinear load and power electronic devices,the problem of power quality is becoming more and more serious.At the same time,the new precision equipment and intelligent equipment begin to popularize,and put forward strict requirements on the quality of power supply.Therefore,it is of great significance to study the disturbance of power quality and detect it accurately.FFT,as an important member of spectrum analysis method,is used very frequently in the field of detection.The further developed APFFT has extremely low spectral leakage and "phase invariance".The derived all-phase time-shift phase difference method in the field of detection has been applied,and achieved a good detection effect.In this paper,based on the full phase time shift phase difference method,three detection methods for harmonics,harmonics and disturbances are discussed respectively by improving the existing problems.In this paper,the all-phase time-shift phase difference method is studied in depth.Firstly,this paper expounds the principle of full phase time shift phase difference method,lists the problems existing in the algorithm in power quality detection,analyzes them in detail in theory,and probes into the root causes of the problems.Then,the design simulation experiment is verified,and the results show that the problems raised are real and the analysis is accurate.Aiming at the problem of frequency offset detection anomaly in all-phase time-shift phase difference method,a new inter-harmonic detection algorithm is proposed by introducing spatial spectral estimation algorithm.Firstly,the signal frequency is detected by the fast TLS-ESPRIT algorithm,and the frequency offset is calculated by combining it with the peak spectral line information.Then,the amplitude of the peak spectral line is corrected by using the frequency offset.Finally,the phase value is obtained from the phase spectrum.The validity of the proposed algorithm is verified by the simulation comparison with the all-phase time-shift phase difference method.Compared with the literature published in recent years,the results show that the algorithm can detect the harmonic between them more accurately.Aiming at the problem that APFFT can not carry out disturbance location,the perturbation location method based on SVD is introduced to optimize,and a perturbation detection method based on APFFT and SVD is studied.Firstly,the starting and stopping time of transient disturbance is obtained from the 4th layer component by using SVD decomposition signal.Then,a piece of sampling data is taken from the front and back of the disturbance starting time,and the improved harmonic detection method is used to analyze and obtain the perturbation parameters.The simulation results of single perturbation model and composite perturbation model show that the proposed algorithm has better positioning effect and high detection accuracy of stationary signal parameters.Aiming at the problem of large computation and poor real-time performance of all-phase time-shift phase method,the ratio method is introduced to optimize,and a harmonic detection method based on spectral line interpolation APFFT is studied.Firstly,the signal spectrum diagram is obtained,and the frequency offset of the peak spectral line is calculated by using the amplitude ratio of the highest and sub-maximum spectral lines.Then,the amplitude and frequency are corrected by the frequency offset.Finally,the signal phase value is obtained by phase spectrum.Compared with the three-spectral line interpolation FFT correction algorithm,the harmonic detection method studied is more accurate.