Research On Phase Locked And Harmonic Suppression For Power Grid Voltage Signal Based On Kalman Filtering

With the continuous development of new energy power generation technology,more and more power electronic equipment have been used in power system,in order to meet the new energy power connected to grid and the need of precise control of power electronic equipment,to obtain the grid synchronization information as the control signal is crucial,synchronous information will ensure reliability of power grid and the control performance of power electronic equipment.At the same time,there are more and more nonlinear devices connected to the power supply system,which leads to the distortion of the power grid voltage,which is very bad for the quality of electric power.Therefore,this paper is based on the Kalman filtering method to complete lock phase of the voltage signal of the grid and the harmonic signal extraction analysis.On the basis of the traditional Kalman filtering method,an improved method is proposed to obtain better phase locking and detection results.First of all,the paper analyzes the general scheme of voltage signal of the phase locked loop and the harmonic suppression method,and gives the technical route of phase locking and harmonic suppression.The commonly used methods of grid voltage phase locked method and harmonic detection are studied,and the principle is analyzed and simulation briefly,summarizes the advantages and disadvantages of these methods,and then put forward the method of phase locking and harmonic detection used in this paper.Secondly,the method of single phase grid voltage phase locked loop is studied,and the method of Kalman filter is used to obtain the synchronization information of grid.The basic principle of unscented Kalman filter analysis,introduces the transformation of UT transform instead of the nonlinear function,according to the expected grid synchronization information,state space model of voltage signal is derived to improve the estimation precision of the state variables.The simulation results of different fault states are carried out to verify the effectiveness of the proposed method on the synchronization information tracking.Again,the three-phase grid voltage fault will be analyzed.The causes and damage will be introduced briefly.Using Matlab/Simulink to build power grid voltage fault model,the simulation results are given and the voltage balance of sag and unbalanced of sag are analyzed,then establish the state space model of the three-phase grid voltage,the simulation method based on Kalman filter is carried out,through the analysis of the simulation results,the improvement scheme based on the hysteresis comparator and effective value method is proposed,and verified by simulation,indicating the effectiveness of the proposed method.Finally,aiming at the problem of harmonic distortion in power system,the voltage harmonic signal detection method based on Kalman filter is proposed,based on the analysis of the harmonic voltage of power grid,the state space model of voltage harmonic signal will be established,according to the simulation model,the harmonic content and the performance of the method will be analyzed.This paper presents an improved method to estimate the noise covariance matrix of the system.This method can improve the detection speed and steady state precision.