Harmonic Current Prediction Method Based On The Variable Step Size LMS Algorithm For APF

Due to the rapid development of power electronic and control theory technology,power electronic devices and nonlinear loads are widely applied to many industries,which leads to the increasingly serious harmonic pollution problem.Active power filter as the most direct,effective harmonic Suppression,has become a hot research topic in the application of power electronic technology.Because that the traditional methods of the harmonic detection can't solve the problem of time delay caused by control process of APF system,the harmonic prediction method has been proposed.This paper mainly researched the realization of predictive control strategy in APF,in order to solve the problem of harmonic pollution.In this thesis,firstly the reason and harm of harmonic in power system was introduced,and then leading to the active power filter,secondly through the analysis of the structure and working principle,the mathematical model was established.Based on the classical instantaneous reactive power theory,a prediction link is introduced as the system's harmonic current detecting method,and then makes a detail analysis to it.Due to the traditional fixed step LMS algorithm is unable to achieve both fast convergence and high steady accuracy,a variable step size LMS prediction algorithm is put forward.This algorithm uses the amplitude factor and the total weighted error to regulate the step size,which successfully solves the contradiction of the fixed step algorithm.And its effectiveness is finally verified by simulation results.At the end of this thesis,an experimental platform is built for active power filter system,and the effectiveness of the model is verified by the experimental results.According to the the experimental results the prototype which is designed in this paper,can effectively control the harmonic,and meet the requirements of the expected experiment.