Research On The Control Strategy Of Multilevel Active Power Filter

The continuous development of power electronics technology has greatly promoted the effective and controllable applications of electric energy,but a t the same time it has brought great harmonic problems to the power system.Nowadays there are two kinds of measures to solve the harmonic problems: one is to improve the topology of the power electronic equipment itself and reduce the generated harmonic.The other is to use the harmonic suppression equipment to improve the harmonic problem,usually there are two kinds of measures,which are passive filter and active filter.The active filter can be used to solve the harmonic problems dynamically,so it has been widely used.But at the same time,because the switching frequency of the high-power electronic components is low,it is far from the requirement of the active power filter to solve the harmonic problems.So it is mainly used in small and medium power occasions.In order to use the active power filter in the high-power occasions,its topology and control algorithm are improved usually.This paper mainly studies the active power filter(Active Power Filter)based on the cascaded H bridge.In this paper,the relevant background and research status of active power filter are analyzed.On this basis,the basic principles are described in detail.Then,the common multilevel topology is analyzed and compared.The active power filter based on cascaded topology is mainly studied,and its topology is given.At the same time,the cascaded converter based on carrier phase shift modulation(carrier phase modulation)algorithm is simulated,and the effect of cascade number on its output performance is analyzed.On the basis of this,the traditional ip-iq algorithm is analyzed.According to the disadvantage of slow detection speed of the traditional ip-iq algorithm due to the low pass filter,the paper proposes a variable step size LMS/LMF adaptive filter algorithm.The adaptive filter can not only change the step size according to the change of original signal,but also change the proportion of the Least Mean Square(LMS)algorithm and the Least Four-order Moment(LMF)algorithm,which makes the advantages of high detection accuracy of LMF and high detection speed of LMS fully played.The simulation results show that the proposed algorithm is effective,and the speed of harmonic current is improved obviously.In view of the DC side voltage fluctuation in the active power filter,the realization algorithm of the cascaded 7 level active power filter is given.On this basis,the simulation of active power filter is carried out,and the simulation model is given.Fourier analysis is carried out on the compensation result,and the simulation results show the correctness of the proposed algorithm and model.The model is built to verify the algorithm proposed in this paper,and the related circuit is designed.On this basis,an experimental prototype based on DSP+FPGA is built.The experimental results demonstrate the correctness and feasibility of the proposed algorithm.