The Study Of Three Level APF With LCL Filter

With the rapid development of manufacturing and production technology,the technology of power electronics has been concerned and applied widely.However,the rapid increase of the nonlinear loads in power electronics leads to a large number of harmonic currents injected into the power grid,which causes pollution of the grid voltage.Therefore,the governance of the grid harmonic pollution becomes the focus of scholars,and the active power filter as a device to control the harmonic pollution effectively has also become the focus of research.This paper describes the background of harmonic generation firstly,the significance of harmonic elimination and the advantages of LCL filter.A diode clamped three-level topology and several modulation methods for the APF are proposed.At the same time,the principle of three-level APF is expounded with modulation strategy.For the system of the three-level APF,the main circuit,control circuit and drive circuit design is finished.In addition,the structure of LCL filter is analyzed in parameter calculation in detail.Secondly,this paper introduces the principle of two harmonic detection methods in detail,and compares the difference between the two methods.This paper proposes a compound current loop controller structure which includes the repetitive controller and the PI controller,the performance was analyzed by the amplitude frequency characteristic curve;To solve the problem of neutral point potential balance of threelevel topology inherently,this paper also presents a control method of injecting zero sequence components into the modulation signal.According to the practical engineering application,the method is improved.The method after improving can also ensure the balance of neutral point.At the same time,it avoids the influence of injection components on the compensation performance of the system.Finally,based on the MATLAB simulation platform and experimental platform built by TMS320F2812,experiments carry out.The simulation and experimental results show the proposed method and treatment is correct and practicable,but also demonstrated system of the three-level APF has good harmonic compensation performance fully.