Design And Control Of Three-level Parallel Active Power Filter

Non-linear electricity load,especially power electronic devices in the power system in the widespread application of a large number of harmonic current into the power grid,resulting in a large number of harmonics into the utility power system,and causing serious problem.Active Power Filter(APF)is an effective method to solve this harmonic pollution problem.This paper takes APF's control algorithm research and design as the research focus.First of all,active power filter operation requires real-time monitoring of grid frequency and phase,and can be stable and accurate operation in the unbalanced and distortion grid environment.This paper based on the traditional SRF-PLL,a software phase-locked loop based on SOGI is designed.The method uses a new second-order generalized integral.The positive sequence and the negative sequence quadrature component of the three-phase grid in the ?? coordinate system are generated,and then the phase sequence of the positive sequence is locked by the phase-locked loop.The method has the characteristics of real-time and high precision.Secondly,the active damping type LCL output filter is the key technology of active power filter.In this paper,based on the analysis of the three-phase active power filter modeling foundation and the digital delay generation mechanism,this paper establishes a detailed mathematical model of LCL-type active power filter.Then,the characteristics of active damped LCL filter in the presence of delay are studied,and the influence of feedback coefficient,digital delay and grid impedance on filter characteristics is analyzed.Thirdly,In this paper,frequency domain analysis and design are carried out for output current control.In particular,this paper designs a multi-proportional resonant controller with proportional-integral controller to complete the output current tracking.This method can improve the open-loop gain at the harmonic frequency and improve the compensation effect.The control effect is verified by PSIM simulation software.Finally,in order to verify the modeling method and the control algorithm used in this paper,a 10 kVA three-phase three-level APF experimental prototype is proposed,and the detailed experimental results are given.