Research On Control Strategy Of Shunt Active Power Filter

With the rapid development of national distributed energy and the rapid progress of power electronics technology,a large number of power electronic devices and non-linear loads are not only widely used in industrial occasions,but also gradually spread in every corner of people's daily life.While they promote the development of national science and technology and bring convenience to people,they also inject a large number of harmonics into the power system due to their non-linear characteristics.And reactive power,power quality of power grid is facing severe challenges.Active power filter(APF)has been widely studied and used because of its high-precision harmonic compensation characteristics and fast and stable performance.In this paper,the LCL three-level shunt active power filter is taken as the research object.The LCL active power filter is deeply studied and discussed from the aspects of working principle,mathematical model of main circuit,device capacity and parameter design,modulation strategy,performance of LCL interface filter and system current control strategy.Firstly,this paper analyses the working principle of LCL Three-level Active Power filter,establishes the main circuit mathematical model in the static coordinate system and the rotating coordinate system respectively,analyses and compares the modulation strategies of active power filter,chooses the SVPWM modulation scheme for the system and completes the simulation model.On this basis,the main circuit of active power filter is completed.Design of key road parameters.Then,aiming at the resonance problem of LCL interface filter of active power filter,passive damping strategy is selected as the system resonance suppression scheme.Four kinds of LCL passive interface filter topologies are given.Four kinds of LCL passive interface filters are theoretically analyzed from three aspects of filter damping branch loss,high-order harmonic filtering accuracy and robustness.On this basis,four kinds of LCL passive interface filters are built as active power filter simulation models,and the simulation comparison is completed.This paper presents the conclusion that the Case 4 LCL interface filter is superior to the other three passive filters in terms of damping branch loss,high order harmonic filtering accuracy and robustness.In addition,aiming at the accuracy of harmonic current compensation of shunt active power filter,the current control strategy of shunt active power filter is studied in this paper.The limitation of proportional resonance control strategy is pointed out through theoretical and simulation analysis.Based on this,an improved vector resonance current control strategy based on static coordinate system is proposed.The feasibility of the improved current control strategy is verified by the analysis of its controller characteristics.Furthermore,an improved parameter design method of vector resonance controller is given,which is used for the control of this paper.Case 4 LCL filter is used to design the parameters of current controller.The simulation results show that the proposed current control strategy has higher harmonic compensation accuracy than the traditional specified sub-harmonic control strategy.Finally,this paper chooses DSP as the digital processor of the system,completes the related hardware and software design,builds the experimental platform of LCL Three-level Active Power filter,and verifies the validity of the current control strategy and controller parameter design method of the proposed LCL active power filter through experiments.