Research On Control Strategy Of Three-phase Four-switch Shunt Active Power Filter

The vigorous development of power electronic technology makes more power electronic equipments applied to life,which has brought great convenience to people.At the same time,the harmonic pollution caused by the operation of a large number of non-linear loads has also greatly influenced the power quality.Active power filters(APF)have outstanding performance in harmonic control,reactive power compensation,and improvement of power grid power quality.The research object of this dissertation is the three-phase four-switch shunt active power filter(TFSSAPF)suitable for low-voltage,medium-and small-capacity harmonic control and reactive power compensation requirements under three-phase three-wire system.Compared with the traditional six-switch APF,TFSSAPF reduces the number of switching devices,reduces the system cost,and simplifies the corresponding auxiliary circuit.From the current development trend of APF,TFSSAPF has good application prospects and far-reaching research significance.Based on a review of a large number of relevant domestic and foreign literature,we first understood the importance of TFSSAPF in the field of low-voltage,mediumand small-capacity harmonic control and reactive power compensation through understanding of the current state of APF research and development prospects.Based on this,we identified TFSSAPF as this dissertation' research object.Next,this dissertation establishes a mathematical model of TFSSAPF in a static abc coordinate system,and transforms the mathematical model into a dq rotating coordinate system through coordinate transformation,which is convenient for subsequent analysis and research.After the mathematical model is established,This dissertation compares and analyzes the two harmonic current detection methods of source side current detection method and load side current detection method,and then studies the overall control strategy of TFSSAPF.the fuzzy adaptive PR controller is introduced to develop a current control strategy based on fuzzy adaptive PR.For the modulation strategy,the traditional four-switch SVPWM algorithm has been optimized to make the algorithm more simple and intuitive;then considering that the instability of the DC-side voltage will affect the compensation performance of the entire system,this dissertation develops a voltage-stabilization strategy for the DC-side voltage and an equalization strategy for the two split capacitors.Based on the theoretical analysis,the corresponding TFSSAPF overall simulation model was designed and built on MATLAB software,The simulation results show that after the grid performs harmonic current compensation through the system designed in this dissertation,the current THD value can be reduced to within the scope of the relevant national technical regulations.Finally,build the corresponding experimental platform according to the design of this dissertation,and verify the correctness and feasibility of the system design of this dissertation through the experimental results.