Research On Detection Method And Control Strategy Of Unified Power Quality Controller

With the rapid development of modern industry,more and more non-linear loads and impulsive loads are connected to the power grid,which makes the power quality problem more and more serious.On the other hand,with the progress of science and technology,the demand for power quality of electrical equipment is becoming higher and higher.Therefore,how to improve power quality has become one of the hot research directions in the field of electrical engineering.As a comprehensive compensation device that can improve various power quality problems,Unified Power Quality Controller(UPQC)has broad development prospects.Firstly,several existing topologies of UPQC are described.Then three-phase three-wire left-series right-parallel UPQC is selected as the research object,and its working principle and power flow are analyzed in detail.Secondly,several harmonic detection methods based on instantaneous reactive power theory are introduced.Aiming at the problem of asynchronization of distorted voltage and current detection in traditional detection methods,the detection method is improved.The improved UPQC integrated detection method can extract compensating command signals quickly and synchronously when the grid voltage fails.In addition,an improved digital low-pass filter based on optimized moving average filter is proposed to improve the performance of the low-pass filter used to extract the fundamental wave in the detection method.This filter combines the advantages of fast response speed of moving average filter and high precision of Butterworth filter.Compared with traditional moving average filter,the optimized moving average filter reduces the storage space,and can be used to improve the accuracy of distortion detection and the timeliness of dynamic response.The detection method is simulated by MATLAB/Simulink.The simulation results show that the detection method is effective.Thirdly,aiming at the different compensation targets of UPQC on series and parallel sides,the mathematical models of series and parallel compensation parts of UPQC are established respectively,and the voltage and current controllers are designed by decoupling.The traditional PI controller is used in the series part control strategy to track the change of voltage compensation instructions quickly.In the control strategy of parallel part,vector resonant controller is used instead of traditional PI controller to achieve the purpose of tracking current compensation without static error,and to compensate specific sub-harmonics.The simulation results show that the two control strategies can effectively compensate the voltage and current distortion.Finally,the main circuit parameters and basic hardware circuit of UPQC system are designed.The software is designed by CCS.A set of UPQC experimental platform with TMS320F2812 as the core processor is built,and the prototype experiment is carried out.The experimental results show that the detection method and control strategy adopted in this project can effectively improve many kinds of power quality problems.