Research On Control Method Of Unified Power Quality Controller Base On Coupled Controllable Reactors

Electric energy plays an increasingly important role in the production of modern life.It is currently the most widely used clean energy.However,power quality issues are becoming increasingly prominent.Power supply quality problems seriously threaten the stable operation of modern industrial parks.The unified power quality controller(UPQC),as a device that can comprehensively solve various power quality problems from the grid side and the load side,has a broad application prospect.However,due to the limitation of the voltage resistance of power electronic devices,at present,most UPQC can only be used in low-voltage distribution networks,which seriously restricts the use of UPQC.Therefore,a solution that enables UPQC to be applied to higher voltage levels is urg ently needed.Aiming at the above problems,this paper proposes a new UPQC topology structure with parallel side coupled thyristor controlled reactor(TCR).The control algorithm of the corresponding structure is designed and verified by simulation.(1)The article analyzes the working principle of the UPQC with traditional structure and finds the reasons for restricting the application of UPQC to higher voltage levels.On this basis,a new UPQC topology structure with coupled thyristor control reactor is proposed.After the thyristor control reactor and the compensation capacitor are connected in parallel,the coupling inductor(Hyristor-Controlled LCcoupling,TCLC)is connected between the grid and the active part on the parallel side.The mathematical model of the TCLC part is established,its working principle is analyzed,and the TCLC control algorithm based on the open-loop control of the TCLC part is proposed.The system parameters of TCLC are designed and the design check calculation is carried out.(2)The article establishes the overall mathematical model of the parallel side.On the basis of the model,a control method for separate compensation of loa d reactive power and load side harmonic current is proposed.The TCLC part detects the reactive power on the load side by using Open loop control-based control algorithm performs preliminary compensation of reactive power.The parallel side active inverter part is controlled by PI algorithm based on closed loop control,which realizes the differential compensation of reactive power and harmonic current on the load side,and the voltage control on the common DC side is added.According to the respective operating characteristics of the TCLC part and the active inverter part of the parallel side,the two parts realize the complementary advantages,and make up for the shortcomings of the independent work of each other.The separate control of the TCLC part and the active inverter part of the parallel side is achieved,and the control goal of mutual cooperation is achieved.Finally,the working principle and control method of the parallel side are verified by simulation.(3)The article proposes a series-side topology structure based on a series transformer,and establishes a positive and negative sequence mat hematical model of the structure.On this basis,a voltage inner loop current outer loop control algorithm based on the mathematical model is proposed.Final ly,the parameter design and simulation verification of the whole device are carried out,which pro ves the correctness and feasibility of the new UPQC proposed in the article.