Research On Three-phase Three-wire D-STATCOM Control Strategy

In the distribution network,many power electronic devices are used in the fields of life and industry.The non-linear and impact load devices composed of power electronic devices cause the current in the distribution network to contain harmonics;a large number of asynchronous motors,frequency control The application of devices in the power grid consumes a large amount of reactive power,causing a series of problems such as voltage instability,power factor reduction,and three-phase unbalance in the distribution network,affecting power quality.The D-STATCOM static synchronous compensator can not only solve the three-phase voltage unbalance problem of the power grid,but also eliminate the harmonics and compensate the reactive power of the system,and proposes a new direction for improving the power quality of the distribution network.Therefore,this paper proposes a research on the control strategy of three-phase three-wire D-STATCOM.It mainly focuses on D-STATCOM's reactive current detection technology and reactive power compensation control strategy.This paper first establishes the mathematical model of three-phase three-wire D-STATCOM system,and establishes a dynamic mathematical model with the topological structure diagram of three-phase three-wire D-STATCOM.Secondly,this dissertation proposes a phase-locked loop ip-iq detection algorithm,which can be used to obtain the characteristics of positive and negative voltage sine and cosine information of the fundamental wave of the power grid when the grid voltage is distorted and asymmetrical,and the traditional ip-iq Compared with the method,the influence of the phase-locked loop on the compensation current detection can be effectively eliminated,the accuracy of the compensation current detection is improved,and the compensation performance of the D-STATCOM is further improved.Finally,verify the validity of the detection method and set the situation of unbalanced and distorted three-phase power grid voltage separately,and carry out dynamic simulation verification.Based on this,based on the adaptive PI double closed-loop control strategy,this paper proposes a voltage outer-loop voltage squared voltage regulator control method to control the variables and achieve fast tracking of the DC side voltage,so that the DC side voltage is stable,current The inner loop introduces adaptive PI control.The control strategy has good effectiveness,feasibility and application prospects.Finally,a three-phase three-wire D-STATCOM prototyping experiment is built to verify the proposed PLL-free detection method and the improved self-adaptive PI double-closed-loop control strategy.It is feasible and feasible in the three-phase three-wire D-STATCOM system.Effectiveness,good effect on reactive power compensation of three-phase three-wire D-STATCOM system.