Research On Three-Sequence Synchronous Control Strategy Of Static Var Generator Based On Fuzzy Adaptive PI Control

The structure of power system is becoming more and more complex and the scale of power system is expanding day by day,so the requirement of power quality is getting higher and higher;and reactive power balance in power system is also highly valued.With the increasing maturity of reactive power compensation technology,static var generator(SVG)is widely used in system.Through the reasonable design of control strategy,SVG can not only realize the effective compensation of reactive power,but also solve the three-phase unbalance problem caused by three-phase load asymmetry,which can effectively improve the reliability of power supply and the quality of power.Therefore,SVG will still be widely used in the future.Aiming at the particularity of three-phase four-wire system,four-bridge rectifier is chosen as the main topology of SVG,and an improved DQ detection method is designed as the current detection scheme in three-phase asymmetric load system.The simulation analysis verifies the method,which can detect positive,negative and zero-sequence current.Design Three-sequence synchronous control strategy for unbalanced load system,taking into account the compensation of positive-sequence reactive power,negative-sequence and zero-sequence current.Aiming at the AC pulsation characteristics of zero sequence current,repetitive control links are connected in series before the closed-loop control of zero sequence current.Based on the inner membrane principle,errors are accumulated to participate in the calculation,thus reducing the error of zero sequence compensation.In addition,In order to improve the adaptability of SVG compensation,a fuzzy adaptive PI controller is designed,and the PI parameters are adjusted adaptively according to the change of error signal.The above designed control methods are validated by the simulation of the model built by MATLAB/Simulink: Three-sequence synchronous control strategy can realize positive,negative and zero-sequence synchronous compensation.Through improvement,the precision of zero sequence control loop is improved effectively;the adaptability of SVG compensation is effectively improved by reasonable design of fuzzy adaptive PI controller.