Research On Unified Power Quality Conditioner With Active Disturbance Rejection Control

With the increasing complex of modern power grid and diverse types of power load,the phenomenon that various power quality problems occur in the same power distribution lines or electrical load becomes common.It leads to the production of unified power quality conditioner(UPQC).UPQC is an ideal facility to cope with several power quality problems at the same time,like voltage sag,voltage fluctuation,unbalanced three-phase voltage,harmonics and reactive power.This paper takes the three-phase three-wire series in left and parallel in right type UPQC as research object.Based on the introduction of existing control method of parallel and serial unit,two control strategies are confirmed to be studied,IPIQ control strategy and DCVC control strategy.Both of them adopt PID controller.This paper analyzes the basic principle,advantages and disadvantages of PID control,as well as the conception,basic principle and elements of active disturbance rejection control(ADRC),which shows that ADRC is better than PID.Then the principle of liner ADRC(LADRC)is expatiated and the stability of it is proved.Based on the work above,the mathematical model of UPQC is established,based on which the active disturbance rejection controller of UPQC is designed.Then the simulink model of UPQC is built on Matlab platform.First,this paper compared the compensation effect of IPIQ control strategy with DCVC control strategy.Result shows that both of the two strategies can compensate the voltage sag and harmonic current in real time.From the compensation effect,DCVC control strategy is better than IPIQ control strategy.While IPIQ control strategy can compensate harmonic current and reactive power separately and DCVC control strategy can not.Then compared the compensation effect of IPIQ control strategy and DCVC control strategy with their ADRC strategies,IPIQ-ADRC and DCVC-ADRC.Result shows that ADRC can promote the compensation effect of IPIQ control strategy and DCVC control strategy.The employment of ADRC has no influence on harmonic current compensation ability of DCVC control strategy,but total harmonic degree(THD)of the load voltage after compensation declined about 20 percent.As for IPIQ control strategy,the employment of ADRC not only can reduce the THD of load voltage,but also can promote theharmonic current compensation effect for 10 to 40 percent.