Simple control strategies of the active filters within a unified power quality conditioner (UPQC)

Unified power quality conditioner (UPQC) consists of combined shunt and series active power filters for improving both the power quality on the source side and on the load side. The paper presents a simple method for controlling the series filter under unbalanced and distorted load conditions by using a three phase locked loop (PLL). Two methods for controlling the shunt filter are analyzed. The model of the entire system is presented and considerations on the starting procedure are highlighted. The simulation is performed by using the Matlab-Simulink environment. The improvements of the power quality are analyzed by comparing the THD on the source side before and after use of the UPQC.