Modified Control Technique for Series and Shunt Converters of UPQC to Enhance Power Quality

In this paper, a modified control technique is developed for a unified power quality conditioner (UPQC). This UPQC consists of shunt and series voltage source converters (VSCs). A modified control algorithm of shunt VSC is developed by extracting the active and reactive components of load currents using the second order generalized integrator (SOGI). These active and reactive components are processed to get instantaneous active and reactive powers, which are used to estimate reference currents. Moreover, a multiplying factor (m) is used for series VSC to regulate the load voltages under abnormal conditions such as voltage sag/swell in the three-phase AC grid. The proposed control technique is capable to compensate the voltage sag/swell and to reduce the current harmonics. A comprehensive study is made on the performance of proposed control technique at various conditions of AC mains. The UPQC is used in a three-phase three-wire AC distribution system on a developed prototype of UPQC in the laboratory to verify the proposed technique.