This paper presents a technical review of power quality problems associated with the renewable based distributed generation systems and how custom power devices (CPD) such as STATCOM, DVR and UPQC play an important role in power quality improvement. IEEE and IEC standards for grid connected renewable energy systems are one of the critical points of interest for the selection of custom power dev...

The paper introduces the modified UPQC topology with reduced switching losses. UPQC is a versatile custom power device which consists of two inverters connected back to back and deals with both load current and supply voltage imperfections. It can simultaneously perform as shunt and series active power filters. The series part of the UPQC acts as Dynamic Voltage Restorer (DVR). It is used to ma...