The unified power quality conditioner: The integration of series active filters and shunt active filters

This paper deals with "unified power quality conditioners" (UPQCs) which aim to integrate series active and shunt active filters. The main purpose of a UPQC is to compensate for voltage flicker/imbalance, reactive power, negative sequence current and harmonics. In other words, the UPQC has the capability of improving power quality at the point of installation on power distribution systems or industrial power systems. This paper discusses the control strategy of the UPQC, with the focus on the flow of instantaneous active and reactive power inside the UPQC. Some interesting experimental results obtained from a laboratory model of 20 kVA, along with theoretical analyses, are shown to verify the viability and effectiveness of the UPQC.