Novel unified power quality conditioner of two DC links connected with virtual impedance

A UPQC is combined series converter and parallel converter (also called shunt converter) to enhance the voltage and current quality. Commonly, series and parallel converter share a DC capacitor, which is coupling and effecting compensation in some conditions. This paper proposed a novel topology of UPQC, its series converter and parallel converter both have capacitors in DC-link, and connected by a bidirectional DC-DC converter. The bidirectional DC-DC converter is taken as a virtual resistor to mitigate series and parallel converter's coupling in DC-link. And then from mathematical model and control algorithm to analyze the characteristic of proposed topology. At last, compare the performance of traditional UPQC, resistor connected UPQC and proposed UPQC in voltage sag, harmonic and unbalance conditions. The results proved that the proposed topology have a great performance.