Five-Leg Single-Phase Transformerless Unified Power Quality Conditioner

In this paper, a transformerless single-phase unified power quality conditioner (UPQC) based on a three-leg converter and a conventional shunt converter is proposed. The proposed five-leg converter can compensate both voltage swell and sag events. During rated conditions and voltage sags the system operates with high modulation index. Furthermore, since the conventional shunt converter provides grid current control, the shared-leg current can be minimized. The system model, a scalar pulse-width modulation (PWM) technique, and overall control strategies are presented. Simulation and experimental results are addressed to evaluate the feasibility of the proposed system.