Single-phase AC-DC-AC multilevel converter for grid overvoltage based on an H-bridge connected in series to the five-leg converter

In this work an ac-dc-ac multilevel power converter is investigated. The developed configuration is composed of one single-phase ac-dc-ac three-leg module and two H-bridges, one of them connected in the shared part of the system to employ multilevel voltages to input and output converter, and the other one connected on the grid side for input overvoltage. The converter is employed in applications with same input and output frequency, such as uninterrupted power supply (UPS) and unified power quality conditioner (UPQC) without isolation transformer. System model, an overall control strategy to adjust the grid power factor, amplitude and frequency of load voltage, and a space vector pulsewidth modulation (SV-PWM) strategy to balancing dc-link voltages are presented. This system is operated with asymmetrical dc-link voltages to increase the number of voltage levels and reduce the harmonic content of the converter input voltage. The proposed converter is compared in terms of harmonic distortion and semiconductor losses with conventional structures. Simulation and experimental results demonstrate the operation of the proposed topology.