A soft-switched three-port single-stage inverter for photovoltaic-battery systems

This paper proposes a soft-switched three-port single-stage inverter (TPSI) for a photovoltaic (PV)-battery system. Compared to the existing soft-switched TPSIs, the proposed TPSI has the advantages of using the least number of switches and that all of the switches are capable of being turned on under the zero voltage switching (ZVS) condition. A prototype of the TPSI without using electrolytic capacitors is built to verify the proposed topology. Experimental results show that the proposed TPSI is effective in managing the power flows among the three ports while maintaining the desired sinusoidal voltage at the load port.

I. Introduction

There has been a growing interest in using photovoltaic (PV) systems as distributed generation to supply local loads and the utility grid in recent years. Due to the intermittence characteristics of the solar energy, energy storage devices, such as batteries, are usually used to balance the power between the PV system and the load. Either a three-port converter that connects two sources or an individual converter for each source can be used to manage two different energy sources to supply the load. A three-port converter is preferable owing to its lower cost and higher power density [1]. For those applications where the voltage of the PV energy source is low, an isolated topology is desired for the converter [2].