New power conversion topology for battery-less PV generation system with the functions of grid-connection and isolated grid

Abstract

This paper proposes a photovoltaic power conversion topology (PVPCT). The proposed PVPCT is connected to the utility grid, a PV array and emergency loads. The proposed PVPCT comprises a boost DC-DC power converter (DDPC) and a three-port power converter (TPPC). The TPPC has three ports: a DC port, a grid port and an isolated grid port. The input for the boost DDPC is connected to a PV array and the output from the boost DDPC is connected to the DC port of the TPPC. The grid port connects to the utility grid, and the isolated grid connects to emergency loads. The isolated grid port continuously supplies an uninterruptible voltage with constant amplitude and constant frequency for emergency loads, without the need of battery regardless of whether the utility grid is nominal or interrupted in the condition of sunshine. Hence, the proposed PVPCT can continuously supply high-quality uninterruptible power to the emergency loads, such as charger of cell phone during the natural disasters. In addition, the power circuit is simplified and isolating transient is smooth due to the use of TPPC, and the initial cost and maintenance cost are reduced due to no use of battery. The proposed PVPCT has six operation modes for four conditions. A prototype is set-up for validating the performance of proposed PVPCT. The experimental results of the proposed PVPCT have the expected performance.

Keywords

• Renewable energy
• Isolated grid
• Power conversion interface
• Solar energy
• Three-port power converter