An integrated three-port inverter for stand-alone PV applications

This paper presents a novel concept of integrated three-port interface for stand-alone photovoltaic applications. The three-port topology interfaces one solar panel input port and one bi-directional battery port to an isolated output port which generates a rectified sinusoid voltage. Then an unfolding circuit can be adopted to generate an ac wave with very high efficiency because it is operated at very low frequency (50/60Hz). Therefore, this proposed structure uses only one switch-mode conversion stage to replace several independent converters and inverters in order to reduce component count and save the cost, making itself a valuable choice for low cost low power standalone PV system. The circuit operation and control architecture of the three-port interface are presented. It can achieve maximum power harvesting for the solar port, battery charge control for the battery port, while keeping a regulated rectified sinusoid output. The experiments of the three-port interface confirm the topology operation and its ability to achieve the multi-functional power management control.