Abstract: Because the output power of off-grid photovoltaic power generation system is intermittent and unstable due to natural factors,it is necessary to introduce energy storage system and its associated multi-input converter to cut the peak and fill the valley of photovoltaic output.Considering that the Buck/Boost circuit as a traditional energy flow bridge,uses more switching devices,a three-port converter with Boost circuit as the main circuit was proposed.It has the advantages of fewer devices,low cost and simple control on the basis of realizing the bidirectional energy conversion function at the energy storage terminal.Starting from the principle of system topology,this paper elaborated the energy flow mode under the dual-input and dual-output operation mode of the system,then discussed the specific control mode,and finally verified the correctness and feasibility of the system through simulation and experiment.

Key words: three-port converter, photovoltaic power generation, off-grid system, energy flow mode