Due to the intermittent feature of renewable energy sources, energy storage units are needed in order to balance the electricity generation and consumption. Interface circuit is an important component of the energy storage system. This paper presents a non-isolated four-port dc-dc converter for the independent photovoltaic power generation system. The proposed four-port dc-dc convert is used to interface four power ports. These are photovoltaic cells (PV) port, battery port, super capacitor port and load port separately. The circuit topology is derived by integrating several parallel Boost converters. The operation principles and the performance are analyzed in detail. The mathematical model of the proposed converter is built. The four-port dc-dc converter can realize energy bidirectional flow among PV, energy storage medium and load. It can also realize the DC bus voltage stable and ensure balance of system power. Finally, simulation results are given to verify the validity and feasibility of the non-isolated four-port dc-dc converter in the independent photovoltaic energy generation system.