Abstract: In order to solve the stability problem of grid-connected inverters under the condition of weak power grid, a grid-connection and stand-alone integrated PV-storage power system based on low-voltage DC distribution network is proposed. The system includes photovoltaic components, energy storage, DC distribution grid, AC & DC loads and multiple power converters. According to the three-level energy management strategy of photovoltaic, energy storage and distribution grid, the system is divided into four working states: 1)stand-alone state with photovoltaic power generation; 2)grid-connected operation with photovoltaic power generation; 3)stand-alone state with energy storage power supply; 4)grid-connected operation with grid power supply. The simulation of each working condition in Matlab/Simulink verifies the correctness of the proposed system.

Key words: DC grid-connection, PV-storage power generation, grid-connection and stand-alone integrated, energy management