Power management strategy research for DC microgrid with hybrid storage system

Due to the defects of the way of the traditional grid power supply, microgrid arises at the historic moment. At present, DC microgrid is an effective solution to integrate renewable energy sources which are DC power supply with DC loads. In allusion to the power unbalance intra-microgrid and the wide fluctuation of DC bus voltage due to unstable output of DC micro resources in DC microgrid, A DC microgrid structure consisting of photovoltaic generation system, hybrid energy storage systems and AC main grid, is researched in this paper. A novel power management strategy for this DC microgrid is proposed. The control strategy divides the DC bus voltage into seven ranges by six critical voltage values which are employed as the represents of power states, and according to the range which the bus voltage belongs to, the operation mode of the system can be automatically judged and switched freely. A hybrid energy storage system in this microgrid that contains two complementary type storage elements --- battery and super-capacitor, can enhance the reliability and flexibility of the system based on their special supply logical. Experimental results show that above-mentioned control strategy is feasible through the MATLAB/SIMULINK simulation platform.