State of Charge Equalization Strategy of Multi-storage Units with Different Capacities

In order to simultaneously achieve accurate distribution of output current and state of charge(SOC) equalization of different capacity energy storage units(ESUs) in DC microgrid, on the basis of traditional droop control, a droop control based on a consistent algorithm is proposed. It will be as sociated with the droop coefficient with the relative capacity factor of distributed energy storage unit(DESU) and the SOC to eliminate the influence of different capacities on SOC equalization so as to achieve SOC equalization during charging and discharging. And in order to improve the SOC equalization speed, the state predictor is added to the multi-intelligent algorithm to ensure that the SOC equalization speed is effectively improved on the basis of implementing control performance. The voltage equalizer is designed to compensate the bus voltage to solve the problem of bus voltage deviation from the rated value. To verify the effectiveness of the proposed strategy, a simulation model is built in Matlab/Simulink. The simulation results prove that the proposed strategy achieves the objectives of SOC equalization among ESUs, accurate current distribution and small bus voltage deviation. At the same time, the SOC equilibrium speed is increased.