Improved droop control based on State-of-Charge in DC microgrid

Abstract

Droop control is commonly used in DC microgrids to manage and control DC microsources, which can effectively achieve power distribution. However, in the conventional droop control, the constant droop coefficient will cause the battery to overcharge and overdischarge. Moreover, it is unable to regulate the bus voltage when load power changes. To solve this problem, an improved droop control strategy based on state of charge (SOC) of the batteries is proposed. It adopts exponential droop coefficients relating to the SOC value to achieve better SOC balance and bus voltage regulation. The improved droop control expression is given first. Then, a simulation model based on improved droop control for two sets of batteries in a DC microgrid to provide power to the load under island conditions is established. Comparison study is conducted between the conventional and proposed method. Simulation results show that the proposed method achieves better bus voltage regulation and current sharing.