An improved droop control strategy of energy storage system for unbalanced load in micro-grid

Abstract

In micro-grid system, voltage and current can become unbalanced due to unbalanced load, causing power quality and operation security problem. In this paper, an improved droop control strategy based on three-phase independent control is proposed. In this method, the independent droop control curve of each phase is formed by considering three-phase active power, reactive power and voltage respectively. The influence of unbalanced impedance parameters of energy storage system can be eliminated by fine-tuning each independent droop coefficient. The voltage and current imbalance can be solved by adjusting the secondary regulation value of each phase independently. A simulation model and experimental system are set up to verify the feasibility of the algorithm. The results show that the control strategy can improve the power quality of micro-grid with good stability in the unbalanced three-phase system.