A Multifunctional and Wireless Droop Control for Distributed Energy Storage Units in Islanded AC Microgrid Applications

A multifunctional and wireless droop control method for distributed energy storage units (DESUs) in ac microgrids is presented in this paper. This paper achieves the state-of-charge (SoC) balancing by employing the SoC-based P-f droop control method locally for the purpose to prolong the service life of DESUs and effectively utilizing the available capability of the DESUs. Besides, inspired by the conventional P-f droop control, a integral Qdt - V droop control is proposed in this paper to eliminate the reactive power sharing errors. The integral Qdt - V droop control is realized by reducing the voltage proportional to the integration of the reactive power instead of the reactive power itself. Meanwhile, the voltage compensation term which is proportional to the integration of the accurately shared active power is added to this method in order to restore the voltage to the acceptable range. The control strategy is straightforward to implement and does not require communication links as well as the gain scheduling. This paper also presents the analysis of the corresponding small-signal stability of the proposed droop control method. Simulation and experimental results are provided to validate the feasibility and effectiveness of the proposed approach.