A novel adaptive droop-based SoC balancing control strategy for distributed energy storage system in DC microgrid
Liangliang Guo, Xinrui Liu, Xinyu Li, Rui Wang, Hanwen Ren, Zhiliang Wang, Qiuye Sun
Abstract
To solve the problems of SoC imbalance, uneven current distribution and DC bus voltage deviation in microgrid energy storage system, an improved adaptive droop control strategy is proposed in this paper. In the primary control layer, a novel adaptive droop SoC balancing controller (ADSB) is designed to realize the adaptive change of droop coefficient by establishing the real-time relationship between SoC value and droop coefficient, so as to promote the SoC balance among distributed energy storage units (DESUs). In addition, based on the characteristics of hyperbolic tangent function (tanh), an adaptive acceleration term is introduced to further improve the balancing speed of SoC. In the secondary control layer, a virtual voltage equalization controller (VVEC) is designed to reduce the influence of line impedance on SoC balance. To solve the problem of bus voltage deviation in microgrid, a secondary average bus voltage compensator (ABVC) is designed. In order to realize low-bandwidth communication in sparse communication networks, multi-agent consensus algorithm (MACA) is used to perform local estimation of global mean variables. In addition, the stability analysis of the proposed control strategy is carried out to ensure the stable operation of the system in theory. Finally, the control method proposed in this paper is evaluated comprehensively on MATLAB/Simlink simulation platform and hardware-in-the-loop (HIL) experimental platform. The results show that, compared with the existing methods, the proposed control strategy can achieve SoC balance faster, has higher current allocation accuracy, and has better ability to maintain bus voltage stability. • The speed of SoC balance is significantly improved. • The influence of the line impedance on the accurate current distribution is reduced. • The DC bus voltage fluctuation amplitude is small and has strong recovery ability. • The SoC can still converge orderly under communication delay.