Hybridization of energy storages with different ramp rates in DC microgrids

Hybridization of Energy Storages (ESs) with different characteristics is an effective and economic solution to enhance system performance. Hybrid Energy Storage System (HESS) in centralized coordination is normally implemented. To maintain system operation in case of communication failure, a novel algorithm is proposed for HESS distributed control in this paper. DC bus voltage is regarded as the global information carrier for indication of system power balance. All ESs are configured as slack terminals with droop control for obtainment of the reference bus voltages. Localized Low Pass Filters (LPFs) are added to ESs with low ramp rates to realize system net power decomposition and ESs power scheduling in distributed manner. To overcome the disadvantages of distributed control including voltage deviation and power sharing errors, multi-level Energy Management System (EMS) is applied. HESS distributed control is scheduled as the primary control. Bus voltage restoration and power sharing compensation are implemented in secondary control. Autonomous SoC recovery for ESs with high ramp rates is applied in tertiary control. Load shedding and generation curtailment are used to limit system net power range. MATLAB Simulink model is developed for the verification of the proposed method.