Flexible Voltage Control Strategy Considering Distributed Energy Storages for DC Distribution Network

In this paper, a flexible voltage control strategy, which takes good use of the distributed energy storage (DES) units, is proposed to enhance the voltage stability and robustness of dc distribution network. The characteristics of ac/dc interface in network are analyzed, and the virtual inertia and capacitance are given to demonstrate the interactive influence of the ac and the dc systems. The control strategy for DES which is located at the ac microgrid or at the network terminal bus is designed based on the interactive characteristics, enabling the DES to respond to both voltage variation of dc network and frequency change of utility ac grid. A cascading droop control strategy is proposed for DES in dc microgrid to relieve the pressure of voltage deterioration of dc network buses which connect the dc microgrid. The proposed comprehensive flexible control strategy for DESs at different interfaces features independence of communication as well as enhancement of system robustness, and reduces the impact of dc distribution network on utility ac grid. The performance of the proposed control strategy is validated under different operating conditions of the dc distribution network.