A Wireless Power Sharing Control Strategy for Hybrid Energy Storage Systems in DC Microgrids

In order to compensate multiple time scales power fluctuation resulted from distributed energy resources and loads, hybrid energy storage systems are employed as the buffer unit in DC microgrid. In this paper, a wireless hierarchical control strategy is proposed to realize power sharing between energy density storage unit and power density storage unit in reasonable fashion. Primary control introduces change rate of voltage as virtual information carrier, and urges supercapacitor unit to pick up major dynamic power immediately in the load switching moment, by setting sensitivity of different storage interface converters. The steady state error produced in primary control is eliminated by secondary control, in which voltage magnitude is maintained and zero steady state current in supercapacitor is guaranteed. In this framework, autonomous and coordinated control is achieved using only local information of each unit, therefore economic and reliability issues born along communication network can be avoided. The feasibility and effectiveness of the proposed control strategy are validated by experimental results.