Research on parallel control strategy of hybrid energy storage units in DC microgrid

With more and more implementation of renewable energy sources within power systems, energy storage technologies will be ever more important for improving system stability and power quality.Compared with the single energy storage system, hybrid energy storage system has more advantages in view of characteristics about present storage elements.However, present hybrid energy storage technologies are mainly based on master-slave control strategy which needs high bandwidth communication.Consequently, its reliability is reduced and that kind of control is not suitable to distributed DC microgrid.Considering the expansion and redundancy of same type storage units, this paper presents a novel parallel control strategy for hybrid energy storage units.In this control system, batteries use U-I droop control and supercapacitors use U'-I droop control.By using local information about storage units alone, the system can compensate different frequency components with different type storage units and share power among same type.Finally, the simulation and experimental results are presented to verify its correctness and effectiveness. © 2016, The editorial office of Transaction of China Electrotechnical Society. All right reserved.