Coordinated control strategy of a DC grid with energy storage system

DC grid has a prospect of application in collecting and transmitting large-scale renewable energy over long distance. However, the randomness and fluctuation of the renewable power may hamper the stable operation of DC grid. Energy storage device is able to actively absorb or supplement active power, which can be used to smooth the power fluctuation. The paper investigates a DC grid topology with energy storage and proposes a coordinated control strategy. The proposed strategy enables coordinated control of the renewable energy output power, pumped storage power and the grid consuming power. During the steady state, the control strategy enables the system DC voltage stable and power flow of the grid under zero-error control. During the faulted time, the coordinate control strategy enables the converter fast response and maintains the system DC voltage within safety margin. The effectiveness of the coordinated control strategy is verified by simulation in PSCAD/EMTDC.