Hierarchical coordination control in DC distribution system

Compared with conventional AC distribution system, DC distribution system is provided with significant advantages in various aspects. Coordination control is one of the key technologies to guarantee reliable and economic operation. Aiming at the DC distribution system with photovoltaic array, this paper proposes a hierarchical coordination control. This control strategy consists of local control and optimal dispatch, based on the local information, the local control can realize smooth operation in steady-state mode and secondary voltage recovery in harsh operating condition, which has fast response speed without communication; optimal dispatch system provides operation instructions for the local controller by optimal power flow control. The simulation results of PSCAD/EMTDC indicate that the global optimization can be achieved effectively by means of optimal dispatch, and the DC voltage remains stable due to the local control strategy under various operating conditions. This hierarchical control strategy realizes clearly information transmission, and coordination control between optimal dispatch and local control is achieved, thus keeps system operate smoothly and economically.