Coordination Secondary Control for Autonomous Hybrid AC/DC Microgrids with Global Power Sharing Operation

This paper presents a coordination secondary control strategy for autonomous hybrid AC/DC microgrids with global power sharing operation. In the previous work, primary control with droop control method was applied to distributed generators to ensure local power sharing without communication links in either ac or de microgrid. An extension of local power sharing for individual microgrid is the global power sharing for hybrid microgrids. With global power sharing control, all distributed generators throughout the hybrid system are capable of sharing the entire ac and de loads without any information exchange. The coexistence of local power sharing and global power sharing in hybrid system is thereafter defined as generalized primary control, which is usually employed for fully decentralized power management throughout the whole hybrid system. To eliminate the inherent voltage/frequency deviations caused by the generalized primary control, the secondary control is usually applied to each distribution generator for voltage/frequency restoration. This however will degrade the performance of global power sharing operation because of its characteristics of voltage/frequency deviation dependence. To achieve voltage/frequency restoration while maintaining the global power sharing operation, a coordination secondary control was proposed and the effectiveness of the proposed method has been verified by the simulation results.