Transmission Loss Optimization-Based Optimal Power Flow Strategy by Hierarchical Control for DC Microgrids

This paper proposes an efficient power flow sharing and voltage regulation control method based on hierarchical control to minimize the transmission loss of dc microgrids. Different from the conventional optimal power flow algorithm for the dc grids, the proposed approach needs neither prior knowledge of the grid's conductance matrix nor the load distribution matrix, which means improvement of the expansibility and reduction of the cost. At the primary control level, a voltage droop characteristic is set for each converter to improve the stability and reliability of the grid. The secondary control level aims to regulate the power flow of the microgrid to the optimal condition. The two control levels exchange information by low bandwidth communication. The validity of the proposed approach is verified by both simulation results of a dc microgrid based on IEEE 14-bus system and experimental results on a 50-V two-terminal prototype dc microgrid.