Grey Start Strategy for Hybrid AC/DC Microgrid in Semi-Black State

The stable and quick restoration is necessary for resilient microgrids. This paper proposes the new concept of grey start and its strategy as a restoration mode for hybrid AC/DC microgrid in semi-black state when the system blackout occurs. Firstly, an optimal reconstruction model of the whole network is established and solved by biogeography-based optimization (BBO) algorithm. Secondly, the classification and evaluation model of distributed generations (DGs) is established by using improved BP artificial neural network (ANN). Thirdly, optimal path planning is realized. In addition, to improve the stability during the process of grey start restoration, the control methods of different DGs after classification are discussed. In comparison with conventional black start restoration mode, the restoration time is shortened, and the fluctuation of bus voltage is suppressed. The feasibility of the proposed grey start strategy is verified by the results of numerical example analysis and MATLAB/Simulink simulation, respectively.