Closed-Loop Hierarchical Operation for Optimal Unit Commitment and Dispatch in Microgrids: A Hybrid System Approach

To contribute to a smart grid, the unit commitment and dispatch (UCD) is a very important problem to be revisited in the future microgrid environment. This paper studies the UCD problem by taking account of both traditional thermal units and distributed generation units while considering demand response and carbon emissions trading. First, the UCD problem is reformulated as an optimal switching problem of a hybrid system. The reformulation allows for convenient handling of time-dependent start-up cost by dynamic programming. Then, we propose a closed-loop hierarchical operation (CLHO) algorithm, which produces the optimal schedule with a closed-loop feature. Theoretical analysis shows the equivalence of the reformulation and the effectiveness of the CLHO algorithm. Finally, the closed-loop feature and the effectiveness of the proposed algorithm are further verified by simulations. The simulations also show that low emission allowance and high emissions trading price can reduce the total carbon emissions.