Robust optimization of unit commitment with wind power considering composite flexibility constraints

The availability of power system flexible resources depends on the network flexibility, which plays a vital role in operation security of power systems with large-scale renewable energy. In this paper, a robust optimization method of unit commitment with wind power considering the composite flexibility constraints is proposed, which can ensure the availability of node flexible resources and then improve composite flexibility of power system. Firstly, the composite flexibility constraints of unit commitment problem are established. The composite flexibility reflects the mechanism of the interaction between node flexibility and network flexibility, which can consider the availability of node flexible resources and enable more accurately assessment of the system operation flexibility. Secondly, the concept of network flexibility balance degree is proposed to guarantee the overall network flexibility balance, and the network flexibility balance degree and key line constraints are developed to guarantee the system network balance level and the network flexibility of key lines, while improving the convergence speed of solving algorithm. Finally, the effectiveness of the proposed method is investigated through the case study on modified IEEE 24-bus system.