Research on Optimal Dispatching Approach on Power System Flexibility

The power fluctuation of system is intensified and the flexibility is reduced due to large scale variable renewable energy sources (VRES) are integrated into the grid. This paper firstly summarizes the existing evaluation metrics and optimal dispatching approaches about the flexibility. Secondly, an evaluation metric named system flexibility interval is established and it reflects the range of power fluctuation that system can tolerate. Then, this paper proposes a dispatching approach of improving system flexibility by optimizing the day-ahead dispatch scheme of the units considering that the actual fluctuant power may deviate far from the predictive value. The proposed approach aims to raise the flexibility of system to reduce operational risk. In the example analysis section, the feasibility of the proposed approach is tested well based on the modified IEEE39 system. The result shows that the system is more flexible and the economic cost increases very little when using the dispatching approach proposed in this paper than conventional approach.