Optimal Allocation of Energy Storage System Considering the Risk of Insufficient Flexibility in Distribution Network

To solve the problem of insufficient flexibility caused by high proportion of wind and solar resources accessing to distribution network, an energy storage system (ESS) allocation model considering the risk of insufficient flexibility is constructed. Firstly, the traditional confidence interval calculation method is improved by the conditional value-at-risk (CVaR), and the conditional confidence interval of net load power is proposed. Secondly, the flexibility boundary of distribution network is constructed, and the risk cost caused by the over-limit of net load fluctuation is calculated to form the risk cost model of insufficient flexibility. Thirdly, the bi-level optimal allocation model of ESS considering flexibility, economy and reliability is constructed by fully calling the flexible resources. The upper layer is the ESS allocation decision layer, and the lower layer is operation optimization layer. Finally, case study is analyzed based on IEEE33 system to verify the effectiveness of the model.