Planning for Energy Storage System Considering Risk of Inflexibility in Active Distribution Network

To cope with the stochastic power fluctuation of active distribution system (ADN) under high-penetration photovoltaic(PV), based on the flexibility planning theory, an ESS planning method that takes into account risk of inflexibility is proposed. Firstly, the confidence interval calculation method is improved based on the conditional value-at-risk (CVaR), and the inflexibility risk cost model is constructed from the perspective of flexibility resource and demand balance to evaluate the potential loss caused by the stochastic fluctuation of flexibility demands exceeding the flexibility boundary threshold. Then, considering the flexibility improvement methods such as grid reconstruction, voltage control and ESS output adjustment, a bi-level optimal ESS planning model considering flexibility, safety and economy is established. The upper-level focuses on obtaining minimum capacity and appropriate distribution of ESS; the lower-level focuses on solving the coordinated operation strategy of flexibility resources. Finally, The IEEE 33 system is selected for example, and results verify the rationality and validity of the proposed method.