Optimal Siting and Sizing of Grid-forming Battery Energy Storage System for Renewable Power Systems

With more and more volatile renewable energy sources are integrated into the grid, the system strength of modern power grid is significantly reduced, which may lead to small-signal stability (SS) problems. It is widely recognized that grid-forming energy storage systems (GFM ESS) have the advantages of flexibility and effectiveness in enhancing system strength, and can also play an essential role in smoothing the fluctuations of renewable energy, but how to simultaneously consider the fluctuation smoothing from the energy perspective and the enhancement of support capacity from the system strength perspective in the planning stage remains to be explored. In order to fill this research gap, this paper develops a GFM ESS planning method that considers system strength enhancement and renewable energy fluctuation smoothing, so as to achieve the desired stability margin level and grid connection criteria. To this end, this paper first quantifies the influence of the location and sizing of GFM ESS on the system strength based on the generalized short-circuit ratio framework. On this basis, the optimization problem of GFM ESS with system strength constraints and renewable energy grid-connection fluctuation criteria constraints is identified as a problem with eigenvalue constraints. Finally, an iterative method based on quadratic support function is proposed to solve the planning problem. Case studies in modified IEEE 39-bus system validate the effectiveness and efficiency of the proposed method.