Optimal Energy Storage Capacity and Power Transfer Limit Planning for Grid-connected Microgrid

Energy Storage System (ESS) in microgrid is receiving more and more attention in recent years because of the great benefits it brings from both security and economy perspectives. Optimal energy storage capacity (ESC) planning is one of the most important requirements of microgrid management. On the other hand, the planning problem of the interval limiting the transfer power between microgrid and the main grid, which is called power transfer limit (PTL), is another significant issue. ESC and PTL are coupled with each other, and jointly determine the optimal operation cost of the microgrid. High investment costs of ESC and capacity costs of PTL necessitate accurate modeling and optimal planning in order to minimize the total cost. In this paper, a bi-level planning method is proposed for optimal ESC and PTL in a grid-connected microgrid with uncertain load demand and photovoltaic (PV) power. The optimal operation cost considering all-scenario- feasibility and nonanticipativity is calculated at the lower level with the trial planning decisions while the planning decisions are updated at the upper level. The proposed method is performed on a real system and the results show the effectiveness.