Optimal PV-BESS Sizing with Variable Efficiency: A Bi-Level MILP Approach

초록

Along with the increase in renewable energy, battery energy storage systems combined with photovoltaics are also increasing. A majority of previous studies on scheduling and sizing of battery energy storage systems uses constant efficiency assuming that the charging and discharging efficiencies are invariable. However, the efficiencies are dependent on the state of charge and the C-rate. Therefore, in this study, a optimization model of a battery energy storage system that considers the charging/discharging efficiency as a stepwise function dependent on the state of charge and the C-rate is proposed. In addition, the problem of optimal scheduling and sizing based on the proposed model is presented. Because the proposed model includes a number of binary variables, the sizing problem is solved through bi-level optimization. The result shows that the net present value improvement from applying scheduling is larger than that from optimal sizing, considering variable efficiency in both cases. © 2026 IEEE.

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