Abstract
The increasing integration of variable renewable energy sources, combined with the rapid electrification, is introducing new operational challenges in modern power systems. In distribution grids, additional load demand can lead to voltage violations, increased peak loading, and reduced grid stability. Battery energy storage systems (BESS) have emerged as a promising solution to improve grid flexibility and support secure network operation under evolving conditions.
This thesis develops a linear optimization framework based on the linear distribution power flow (LinDistFlow) approximation to determine the optimal placement and sizing of BESS in the CINELDI medium-voltage reference grid. This is a 124-bus, 22 kV radial distribution system representative of a Norwegian medium-voltage (MV) distribution grid. The model simultaneously minimizes voltage deviations and battery investment cost over 8760 hourly time steps, corresponding to one year, with voltage limits enforced as soft constraints. Load levels from 100 % to 160 % of the base case, corresponding to peak system demands of 5.231 MW to 8.370 MW, are simulated to evaluate how storage requirements evolve as system stress increases.
The results reveal that only four out of nine candidate buses in the CINELDI MV grid are selected as optimal for BESS allocation by the optimization, while a single location, bus 89, located deep within a radial branch, dominates across all load levels. Restricting storage to bus 89 alone produces system-level voltage performance within 1 % of the fully distributed solution. Storage requirements are negligible below approximately 130 % load level, but increase nonlinearly beyond that threshold, reaching nearly 100 MWh of energy capacity and 8 MW of power capacity at 160 % load level. The results highlight that linear optimization provides an efficient and systematic framework for navigating the trade-offs between storage placement, sizing, and voltage performance in distribution grid planning. The findings further demonstrate the potential of BESS to support voltage regulation and improve operational flexibility in future MV distribution grids.