Computational Optimization of a Candidate BESS Discharge Set-Point in the Sulselrabar 150-kV System

Abstract

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Battery energy storage systems can reduce network losses and support voltage regulation, but their technical benefits depend strongly on location and operating power. This study evaluates a candidate BESS at the Sungguminasa 150-kV bus in the South, Southeast, and West Sulawesi (Sulselrabar) interconnected system, Indonesia. The study uses a 43-bus representation derived from historical PLN/AP2B system data documented for 21 May 2019. The published base case comprises 50 transmission lines, a total transmission loss of 12.123 MW, a maximum reported branch transfer of 171.25 MW on the Tallasa-Sungguminasa corridor, and a minimum 150-kV bus voltage of 148.091 kV (0.9873 pu). Sungguminasa was selected as the candidate BESS location because it lies on the highest-transfer corridor. Five discharge-power set-points, namely 0, 25, 50, 75, and 100 MW, were evaluated using a calibrated steady-state scenario model. The minimum active loss of 11.425 MW occurred at 75 MW, corresponding to a 5.76% reduction from the historical base loss. Increasing the set-point to 100 MW increased losses to 11.654 MW, demonstrating diminishing technical benefit and power-flow redistribution. The results identify 75 MW as the best discrete discharge set-point among the investigated cases. This value is an operating-power result, not a complete BESS energy-capacity specification, because energy duration, state of charge, degradation, and economic performance were not modelled.