To support the government’s Net Zero Emission target under National Energy Policy (KEN) No. 79/2014, aiming for 23% renewable energy by 2025 and 31% by 2050, the isolated Belitung 70 kV power system has an 81.52 MW capacity with a 24.4 MW spinning reserve. Load growth is projected at 6% annually per the 2021–2030 RUPTL, estimating a 59 MW load by 2027. To meet this demand, a 5 MWp photovoltaic (PV) plant with a 2.2 MWh Battery Energy Storage System (BESS) is planned for interconnection at Manggar Substation (GI Manggar). Technical challenges include harmonics, voltage and frequency stability, and Low Voltage Ride Through (LVRT) capability. Simulations using DigSILENT PowerFactory 2024 evaluated load flow, harmonic distortion, transient frequency stability, and LVRT based on the 2020 PM ESDM Grid Code. Results indicated improved system performance after PV and BESS integration, reducing power losses from
0.52 MW to 0.41 MW and increasing spinning reserve from 21.78 MW to 29.09 MW. Minimum frequency improved significantly from 15.36 Hz to 49.63 Hz with rapid recovery. System voltage remained within tolerance, and voltage and current harmonics stayed well below the 5% limit. The PV plant successfully stayed connected during voltage dips down to 0.5 p.u. In conclusion, integrating the PV plant and BESS enhances system efficiency, reliability, and stability while fulfilling all technical standards of the 2020 Grid Code.