Impact Assessment of Renewable Energy Integration: A Case Study on Sephu Solar PV Plant Integration

This paper examines the impact of integrating renewable energy resources into the Bhutan power grid, focusing specific on integration of 18 MW Sephu Solar Photovoltaic (PV) plant. The study evaluates grid stability and performance under different penetration levels of solar power. Dynamic simulation were carried using Power System Simulator for Engineering (PSSE) software to analyze two critical scenarios: the sudden disconnection of the PV plant and the occurrence of a three-phase fault at the point of coupling (POC). Further the study examines the effects of these scenarios on key system parameters such as bus voltage, system frequency, and the power output of conventional generator. The results show that the sudden disconnection of the PV plant causes voltage and frequency drops, with the severity increasing as the penetration level of solar power increases. Similarly, a three-phase fault at the PV connected bus results in substantial voltage fluctuations, including a temporary drop to zero, followed by oscillations that stabilize over time. These effects become severe with higher solar power penetration levels, underscoring the importance of addressing potential stability concerns. The study highlights the necessity of implementing proper under-voltage and under-frequency load-shedding relay settings at key substation to prevent unintended disconnection of the PV plant. Additionally, upgrading transformers at the 66/33 kV Gewathang substation is essential to accommodate reverse power flow resulting from the solar PV integration at Sephu.