VOLTAGE STABILITY ASSESSMENT OF LARGE-SCALE PHOTOVOLTAIC SYSTEMS USING SIMULATION-BASED MODELLING AND VCPI ANALYSIS

Abstract

The increasing electricity demand presents significant challenges for the power system in maintaining stable and reliable operation. These challenges place stress on electrical power grids, particularly the distribution system, and may lead to power disruptions and blackouts if not managed effectively. This research focuses on analyzing voltage stability to ensure that voltage levels remain within the acceptable range of 0.95 pu to 1.05 pu under both normal and increased loading conditions. As electricity demand increases, voltage instability can occur and requires effective assessment methods to identify buses that are prone to instability, since initial voltage values are not enough to determine stability. The methodology is proposed using MATLAB software to assess the voltage stability of the IEEE 57-bus test system. The Voltage Collapse Proximity Index (VCPI) is used as an effective indicator to identify the weakest and the most stable buses in the network. The analysis shows that Bus 18 is the weakest bus and Bus 23 is the most stable bus. Next, solar PV is integrated into both buses, and the system is tested under load increment conditions of 30% and 60%. The results reveal that the optimal placement for solar PV is only at the weakest bus, Bus 18, with a suitable capacity of 130 MW for both load increments. Additionally, the VCPI values decrease after installing solar PV, demonstrating that solar PV can support the higher load demand while enhancing grid resilience and reducing the risk of voltage instability.