Assessing the impact of grid strength and inverter-based renewable energy penetration on voltage stability stability

Abstract:
In the context of new climate change mitigation and adaptation targets, there is a growing interest in low-carbon energy sources such as renewables. The share of wind and solar power plants is increasing in the conventional power system, with the aim of displacing conventional fossil power plants. Based on power electronic converters, their integration has an impact on the power system robustness. The connection of IBRs could weaken the stability of the power system, and pose a limit on grid connection and further integration of renewable energy systems. This paper assesses the impact of system strength level on photovoltaic power penetration and voltage stability. The analysis was carried on the IEEE-9 bus in the DigSILENT PowerFactory software. The system strength was modified by varying the grid impedance at the point of common coupling of the photovoltaic plant. The effects of system strength on photovoltaic power penetration were analysed with regard to voltage stability at the point of common coupling using the short circuit ratio index. The results showed that in the case of an adjacent connection of the PV plant, with a synchronous generator, a decrease in short-circuit ratio and an increase in PV penetration rate did not affect the voltage stability. Whereas, an early disconnection or absence of the synchronous generator, and a declining short-circuit ratio led to voltage stability issues at the point of common coupling.