Identification and Risk Assessment of Voltage Sag Regions under Distributed Renewable Energy Integration Scenarios

With the large-scale integration of new energy sources into distribution systems via power electronic inverters, the system’s voltage support capability and voltage sag propagation characteristics under fault conditions have changed. Traditional methods for voltage sag domain analysis and risk assessment face insufficient applicability in scenarios with high penetration of new energy sources. To address these issues, this paper takes the IEEE 30-bus system integrated with new energy sources as the research object. Based on establishing a mathematical model of new energy inverter faults, the voltage sag domain at each system node is calculated and identified, and the variation patterns of the voltage sag domain under different levels of new energy penetration are analyzed. On this basis, two structural indicators—node sag domain overlap degree and node electrical connectivity—are introduced. Combined with the voltage sag frequency indicator and voltage sag energy indicator, a multi-dimensional node voltage sag risk assessment indicator system is constructed. The Analytic Hierarchy Process is employed to determine the weights of each evaluation indicator, and the Technique for Order Preference by Similarity to Ideal Solution is used to conduct comprehensive scoring and ranking of voltage sag risks across system nodes. Case study results show that increased penetration of new energy sources alters the distribution characteristics of the system's voltage sag domain, and voltage sag risks at nodes in certain regions with concentrated new energy integration significantly increase.