Evaluation of Dynamic Equivalent in Renewable-Integrated Power Systems

Abstract:
Electromagnetic transient (EMT) simulations are essential for analyzing power systems undergoing rapid transformation due to growing shares of converter-interfaced renewables. However, full EMT studies of large networks are computationally intensive. This paper evaluates a coherency-based dynamic equivalencing framework that extends classical aggregation and Ward reduction to systems with both synchronous machines and inverter-based resources (IBRs). The IEEE 9-bus system is used as a benchmark, and the reduced equivalents are validated under severe faults. Scenarios include conventional generation as well as renewable integration through grid-forming and gridfollowing inverters, with sensitivity studies on inertia variations. Comparative EMT simulations show that the reduced models capture the dynamic response of the full system with good accuracy while lowering complexity. The results demonstrate the applicability and limitations of classical dynamic equivalencing for EMT analysis of renewable-integrated power systems.