Stability Analysis of Oscillations Induced by Converters in a Microgrid Considering Dynamic Loads

Abstract

Microgrids are gaining attention as a core framework for next-generation power supply systems due to their high flexibility and capability to integrate renewable energy resources. Nevertheless, their stability analysis still predominantly relies on small-signal approaches. Most prior studies assume series RL loads, whereas induction motor (IM) loads which are widely present in industrial and isolated microgrid applications have not been adequately addressed. However, previous research indicates that IMs can exhibit instability phenomena that are not observed in systems with RL loads. To address this gap, this study constructs a full nonlinear state-space model of an inverter-based microgrid including IM loads and performs stability analysis from a large-signal perspective. The Takagi-Sugeno (TS) multimodeling method is employed to decompose the nonlinear system into a set of linear submodels, enabling the application of Lyapunov-based estimation of the Domain of Attraction (DOA). Using this framework, the stable operating region of the system is quantitatively analyzed. Furthermore, it is demonstrated that inverter parameters such as the reactive power droop coefficient or the proportional gain of the voltage controller influence the size of the DOA, and that the stability region can be effectively expanded through appropriate parameter tuning. The proposed DOA-based parameter tuning method shows strong potential as a stability-oriented controller design framework for microgrids including dynamic loads such as induction motors.