Transfer Function Modeling Approach for Inverter-Dominated Grid

In modern power grids, an increasing number of renewable sources are integrated via inverters, affecting the inertia of the overall power system. Thus, a low-inertia system formed is potentially vulnerable to fast grid collapse and catastrophic failures in case of any disturbances. The study of low-inertia systems is an important aspect of the stability and control of the power grid. The stability studies require system model representation in the time or frequency domain. The traditional modeling method is the state-space approach which requires detailed system knowledge that may not be available always. The impedance-based approach is computationally efficient but fails to provide information about the internal states of the system. To overcome these drawbacks, we develop a transfer function-based approach. The purpose of this study is to present a computationally efficient modeling method for a converter system that incorporates internal knowledge of the system. It provides flexibility in understanding the stability of the overall system through Bode, Nyquist, and pole-zero plots. The proposed Transfer Function-based approach is applied to the generalized model of the converter consisting of two types of inverters Grid Forming (GFM) and Grid Following (GFL), and its stability assessment is carried out in MATLAB.