An Integrated State-Space Model For Grid Feeding and Grid Forming Inverters

As the penetration of power electronic-based resources increases, the power grid dynamics changes. The impact of the phase-locked loop (PLL) and hierarchical controllers used in grid feeding and grid forming voltage source inverters (VSI) can cause stability issues based on energy resource dynamics and grid conditions (weaker or stronger). To understand the stability conditions and design appropriate control methods to reduce the oscillations, there is a need to develop an integrated closed-loop model especially to capture the integrated dynamics on the inverter modes of operation (grid-forming and grid feeding). In this digest, we demonstrate a method to develop a state-space mathematical framework that can capture the closed-loop system dynamics of VSI in both modes of operation as well as during the transition. The proposed model is verified with time-domain simulations under different perturbation scenarios and used for controller tuning.