Admittance-Based Modeling of Grid-Following Converters for Time-Domain Simulations of Multi-Converter Electrical Power Systems

Accurate and efficient time-domain simulations are indispensable for integrating converter-interfaced energy resources into the evolving power grid. This paper proposes an admittance-based model (ABM) of grid-following converters (GFCs) for numerically efficient time-domain simulations. Specifically, the linear components of GFCs with fast dynamics are formulated as transfer functions, while the slow nonlinear components are kept without any model reduction. The transfer function- based admittance formulation preserves/includes the dynamic characteristic between the desired input/output variables of the fast sub-system. The proposed ABM also achieves an enhanced interfacing with external networks and does not require an extra time-step delay as opposed to the conventional implementation of state-space average-value models (SS-AVMs) of converters. The proposed ABM of the GFCs is validated through computer simulations and compared with the SS-AVM. It is shown that the proposed ABM is able to use larger time-steps and achieve higher numerical accuracy compared to SS-AVM, making it capable of simulating larger multi-converter systems using specific available simulation hardware.