Model Order Reduction of Voltage Source Converters Based on the Ac Side Admittance Assessment: From EMT to RMS

Abstract

Time-averaged electromagnetic (EMT) power electronics models can comprise tens of state variables, and in upcoming converter-dominated power systems, this can cause a substantial computational burden. The level of detail in their modeling, however, is typically much greater than what is typically necessary for transient stability (RMS) tools. Hence, there is a reasonable need for using reduced-order models of power electronics devices in accordance with the study needs and the related frequency range of interest. This paper focuses on modeling the time-averaged voltage source converter (VSC) for the application in ac system stability studies where the small-signal assumption holds for converter variables. The impact of simplifications and converter parameters in VSC's model accuracy is evaluated first as observed from the ac-side admittance. Subsequently, based on the previous assessment, a limited set of VSC reduced-order models is established and analyzed – which is the main paper contribution. The parametric sensitivity analysis is conducted to establish the validity boundaries of the proposed models in the frequency domain. Finally, the recommendations for the use in different power system studies are provided.