Nonlinear Modeling of Multi-Converter Systems Within DC-Link Timescale

The emergence of various power electronic devices, including voltage source converters (VSCs), has greatly changed the dynamics of power systems. It is a great challenging to put forward new theories for modeling, analysis, and understanding of power-electronic-based power systems. In this paper, we first establish a detailed nonlinear model of multiple VSC systems, and then, by using the singular perturbation technique, obtain a reduced-order nonlinear model within the DC-link timescale. The latter model consists of differential algebraic equations (DAEs) and keeps slow dynamics in transient processes, showing a balance between computational accuracy and system complexity. Furthermore, the model is compared with the traditional electromechanical dynamical model of power systems, which are dominated by synchronous generators (SGs). Our model of multi-converter systems can be put into a similar diagram to the traditional power system dynamics, with which most of power electrical engineers are familiar. Finally, wide simulation results verify the efficiency of the proposed model.