Dynamic Model and Control of AC–DC–AC Voltage-Sourced Converter System for Distributed Resources

This paper introduces a dynamic model of the ac-dc-ac voltage-sourced converter (VSC) system which provides a linear relationship between the input and output variables. The model is developed in two steps. First, the exact abc frame switched model of a VSC is transformed to a switching reference frame (SRF). Then, the SRF model is transformed to an appropriate dq0 reference frame. The fundamental-frequency dynamic model of the VSC is deduced from the dq0 model and provides a set of single-input single-output controls for the VSC system. The fundamental-frequency steady-state model of the VSC system is deduced from the dynamic model and provides a closed-form solution to the VSC system. The developed models are used to design controllers and define steady-state settings, e.g., modulation indices, for electronically-coupled distributed resources. The developed models are applied to a test system and the results are validated based on time-domain simulation studies in the PSCAD/EMTDC environment