Multivariable Dynamic Model and Robust Control of a Voltage-Source Converter for Power System Applications

This paper proposes a new multivariable dynamic model and a control approach for a voltage-source converter (VSC) based on adopting instantaneous real- and reactive-power components as the VSC dynamic variable. Using power components as the dynamic variables reduces the degree of nonlinearities of the VSC model in comparison with the conventional VSC model that uses qd current components as variables. Furthermore, since waveforms of power components are independent of the selected qd coordinates, the proposed control is more robust to the conventionally unmodelled dynamics such as dynamics of the VSC phase-locked loop system. The proposed control system regulates the VSC AC-side real- and reactive-power components, and the DC-side voltage. This paper also introduces an overcurrent limiting mechanism, based on limiting the VSC power exchange during abnormal conditions, for the proposed control system. The proposed model and control are applied to a VSC-based reactive power compensator and simulation results based on PSCAD/EMTDC software are presented.