Impact of Virtual Oscillator Control on the instantaneous properties of VSC output voltage in distorted island grids

Abstract

This paper investigates the instantaneous properties of voltage and frequency of Voltage Source Converters (VSCs) when they are controlled by Virtual Oscillator Controllers (VOC) in a distorted island grid. Under time-averaged measurements, the VOC exhibits well known linear droop characteristics, which make them a good candidate for control in island grids. However, the instantaneous properties of VOC are influenced by the nonlinear dynamics of the Van der Pol oscillator and provide better synchronization properties under distorted voltage conditions compared to the conventional droop controller. This is shown in a simulation study of parallel operation of two inverters serving a non-linear load that reveals a more stable synchronization at the expense of voltage quality in the case of the VOC compared to the conventional droop controller. These results provide convincing evidence for the adoption of a more complex controller as the VOC in island grids that will naturally be more vulnerable to voltage distortions. At the same time, these results encourage further explorations into other potential benefits of VOC in island grids.