State observer to improve the VSG control stability

This paper proposes an observer-based current controller for a virtual synchronous generators (VSG) to improve its operational performances. First, the model and the controllers are analytically described. Two controller are compared to the proposed one (PI integrating a state observer): a traditional PI and a PI integrating virtual impedances for filtering. Secondly, the advantage of the observer in the current controller loop for the VSG application is studied and compared to the other controllers. Finally, experimental results validate the capacity of the VSG-based inverter to supply unknown and unpredictable loads, thanks to the integration of the observer in the current control loop.