State observer to improve the VSG control stability

International audienceThis 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. Nomenclature Symbol Definition ωr and ω 0 Machine rotor electrical angular velocity and its base value, ωr = ωrotor/ω 0 i d and iq Machine dq stator output current V DC Inverter input DC voltage α d and αq dq inverter output duty ratio V i , V d i and V q i Unifilar and dq inverter voltage considering: V i = α. V DC 2 E, e d and e q Single-line and dq filter voltage Vg, V d g and V q g Single-line and dq grid voltage i L , i d L and i q