Self-Synchronizing Current Control of a Three-Phase Grid- Connected Inverter in the Presence of Unknown Grid Parameters

Three-phase inverters for grid-connected applications typically require some form of grid voltage phase detection in order to properly synchronize to the grid and control real and reactive power generation. This phase detection is usually based upon some type of grid voltage sensing. However, in the present work a method is proposed whereby the phase angle of the grid can be accurately identified solely via the grid current feedback. This phase observer is incorporated into a current controller which can manage the real and reactive power. The design of this combined observer/controller system is motivated and validated via a Lyapunov stability analysis. Controller Hardware-in-the-Loop results under various operating conditions are provided for further validation and realization.