Backstepping Control for Single-Phase Grid-Connected Inverter Utilizing Variable Structure Observer

In this paper, a backstepping nonlinear control scheme has been designed for a single-phase grid-connected inverter system with local load. The main objective of the proposed controller is to simultaneously improve the quality of the local load voltage while injecting clean current to the grid with unity power factor. Furthermore, this control approach ensures the seamless transfer between grid-connected and standalone operation modes without adjusting the controller structure. The proposed control structure utilizes a variable structure nonlinear observer to avoid using the numerical derivative of the output voltage. Moreover, the variable structure component of the observer makes it robust to a wide range of operating conditions. The proposed combination of controller/observer is validated by a Lyapunov stability analysis as well as via instantaneous dynamic circuit simulation in PLECS software.