Output Feedback Control of a Single Phase Voltage Source Inverter Utilizing a Variable Structure Observer

A robust nonlinear controller is presented for output tracking of a single phase LC-filtered voltage source inverter. The proposed control uses a second order system model to develop an output feedback control scheme based on a variable structure observer. The use of this nonlinear observer allows for elimination of costly current sensors and the ripple and noise which is inherent in such measurements in a PWM switching environment. The variable structure component of the observer allows for it to be robust to a wide range of load conditions. This combined controller/observer scheme is validated by a Lyapunov stability analysis which proves convergence of the tracking errors and boundedness of all signals in the closed loop system. Further validation and performance evaluation is provided by experimental results which demonstrate the steady-state and transient performance of the scheme under a highly nonlinear rectifier load.