Disturbance-Observer Assisted Controller for Stand-Alone Four-Leg Voltage Source Inverter

In this paper, a newly disturbance-observer based control strategy for stand-alone four-leg VSI has been proposed and analyzed. The disturbance-observer operates together with a simple and effective resonant controller in order to regulate the inverter output voltage. In particular, the resonant controller regulates the output voltage fundamental harmonic, whereas the disturbance observer is designed for compensating output voltage harmonics when non-linear loads have to be fed. The new control strategy effectiveness and performance have been validated at first through a full MATLAB/Simulink model and then by experimental results on a dedicated 40 kVA three-phase 4-leg.