Digital Deadbeat and Repetitive Combined Control for a Stand-Alone Four-Leg VSI

This paper deals with a newly conceived combined control topology. Deadbeat and repetitive controllers are proposed to operate jointly in a four-leg voltage-source inverter for stand-alone applications. In such a mode of operation, a dedicated controller has to regulate the inverter output voltages, which are measured at the output of the power filter. In the proposed combined control, the deadbeat rapidly compensates the output voltage variations due to load changes, whereas the repetitive control provides the required harmonic compensation capabilities that are mandatory to comply with the standards when balanced and unbalanced nonlinear loads have to be fed. As a consequence, high dynamic performance is assured, as well as harmonics in the output voltages are almost absent. In fact, the achieved experimental tests have verified that resulting output voltage total harmonic distortion is around 0.5%, and in the case of highly unbalanced and nonlinear loads, compensating also the distortion introduced by the switches’ deadtime.