Control of H-bridge based multilevel converters

Multilevel converters are suitable for high voltage and high power applications. Among them H-bridge ones have encountered good success due to their simpler layout and the reduced number of components over the counterparts. H-bridge multilevel converters used as active rectifiers represent an attractive solution in traction systems due to the possibility to reduce the AC filter size and to boost the DC voltage. Moreover they can feed many DC loads at the price of considerable difficulties in ensuring stability of the overall system. The passivity based theory seems suitable to address and solve such a kind of problem. The main idea is to design a nonlinear controller whose function is to shape systems energy aiming to obtain the desired behavior. A comparison is made between a control technique using classical PI controllers and a passivity based control.