Two passivity-based approaches to the control of the H-bridge-based multilevel rectifier

This paper deals with a multilevel H-bridge based front-end rectifier to be used in high voltage high power applications. The main control issue for such type of converter is stabilization. In fact, voltage unbalancing across the distinct DC links can lead to system instability. In this paper two passivity-based control (PBC) algorithms for the H-bridge-based multilevel rectifier are analysed and compared. The use of the passivity-based control properly fits stability problems related to this type of converter. Two approaches for the PBC design have been considered: the first one is developed considering the overall multilevel converter; the second one is developed by splitting the system into n subsystems and controlling them independently. The partition of the multilevel converter is done on the basis of energy considerations. The main advantage of the second approach is the separate control of the different DC-links and a more flexible loading capability.