Unified power flow controller (UPFC) based on chopper stabilized diode-clamped multilevel converters

As the diode-clamped, multilevel converter has been found to have attractiv e features for STATCOM application, there is interest in extending it to UP FC application by using multilevel converters as the series and the shunt c onverters. Unfortunately, as is demonstrated in this paper, the de voltages at their de links, are inherently unstable. Faced with this impasse, a sol ution is sought in a system of local feedback controlled Class B choppers t o equalize the dc.Laboratory experimental model establishes the feasibility of the proposal. Digital simulations show that current ratings in the chop pers need be only 10% of the current ratings in the converters. The chopper cost is estimated as 1% of the cost of the multilevel converters.