Asymptotic rejection of sinusoidal disturbances based voltage balance control in back-to-back power converters

Abstract

SUMMARYThis paper addresses the imbalance problem of the dc-link capacitor voltages in the three-level diodeclamped back-to-back power converter. In order to cope with it, a mathematical analysis of the capacitor voltage difference dynamics, based on a continuous model of the converter, is first carried out. It leads to an approximated model which contains explicitly several sinusoidal functions of time. In view of this result, the voltage imbalance phenomenon can be addressed as an output regulation problem, considering the sinusoidal functions as exogenous disturbances. Thus, a novel approach to deal with the mentioned problem in the backto-back converter is presented. Then, the particular features of the disturbances are used to design several controllers. They all follow an asymptotic disturbance rejection approach. In this way, the estimations of the disturbances are used to apply a control law that cancels them while regulating the capacitor voltage balance as well. Finally, the performance of the proposed control laws is evaluated, presenting the simulation results obtained when the different controllers are implemented.

Voltage balancing in three-level neutral-point-clamped converters via Luenberger observer

“…Therefore, since this sinusoidal disturbance appears explicitly in (21), it leads to rewrite this final expression as…”