A generalized capacitors voltage estimation scheme for multilevel converters

In this paper a generalized scheme for capacitors voltage estimation for multilevel converters based on the converter switching states and using only a single voltage sensor at the AC side of the converter is proposed. The estimation of the capacitors voltage is performed after a capacitor is switched on or off and hence the estimation frequency is dependent on the converter switching frequency. In between the switching periods, the scheme can keep track of the capacitors voltage by monitoring the current flowing through the capacitor until the next transition. The effectiveness of the proposed scheme is demonstrated on a single-phase 7-level cascaded H-Bridge multilevel converter based STATCOM by simulation in the Matlab/Simulink environment.