DC voltage estimation methods for multilevel converter operating with reduced number of sensors

Two methods for the estimation of the DC voltages in the capacitors associated to the DC buses in a cascaded multilevel converter topology are analyzed. To reduce the number of voltage sensors, available information from inductor currents and line voltage sensors is used as input to a discrete time model of the converter. Additionally, information from the switching state of each converter´s cell is used allowing an estimation of voltages in each capacitor. Both methods are developed, implemented and simulated for a 9 level three-phase cascaded multilevel converter when it is operated as a controlled rectifier at unity power factor. The analyzed methods have low computational cost allowing its implementation in real time.