Analysis and design of a single DC source hybrid multilevel rectifier

This paper presents an analysis and design of a single dc source hybrid multilevel rectifier, which can be used as the input converter of a regenerative adjustable speed drive. The hybrid multilevel converter is composed of a three-phase three-level neutral-point-clamped (NPC) converter connected in series with an H-bridge cell per phase. The NPC converter operates at the output fundamental frequency and processes the entire active power. Therefore, the H-bridge cells, which operate under pulse width modulation, do not process active power and they can be supplied only by capacitors. A modulation strategy based on geometric approach is used to maintain the dc capacitor voltages regulated without distorting the output line-to-line voltages. Distinct dc voltage configurations are analyzed and their impact on the passive filter minimization is verified. Experimental results are included to evaluate the performance of the hybrid multilevel rectifier.