Topological and Modulation Design of a Buck-Boost Three-Level Dual Inverter

To date, buck-boost inverters have mostly been reported with two-level inverter topologies. For improved output waveform quality, this paper presents the design of a buck-boost three-level dual inverter supplied by a single DC source. The proposed inverter is implemented by cascading two three-phase voltage-source bridges at their AC outputs with only an additional switch added to their common DC network for inductive energy boosting. The designed inverter can be controlled using a carefully formulated modulation scheme, which ensures the proper sequencing and placement of three distinct states in a switching cycle, while at the same time, avoids any short-circuiting of capacitive elements. If desired, the modulation scheme can also be fine-tuned to allow the proposed inverter to operate with reduced common mode voltage generated, hence minimizing bearing and ground leakage currents commonly reported to have caused motor malfunctioning. All findings presented in the paper have been confirmed experimentally using an implemented laboratory prototype