Novel symmetric hybrid multilevel topologies are introduced for both single-and three-phase medium-voltage highpower systems. The topology conception is presented in detail, where a three-level switching cell with low component count, and its modulation pattern give the origin of the proposed converters. Voltage sharing and low output-voltage distortion are achieved. The theoretical frequency spectra are derived. Switching devices are separated into high-and low-frequency devices, generating hybrid converters. Five-level three-phase topologies are generated from only three insulated dc sources, while the number of semiconductors is the same as for the cascaded H bridge. Both simulation and experimental results are provided showing the validity of the analysis.

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DC -DC step-up converters for high-output voltage applications typically demand high voltage devices, leading to high conduction and switching losses. This identified demand has motivated research on active clamping and multi-level topologies. On this context, this study presents the study of a novel DC -DC boost converter with three-level boost-type active clamping, zero-voltage switching (ZVS) soft-switching and constant frequency pulse-width modulation. As shown analytically and through experimental results, high efficiency and reduced voltage ratings for the power semiconductors are achieved, thus, making the topology suitable for converters requiring high-output DC voltage. Furthermore, a topological modification for achieving ZVS operation in all semiconductors and other types of switching cells for boost-type converters is introduced.

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