Sistemas de conversão estática baseados em conversores multiníveis modulares em cascata com células do tipo meia-ponte: aplicação em sistemas CA-CC-CA monofásicos e sistemas com terminais abertos.

Abstract

This thesis proposes two modular energy conversion systems based on a modular multilevel topology with double-star chopper-cells (DSCC), whose arms are mounted from the series association of submodules (SMs) — identical cells arranged in half bridge. The first system is applied to single-phase AC-DC-AC conversion by means of three converters with shared legs. Among these converters, hybrid versions are proposed leading to a reduction of conduction losses, although restricted to operation with equal input and output frequencies. As discussed, the modular system can operate with different frequencies, but the DC link requires higher voltage capacity than in operation with equal frequencies. The single-phase converters are evaluated for output-voltage and input-current regulation with harmonic compensation capability. The second system is applied to three-phase machine drive with open-end windings (OEW), whose purpose aims to improve the output waveforms and to provide to the modular DSCC inverter the short-circuit tolerance on the DC link. Thus, this system uses a low-scale modular DSCC inverter and a two-level (2L) inverter operated at fundamental frequency for reducing switching losses. In general, the proposed systems are studied in the interests of maximizing output quality from the modular DSCC topology, with total loss reduction. The operating limits are investigated and, for a proper operation of the proposed systems, techniques of generation of the pole-voltage references are presented — depending on the topology. In addition, an algorithm to reduce the number of carriers is proposed for the modulation strategy with phase-shifted carriers. Finally, the performance of the systems is evaluated by simulation and experimental results.