Fontes CA de potência: contribuição ao estudo e ao desenvolvimento de topologias híbridas

Abstract

In this thesis an study of AC Power Source (ACPS) topologies that guarantee the synthesis of high quality voltage waveforms (in comparison to the reference signal) without penalizing the system efficiency is carried out. It must be highlighted that these features can be achieved by employing hybrid topologies, which are composed of a switched-mode power amplifier and a linear power amplifier (LPA). The former amplifier (called main amplifier) processes almost the entire load power, while the second one (called correction amplifier) is responsible for the compensation for any distortion at the output voltage waveform, thus, processing a small amount of the load power. In this way, it is possible to combine both the high efficiency of switched-mode power amplifiers with high quality voltage waveforms characteristic of linear power amplifiers. This work is mainly focused on hybrid topologies in series configuration (series connection between main and correction amplifiers). This allows to employ a low voltage/low power LPA. It must be noticed that this configuration is especially suitable for ACPS applications, when, for example, the mains voltage is intended to be emulated (including high order harmonics, controlled disturbances, etc.), since the LPA experiences low voltage levels in comparison to those synthesized by the ACPS. Throughout the thesis are proposed and theoretically/ experimentally analyzed two novel ACPS topologies, which employ multilevel inverters as main amplifier. The analysis take into account the operation, modulation strategy and design methodology of the power and control circuits (of both main and correction amplifiers). Experimental results are presented (Total Harmonic Distortion and converter efficiency) in order to validate the proposed approach.