| Summary: | 碩士 === 國立清華大學 === 電力電子產業研發碩士專班 === 98 === The major purposes of this thesis are to develop a single-module high-frequency isolated three-phase inverter and a Scott-T modular connected low-frequency isolated three-phase inverter. All are equipped with different types of three-phase switch-mode rectifiers, and proper digital controls using digital signal processor (DSP) are conducted to yield good inverter output performance.
First, a single-phase inverter is designed and implemented, which possesses excellent and robust output voltage waveform tracking characteristics via the proposed sophisticated current and voltage control schemes. The established single-phase inverter is then employed to form a low-frequency isolated Scott-T modular connected three-phase inverter, only two inverter modules and a Scott-T transformer bank are employed. Some measured results are provided to demonstrate its operating performances, including voltage waveforms under unbalanced and nonlinear loads, and three-phase imbalance, etc. Second, a high-frequency isolated three-phase inverter is constructed. It consists of a single-module six-switch three-phase inverter and a LLC resonant DC/DC converter to establish the isolated DC-link with well-regulated voltage. The comparative performance evaluation for these two types of three-phase inverters is conducted. Specifically speaking, the high-frequency isolated inverter possesses less output voltage waveform distortion in powering nonlinear loads. However, its rating enlargement is more difficult owing to the inherent limits of high-frequency power transformer.
Finally, the development of three types of three-phase switch-mode rectifiers (SMRs) is made, and they are utilized to serve as the front-ends of the developed inverters. These include three-phase single-switch (3P1SW) SMR, three-phase bridgeless SMR and three-phase single-switch zero-current-transition (3P1SW ZCT) SMR. The established different SMR-fed inverter systems are assessed their performances comparatively by measured results.
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