| Summary: | 碩士 === 國立宜蘭大學 === 電機工程學系碩士班 === 102 === This thesis presents a soft-switching three-phase AC voltage regulator, which includes a modular three-phase transformer series compensation AC voltage regulator, a three-phase capacitor series compensation AC voltage regulator and a three-phase unified power quality conditioner. All of the proposed voltage regulators can compensate the voltage disturbances such as under-voltage, over-voltage, voltage sag, voltage swell and three-phase unbalanced load. The proposed three-phase AC voltage regulators are modular configuration that each phase is composed of a three-arm topology which operates as a rectifier and an inverter. The low frequency arm is switched at line-frequency synchronized to the voltage source to achieve low switching losses. The rectifier arm is switched at high switching frequency to perform power factor correction and simultaneously transfers the power demand by the load to the dc link capacitor. The inverter arm is also switched at high switching frequency for the output voltage regulation. Using simple resonant units, all main switches of high frequency arm are operated at zero-voltage-switching (ZVS) turn-on, while all auxiliary switches are operated at zero-current-switching (ZCS) turn-off. The topology has the advantages of reducing the switching losses, and EMI greatly. Besides operating at unipolar PWM voltage switching, the input current and the output voltage harmonics can be reduced. Moreover, the proposed feed forward controller, based on the energy balance concept, is proposed to control the voltage of energy-storage capacitors. The energy change in energy-storage capacitors can be fast compensated so that the transient performance can be improved. Finally, some simulation and experimental results are presented for verification.
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