| Summary: | 碩士 === 國立宜蘭大學 === 電機工程學系碩士班 === 101 === This thesis presents a soft-switching single-phase three-arm dynamic voltage restorer (DVR), which includes a double conversion voltage regulator, a transformer series compensation dynamic voltage restorer, a capacitor series compensation dynamic voltage restorer, a transformerless series compensation dynamic voltage restorer and a unified power quality conditioner. All of the proposed DVRs can compensate the voltage disturbances such as voltage swell, voltage sag, over-voltage, under-voltage and harmonics. The proposed DVR is composed of a three-arm topology which operates as a rectifier and an inverter. 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. The low frequency arm is switched at line-frequency synchronized to the source voltage to achieve low switching losses. 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. Rather than the conventional four-arm topology, the proposed three-arm topology not only reduces the number of main switches but also increases the system reliability and simplifies the control circuits. 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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