| Summary: | 碩士 === 國立交通大學 === 電機與控制工程系 === 87 === To increase the power density of the PWM inverter of modern uninterruptible power supplies (UPS), one approach is to increase the switching frequency, however, additional switching losses are usually accompanied with the increasing switching frequency. This thesis applies soft-switching technique in reducing switching losses of PWM inverters used for medium power UPS. The operational principle and switching loss analysis of the H-bridge inverter using bipolar PWM modulation technique have been studied in detail. After evaluation of various soft-switching techniques, a clamped-mode resonant pole inverter (CMRPI) soft-switching technique was adopted in realization of the PWM inverter circuit. Detailed circuit analysis and computer simulation of the developed soft-switching PWM inverter were given. We have constructed a soft-switching PWM inverter with switching frequency of 100 kHz. The rated output power of this prototype PWM inverter is 1kW, its DC bus voltage is 180 V, and its output ac voltage is 110 V. Experimental results show that the constructed soft-switching PWM inverter can reach an efficiency improvement of 4% at rated output.
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