| Summary: | 博士 === 國立臺灣科技大學 === 電機工程系 === 88 === This dissertation presents the design and implementation of single-phase half-bridge multi-function uninterruptible power supplies. The system provides combined functions of battery bank energy storage, power factor compensation, harmonics elimination and uninterruption of power supply. When the utility is in normal operation, the proposed system will not only supply DC power for battery charging and DC load, but also function as an active power filter for improving the power factor and reducing the current harmonics on the utility side. If the utility power fails, the proposed system will function as an inverter immediately to supply the battery power to the load.
Analysis and simulation for the proposed system is given first. A personal computer is then used to implement digitized control of the proposed system to facilitate experimental evaluations for two 1kVA prototypes. A current-controlled scheme is used for parallel control, load sharing and load transfer according to the load rating and condition to increase the power capacities and reliability. To overcome the transient delay due to the mode change, a power balance and feedforward control method is applied to improve the performance.
Experimental results indicate that the proposed system can not only function as a high performance uninterruptible power supply for fluorescent lamps with electronic ballast, but also reduce the total harmonic distortion of input current to lie within 8% and with near-unity power factor for nonlinear load. In addition, the change of modes can be finished within 1.5ms in both the cases of power failure and power recovery. This indicates that the system can be operated successfully as an uninterruptible power supply.
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