| Summary: | 碩士 === 國立臺灣科技大學 === 電機工程系 === 102 === This thesis is concerned with the implementation of on-line three-phase uninterruptible power supply systems. When the AC mains is normal, the three-phase power factor corrector converts the mains voltages into a constant DC and also provides boost/buck converter standalone charge to the battery bank. Then, a three-phase three-leg power inverter creates balanced three-phase sinusoidal voltages with low harmonic distortion across the load terminals. If the AC mains fails, the system will supply the battery power to the load under the discharge mode. In the three-phase power factor corrector, a DC voltage closed-loop control which stabilizes the DC voltage is adopted to maintain the balance of the utility source and make the input power factor close to unity with low current harmonics. As to the management of battery bank, the charging/discharging schemes are fulfilled by the boost/buck converter. While in the three-phase power inverter, a AC voltage closed-loop control is adopted to facilitate the independent control of voltage for balanced, unbalanced as well as nonlinear loads.
The control scheme of the system is implemented by a 32-bit digital signal processor(DSP, TMS320F28335) to reduce the hardware components.
The experimental results for 3 kW balanced liner resistive load, 2 kW unbalanced resistive load and 2 kW nonlinear load show that the total harmonic distortions of output are 0.82%, 1.55% and 4.41%, respectively. It is seen that the efficiency of UPS is 84.3% and 87.4% can be achieved for AC normal and AC off operation modes respectively. In conclusion, the experimental results demonstrate that the controller successfully achieves the steady-state RMS voltage regulation specification as well as the total harmonic distortion and the dynamic response requirements of major UPS standards.
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