| Summary: | 碩士 === 國立中興大學 === 電機工程學系 === 91 === Abstract
This thesis contains the implementation of an off-line UPS and design of a digital controller for its voltage output regulation. The system is composed of three major units: the dc/ac voltage conversion module, the battery charger, and the output voltage regulator. First, we utilize the boost dc/dc converter to boost the 24V battery voltage up to a higher working voltage (dc-link voltage). The dc-link voltage is cascaded with a dc/ac converter (inverter) and a passive LC filter to be transformed into the 110V, 60Hz voltage. Two 12V batteries are connected in series to provide the system with a 24V dc voltage source. Due to distinct charging characteristics of the two batteries, charging energy allotment may unbalance. To overcome this problem, we use the flyback converter with two output windings to charge the batteries individually. The mathematical model is derived from the open-loop step response. In order to achieve the voltage output regulation, we propose two control strategies ─ PI control and variable structure control (VSC). A TMS320LF 2407A digital signal processor (DSP) is employed as the control platform for control law implementation and system integration. Both computer simulations and experiments are conducted. It is seen that the VSC is superior to PI control in robustness and therefore can achieve a steady state voltage output in spite of load variations.
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