High frequency link Uninterruptible Power Supply (UPS) system

Abstract

The main aim of this thesis is to propose, design, simulate and build a new UPS system which can be used for compact applications. The idea of the proposed system is to operate the transformers within the UPS at high frequency so that the size and the weight are kept to minimum. In order to achieve this aim, the transformer within the UPS system is operated at high frequency; however it also carries two 50 Hz waveforms at 180 phase shift so that the transformer does not see this 50 Hz frequency. A cycloconverter is then used to reconstruct the 50 Hz waveform for the UPS output. The UPS system is simulated using PSPICE software at high frequency link of 500 Hz, 1 kHz, 5 kHz and 10 kHz. The simulation results show that the transformer only passes the high frequency component while the 50 Hz frequency is ‘hidden’ within the transformer. The proposed UPS system is then built using MOSFETs IRF740 as the main switches for the inverter and cycloconverter circuits. A Chipkit-uno32-development-board is used to control the MOSFET switches. Simulated and practical results show the viability of the proposed UPS system.