M.Ing. (Electrical and Electronic Engineering) / The main purpose of the study is to propose an unique unity power factor AC-DC converter topology, with isolated output. The proposed converter is obtained by merging the unity power factor boost converter and the full bridge resonant transition converter. The converter is unique as resonant switching techniques are used to obtain a zero voltage switching boost stage, resulting in an all soft switching converter. The result is lower levels of conducted EMI, as well as lower switching losses. Conventional topologies utilize more than one converter stage to obtain the required results, whereas _ the proposed converter results in a single step solution. As the purpose of the proposed converter is power factor regulation resulting in lower levels of conducted EMI, the study is commenced with a review of the definitions and equations for both power factor and EM!. Thereafter sources and propagation of conducted EMI are discussed. To gain a better understanding of the operation of the proposed converter, the operation of the unity power factor boost converter, as well as the full bridge resonant transition converter are discussed in depth. A switching cycle of the proposed converter is divided into different intervals, and analytical equations for the relevant currents and voltages for each interval are derived seperately. Possible control schemes are introduced and where applicable, conditions for zero voltage switching are given. It is concluded that a constant frequency PWM controller is the most ideal control scheme to ensure proper operation of the converter. A simple design procedure is presented by which the size of the most important circuit parameters can be designed in terms of the desired switching frequency and permissable duty cycle variation. Finally, experimental results obtained from the practical converter, are given. Deviations from the ideal are interpreted and methods of improving the performance are suggested.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:uj/uj:4146 |
| Date | 18 February 2014 |
| Creators | Van der Berg, Marinus |
| Source Sets | South African National ETD Portal |
| Detected Language | English |
| Type | Thesis |
| Rights | University of Johannesburg |
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