M.Ing. (Electrical & Electronic Engineering) / Switching losses in power electronic converters can be reduced by using snubbers, or resonant circuits. Simple snubbers can be implemented without much effort, but then energy is still dissipated, which reduces the efficiency of the converter. Regenerative snubbers are known, but these usually require complicated additional circuits. The use of nonlinear capacitors as turn-off snubbers has been investigated, and proved profitable. The main reason for this is the much smaller amount of energy which is stored in the the nonlinear capacitors, compared to linear capacitors. Resonant circuits reduce switching losses by allowing switchings to occur when the voltage across the switching device, or the current through the switching device is zero. This effect is called soft-switching and to obtain this, resonance between an inductor and capacitor is usually involved. Resonant circuits have the disadvantage that the installed switching power cannot be used optimally. This drawback has been reduced by using a saturable inductor in the resonant circuit. This thesis considers the use of both nonlinear capacitors and nonlinear inductors in a resonant phase arm. It was found that the nonlinear resonant elements lead to very low overdimensioning of the switching devices, and minimal switching losses in such a phase arm. Very few additional components are used, which keeps the cost of the converter down. A 1.5kW converter was constructed in which the double nonlinear resonant phase arm was implemented. This converter was investigated both experimentaly, and by means of computer simulations. The converter is also compared with the current state of the art. It is concluded that resonant phase arms with both. nonlinear inductors and nonlinear capacitors can function effectively in power electronic converters. Some important advantages are also assosiated with the use of the double nonlinear resonant circuit.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:uj/uj:12421 |
| Date | 29 September 2014 |
| Creators | De Villiers, Johannes Reinach |
| Source Sets | South African National ETD Portal |
| Detected Language | English |
| Type | Thesis |
| Rights | University of Johannesburg |
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