Doctoral Degrees (Electrical and Electronic Engineering)

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Browsing Doctoral Degrees (Electrical and Electronic Engineering) by browse.metadata.advisor "Beukes, H. J."

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    A detailed analysis of the imperfections of pulsewidth modulated waveforms on the output stage of a class D audio amplifier
    (Stellenbosch : University of Stellenbosch, 2009-03) Koeslag, Francois; Mouton, H. du T.; Beukes, H. J.; University of Stellenbosch. Faculty of Engineering. Dept. of Electrical and Electronic Engineering.
    Although the Class D topology offers several advantages, its use in audio amplification has previously been limited by the lack of competitiveness in fidelity compared to its linear counterparts. During the past decade, technological advances in semiconductor technology have awakened new interest since competitive levels of distortion could now be achieved. The output stage of such an amplifier is the primary limiting factor in its performance. In this dissertation, four non-ideal effects existing in this stage are identified and mathematically analysed. The analytical analysis makes use of a well-established mathematical model, based on the double Fourier series method, to model the imperfections introduced into a naturally sampled pulsewidth modulated waveform. The analysis is complemented by simulation using a strategy based on Newton’s numerical method. The theory is verified by a comparison between the analytical-, simulated- and experimental results.
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    Development and analysis of a distributed control strategy for power electronic converters
    (Stellenbosch : Stellenbosch University, 2002-03) Du Toit, J. A. (Jacques Andre); Beukes, H. J.; Stellenbosch University. Faculty of Engineering. Dept. of Electrical and Electronic Engineering.
    ENGLISH ABSTRACT: The dissertation presents an alternative approach to the control of power electronic converters. The conventional approach is to use a centralized controller with one or more measurement systems providing feedback. As converters become larger, in both power rating and complexity, a number of drawbacks to this approach emerge. The number of physical data paths increases and voltage isolation becomes a problem. This has an adverse effect on the manufacturability as well as the reliable operation of the system as a whole. An alternative is to use a distributed control approach, where a number of smaller integrated control and measurement units are used. These units communicate with the central controller via a serial daisy-chain communications link. The dissertation investigates the design of such a controller as well as the application of distributed control in a number of emerging converter topologies. It was shown that centralized control has its limitations in modem power electronics in terms of reliability, maintainability and manufacturability. A feasible distributed control strategy was proposed and implemented and the operation was verified in an experimental converter system.