Thesis--M. Phil., University of Hong Kong, 1978.

D. Tech. Electrical Engineering. / A matrix converter is a forced commutated converter which uses an array of controlled bi-directional switches as the main power processing elements to create a variable voltage system with unrestricted frequency. It does not contain any DC link circuit and does not require any large energy storage elements. The output frequency is theoretically infinitely variable as opposed to cyclo-converters. This study will evaluate present modulation techniques for matrix converters. Chapter 2 will review the present direct and indirect modulation techniques for Matrix Converters. Chapter 3 develops the indirect modulation model, based on space vector modulation techniques. In chapter 4 various state space models are developed and an optimised switching pattern, based on the least square error, is developed.

Current research and the price of semiconductors are making Matrix Converter topologies more attractive and practically viable for many applications. One of the key benefits claimed for the matrix approach is the possibility of greater power density due to the absence of a DC link. To capitalise on this it is necessary to make the input filter small by having a sufficiently high switching frequency. In order to arrive at optimised solutions in terms of filtering, heatsinking and packaging, it is important to have accurate models to predict power circuit losses as a function of operating point and switching frequency. This aim of this thesis is to further the understanding of Matrix Converter current commutation with a focus on switching losses. The commutation process is analysed in detail and a complete loss model for Matrix Converter circuits is developed. The use of circuit simulation software in the prediction of switching losses is investigated and comparisons are made with experimentally measured results. The loss model is used to compare Matrix Converter losses with a functionally equivalent sinusoidal front end inverter. A review of soft switching techniques for Matrix Converter circuits is given. A new auxiliary resonant soft switching Matrix Converter is presented which overcomes many of the problems of the previously proposed circuits. The design, construction and testing of a 6kW prototype soft switching Matrix Converter is presented to evaluate the feasibility of the topology.

published_or_final_version / Electrical Engineering / Master / Master of Philosophy

published_or_final_version / Electrical Engineering / Doctoral / Doctor of Philosophy

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