Power Electronic design of a Multi MW dc/dc converter

Abstract

• In this thesis, two topologies from a Zero voltage switching family are compared in terms of the power losses and weight of the magnetic components. These prerequisites are dictated by the purpose of the application - an offshore converter platform for an HVDC line. Two candidates were chosen: a Single active bridge dc/dc converter and a Dual active bridge dc/dc converter. The both topologies are implemented in Simulink at 2 different operating frequencies: 2 kHz and 10 kHz. The power rating of the application is 2.7 MW. The input and the output voltages are 3.6 kV and 40 kV respectively. Because of the fact that the specificity of the application does not imply a constant power supply the converters are tested in terms that they should remain in the lossless switching range even when the input power is reduced. • The both converters have very high efficiency. The simulations have shown, that the DAB topology does not have any switching losses at all, neither in the transistors nor in the diodes. The primary side of the SAB topology operates without any switching losses in the transistors as well, though pretty high reverse recovery losses were observed in the rectifying stage. The converters performed very well with the reduced power supply and remained in the soft-switching region far below the 40 % of the nominal supply.