Silisyum Karbür Güç Yarı İletkenlerine Dayalı Yüksek Verimli Da-Da Çevirgeç Uygulamaları

Abstract

In this thesis, high efficiency DC-DC converters have been implemented for two different application areas using new generation Silicon Carbide (SiC) power semiconductors. In this context, A 20 kW, 20 kHz high frequency (HF) link maximum power point tracking (MPPT) converter for a grid-connected PV supply, based on all silicon carbide (SiC) power semiconductors, is presented as the first application. In the developed converter, SiC power MOSFETs are used in the low-voltage PV panel side and SiC Schottky diodes on the high voltage DC output, in order to maximize the power conversion efficiency and the power density. Operating principles of the resulting dual H-bridge MPPT converter and the practical aspects of the converter design and its circuit layout, are described in detail. The implemented converter performance is compared with that of a classical Si-IGBT and hybrid-IGBT based MPPT converter in terms of efficiency. This configuration can compete with the non-isolated MPPT converter topologies, such as the boost converter commonly used in grid-connected PV systems. This is due to the enhanced common-mode EMI performance as compared to non-isolated MPPT topologies, resulting in a competitive high efficiency PV converter design with galvanic isolation. It has been shown that the converter size can be shrinked up to a power density of 1.6 kW/lt, with a DC-DC converter full-load efficiency of 98%. The resulting compact and highly efficient SiC power MOSFET based HF link MPPT converter is suggested to be a part of grid-connected, multi-string PV supplies with simple inverter topologies in the future.

In the second part of the thesis, the design and implementation of a generalized dual-active bridge (DAB) converter for use in either 700 V / 28 V, 11.2 kW electric bus charger applications, or 400 V / 14 V, 3.7 kW electric vehicle applications is presented. The DAB converter is implemented by SiC power MOSFETs on the high voltage (HV) side, and coolMOS switches on the low voltage (LV) side. Interleaved operation of two such DAB converters can be configured for 2 x 5.6 kW rated power operation. Operating principles and control of the implemented DAB converter are assessed and the corresponding operating modes of are discussed. The operating performance of the developed DAB converter, such as the switching characteristics of SiC power MOSFET modules, voltage and current waveforms and operating efficiency have been assessed for various operating conditions both by computer simulations and laboratory tests. Nanocrystalline core based high frequency AC inductor design have been discussed for a 1 kW/l converter power density. Excellent performance results for 50 kHz switching frequency have been obtained from the developed 5.6 kW DAB converter, with operating efficiencies measured as 97% at full-load, and 98% at half-load.