Modellistica e progettazione di convertitori elettronici di potenza DC-DC

The present PhD dissertation deals with average modeling, design and experimental verification of power electronic converters. This takes the DC-DC Boost converter as a reference, together with some converter topologies derived from it, such as the interleaved PFC Boost converter. More specifically, in the first part of the dissertation DC-DC converters fundamentals are briefly introduced, i.e. their operating mode, their basic circuit topologies and their parallel and series connections, as well as the basic problems inherent to the design stage of DC-DC converters. Subsequently, this PhD dissertation focuses on the mathematical modeling of the Boost DC-DC converter by means of the averaging technique. In particular, appropriate equivalent switching signals are introduced in order to take into account each converter operating state properly, together with the switch commutation phenomena. In addition, a suitable inductor model is introduced in order to improve inductor losses estimation. As a result, the proposed averaged models are dependent on the switching frequency, still preserving a ripple-free representation of the state variables of the system. The proposed averaged modelling approach enables an enhanced power losses estimation by accounting for switching and current ripple phenomena, over both Continuous Conduction Mode (CCM) and Discontinuous Conduction Mode (DCM). The worth and effectiveness of the proposed modelling approach has been validated through several simulation studies, which are performed in the Matlab-Simulink and SIMetrix/SIMPLIS environments. The last part of this thesis the Boost PFC converters and new silicon carbide power devices, already available in the market, is provided. In particular, with a constant increase of the switching frequencies and the converters power density, new and most efficient solutions are required, for both circuit topologies and power semiconductors. In this context is presented an extensive experimental analysis of a two-phase Interleaved PFC Boost converter. It aims to highlight the most important features of two-phase interleaved PFC converter operation, in terms of both performances and electromagnetic compatibility issues. This has revealed a low level of harmonic pollution and an excellent result in terms of efficiency at rated load, but also potential conducted EMI issues within low and medium frequency ranges. Efficiencies, switching frequencies and operating temperatures, even in these circuit topologies, are strongly dependent on the power electronics devices used. For this reason it has been dealt an experimental study on the silicon carbide semiconductors. Experimental results are finally reported and discussed; they shown that the reduced power dissipation and the low impact of the parasitic elements, that characterize such semiconductor devices, make these components an interesting solution in the realization of compact and highly efficient energy conversion systems

Modellistica e progettazione di convertitori elettronici di potenza DC-DC

The present PhD dissertation deals with average modeling, design and experimental verification of power electronic converters. This takes the DC-DC Boost converter as a reference, together with some converter topologies derived from it, such as the interleaved PFC Boost converter. More specifically, in the first part of the dissertation DC-DC converters fundamentals are briefly introduced, i.e. their operating mode, their basic circuit topologies and their parallel and series connections, as well as the basic problems inherent to the design stage of DC-DC converters. Subsequently, this PhD dissertation focuses on the mathematical modeling of the Boost DC-DC converter by means of the averaging technique. In particular, appropriate equivalent switching signals are introduced in order to take into account each converter operating state properly, together with the switch commutation phenomena. In addition, a suitable inductor model is introduced in order to improve inductor losses estimation. As a result, the proposed averaged models are dependent on the switching frequency, still preserving a ripple-free representation of the state variables of the system. The proposed averaged modelling approach enables an enhanced power losses estimation by accounting for switching and current ripple phenomena, over both Continuous Conduction Mode (CCM) and Discontinuous Conduction Mode (DCM). The worth and effectiveness of the proposed modelling approach has been validated through several simulation studies, which are performed in the Matlab-Simulink and SIMetrix/SIMPLIS environments. The last part of this thesis the Boost PFC converters and new silicon carbide power devices, already available in the market, is provided. In particular, with a constant increase of the switching frequencies and the converters power density, new and most efficient solutions are required, for both circuit topologies and power semiconductors. In this context is presented an extensive experimental analysis of a two-phase Interleaved PFC Boost converter. It aims to highlight the most important features of two-phase interleaved PFC converter operation, in terms of both performances and electromagnetic compatibility issues. This has revealed a low level of harmonic pollution and an excellent result in terms of efficiency at rated load, but also potential conducted EMI issues within low and medium frequency ranges. Efficiencies, switching frequencies and operating temperatures, even in these circuit topologies, are strongly dependent on the power electronics devices used. For this reason it has been dealt an experimental study on the silicon carbide semiconductors. Experimental results are finally reported and discussed; they shown that the reduced power dissipation and the low impact of the parasitic elements, that characterize such semiconductor devices, make these components an interesting solution in the realization of compact and highly efficient energy conversion systems