Metodologia de otimização de conversores estáticos com paralelismo de células boost aplicado à célula a combustível

Abstract

This thesis presents an optimized design methodology for non-isolated static converters with Nboost cells in parallel, that process energy between a renewable energy source and a DC bus. The method scans for the best solution in view of the maximum efficiency for the minimum volume. It combines distinct technologies and cell numbers and picks a set of solutions in accordance to the preselected discrete parameters range for each operation point, which is described by three parameters ( IL@fs@J). It also searches in databases for the components in which the arrangement leads to the best performance regarding the design requirements. Among the possible solutions, the method chooses the solution that yields the maximum efficiency and/or the minimum volume for the continuous conduction mode as well as for the discontinuous conduction mode. Thus, it is possible to design converters with high efficiency and reduced volume for high static gain applications. This study also presents the components modeling and the converter static gain curves, considering parasitic resistances and their impact. By identifying the parameters that prevent converters, as simple as a boost converter, from achieving high static gain, it is possible to apply techniques that mitigate the impact of these undesired effects, allowing converters to operate closer to their ideal static gain. The input and output filter design of the converter reflects the dynamic behavior of a fuel cell, making it possible to reduce its volume and to increase its efficiency without hindering or damaging the power supply operation. As auxiliary tools to design a project and to understand the results, in this proposal, the behavior of the input and output currents and the impact that they produce on the output converter voltage are analyzed. By selecting the adequate number of cells and the operation mode, it is possible to find operation conditions where the current ripple is drastically reduced. As a result, the filtering capacitors can be significantly reduced and there is also the possibility of reducing the inductor size irrespective of the operation mode used.