| Summary: | As waste heat recovering techniques, especially thermoelectric generator (TEG technologies, develop during recent years，its utilization in automotive industry is attempted from many aspects. Previous research shows that TEG as a waste heat harvesting method is feasible. Even though efficiencies for TEGs are as low as 3-5% with existing technology, useful electricity generation is possible due to the great amount of waste heat emitted from the internal combustion engine operation. This thesis proposes the innovative concept of thermoelectric-generator-based DC-DC conversion network. The proposed structure is a distributed multi-section multi-stage network. The target is to tackle problems facing the traditional single-stage system and to advance TEG application in automotive settings. The objectives of the project consists of providing optimal solution for the DC-DC converter utilized in the network, as well as developing a systematic and bottom-up design approach for the proposed network. The main problems of the DC-DC converters utilized in the TEG system are presented and analyzed, with solution to dynamic impedance matching suggested. First, theoretically-possible approaches to balance the large TEG internal resistance and small converter input resistance are discussed, and their limitations are presented. Then, a maximum power point tracking (MPPT) regulation model is developed to address the temperature-sensitive issue of converters. The model is integrated into a TEG-converter system and simulated under Simulink/Simscape environment, verifying the merits of MPPT regulation mechanism. With the developed model, MPPT matching efficiency over 99% is achieved within the hot side temperature range of 200°C ~300°C. A design flow is suggested for the proposed network. Analysis is conducted regarding aspects of the design flow. Several state-of-the-art thermoelectric materials are analyzed for the purpose of power generation at each waste heat harvesting location on a vehicle. Optimal materials and TE couple configurations are suggested. Besides, a comparison of prevailing DC-DC conversion techniques was made with respect to applications at each conversion level within the network. Furthermore, higher level design considerations are discussed according to system specifications. Finally, a case study is performed comparing the performances of the proposed network and traditional single-stage system. The results show that the proposed network enhances the system conversion efficiency by up to 400% in the context of the studied case.
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