Soft-Switched BI-Directional Single-Stage AC-Dc Power Converters for g2v and v2g Mode of Operation



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State-of-the-art research on electric vehicle (EV) battery chargers puts increased emphasis on enhancing the power density and efficiency of the power conversion. The conventional EV battery chargers are developed with two cascaded power conversion stages. The first stage converts the AC voltage to a DC voltage employing power factor correction (PFC). The second stage is an isolated DC-DC converter stage. These two stages are interconnected by DC-link capacitors. This two-stage battery charger suffers from low overall efficiency due to two different power conversion stages. At the same time, power density is limited due to the inevitable presence of the intermediate DClink capacitors. Generally, high-value electrolytic capacitors are selected for the DClink. More importantly, the battery charger is placed close to the internal combustion engine under the hood in the case of plug-in hybrid EV (PHEV), where the ambient temperature is more than 150◦C. The electrolytic capacitors are most susceptible to failure at high ambient temperature, thus the reliability of the conventional two-stage EV battery charger is low in the high-temperature environment. This dissertation proposes a family of novel isolated single-stage bi-directional ACDC converter topologies with novel soft-switching modulation techniques for level 1 and level 3 EV battery charging application to address the shortcomings of the conventional two-stage battery chargers. The proposed converters achieve PFC and DC voltage regulation in one stage, thus provides higher efficiency. At the same time, the converter power density and reliability are also improved due to the elimination of intermediate DC-link capacitors. The operation of the proposed converters is demonstrated in the developed converter prototypes enabling grid to vehicle, and vehicle to grid mode of operation. In addition, this dissertation also proposes a novel low-cost high-temperature gate driver for the SiC MOSFETs. The proposed gate driver is used in the PHEV battery chargers, where the ambient temperature is more than 150◦C.



SiC MOSFET, EV Battery Charger, AC-DC Converter


Portions of this document appear in: Nayak, Parthasarathy, Kaushik Rajashekara, and Sumit Kumar Pramanick. "Soft-switched Modulation Technique for a Single Stage Matrix-type Isolated DC-AC Converter." IEEE Transactions on Industry Applications (2018). And in: Nayak, Parthasarathy, Sumit Kumar Pramanick, and Kaushik Rajashekara. "Isolated Single Stage AC-DC Converter Topologies with Regenerative Snubber Circuit for EV Application." In IECON 2018-44th Annual Conference of the IEEE Industrial Electronics Society, pp. 1285-1290. IEEE, 2018. And in: Nayak, Parthasarathy, Sumit Kumar Pramanick, and Kaushik Rajashekara. "A Soft-Switched PWM Technique for a Single Stage Isolated DC-AC Converter with Synchronous Rectification." In 2018 IEEE Energy Conversion Congress and Exposition (ECCE), pp. 6733-6738. IEEE, 2018.