Design of a SiC Based Variable Voltage Converter for Hybrid Electric Vehicle 2019-01-0605
Variable Voltage Converter (VVC) or generally called Boost Converter is adopted in Power-Split structure of hybrid electric vehicles (HEVs) to optimize the Electric-Drive (e-Drive) system design and improve system performance. The power semiconductor, usually the Silicon (Si) IGBT and diode as the key component, impacts the VVC and the whole vehicle performance.
The development of new type of semiconductor, Silicon Carbide (SiC) MOSFET, brings the new opportunities to VVC for further design optimization and performance improvement. First of all, SiC MOSFET has lower conduction loss (especially at low current range) and switching loss than traditional Si IGBT, leading to the loss reduction of TBD% at wide VVC power range. In addition, SiC MOSFET is expected to be operated at higher switching frequency due to its fast switching speed and low switching loss, which helps to increase VVC switching frequency without sacrificing efficiency. Higher switching frequency of VVC can reduce power inductor and capacitor size by TBD% and TBD%, respectively. With smaller size, the power inductor and capacitor weight and losses can be reduced as well. Third, the SiC MOSFET with 1200V voltage rating is intended for VVC with high output voltage (e.g. 600V or higher). Higher VVC boost voltage, which is the DC link voltage of three-phase Motor-Inverter and Generator-Inverter, reduces inverters power loss, because the inverter output current can be reduced for the same output power. In other word, high voltage rating of SiC MOSFET reduces e-Drive system power loss and can improve the whole vehicle fuel economy by TBD%.
This paper designs a VVC for HEV, based on commercial SiC MOSFET power modules. The hardware prototype is built and tested. The SiC based VVC is evaluated and the benefits of it on power loss, size, and weight (comparing to Si based VVC) are quantified.
Fan Xu, Baoming Ge, Lihua Chen, BORIS CURUVIJA
Ford Motor Co., Ltd., Ford Motor Co Ltd, Ford Motor Company