I. Introduction
With the development of human society, the automobile has become an indispensable means of transportation. It is a small, fast, independent driving, and therefore popular. However, with the widespread use of traditional cars, environmental problems have also become prominent. The data show that excessive carbon dioxide emissions are the main cause of global warming, with 25% of emissions coming from automobile exhaust. Therefore, the adoption of more environmentally friendly energy as a vehicle power has become an inescapable responsibility. To this end, governments and enterprises will be the future direction of automotive development in energy saving and emission reduction, electric vehicles emerged[1].