High voltage electric vehicles : Benefits and challenges

Abstract

Electric vehicles have developed rapidly over the years, because they can reduce carbon emissions and slow down the impact of global warming. On the other hand, their higher energy efficiency and driving experience have also been favored by many consumers. The electric vehicles' (EV) energy efficiency improvement, performance, and the increase of the system voltage are the major interest of many automobile manufacturers, which can maintain or reduce the system current and increase the motor and charging power. In addition, it has a very positive effect on expanding the driving range and charging speed. Compared with the traditional 400V system, the 800V high-voltage system has been widely publicized and studied in recent years, but the specific performance of these two systems under different driving cycles is rare. This thesis aims to provide a comprehensive dynamic performance comparison between the 400V and 800V EVs system in terms of state of charge (SoC) saving, torque, maxim dc current needed, and charging power. This thesis adopts the mainstream commonly used PMSM motor and FOC control strategy, configures the basic architecture of electric vehicles, and compares its performance in different driving cycles under 400V and 800V systems by increasing the battery voltage, to verify the specific performance of 800V systems. The thesis findings verified that 800V systems has get better SoC savings comparing to 400V systems, especially during high acceleration speed driving scenarios, whereas the most prominent benefit is the DC current can be decreased significantly with energy efficiency improves. Results also shows the 800V charging system can nearly cut EV battery charging time in half when the current is equal with 400V systems. Challenges for implementing 800V system: infrastructure hinder, SiC semiconductor industrialize maturity, motor and battery technology improvement and future research directions have been concluded and discussed.