Functional Safety Development of Bi-directional on-board charger for new energy vehicles 2020-01-0608
BOBC (Bi-directional on-board charger) is a power conversion system component for AC charging and discharging of new energy vehicles. It has two working modes: AC charging mode and AC discharge mode. In the two working modes, the BOBC belongs to both the controller and the actuator.
In some extreme cases such as communication and control failure of the AC charging mode, new energy vehicles have the risk of high-voltage battery overcharging and overtemperature, which will lead to high-voltage battery fire or even explosion. In the AC discharge mode, it involves the actual operation of the users on electricity, and the risk of short circuit and open circuit may happen in the process, which endangers the safety of the users. Based on the risks brought by the two working modes, it should pay more attention to the safety of the BOBC. ISO26262 provides the corresponding guiding analysis method and quantitative index for the hazard caused by the failure of automobile electronics and electrical appliances. It is necessary for BOBC to carry out functional safety design according to ISO26262.
This paper focuses on the functional safety development of the BOBC, including item definition, hazard analysis and risk assessment, functional safety requirements and technical safety requirements.
The boundary range, system functions and vehicle operating conditions of the BOBC will be described in item definition. They will be provided as input conditions for hazard analysis and risk assessment in the next step. During hazard analysis and risk assessment, functional safety goals and ASIL levels will be determined by identifying severity, exposure probability and controllability. The functional safety requirements will be determined according to the functional safety goals, and then the technical safety requirements according to the functional safety requirements.
Jian Liu, Wei Li, Jiwei Wen, Tianqiang Zhang, Deping Wang, Tao Jiang, Rui Jiang, Qi Sun