Vehicle electric machine control strategy

摘要

A vehicle having a traction battery and at least one electric machine for propelling the vehicle is provided. A high voltage DC bus electrically connects the traction battery to the electric machine. A controller monitors and commands power flow through the DC bus, the electric machine, and the battery. In response to a key-off event, the controller immediately discharges the DC bus by providing a current to the electric machines. This discharge continues until the voltage on the DC bus reaches a threshold. As the speed of the electric machine decreases towards a speed threshold, the voltage in the DC bus is maintained. Once the electric machine speed reduces past the threshold, the DC bus discharges the remaining voltage in the DC bus at a rate slower than the first immediate discharge.

主权项

1. A method of controlling voltage on a bus comprising:
discharging the bus at a first rate, while a speed of an electric machine electrically connected with the bus exceeds a threshold speed, until a voltage on the bus achieves a threshold voltage; in response to the voltage achieving the threshold voltage, maintaining the voltage at the threshold voltage while the speed decreases to the threshold speed; and in response to the speed achieving the threshold speed, discharging the bus at a second rate less than the first rate such that energy dissipated during bus discharge is greater than energy released by the electric machine during speed reduction to prevent the voltage from exceeding the threshold voltage.