Method and apparatus to operate a powertrain system including an electric machine having a disconnected high-voltage battery

A method for operating a powertrain system including an electric motor/generator, comprising:

• determining a first torque command for the electric motor/generator responsive to an operator torque request;
• determining a regenerative torque command for the electric motor/generator responsive to a commanded voltage across a high-voltage DC bus and a monitored voltage across the high-voltage DC bus;
• determining a speed-related torque command for the electric motor/generator responsive to a commanded rotational speed for the electric motor/generator;
• upon detecting a fault associated with a high-voltage DC electrical bus resulting in disconnection of the high-voltage DC electrical bus from a high-voltage energy storage system, operating the electric motor/generator in a fault tolerant electric generation mode comprising:
• employing low-voltage electrical power to energize the high-voltage DC electrical bus;
• adjusting control parameters to effect operation of the electric motor/generator in the fault-tolerant electric generation mode;
• imposing limitations on the regenerative torque command, said limitations comprising a first torque limit associated with torque generating capability of the electric motor/generator, a second torque associated with closed-loop power control and a third torque limit associated with closed-loop voltage control;
• operating an internal combustion engine to transfer torque to the electric motor/generator unit and to generate tractive torque output from the powertrain system;
• and
• operating the electric motor/generator in the fault-tolerant electric generation mode responsive to the regenerative torque command and the imposed limitations;
• else:
• operating the electric motor/generator responsive to the speed-related torque command in response to one of a commanded speed and a preferred speed profile and a measured rotational speed of the electric motor/generator when operating responsive to a command to control rotational speed of the electric motor/generator;
• or
• operating the electric motor/generator responsive to the first torque command.

A method for operating a powertrain system including an internal combustion engine and an electric machine, comprising:

• determining a first torque command for the electric machine responsive to an operator torque request;
• determining a regenerative torque command for the electric machine responsive to a commanded voltage across a high-voltage DC bus and a monitored voltage across the high-voltage DC bus;
• determining a speed-related torque command for the electric machine responsive to a commanded rotational speed for the electric machine;
• upon opening a high-voltage switch of a high-voltage DC electrical bus electrically connected between a power inverter module and the electric machine, operating the electric machine in a fault tolerant electric generation mode comprising:
• disabling gate drive pulses to an inverter electrically coupled to the electric machine;
• employing a low-voltage battery to energize a high-voltage bus capacitor of the high-voltage DC electrical bus;
• adjusting control parameters to operate the electric machine in a fault-tolerant electric generation mode, comprising determining a regenerative torque command comprising a commanded power divided by rotational speed of the electric motor/generator;
• starting the internal combustion engine to spin the electric machine;
• and
• upon the electric machine achieving a predetermined rotational speed:
• activating the inverter module;
• operating the electric machine in the fault-tolerant electric generation mode when the high-voltage bus capacitor achieves a predetermined voltage level responsive to the regenerative torque command;
• and
• controlling an auxiliary power module to electrically charge the low-voltage battery;
• else:
• operating the electric machine responsive to the speed-related torque command in response to one of a commanded speed and a preferred speed profile and a measured rotational speed of the electric machine when operating responsive to a command to control rotational speed of the electric machine;
• or
• operating the electric machine responsive to the first torque command.