Method and apparatus for controlling a high-voltage battery connection for hybrid powertrain system

Method for operating a hybrid powertrain system including an engine and first and second torque machines coupled to a transmission device to transfer torque to a driveline and a high-voltage electric circuit including a high-voltage battery, a DC link coupled to first and second inverters electrically connected to the first and second torque machines, and a switch configured to interrupt electric power flow between the high-voltage battery and the first and second inverters when controlled to an open state, the method comprising:

• commanding a motor torque output from the second torque machine in response to an operator torque request;
• determining a preferred DC link voltage to achieve the commanded motor torque output from the second torque machine;
• and
• controlling the switch to selectively interrupt the electric power flow between the high-voltage battery and the first and second inverters to achieve the preferred DC link voltage.

A hybrid powertrain system, comprising

• an engine and first and second torque machines coupled to a transmission to transfer torque to a driveline;
• a high-voltage electric circuit comprising a high-voltage battery, an inverter module, and a switch, the high-voltage battery electrically connected via a DC link to the inverter module, the inverter module electrically operatively connected to the first and second torque machines, and the switch configured to interrupt electric power flow between the high-voltage battery and the inverter module when controlled to an open state;
• and
• a controller monitoring voltage of the high-voltage battery and a voltage across the DC link, determining a preferred voltage across the DC link, controlling the switch to interrupt electric power flow between the high-voltage battery and the inverter module in response to the voltage of the high-voltage battery, the voltage across the DC link, and the preferred voltage across the DC link.