Patent ID: 8860348

Claim:
Method for operating a hybrid powertrain system including a high-voltage electric circuit comprising a high-voltage battery electrically connected to a high-voltage bus including first and second sides, and a DC link including first and second DC link rails coupled to first and second inverters electrically connected to first and second torque machines, the method comprising: receiving a motor torque command for the second torque machine; determining a preferred DC link voltage set for achieving the motor torque commanded from the second torque machine; and when the preferred DC link voltage is greater than an output voltage of the high-voltage battery: selectively decoupling the high-voltage battery and the DC link using a switch device comprising at least one pair of switch elements connected in parallel, wherein no electrical power flows between the high-voltage battery and the DC link when the high-voltage battery and the DC link are decoupled, and driving voltage of the DC link to achieve the preferred DC link voltage with voltage solely provided from the first inverter to the second inverter while the high-voltage battery and the DC link are decoupled, the voltage provided from the first inverter is generated using mechanical power transferred from an engine to the first torque machine independent of the output voltage of the high-voltage battery; wherein the switch device is placed between the first side of the high-voltage bus and the first DC link rail while the second side of the high-voltage bus is always directly coupled to the second DC link rail, the high-voltage battery and the DC link selectively decoupled by controlling the switch device to decouple the first side of the high-voltage bus from the first DC link rail; wherein the first side of the high-voltage bus and the first DC link rail both comprise one of a positive polarity and a negative polarity and the second side of the high-voltage bus and the second DC link rail both comprise the other one of the positive polarity and the negative polarity.