Alternating current battery heating in electrical system having multiple electric motors

A method for performing alternating current (AC) heating of a battery pack in a multi-motor electrical system having a plurality of inverter circuits connected to the battery pack and a plurality of electric motors connected to the battery pack via a corresponding one of the inverter circuits, the method comprising:

• in response to predetermined entry conditions:
• monitoring respective motor temperatures of the electric motors via an electronic controller;
• selectively injecting respective direct-axis (d-axis) currents into the electric motors via manipulation by the electronic controller of a corresponding d-axis voltage command thereto;
• generating an alternating current (AC) battery current via simultaneous operation of the electric motors using the d-axis currents;
• and
• heating the battery pack using the AC battery current by coordinating an injection of the d-axis currents, such that the respective motor temperatures do not exceed a predetermined motor temperature limit, wherein the predetermined entry conditions include a battery temperature of the battery pack being less than a minimum charging temperature prior to or in conjunction with initiating a charging event of the battery pack.

A motor vehicle comprising:

• a vehicle body;
• road wheels connected to the vehicle body;
• and
• a multi-motor electrical system including:
• a traction battery pack having a battery temperature;
• a plurality of inverter circuits connected to the traction battery pack;
• a plurality of electric traction motors connected to the traction battery pack via a corresponding one of the inverter circuits, and to one or more of the road wheels;
• and
• an electronic controller in communication with the inverter circuits, the electronic controller being configured, in response to predetermined entry conditions including the battery temperature being less than a minimum charging temperature prior to or in conjunction with initiating a charging event of the traction battery pack, to:
• monitor respective motor temperatures of the electric traction motors;
• selectively inject respective direct-axis (d-axis) currents into the electric traction motors via manipulation of a corresponding d-axis voltage command thereto;
• generate an alternating current (AC) battery current via simultaneous operation of the electric motors using the d-axis currents;
• and
• heat the traction battery pack using the AC battery current by coordinating an injection of the d-axis currents, such that the respective motor temperatures do not exceed a predetermined motor temperature limit, including alternating operation of the electric traction motors responsive to a motor temperature one of the electric traction motors reaching the predetermined motor temperature limit.