Patent ID: 11970072
Assignee: GM GLOBAL TECHNOLOGY OPERATIONS LLC
Field: Transport (Mechanical engineering)
Classification: CPC B  H | IPC B  H

Claim 18:
19. A method of operating a vehicle electrical system comprising:
providing a rechargeable energy storage system (RESS) having a first voltage;
providing a power inverter electrically connected to the RESS;
providing an electric motor having a plurality of machine windings with each of the machine windings including a polyphase terminal electrically connected to the power inverter, and the electric motor further having a neutral terminal separate from the polyphase terminals;
providing an accessory load selectively connected to one of the RESS and the neutral terminal of the electric motor; and
providing a controller electrically connected to the power inverter and configured to transmit a plurality of control signals to the power inverter in response to the controller receiving a command for a buck operation;
providing a first accessory load switch disposed between the neutral terminal of the electric motor and the accessory load;
providing a second accessory load switch disposed between the RESS and the accessory load, wherein the power inverter includes semiconductor switches S1, S3, and S5 each disposed between the RESS and a corresponding one of the polyphase terminals, and includes semiconductor switches S2, S4, and S6 each connected between the accessory load and a corresponding one of the polyphase terminals, wherein the semiconductor switches S1-S6 cooperatively convert direct current (DC) power from the RESS to alternating current (AC) power for powering the electric motor via high-frequency switching;
generating, using the controller, a plurality of control signals in response to the controller receiving a command for a buck operation;
cycling the power inverter between a first operational state, a second operational state, and a third operational state in response to the power inverter receiving the control signals from the controller,
wherein when in the first operational state, the power inverter connects the RESS to the plurality of machine windings of the electric motor such that current flows from the RESS through the polyphase terminals to the accessory load via closing the first accessory load switch, opening the second accessory load switch, closing one of the semiconductor switches S1, S3, and S5 and opening the remaining semiconductor switches S1-S6;
wherein when in the second operational state, the power inverter disconnects the RESS from the plurality of machine windings of the electric motor and interrupts current to the machine windings, such that the power inverter steps down the first voltage of the RESS to the second voltage of the accessory load, via closing the first accessory load switch, opening the second accessory load switch, opening the semiconductor switches S1, S3, and S5 to disconnect the RESS from the polyphase terminals, and closing one or more of the remaining semiconductor switches S2, S4, and S6 to allow current to flow from one or more of the polyphase terminals to the accessory load; and
wherein when in the third operational state, the RESS directly charges the accessory load without stepping down the voltage via opening the first accessory load switch and closing the second accessory load switch.