Voltage generation with high modulation indices in inverter drives

A method for driving a load through a driving circuit including a plurality of switching devices, the method comprising:

• receiving a reference voltage signal indicating a target voltage to be generated by the driving circuit to drive the load, the reference voltage signal corresponding to a reference space vector in a reference frame in which a field flux linkage component and a torque component of the reference voltage signal are decoupled to orthogonal directions, wherein the reference space vector represents a combination of the decoupled field flux linkage component and the torque component of the reference voltage signal;
• determining that the reference space vector falls within a holding region in which the reference voltage signal is subject to over-modulation;
• determining a first holding angle and a second holding angle;
• when an angle of the reference voltage signal is smaller than the first holding angle, setting an angle of an adjusted reference angle to 0 degree;
• when the angle of the reference voltage is between the first holding angle and the second holding angle, setting the angle of the adjusted reference voltage equal to the angle of the reference voltage;
• when the angle of the reference voltage is between the second holding angle and 60 degrees, setting the angle of the adjusted reference voltage to 60 degrees;
• and
• providing the adjusted reference voltage signal to the plurality of switching devices to drive the load.

An electric motor propulsion system of an electric vehicle, the system comprising:

• an electric motor configured to output torque for propelling the electric vehicle;
• and
• a motor control system configured to control operations of the electric motor, wherein the motor control system includes a driving circuit including:
• a plurality of switching devices electrically connected to the electric motor;
• and
• a controller electrically connected to the plurality of switching devices, wherein the controller is configured to:
• receive a reference voltage signal indicating a target voltage for the driving circuit to generate to drive the electric motor, the reference voltage signal corresponding to a reference space vector in a reference frame in which a field flux linkage component and a torque component of the reference voltage signal are decoupled to orthogonal directions, wherein the reference space vector represents a combination of the decoupled field flux linkage component and the torque component of the reference voltage signal;
• determine that the reference space vector falls within a holding region in which the reference voltage signal is subject to over-modulation;
• determine a first holding angle and a second holding angle;
• when an angle of the reference voltage is smaller than the first holding angle, set an angle of an adjusted reference to 0 degree;
• when the angle of the reference voltage is between the first holding angle and the second holding angle, set the angle of an adjusted reference voltage equal to an angle of the reference voltage;
• when the angle of the reference voltage is between the second holding angle and 60 degrees, set the angle of an adjusted reference voltage to 60 degrees;
• and
• provide the adjusted reference voltage signal to the plurality of switching devices to drive the electric motor.