Method and system for controlling pulse width modulation in a power inverter in electric drives

A method for controlling a power inverter coupled to an electric motor in an electric drive system of an automobile, where the electric motor comprises a sinusoidally-wound alternating current (AC) motor, the method comprising:

• responsive to either a commanded torque of the electric motor being above a first torque level, or a commanded speed of the electric motor being above a first speed level, controlling the power inverter with a discontinuous pulse width modulated (DPWM) signal to generate a modulated voltage waveform for driving the electric motor;
• responsive to both a commanded torque of the electric motor being below the first torque level but not substantially zero, and a commanded speed of the electric motor being below the first speed level but not substantially zero, controlling the power inverter with a continuous pulse width modulated (CPWM) signal to generate the modulated voltage waveform for driving the electric motor;
• and
• responsive to both a commanded torque of the electric motor being less than 1% of rated torque for the electric motor, and a commanded speed of the electric motor being less than 1% of rated speed for the electric motor, controlling the power inverter with the DPWM signal to generate the modulated voltage waveform for driving the electric motor.

An automotive electric drive system comprising:

• an electric motor;
• a power inverter coupled to the electric motor;
• and
• at least one processor coupled to the electric motor and the inverter, the at least one processor being configured to:
• responsive to either a commanded torque of the electric motor being above a first torque level, or a commanded speed of the electric motor being above a first speed level, controlling the power inverter with a discontinuous pulse width modulated (DPWM) signal to generate a modulated voltage waveform for driving the electric motor;
• and
• responsive to both a commanded torque of the electric motor being below the first torque level, and a commanded speed of the electric motor being below the first speed level, controlling the power inverter with a continuous pulse width modulated (CPWM) signal to generate the modulated voltage waveform for driving the electric motor.