Method and system for controlling a power inverter in electric drives

A method for modifying a signal controlling a power inverter in an electric drive system, having a minimum pulse width and a maximum pulse width, of an automobile, the method comprising:

• utilizing a first voltage distortion compensation method to modify the signal if a modulation index of the signal is less than a first modulation index value, the first voltage distortion compensation method comprising:
• receiving the signal, a duty cycle of the signal having a range from a minimum achievable duty cycle to a maximum achievable duty cycle;
• producing a second signal if the duty cycle of the signal is within an output voltage distortion range outside of the minimum and maximum pulse widths and less than a first clipping value, the second signal having the minimum achievable duty cycle;
• producing a third signal if the duty cycle of the signal is within the output voltage distortion range and one of the duty cycle of the signal is at least equal to the first clipping value or the duty cycle of the signal is not greater than a second clipping value, the third signal having a closer one of the minimum and maximum pulse widths to the duty cycle of the signal, the second clipping value being greater than the first clipping value;
• producing a fourth signal if the duty cycle of the signal is within the output voltage distortion range and greater than the second clipping value, the fourth signal having the maximum achievable duty cycle;
• and
• transmitting one of the second, third, and fourth signals to the power inverter;
• and
• utilizing a second voltage distortion compensation method to modify the signal if the modulation index is at least equal to the first modulation index value, the second voltage distortion compensation method comprising:
• monitoring an output voltage vector of the power inverter, the power inverter having a switching cycle with a plurality of phase legs and a zero vector, the output voltage vector being based on the switching cycle of the power inverter;
• producing a modified switching cycle by modifying a duty cycle of each of the plurality of phase legs by a duty cycle of the zero vector when the output voltage vector is in a distortion region;
• and
• providing an output signal to the power inverter, the output signal having the modified switching cycle.

An automotive electric drive system comprising:

• an electric motor;
• a power inverter coupled to the motor;
• and
• at least one processor coupled to the electric motor and the inverter, the at least one processor being configured to:
• modify a signal controlling the power inverter utilizing a first voltage distortion compensation method if a modulation index of the signal is less than a first modulation index value;
• modify the signal utilizing a second voltage distortion compensation method if the modulation index is at least equal to the first modulation index value;
• modify the signal utilizing a third voltage distortion compensation method if the modulation index is at least equal to a second modulation index value, the second modulation index value being greater than the first modulation index value and a switching frequency of the power inverter is at a maximum value;
• and
• modify the signal utilizing the first voltage distortion compensation method if the modulation index is at least equal to the second modulation index value and the switching frequency of the power inverter is not at the maximum value.