Sinusoidal PWM techniques with additional zero-sequence harmonics

Different sinusoidal PWM methods with the addition of different zero-sequence harmonics are generally investigated and compared for both two and three level invertors. It is well known that these methods increase the region of the fundamental voltage component before overmodulation and decrease the harmonic motor losses: first of all for the high level of the fundamental voltage. For three-level invertors, the addition of zero sequence harmonics decrease the motor harmonics losses for dipolar (for low region of fundamental voltage) and increase it for unipolar (for higher region of fundamental voltage) modulations. In comparison with the loss-minimized PWM, the sinusoidal PWM techniques can be more simply realized but the motor harmonic losses are 10-30% higher