Linear and trapezoidal-inverted sub-cycle period VFPWM-based torque ripple reduction of interior PMSMs for electric vehicle applications

PWM techniques with a constant switching frequency can create distinct tonal bands in the harmonic spectrum of stator current of an AC machine. These tonal bands can negatively impact acoustic noise, vibrations, and electromagnetic interference. Reducing the magnitude of dominant harmonics by spreading the harmonic energy spectrum is one method to mitigate this problem. Harmonic energy is spread effectively using variable switching frequency PWM schemes. Another significant issue in AC drives for electric vehicles is the presence of ripples in the electromagnetic torque generated. The electromagnetic torque ripple is effectively reduced along with the spreading of harmonic energy, by the application of the suggested linear and trapezoidal-inverted variable switching frequency schemes. The effectiveness of the presented schemes are tested both below and above base speed, by using an interior type PMSM which is suitable for EV applications.