Novel modulation techniques for DC-side commutated inverters

The author presents three novel modulation techniques for DC-side commutated inverters where the single commutation circuit is activated only once per switching period. The new techniques are modifications of the sinusoidal modulation with sawtooth carrier, space vector modulation and current-hysteresis modulation with constant switching frequency. The techniques are compared, with the traditional modulation with a triangle carrier by harmonic analysis, and the motor harmonic losses are calculated. Additionally a simplified method to compare modulation techniques based on the motor losses is presented, which requires less computation time than the traditional Fourier analysis