Harmonic imbalance in asynchronous PWM schemes

The harmonic content, both integral and non-integral, of an asynchronous three-phase PWM scheme is analyzed. The effects of both quantization and blanking time are included. It has been shown that in a three-phase inverter with asynchronous modulation the nonintegral harmonic line currents produced form unbalanced sets. The percentage imbalance for a particular order is a function of the harmonic order only. For practical frequency ratios, the absolute amplitude of the current imbalance is small due to the small amplitude of the nonintegral components.<
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