Optimal Interleaved Pulsewidth Modulation Considering Sampling Effects

Previous works on interleaved operation of switching power converters are based on the assumption that natural-sampling pulsewidth modulation (PWM) is used. Various interleaving strategies have been reported to minimize EMI filtering requirements, eliminate system resonance at certain frequencies, or minimize total harmonic current distortion through optimization of the interleaving phase shift angles. In a digitally controlled converter, the PWM reference is updated only at discrete sampling points, which is equivalent to using regularly sampled PWM. Harmonic cancellation effects among interleaved converters are affected by such regular sampling such that interleaving strategies optimized based on natural-sampling become non-optimal or suboptimal. This work first presents mathematically models that can be used to quantify the sampling effects on interleaved voltage-source converter harmonic behavior. The effects of different sampling methods are analyzed and compared using the models. Possible modifications to the interleaved carrier phase shift angles to compensate for the sampling effects are developed and demonstrated for different system optimization objectives including minimization of total harmonic distortion in dc-link or phase output currents.