The significance of zero space vector placement for carrier based PWM schemes

Pulse width modulation has been one of the most intensively investigated areas of power electronics for many years, and the number and combination of permutations seem to be endless. However, a general hierarchial consensus appears to have emerged from this work which ranks space vector modulation techniques, regular sampled modulation and sine-triangle modulation strategies in decreasing order of merit based on harmonic performance. However, what has not been clearly identified is why space vector modulation should lead to a reduced harmonic current ripple compared to regular sampled modulation, especially since it is straightforward to show that they produce identical low frequency fundamental components. This paper addresses this issue, by showing how it is the placement of the zero space vector component within the carrier interval that determines the harmonic performance of the modulation strategy, rather than any intrinsic differences between the various methods of calculating the switching instances.