Effects of Current Ripple on Dead-Time Analysis of Three-Phase Inverters

Inverter dead-time distortion in output voltages have been widely investigated in the past for three-phase PWM voltage source inverters. Also, there have been some studies about multi-phase inverters with reference to multi-phase drives. Usually, almost sinusoidal output currents are considered, with a single zero crossing for every half fundamental period. High output current ripple introduces multiple zero crossing, leading to modified output voltage distortions. In this paper the effect of the output current ripple has been taken into account, in the case of carrier-based PWM techniques when no any dead-time compensation technique is applied. In particular, the harmonic spectrum of the output voltage distortion has been evaluated on the basis of the multiple zero crossing time interval of output currents. In case of relevant current ripple it is verified a relevant deviation of output voltage harmonics in comparison to the case of almost sinusoidal currents. Theoretical analysis has shown that particular low-order harmonics are affected by the current ripple amplitude, and simulation results confirm the developed analytical approach.