Implementation of carrier-based optimized centered PWM in three-phase three-level inverters

Carrier-based modulation is widely adopted since it offers some benefits compared to space-vector modulation in both two-level and multilevel inverters, such as inherent simplicity, flexibility, reduced computational times, and possibility of implementation on industrial DSPs. Among the numerous types of PWM techniques, the centered PWM (CPWM) is nearly optimal modulation, since it minimizes the RMS of output current harmonics. Despite of CPWM is easy to implement in two-level inverters, the complexity increases in case of three-level and multilevel inverters. In this paper a simplified straight procedure to implement carrier-based optimized CPWM for three-level inverter is presented, equivalent to centered space vector modulation. The proposed method has been implemented by numerical simulations, considering the comparison of resulting modulating signals with the other methods existing in literature and verifying the pulse centering in the output phase voltage waveforms.