Novel carrier phase-shifted SPWM for cascade multilevel converter

A novel carrier phase-shifted sine pulse width modulation (SPWM) strategy was proposed in this paper by introducing unipolar SPWM into cascade multilevel converters. The amount of pulse width modulation (PWM) pulse generators of the proposed modulation strategy is only the half of that of the traditional modulation strategy, which is of significant theoretical and practical value for the digital implementation of cascade multilevel converter. The two modes of novel carrier phase-shifted SPWM were given. The frequency domain modulated model of both modes was deduced. The harmonics feature of both modes was analyzed and compared, which is verified through simulation. Simulation result includes that both modes are equivalent for single phase system, and mode 2 is better than mode 1 at harmonic feature for three phase system. The thermal stability of novel carrier phase-shifted SPWM was analyzed and settled by an easy scheme. Experimental results proved the correctness of theoretical analyses and simulation research. © 2010 Chinese Society for Electrical Engineering.