Phase-shift selective harmonic elimination pulse width modulation for multilevel converter

This paper propose a phase-shift selective harmonic elimination pulse width modulation(PS-SHEPWM) strategy for multilevel converter. Firstly, the two level SHEPWM (Selective Harmonic Eliminated Pulse Width Modulation) equations are solved by using the groebner bases method, and a group of harmonics will be eliminated from the resultant two level PWM waveform; then shift the waveform with a specific phase and add it to the original waveform. In the resultant three level waveform, one extra harmonic will be eliminated and the other harmonics will be suppressed; repeat this phase-shift and waveform adding procedure until all the expected harmonics are eliminated; finally, a multilevel PWM waveform are obtained which can be used to control the multilevel converter. Simulation results verify the validity and ease of implementation of this modulation method. The computation burden to eliminate the same number harmonics of this method is much less than the traditional SHEPWM, and it discards the need to choose initial value in solving the SHEPWM equations whereas almost all the other methods need to do and all the solutions can be found by this method.