Comparative study of four kinds of multicarrier PWM strategies used in NPC three-level converters

In this paper, four kinds of multicarrier PWM strategies used in three-level converters which are called PD-PWM, POD-PWM, COPWM-A and COPWM-B are evaluated in three aspects: influence of the neutral point (NP) potential fluctuation, fundamental amplitude and THD performance of output waveform. The analysis shows that: 1) Comparing with PD-PWM and POD-PWM, CO-PWMA and CO-PWMB have smaller NP potential fluctuation, larger fundamental amplitude whereas worse THD performance, 2) Comparing with PD-PWM and CO-PWMA, POD-PWM and CO-PWMB have better phase voltage THD performance whereas worse line voltage THD performance. Experimental results prove the correctness of the analysis in this paper.