Optimal modulation of harmonic and electromagnetic interference noise in three level NPC converter
2021
Zhen LI | Cheng JIANG | Bowen TIAN
In many high-power AC drives, with the increase of the switching frequency of the converter, the generated harmonic and electromagnetic interference(EMI) noise are getting higher and higher. Aiming at the serious problems of harmonics and EMI noise of three-level neutral-point-clamped(NPC)high-frequency converters, based on the space vector pulse width modulation (SVPWM) strategy, a random SVPWM method based on Markov chain was proposed. In this method, the random number generated by Markov chain could be applied to SVPWM strategy, so that the actual frequency change could be more randomly and evenly distributed on both sides of the theoretical switching frequency, with the output voltage harmonic noise of the actual system with also dispersed in a wide frequency band, and the EMI noise of the converter was also reduced. The simulation results show that the modulation strategy proposed in this paper has a significant improvement in the harmonic distribution compared with the traditional SVPWM strategy, and the conducted EMI noise is also reduced from 140 dB/μV to 120 dB/μV.
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