三电平NPC变换器谐波与电磁干扰噪声优化调制

Optimal modulation of harmonic and electromagnetic interference noise in three level NPC converter

在许多大功率交流传动场合,随着变换器开关频率的提高,所产生的谐波和电磁干扰(electromagnetic interference,EMI)噪声也越来越高。针对三电平中点钳位(neutral-point-clamped,NPC)高频变换器谐波和EMI噪声严重的问题,在空间矢量脉冲宽度调制(space vector pulse width modulation,SVPWM)策略基础上,提出了一种基于Markov链的随机SVPWM方法。该方法将Markov链产生的随机数应用于SVPWM策略中,使实际频率变化更加随机均匀的分布在理论开关频率两侧,实际系统的输出线电压谐波噪声也分散在一个较宽的频段上,同时也降低了变换器的EMI噪声。仿真结果表明:提出的调制策略相比传统SVPWM策略在谐波分布上有明显的改善,传导EMI噪声也从140 dB/μV降为120 dB/μV。

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.