SPWM逆变器输出共模电压影响因素研究

Research on influential factors of output common mode voltage for SPWM inverter

针对SPWM逆变器在工作时会产生共模电压,共模电压诱发的轴电压、轴电流可能损坏电机轴承,产生电磁干扰等降低系统可靠性的问题。本文结合永磁同步电机调制波频率较大的特点,对SPWM逆变器供电下的共模电压频谱及影响因素进行了理论推导和分析,阐述了轴电压和轴电流的产生机理,结合相应的共模模型和计算所得的共模参数,在Matlab/Simulink中对其进行仿真,并分析了死区效应和调制波频率对共模电压的影响。结果表明无死区情况下,载波比对共模电压的影响可忽略不计;而载波频率一定,共模电压基波幅值和总幅值随着死区时间的增大显著增大,谐波含量明显减小;载波比和死区时间不变,调制波频率增大,共模电压基波幅值增大,谐波含量减小。上述结论为进一步研究永磁同步电机轴电流带来重要参考价值。

For the problem that SPWM inverter at working will generate common-mode voltage,common mode voltage induced shaft voltages and currents may damage the motor shaft bearings and produce electromagnetic interference.These problems will reduce system reliability.This thesis carried on a theoretical derivation of the common mode voltage spectrum and analyzed the factors that may affect the common-mode voltage combining the characteristics of the permanent magnet synchronous motor's high frequency of modulation wave,the model was simulated in Matlab/Siniulink combining the corresponding common-mode model and the parameters,analysed the influence of the dead zone effect and frequency of modulation wave on the common-mode voltage.The results show that in the absence of any dead zones,carrier ratio on the common mode voltage can be ignored.When the carrier frequency is a constant,common mode voltage amplitude and total amplitude increases significantly as the dead band time increases,harmonic content obviously decreased.The amplitude of common mode voltage will increase and harmonic content will reduce as modulation frequency increasing when the carrier ratio and dead band time are constant.These specific rule will bring important reference value for the further research of shaft currents of permanent magnet synchronous motor.