Research on Beat Suppression Method in Full Speed Domain of Electric Multiple Units with Multi-mode Modulation
When the output frequency of traction inverter of EMU traction system is close to 100Hz,the torque of traction motor will generate low-frequency pulsation,that is beat frequency phenomenon.Therefore,the basic principle of pulsatile voltage generated by single-phase four-quadrant rectifier was described,and the influence of pulsating voltage on output torque was analyzed.Secondly,aiming at the problem of large modulation delay and real-time change of modulation delay in multi-mode modulation strategy of high-power inverter,a bandpass filter method was proposed to predict the pulsatile voltage.The cut-off frequency and amplitude compensation coefficient of the filter were adjusted in real time according to the current modulation delay which was calculated in real time by the current modulation strategy.Finally,the frequency compensation component was calculated by predicting the pulsatile voltage value and injected into the steady-state output frequency to achieve beat suppression in the full speed domain.The accuracy of pulsatile voltage prediction and the effectiveness of beat suppression were verified by simulation and experiment.
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