The Study Of Multi-mode Modulation Algorithm And Carrier Ratio Change Concussion Restrain

It is well recognized that pulse width modulators (PWM) inverters are the standard solution for AC motor drive. The final aim of PWM is to reduce harmonics and make the output waveform like sine wave as much as possible. To achieve this, lots of methods have been proposed.The inverter of railcar is special, compared with other AC motor drive. It must have very width speed-timing period and the output frequency changes fast, but the permit frequency of the inverter is not so high. In this condition, the multi-mode PWM modulation is used to decrease output waveform distortion and restrain harmonics. This paper pays attention on the utilization of multi-mode PWM modulation. To this mode, the quite important thing is to determine the jump discontinuities which divide the velocity period into several sections, and make sure the carrier ratio in every section is conformed and suitable for modulation. Also, the output voltage and current should be kept steady-going in the jump discontinuity. All of these will be analyzed theoretically in this paper. In addition, this paper also takes theoretical analyze on the improvement of the output voltage and return current by the multi-mode PWM modulation.Based on the strategy developed, the multi-mode PWM modulation for AC motor has been realized in an AC-DC-AC power conversion system. This paper also takes simulation in Matlab/Simulink as additional results of the experimentation. Simulation and experimental results are given to verify the validity of the proposed theoretical analyze.