Study Of The Minimum-Loss PWM Algorithm For Three Phase Voltage Inverter

With the rapid development of green intelligent rail transits,it puts forward higher requirements on power density,output performance and conversion efficiency reliability of auxiliary converters,which ensure stable and comfortable running of rail trains.Based on the high-loss problems of three phase voltage source inverter in auxiliary converters,discontinuous pulse width modulation algorithms are studied and discussed.Furtherly,the correctness and feasibility of the research results are verified with simulations and prototype experiments.A modified generalized discontinuous pulse width modulation algorithm based on continuously adjustable zero-sequence component injection was proposed to decrease switching losses of the three phase voltage inverters in the high-frequency-isolation auxiliary converter.By adjusting the modulator phase angle,different 60° discontinuous PWM algorithms could be implemented and give linear smooth transitions.As a result,a comparative analysis of harmonic characteristics was carried out,and an optimized harmonic analysis method based on time-domain simulation which was further tested by the harmonic distortion factor,was proposed to determine the modulation index with superior harmonic performances.Based on the established loss models,a loss analysis method with the switching loss function and the dead-time effect was proposed,a minimum loss discontinuous PWM algorithm was given.In the overmodulation region,the voltage modulation gain and harmonic distortion were investigated to obtain the upper limit of the modulation index.Subsequently,the modulator was digitally implemented by DSP,and the correctness of the theories analysis and the feasibility of the normalization method were verified by the experimental results.