Research On Harmonic Resonance And Suppression Method Of Railway Traction Power Supply System

With the extensive uses of AC-DC-AC locomotive in electrified railway, the harmonic feature has great change in traction power supply system. The harmonic feature not only contains 3,5,7 inferior low-band harmonics generated by traditional AC-DC locomotive, but also contains high frequency band harmonics from AC-DC-AC locomotive. Research shows that the parameter of traction power supply system can result in harmonic resonance in corresponding inferior and cause over-voltage and over-current under certain situation. As a result of that affect the stability of the traction network and endanger the safety of traction network device. Thus, in this paper, harmonic analysis and suppression method is focused on railway traction power supply system.To begin with the harmonic source of traction power supply system, deep research and analysis was made towards the working principle and harmonic characteristics of AC-DC-AC locomotive grid-side converter. By analyzing the PWM wave of grid-side converter by double Fourier function, characteristic harmonic of grid-side can be get theoretically. And then utilize Matlab to set up converter model in order to get the characteristic harmonic frequency from normal AC-DC-AC locomotive.Secondly, research is carried out on the harmonic transmission path to analyze the harmonic transmission characteristics of traction power supply system. Based on the existing research, we can reduce the order of traction network transmission model and get a traction power supply system equivalent circuit model. By the use of circuit KCL, KVL theorem and uniform transmission line theory, we can analyze the harmonic transmission characteristics of traction power supply system and finally get the resonance frequency and harmonic current gain of traction power supply system.Furthermore, based on the harmonic suppression method that install a passive power filter in locomotive traction transformer auxiliary winding, we proposed a new design towards passive power filter. We get a comprehensive selection of filter through comparing the working theory and characters of single-tuned filter, high-pass filter and double-tuned filter and analyzing the influence of each filter element parameter towards the performance of the filter.Finally, a filter validation method was proposed through setting up locomotive-network simulation system model. Through this model, we compared the performance of locomotive-network simulation system with the one without filter, and the ones that installed single-tuned filter, high-pass filter and double-tuned filter. The parameters were optimized according to design method. The rationality of using passive power filter in locomotive design was validated through this paper.