The Research On The Methods Of Suppressing The Ripplie Of DC-Link Voltage For The Middle Term Of Traction Conventer

In the development of modern high-speed railway, optimization of train itself(including cost reduction, weight reduction) has attracted more and more attention. And to achieve this optimization is also a necessary requirement for the further development of high-speed railway. While in the traditional traction converter system, the secondary harmonic filter of the DC side has disadvantages of bulky and heavy. Besides, the secondary ripple of DC-link voltage can be suppressed by adding in support capacitor and software control. For the reasons, eliminating the secondary harmonic filter will gain the future market. In this paper, combined with relevant technical data of CRH2, methods of suppressing secondary ripple of DC voltage after the cancellation of the second resonator filters were researched.The causes and factors about the secondary ripple of DC-link voltage are analyzed. And the ripple voltage’s influences to the ac side current of rectifie、inverter output voltage、the stator current and the motor torque are analyzed.The way about how to calculate the support capacitor is given and the different results about whether there is a secondary harmonic filter are analyzed. Then the suppression methods for the influence of the ripple of DC-linkvoltage both rectifier side and inverter side are analyzed based on the conventional technologies of converter control. The suppression methods of influence for rectifier system include the control method of dc voltage dynamic compensation and the control method of the dc voltage dynamic compensation mixing with low pass filter. The suppression medhods of influence for inverter system contain correcting the reference voltage vector amplitude via a real time DC-link voltage and changing the work frequency of inverter via ripple voltage. The simulation work of the mentioned methods has been done. And the results indicate that these mothods can achieve its desired suppressing effect.For the problem of suppressing the influence of the ripple of DC-link voltage in inverter system, a method of power compensation controlling was proposed. This method uses obtained secondary pulsating power to calculate compensating voltage ΔusM, ΔwsT and then uses ΔusM, ΔusT to compensate the command voltage usM, usT to suppress the influence of the ripple of DC voltage. Then the basic principle of this method is analyzed, and the implementation scheme is given. Finally, this method is demonstrated by simulating under Matlab/Simulink. The simulation results indicate that the proposed method can suppress the stator’s harmonic current which angular frequency is ω0±2ω.A simulation model of the traction converter unit is built in Matlab/ Simulink. Then the control method of mixed compensation in the rectifier side and power compensation in the inverter side, which are used to suppressing the influence of the secondary ripple of DC-link voltage, are both analyzed as well as the working conditions under traction condition and braking condition. The simulation results indicate that the third harmonic current of grid side has been suppressed as well as the the stator’s harmonic current which angular frequency isω±2ω.