Research On The DC-link Voltage Ripple Rejection Of High Speed Train Traction System

In the electric traction system of high-speed train, a voltage ripple, with the frequency twice as high as that of AC supplied voltage, appears in the DC-link. Because the input power of the single phase four-quadrant rectifier contains the pulse power with 100Hz.The author compares the main circuit diagram of the current CRH in China and analyses the two different ways taking care of the voltage ripple in the DC-link. The reason that double frequency ripple voltage appears in the DC-link is given according to the balance of the power on the four-quadrant rectifier input and output sides. And the expression of the ripple voltage which is about the four-quadrant power and its main circuit parameters value is given too.This voltage ripple can have a degrading effect on the induction-machine performance characteristics. There should be some control methods to reject the voltage ripple. The author analyses the ripple voltage influence to the traction inverter's output voltage and to the motor's torque and current. There is some low-order harmonic wave that it contains the base order and the ripple's frequency's information in the motor's voltage, current and torque. According to the result of analysis two different control methods is researched on the rejection to the DC-link double frequency voltage ripple and they are used in the motor's two different circumstances. When the motor speed is at low speed the duty cycle can be corrected by changing the modulation wave's magnitude for the modulation ratio is high. And the duty cycle can be corrected by changing the modulation wave's frequency when the motor speed is high for the modulation ratio is low. Based on the PSIM simulation software the motor's vector control model is built and the two methods above are simulated by the model. The Myway platform's software and hardware are introduced in the thesis. And the experiments are done according the theory and the results and conclusion are given too. The results and conclusion indicate that the theory is right and usable.