Research On The Suppression Strategy Of Traction-network Harmonic And Dc-side Secondary Ripple In Double-system PETT

With the development of China’s the Belt and Road policy,China’s rail transit industry will be more connected with Europe and other countries to establish an interconnected railway line of the Eurasian railway network.There are differences in traction power supply systems in different regions,so it is necessary to develop an electric locomotive that can operate under multiple power supply systems.The continuous acceleration of high-speed railway also makes the traction drive system develop towards lightweight.The power transformer in the traditional traction drive system has a large volume and high manufacturing cost due to its low power density,which limits the further acceleration of high-speed railway.In view of this,this paper improves the traditional double-system electric locomotives traction drive system,introduces the power electronic traction transformer(PETT)to replace the original traction drive system,and analyzes the secondary ripple voltage problem caused by the inherent characteristics in the system.A comprehensive control method for power quality and secondary ripple voltage of PETT system is designed.This paper first introduces the topology of the traditional double-system electric locomotives traction drive system,presents a new cascaded PETT topology and its research status in detail.The cascaded PETT input and output stages are modeled separately.In order to efficiently and stably transmit power quality,the PETT input,isolation and output stage control strategies are designed accordingly.Then,the high dc-side secondary ripple voltage generated by the inherent characteristics of the PETT input stage affects the power quality of the traction network.In this paper,by introducing a signal delay filter(SDC)into the outer loop of the input stage voltage,the secondary ripple voltage of the high-voltage DC side is suppressed from flowing into the control system,and the harmonic po llution of the current on the traction network side is greatly reduced.By introducing internal mode control in the inner loop of the current,the dynamic response speed and antidisturbance performance of the control system are impro ved,and the coupling problem between the current inner loop and the voltage outer loop is solved,which greatly reduces the design difficulty of the controller.In order to verify the rationality and effectiveness of the proposed method,the simulation results of the PETT/Simulink are established.The simulation results show that the proposed method is effective.Finally,in order to further suppress the secondary ripple voltage of the high and low-voltage dc side,a coordinated control strategy for the secondary ripple voltage of the high and low-voltage dc side is proposed in the isolation stage;Depending on the coordinated control strategy,the secondary ripple power of the high-voltage dc-side is transmitted to the low-voltage dc side to compensates with the secondary ripple power generated in the output stage.the secondary ripple voltage of the high and low-voltage dc side will be ignificantly reduced.For the purpose of proving the effectiveness of the proposed low voltage dc-side secondary ripple voltage coordinated control strategy,in Matlab/Simulink Simulation verification was carried out and experimental verification was carri ed out on the RT-LAB experimental platform.The final simulation and experimental results prove that the proposed high and low voltage dc-side secondary ripple voltage coordinated control strategy is effective.