Low-Frequency Oscillation Suppression of the Vehicle–Grid System in High-Speed Railways Based on H∞ Control

Zhaozhao Geng,Xinxuan Hu,Zhigang Liu,Jing Liu

doi:10.3390/en11061594

Abstract

Recently, a traction blockade in the depots of numerous electric multiple units (EMUs) of high-speed railways has occured and resulted in some accidents in train operation. The traction blockade is caused by the low-frequency oscillation (LFO) of the vehicle–grid (EMUs–traction network) system. To suppress the LFO, a scheme of EMUs line-side converter based on the H∞ control is proposed in this paper. First, the mathematical model of the four-quadrant converter in EMUs is presented. Second, the state variables are determined and the weighting functions are selected. Then, an H∞ controller based on the dq coordinate is designed. Moreover, compared with the simulation results of traditional proportional integral (PI) control, auto-disturbance rejection control (ADRC) and multivariable control (MC) based on Matlab/Simulink and the RT-LAB platform, the simulation results of the proposed H∞ control confirm that the H∞ controller applied in EMUs of China Railway High-Speed 3 has better dynamic and static performances. Finally, a whole cascade system model of EMUs and a traction network is built, in which a reduced-order model of a traction network is adopted. The experimental results of multi-EMUs accessed in the traction network indicate that the H∞ controller has good suppression performance for the LFO of the vehicle–grid system. In addition, through the analysis of sensitivity of the H∞ controller and the traditional PI controller, it is indicated that the H∞ controller has better robustness.

Highlights

With the rapid development of high-speed railways during recent years, plenty of electric multiple units (EMUs) have been put into operation in passenger railways, interurban railways, and high-speed railways in China
The experiments based on off-line and real-time simulations are implemented and tested, and the control parameters based on the H∞ controller and the proportional integral (PI) controller are analyzed in this paper
The critical factor causing the low-frequency voltage oscillation (LFO) of EMUs–traction network in high-speed railway is the application of traditional PI controller

Summary

Introduction

With the rapid development of high-speed railways during recent years, plenty of electric multiple units (EMUs) have been put into operation in passenger railways, interurban railways, and high-speed railways in China. Because of the heavy operation of EMUs and electric locomotives, low-frequency voltage oscillation (LFO) problems happened worldwide. During 2009–2014, LFOs happened in the EMUs depots of Zhengzhou, Nanjing, Shenyang, and some other cities in China [1,2,3,4]. The LFOs cause some severe accidents, which affects EMUs safety and dispatch. The protection logic operation of the line-side converter of EMUs would be triggered due to the larger voltage oscillation amplitude of traction network, which results in traction blockades and makes the EMUs lose traction power [5]. Because of the severe threat to the safety of high-speed railway operation, these problems should be urgently solved

Methods

Discussion

Conclusion