A Novel Approach Based on Extended State Observer Sliding Mode Control to Suppress Voltage Low Frequency Oscillation of Traction Network

Aiming at the phenomenon of traction blockades due to the low-frequency oscillation (LFO) in electrified railways, a control strategy of electric multiple units (EMUs) traction line-side converter (LSC), based on the extended state observer (ESO) sliding mode control (SMC) is proposed in this paper. First, the mathematical model of EMUs LSC in the d-q frame is deduced. Then, the principles and design processes of the proposed control strategy are analyzed in detail, including the combination of the outer loop voltage sliding mode with ESO and the control law of the inner loop. Moreover, the simulation model of doubly redundant LSC of EMUs is built in MATLAB/Simulink. The simulation results are compared with the traditional linear proportional integral (PI) control and the basic SMC. It is shown that the proposed ESO + SMC control strategy has better dynamic and static characteristics. Finally, the simulation model of multiple EMUs connected to vehicle-grid coupling systems is built, and an integrated dSPACE semi-physical experimental platform consisting of eight EMUs and an equivalent traction network is constructed to further verify the suppressing effect of LFO. The experimental results show that, the proposed ESO + SMC can effectively suppress the LFO.