Suppression of Low-Frequency Oscillation in Traction Network of High-Speed Railway Based on Auto-Disturbance Rejection Control

The traction blockade in the depots of multiple electric multiple units (EMUs) is caused by the low-frequency oscillation (LFO) of high-speed railway traction network overvoltage. To suppress LFO, a strategy for optimizing the load characteristics of EMUs rectifier using the auto-disturbance rejection control (ADRC) is put forward. First, a first-order mathematical model is established to describe the characteristics of EMUs rectifier. Second, the nonlinear state observer and feedback control law are designed for state observation and disturbance estimation. By constructing a new nonlinear state-error feedback function, the ADRC is improved. This function’s convergence effect is better than the linear state-error feedback function, and it can solve the problem of the jitter problem of control force to some extent. Third, the outer-loop controller for pulsewidth modulation (PWM) rectifier voltage is designed. The improved ADRC can effectively deal with the contradiction between overshoot and rapidity. Its performance is better than the traditional proportional integral (PI) controller, which is applied in all of the EMUs at present. Finally, the full model of EMUs-traction network electrical coupling system (ETNECS) is constructed. Compared with multivariable controller, the simulation results show that the improved ADRC can ensure the ETNECS stability and suppress the LFO more efficiently.