Low Frequency Oscillation Suppression Method Of High-Speed Railway Traction Network Based On Passivity-Based Control

With the rapid development of high-speed railways in recent years,large quantities of electric multiple units(EMUs)and electric locomotives have been put into operation in the inter-city railways,passenger dedicated lines and speed-up lines,which makes the EMUs-traction network cascade system(ETNCS)more complex.Due to the heavy operation of EMUs and electric locomotives,some voltage low frequency oscillation(LFO)events have occurred worldwide,which results in traction blockade accidents and obstructs the normal operation of high-speed railways.As a possible solution,two passivity-based control strategies based on the Port Controlled Hamiltonian with Dissipation(PCHD)and the Euler-Lagrange(EL)for the single-phase EMUs rectifier are proposed in this paper.First,the Interconnection and Damping Assignment Passivity-Based Control(IDA-PBC)is proposed for the nonlinear characteristic of the single-phase EMUs rectifier.The PCHD mathematical model of the single-phase EMUs rectifier is constructed based on the equivalent circuit and the Generalized State Space Averaging(GSSA)of the rectifier.With the interconnect matrix and damping matrix,the new energy function can be minimized at the equilibrium point of the system,which enables the derivation of the rectifier control law based on the IDA-PBC.The simulation results verify that the IDA-PBC controller has better dynamic and static performance than the traditional proportional integral(PI)controller and it significantly suppresses the LFO of the ETNCS.Furthermore,the LFO signal modal analysis is performed using the fast Fourier transform(FFT)and the estimating signal parameters via the rotational invariance techniques(ESPRIT),which indicates that IDA-PBC can suppress the symmetrical frequency components and effectively reduce the 3rd,5th and other harmonic components compared with the PI control in EMUs.Second,the improved passivity-based control(PBC)strategy is proposed to better suppress the LFO of ETNCS.For the single-phase EMUs rectifier,the EL mathematical model in dq frame is built,which can realize the decoupled of active and reactive power.The equilibrium point of the system is obtained according to the control target of rectifier,and the energy error function of the system is designed on this basis.Using the deduced EL mathematical model and passivity of the rectifier,the improved PBC controller of single-phase EMUs rectifier is designed by the damping injecting method.Compared with the traditional dq current controller and the IDA-PBC controller,the simulation results show that the improved PBC controller not only has better performance,but also has the better suppression effect on LFO and has strong robustness.Last but not least,the RT-LAB all-digital real-time simulation platform and dSPACE semi-physical platform are built to verify the suppression performance of the proposed methods for the LFO.On these platforms,the LFO of ETNCS is successfully reproduced and the effectiveness of the proposed methods for LFO suppression are verified.In addition,the experimental results demonstrate the improved PBC method has better suppression effect.