An Approach to Suppress Low Frequency Oscillation in the Traction Network of High-Speed Railway Using Passivity-Based Control

The traction blockade in depots of multiple electric multiple units (EMUs) is generally considered to be caused by the voltage low frequency oscillation (LFO) of the high-speed railway traction network. As a possible solution, a strategy using single-phase EMUs rectifiers with passivity-based control (PBC) is proposed in this paper. First, the mathematical model of the four-quadrant pulse width modulation rectifier is constructed based on the port controlled Hamiltonian with dissipation. Next, with the insertion of damping, 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 interconnection and damping assignments PBC. Comparison of simulation results with those of the traditional proportional integral (PI) scheme, autodisturbance rejection control and multivariable control verifies that the proposed PBC controller has better dynamic and static performance. Among all strategies considered, the resulting line current has the least total harmonic distortion, and the dc-link voltage of single-phase EMUs rectifier has the least oscillation and the shortest adjustment time, when using the PBC. Meanwhile, the simulations of multi-EMUs accessed a traction network show that the proposed method significantly suppresses the voltage LFO of the traction network. Finally, the LFO signal modal analysis is performed using the fast Fourier transform and the estimating signal parameters via the rotational invariance techniques. It indicates that PBC can suppress the symmetrical frequency components and effectively reduce the third, fifth, and other harmonic components compared with the PI control in EMUs.