Analysis of Low Frequency Oscillation in Electric Railways  

The line-side converter, which can represent an AC-DC-AC drive electric vehicle when analysing the low-frequency oscillation in electric railways, is modeled in dq frame with the proposed single-phase dq-decomposition method. With this model, an under-damped mechanism of the vehicle-grid interaction is confirmed. Besides, a low-frequency stability prediction approach is presented based on the dominant-pole analysis and verified by the simulation and the testing result.

The proposed modeling method and prediction approach benefit in three aspects: It’s more convenient to rebuild the model with a change of either the line-side converter controller or the system condition, much quicker to predict the low-frequency instability and more explicit to guide the modification of the controller software to damp the low-frequency oscillations.