A Practical Approach to Mitigate Low-Frequency Oscillation in Railway Electrification Systems

The low-frequency oscillation (LFO) phenomenon has frequently happened in the railway electrification systems (RES), which often caused the traction atresia of electric trains and protection malfunction of traction network. In this letter, a practical mitigation approach is presented based on impedance analysis, which indicates that changing the operation mode of the electric trains to diode-bridge rectification (DBR) circuit can mitigate the LFO because the impedance of the rectifier is increased. Then, combining the Prony technology, an online identification and mitigation approach, is proposed here for mitigating the LFO phenomenon. Experimental results verify the effectiveness of the proposed method in stabilizing voltage fluctuation of the RES. This method can also identify the oscillatory frequency and the corresponding attenuation factor.