High-Speed Train Impedance Measurement Approach Based on Adaptive Multifrequency Voltage Disturbance

Accurate and rapid impedance measurement of high-speed train (HST) is crucial for small-signal stability analysis in the train-network system. Although using wideband disturbance can effectively reduce measurement time, its limited and inflexible spectral controllability will lead to inferior disturbance performance, compromising measurement accuracy, and potentially jeopardizing safety. To address this issue, this article proposes an HST impedance measurement approach based on adaptive multifrequency voltage disturbance. This approach enables precise control of the disturbance frequency band as well as adaptive adjustment of both disturbance frequency resolution and amplitude. First, an odd-even segmented frequency injection strategy is proposed to avoid the HST's frequency overlapping effect interfering with wideband impedance measurement. Then, an adaptive frequency resolution adjustment method is proposed to improve measurement accuracy in the frequency segments with heavy impedance fluctuation. Furthermore, a controllable multifrequency voltage injection device is designed for HST impedance measurement, which can inject desired wideband voltage disturbance whose spectrum energy is congregated at designated multiple frequencies with average amplitude. Particularly, the disturbance amplitude can be reduced automatically by adjusting the regulatory factor of modulated signal when capacitor voltage fluctuation exceeds the threshold, thereby enhancing measurement safety. Finally, the effectiveness of the proposed approach is well validated through real-time hardware-in-the-loop experiment.