Rapid Impedance Measurement Approach Based on Wideband Excitation for Single-Phase Four-Quadrant Converter of High-Speed Train

Wideband impedances of the single-phase four-quadrant converter (4QC)-based high-speed train are of great significance for small-signal stability analysis in the electric railway system. However, the conventional impedance measurement strategy relies on sweeping the desired frequencies repeatedly that extremely slows down the impedance measurement speed, which, usually, seems incapable for the actual dynamic industrial systems. Addressing this shortcoming, this article proposes a novel impedance measurement approach based on the wideband excitation to greatly enhance its rapidity. Further, to eliminate the frequency overlapping effects under the wideband excitation, the proposed alternate injection strategy realized by the multitone signal can separate the effective frequencies from the coupling frequencies in the $\alpha \beta $ frame. Afterward, the dq -frame data covering all the desired frequencies can be obtained by combining the conventional method and the proposed $\alpha \beta $ -value exchange method ( $\alpha \beta $ -VEM), which can be applied for the impedance calculation. Finally, the results of both simulation and real-time hardware-in-the-loop (HIL) tests can well verify the effectiveness of the proposed approach.