Beat Phenomenon Suppression Method Based on Quasi-Resonant Extended State Observer for PMSM Drives in Railway Traction Applications

In railway traction applications, the traction motor suffers from serious torque and current pulsation owing to the DC voltage fluctuation introduced by the single-phase rectifier. Rather than employing an additional LC resonant filter at the expense of lower power density, software solutions are of more interest. However, conventional feedforward methods through modulation ratio modification or frequency compensation are difficult to achieve high performance. In this paper, a quasi-resonant extended state observer-based method is proposed to suppress the current pulsation and other low-frequency disturbance. Compared to the conventional method, it can effectively suppress current pulsation within the full speed range and it can also be added as a plug-in block to existing controllers. The hardware-in-the-loop (HIL) experiments demonstrate the effectiveness of the proposed beat phenomenon suppression method.