Improved Feedforward Active Filter With Diode‐Clamped Push‐Pull Link for CMV Suppression in PMSM Drive System

ABSTRACT

Hardware‐based methods, such as additional filters, are commonly used to suppress common‐mode voltage (CMV) at the inverter output and mitigate electromagnetic interference (EMI) in permanent magnet synchronous motor (PMSM) drive systems. In this paper, a feedforward active filter based on CMV sampling and compensation is proposed. The equivalent model and transfer function of the active filter are analyzed, and the parameter design method for each filter component is derived. However, the push‐pull link in a traditional feedforward active filter suffers from inherent crossover and amplitude distortions, which introduce errors between the CMV sampling and injection links and degrade the compensation performance. To address this issue, a diode‐clamped push‐pull structure combined with DC bias resistors is proposed. LTspice simulation results show that the improved push‐pull structure effectively eliminates crossover distortion and reduces amplitude distortion compared with the traditional structure. Experimental results on a PMSM drive platform show that the improved feedforward active filter achieves a CMV peak‐to‐peak reduction of approximately 30% compared with the traditional feedforward active filter. Moreover, the proposed method achieves more than 10dB attenuation improvement at the fundamental switching frequency and its harmonics, verifying its superior CMV suppression capability.