Open-loop control for permanent magnet synchronous motor driven by square-wave voltage and stabilization control

In this paper, the open-loop control for permanent magnet synchronous motor (PMSM) driven by a square-wave voltage is proposed. The proposed control is able to transit from the PWM region to the square-wave voltage region via the over modulation region seamlessly. When the PMSM is driven by the square-wave voltage using the proposed control, the low-frequency torque vibration except 6th or 12th order harmonics occurs due to the transition to the square-wave voltage region. Therefore, a variable band pass filter (BPF) is introduced as the reduction method of the low-frequency torque vibration. The low-frequency component in the active current for the stabilization control is extracted by the filter. As an experimental result, the proposed method reduces the low-frequency vibration which can be represented for the torque by over 40%.