Abstract: In view of the noise magnification problem of the classic differentiator and the inherent error problem of low-pass filter, research on the application of tracking-differentiator (TD) in the stator flux estimate is made. Firstly, TD is brought in to pretreat the detected stator current in a bid to suppress noise, and then TD is used to extract the angular frequency information of stator current. On this basis, a programmable 3-stage cascaded LPF based stator flux estimation scheme is presented, in which the stator flux altitude and phase are compensated by optimizing the time constant and the gain constant of 3-stage cascaded LPF by stator current angular frequency. The simulation and experiment results verify the validity and superiority of the proposed scheme.

Key words: Direct torque control, Low-pass filter, Stator flux estimation, Tracking-differentiator