Optimized Operating Point Trajectory for Low Frequency Ride-Through with a Gradient Descent Method in Speed-Sensorless Induction Motor Drives

The adaptive magnetizing current-based low frequency ride-through (LFRT) method has already been presented for speed-sensorless induction motor (IM) drives, ensuring the speed observability at low stator frequencies. However, the current and torque ripples will generate during active zero frequency crossing (AZFC) with magnetizing current changes during LFRT method is enabled. To cope with this problem, this paper proposes a gradient descent-based operating point trajectory optimization method for AZFC. Firstly, the details of LFRT are presented. Then, the current ripples are qualitatively analyzed during AZFC. On this basis, the gradient descent method is developed to optimize the operating point trajectory. The slope angle of operating point trajectory is elaborated to reduce the current ripples. Finally, the effectiveness of proposed method is verified on an ARM-based 2.2 kW IM experimental setup.