Speed Observation of Linear Induction Machines Based on Improved Finite Position Set Phase-Locked Loop with Low Computational Burden

The conventional speed observation method based on finite position set-phase-locked loop (FPS-PLL) suffers from false convergence and high computational burden. Thereof, a speed observation method based on improved FPS-PLL method suitable for linear induction machines is proposed. Firstly, the reason for the false convergence of conventional FPS-PLL is analyzed to be that the cost function has two zeros. Then, a cost function containing only one zero is redesigned to avoid the problem. Thirdly, the iterative search algorithm has been improved by redividing the effective range of the evaluated positions, greatly reducing the computational burden. Finally, the effectiveness of the proposed method is verified with sufficient simulations.