Graphical Multiple-Error Feedback Matrix Design for Stability and Robustness Enhancement of Speed-Sensorless Induction Motor Drives

For speed-sensorless induction motor (IM) drives, the feedback matrix is a significant technique to enhance the stability in low-speed regenerating region. However, further analyzes show it has difficulty for existing methods in maintaining the stability and robustness with parameter uncertainties. To cope with this problem, in this article, a graphical design method of multiple-error feedback matrix (ME-FBM) is presented for adaptive full-order observer. First, the flux error is introduced by projection of current error. Adopting flux error and current error, the ME-FBM is graphically developed to satisfy the stability necessary condition by reconstructing the stability function. As a result, the unstable region is eliminated during low-speed regenerating mode. On this basis, the gains of ME-FBM is graphically selected to reduce the error of estimated rotor flux and improve the robustness against parameter uncertainties at low-stator frequencies. Finally, the effectiveness of proposed ME-FBM is verified on a 2.2 kW IM experimental setup.