An Improved Mathematical Model for Speed Sensorless Control of Fixed Pole Bearingless Induction Motor

Abstract

In a fixed pole bearingless induction motor (FPBIM), the influence of the suspension winding is neglected in the traditional mathematical model, leading to the inaccurate speed estimation of speed sensorless control. Aiming at this problem, this paper proposes an improved mathematical model. First, considering the influence of the suspension winding, the resistance matrix and inductance matrix are extended based on the traditional natural coordinate model and the FPBIM's natural coordinate model (in the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">a-b-c</i> stationary frame) is established. Secondly, through the rotation transformation by an extended transformation matrix, the FPBIM's two-phase stationary coordinate model (in the α-β stationary frame) is obtained and the flux linkage equations are extracted from it. Finally, to verify the effectiveness and feasibility of this improved mathematical model, it is applied to the speed sensorless control based on model reference adaptive system (MRAS). The simulations and experiments show that the FPBIM improved mathematical model gets more accurate speed estimation and better rotation performance under no-load, load, load disturbance and displacement disturbance, while the suspension performance is not affected.