Correction of Field Orientation Inaccuracy Caused by Resolver Periodic Error and Rotor Time Constant Variation for Indirect Field-Oriented Control Induction Motor Drives

This article proposes an algorithm correcting the field orientation inaccuracy caused by resolver periodic error and rotor time constant variation. It is found that the periodic error brings harmonic current vectors and torque ripples while the rotor time constant variation makes dq currents deviate from the reference values. The cross-product of fundamental and harmonic current vectors contains the information of resolver periodic error. The gradient descent method with a variable step is introduced to compensate the periodic error. During the process, the cross-product is minimized. A new form of cross-product calculation is derived to reduce the computation time. The rotor time constant is identified by the reactive-power based model reference adaptive system (MRAS). Voltages and currents in the stationary reference frame are used in the reference model to avoid the influence of resolver periodic error. Appropriate parameters of the MRAS are selected to guarantee the stability. The algorithm is integrated with an induction motor drive which is based on indirect field-oriented control. The feasibility of the proposed algorithm is verified by simulation results and experiments.

I. Introduction

The indirect field-oriented control (IFOC)-based induction motor (IM) drives are widely used in various industry applications for the simple structure, high reliability, and good performance [1], [2]. The position of rotor flux linkage utilized in field orientation is obtained by calculating the sum of the rotor position and the integral value of slip angular frequency. Under severe operation conditions such as high temperature, violent vibration, and serious electromagnetic interference, the resolver is preferred to provide the rotor position because of its capability to avoid failure under these tough conditions [3], [4]. However, the existence of the resolver periodic error is inevitable due to the nonideal signal characteristics [5], [6]. The calculation of slip angular frequency depends on the rotor time constant which varies significantly with temperature, frequency, and saturation [7]. Both the resolver periodic error and the rotor time constant variation can cause field orientation inaccuracy, resulting in performance degradation of the IM drive.