Adaptation of Slip Gain for Modified Transient Vector Estimator-Based Speed Control of Induction Machine Drive

Abstract

Modified transient vector estimator (MTVE) based speed control scheme that combines the high transient-performance features of rotor field oriented control with the robustness features of scalar control is presented in literature. However, MTVE scheme involves the calculation of slip gain to obtain torque reference. Either inaccurate estimation or variation in the estimated slip gain can result in the degradation of performance of MTVE control. In order to overcome this problem, this paper proposes a slip gain adaptation scheme, that is independent of speed of operation. The proposed method uses d-axis component of stator voltage to obtain expression for disorientation factor and works by matching all the control side variables with that of actual machine variables, and uses a simple PI controller to implement slip gain adaptation. The impact of inaccurate slip gain estimate on the dq-components of various currents, voltages, feed-forward components, and hence on the torque and flux of the machine are analyzed in this paper. The proposed adaptation scheme is suitable for wide speed range operation, in contrast to the existing slip gain adaptation methods, where open loop gain is dependent on the synchronous frequency information. The proposed adaptation scheme is validated using detailed simulation and experimental results. Comparison of the proposed adaptation method with the existing methods is also presented in this paper.