Performance of a reactive power-based adaptive estimation of inverse rotor time constant for vector controlled induction motor drives

A detail investigation on an adaptive estimation of rotor time constant is presented here. The adaptation mechanism forms a Model Reference Adaptive System (MRAS) for the online estimation of inverse rotor time constant for high performance Indirect Vector Controlled Induction Motor Drive. The instantaneous and steady state reactive powers are utilised in the proposed MRAS. A merit of the scheme is that the flux computation is not required in both the models (reference model and adjustable model) of MRAS. So, the low speed estimation problems like drift and saturation of integrator (related to flux estimation from voltage model) are overcome. The use of reactive power as a functional candidate of MRAS naturally makes the scheme independent of stator resistance. The workability of the proposed MRAS is verified through extensive simulation and experiment. The stability of the system is investigated and a study on the sensitivity to stator and rotor parameters is reported. The technique is simple and can be implemented in the existing indirect vector controlled system without any additional hardware.