Dual MRAS for Robust Rotor Time Constant Compensation in IFOC IM Drives

The induction motor drive with indirect field-oriented control (IFOC) is widely adopted due to its simple structure and easy implementation. The rotor time constant plays the most crucial role in IFOC. However, the rotor resistance varies with temperatures, and the rotor inductance changes with the current magnitude in practice. Furthermore, an accurate estimation of such parameters is challenging. The parameter mismatch between the actual and the estimated rotor time constant deteriorates the performance of the IFOC vector control due to an error in the estimated rotor flux position. This paper presents the theoretical analysis of the effects of the inductance errors in the conventional Q-MRAS method, which is widely used to compensate for the rotor time constant. Next, this paper proposes the dual MRAS consisting of a novel stator flux-based MRAS and the conventional Q-MRAS. The proposed dual MRAS method can simultaneously compensate for the error of inductance and rotor time constant, thereby improving the performance of IFOC. The robustness and effectiveness of the proposed method have been validated through simulations and experiments.