Active Power Based MRAS for Estimation of Inverse Rotor Time Constant in Field-Oriented Control of Induction Motor Drive

In this paper, an active power (P) based model reference adaptive system (MRAS) is utilized for the estimation of rotor resistance in indirect rotor field-oriented control of induction motor (IM) drives. The rotor resistance is prone to variation because of the variation in temperature during the prolonged operation of drives. Hence, rotor time constant/rotor resistance estimation is very crucial for high-performance IM drives. The reactive power (Q) based MRAS as proposed for this purpose in different literature demonstrates instability in low-speed regenerating mode of operation. Although the functional candidates for P-MRAS are dependent upon the stator resistance terms, the error signal to the adaptation mechanism is independent of any resistance terms like Q-MRAS. Moreover, the mathematical formulation used for calculating reference power <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\boldsymbol{(P_{ref})}$</tex-math></inline-formula> and adjustable power <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\boldsymbol{(P_{adj})}$</tex-math></inline-formula> of the P-MRAS does not involve any integration and/or differentiation terms. The proposed approach is capable of accurately estimating both slow and rapid variations in rotor resistance. The efficacy of the proposed P-MRAS for estimating inverse rotor time constant has been demonstrated experimentally with a 5.5 kW IM drive. A small signal analysis for stability study has also been carried out to full proof the concept.