A New Reactive-Power-Based Model Reference Adaptive Controller for Online Rotor Time Constant Identification of Induction Motors

Reactive power, which is inherently independent of stator resistance, can be used to form a Model Reference Adaptive Controller (MRAC) to estimate the rotor time constant in an indirect field orientation controlled induction motor drive. In this paper, the steady-state reactive power error caused by rotor time constant mismatch is analyzed in detail. Then a modified reactive power model is presented based on Lyapunov's theorem. The stator frequency is incorporated in the adaptive scheme to get per-unit value of reactive power error, thus, the close convergence rate of the rotor time constant is achieved at high speeds and low speeds. Furthermore, this confirms the estimation is available in four quadrants of operation. Experimental results have verified the effectiveness of the proposed method.