Speed regulation of an induction motor using model reference adaptive control

A novel approach of constructing a robust variable-speed drive system using an induction motor supplied from a voltage-source-type PWM inverter is discussed. The inverter is controlled so as to generate the fabricated terminal voltages based on the voltage-decoupled transvector control theory where neither a current feedback loop nor a current limiter circuit is required. Although the hardware for this decoupling method becomes simplified, it still has some disadvantages, such as the discrepancy between the command currents and actual currents. Incorporated into the drive system described herein is the optimal-speed regulator adopting the exact model-matching method, which fulfills the function of a compensator for unfavorable errors. The operating characteristics of the proposed drive system are compared with conventional PI control to verify the effectiveness under various conditions by investigating the transient responses for the step change of the speed command, the load torque, and so forth.