Torque Control of Saturated Induction Motors with Torque per Ampere Ratio Maximization

A novel direct field-oriented torque tracking controller, which guarantees asymptotic torque tracking and maximal torque per Ampere ratio during steady state, has been designed using output-feedback linearizing technique. The efficiency improvement is obtained by adjusting the flux level according to optimization procedure of maximal torque per Ampere (MTA) ratio. Main advantage of MTA control is simplicity of practical implementation and closeness to the optimization criterion of minimum active losses. Nonlinear flux observer and modified flux controller, which take into consideration the effect of magnetic saturation, provide improvement of torque-flux tracking accuracy. The proposed controller assures quite fast dynamics in the torque response and exponential stability. The method is verified by intensive experimentation.