INDIRECT FIELD-ORIENTED INDUCTION-MOTOR DRIVE WITH FUZZY DETUNING CORRECTION AND EFFICIENCY OPTIMIZATION CONTROLS

The detuning correction and efficiency optimisation of an indirect fie ld-oriented induction motor drive for achieving higher efficiency and better field-orientation characteristic are presented. First, the oper ating characteristics of an indirect field-oriented motor drive under detuned condition are studied. A fuzzy controller is used to tune the slip gain online in the field-orientation mechanism to obtain a better decoupling control characteristic. At heavy loads the rated flux of t he motor is set to increase its torque generating capability. The dete rmination of the stator flux current component for obtaining rated flu x is suggested. At light loads, with the motor running at steady state , in addition to fuzzy slip gain adaptation another fuzzy controller i s used to reduce the stator flux current component from its rated valu e to minimise the stator input current and thus improve the efficiency of the motor drive. As the transient due to command or load torque ch ange occurs the current adjustment action is temporary inhibited and t he rated flux component current is set instead to obtain higher torque generating capability. Measured results show that both the efficiency and rotor speed dynamic responses are improved by the proposed fuzzy detuning correction control and efficiency optimisation control approa ches.