Indirect field-oriented induction motor drive with fuzzy detuning correction and efficiency optimisation controls

The detuning correction and efficiency optimisation of an indirect field-oriented induction motor drive for achieving higher efficiency and better field-orientation characteristic are presented. First, the operating 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 the motor is set to increase its torque generating capability. The determination of the stator flux current component for obtaining rated flux is suggested. At light loads, with the motor running at steady state, in addition to fuzzy slip gain adaptation another fuzzy controller is used to reduce the stator flux current component from its rated value to minimise the stator input current and thus improve the efficiency of the motor drive. As the transient due to command or load torque change occurs the current adjustment action is temporary inhibited and the 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 approaches.