Motor flux minimization controller based on fuzzy logic control for DTC AC drives

This work presents a real time optimum flux adjustment fuzzy controller is cooperated with Direct Torque Control (DTC) adjustable speed drive (ASD) for ac Induction motors, in order to achieve the motor drive loss minimization while meeting the load and speed demands. The proposed control scheme includes a DTC controller, a speed controller and an optimum flux adjustment fuzzy control system. The flux adjustment is based on a fuzzy logic search controller (FLSC1) during steady states and on a fuzzy logic controller (FLC2) during transient states motor operation. The proposed control scheme estimates the optimum stator flux which is used as flux reference value for the DTC unit. The fuzzy control system utilizes the motor flux as a control variable in order the motor drive to consume the minimum input power consumption during steady state, while in transient operation the motor flux is optimum recovered based on the motor speed and the operating torque reference errors. This approximate optimal solution implies time-varying rotor flux norm operation in opposition to the classical DTC that operates with constant rotor flux norm. Moreover, the control system includes a State detection unit which recognizes the motor operation state in order to activate the relevant fuzzy unit. Using Simulinc^® programming the control system is tested. The efficiency improvement is validated by power measurements in laboratory using an experimental array of a 3-phase 1 Hp induction motor DTC control drive. The controller implemented using the platform eZdsp from Digital Spectrum based on the DSP TMS320F2812 from TI as computing engine.