Advanced control of induction motor based on load angle estimation

An advanced control system with load angle adjustment is introduced. The method is based on the action of a phase-locked loop, in which a position synchronization of two vectors to obtain a constant command angle between them is realized. In the system presented, the vectors are stator current and rotor flux. The load angle is kept constant by changing the position of stator current vector as a result of tuning its pulsation. Proportional-integral and fuzzy logic controllers are used to control the load angle. Because of using the load angle controller and simple relations for state variables, the proposed idea does not require exact speed measurement. The discussed control system is not sensitive to motor resistance variations. This idea is realized on a fixed-point digital signal processor and field-programmable gate arrays. Experimental results for the control system fed by a voltage-source inverter and controlled using a predictive current controller are presented.