Energy optimization of induction motor drives

This paper deals with energy optimization of induction motor drives. In many applications, efficiency optimization of induction motors represents an important factor of control especially for autonomous electrical traction. In this paper different approaches to improve efficiency in vector controlled induction motor drives at steady state condition are compared. Three methods are possible to control the excitation: Methods based on induction motor losses, methods based on the use of look-up table and methods based on search controllers of minimum. We expose in this paper some methods, which use the search controller techniques. These techniques consist in changing flux level in small steps to keep the output power of the motor constant and find the minimum of input power. These controllers are efficient at steady state condition and do not require knowledge of motor and converter parameters. However, the search controller using the stator current instead of power give similar results to their using power. This technique is less complex and doesn´t need measurement of PWM quantities. The proposed search controller is based on fuzzy algorithm. The advantages of this controller are compared with others known as Rosenbrock method and Golden section. Fuzzy search controller presents a good trade off between convergence time and oscillations of stator current ripple.