FUZZY-LOGIC BASED ONLINE EFFICIENCY OPTIMIZATION CONTROL OF AN INDIRECT VECTOR-CONTROLLED INDUCTION-MOTOR DRIVE

Improvement of adjustable speed drive system efficiency is important n ot only from the viewpoints of energy saving and cooling system operat ion, but also from the broad perspective of environmental pollution. T he paper describes a fuzzy logic based on-line efficiency optimization control of a drive that uses an indirect vector controlled induction motor speed control system in the inner loop. At steady-state light-lo ad condition, a fuzzy controller adaptively decrements the excitation current on the basis of measured input power such that, for a given lo ad torque and speed, the drive settles down to the minimum input power , i.e., operates at maximum efficiency. The low-frequency pulsating to rque due to decrementation of rotor flux is compensated in a feedforwa rd manner. If the load torque or speed command changes, the efficiency search algorithm is abandoned and the rated flux is established to ge t the best transient response. The drive system with the proposed effi ciency optimization controller has been simulated with lossy models of converter and machine, and its performance has been thoroughly invest igated. An experimental drive system with the proposed controller impl emented on a TMS320C25 digital signal processor, has been tested in la boratory to validate the theoretical development.