Design of current and speed controllers for slip energy recovery inductionmotor drive using root-locus technique

The most common problem of the slip recovery system is stabilizing the syst em under power system disturbances, such as the change of supply voltage. T wo back-to-back proportional-plus-integral (PI) controllers are used in a c losed-loop control system, to control the DC-link current and speed. In ord er to estimate parameters of the controllers using root-locus technique, a non-linear transient model of the drive is linearized around the steady-sta te operating point. The performance of the drive in the presence of disturb ance signals is studied and finally the eliminating speed error signal and the continuous variations of the inverter-firing angle are illustrated.