Direct torque control of brushless doubly-Fed machine based on fuzzy logic

The conventional direct torque control(DTC) system employs two hysteresis comparators to regulate the stator flux and torque respectively, DTC sheme is easier and has faster torque response, but bring large torque fluctuation and inconstant switch frequency, etc. A control strategy direct torque control based on fuzzy logic is proposed in this paper. The strategy uses fuzzy logic controller replace the hysteresis comparators and voltage table of conventional direct torque control system. In this strategy a novel expanded rule with 12 sectors of flux represented. The algorithm is easily implemented, and it improves the system performance with decreasing both torque and flux ripples. The results of simulation show that the flux trajectory is closer to a circle, torque fluctuation largely decrease and the static and dynamic performance of the system is improved with the strategy based on fuzzy logic control system compared to the conventional DTC.