An optimal direct torque control strategy for brushless doubly-fed reluctance motors

The brushless doubly-fed reluctance machine (BDFRM) is an attractive low cost solution for applications with limited variable speed ranges. The cost effectiveness of the BDFRM drive can be attributed to the possibility of using a partially rated power electronic converter. This paper proposes a direct torque (and flux) control (DTC) algorithm which should bring several advantages to the BDFRM over the cage induction or other AC machines with DTC. The scheme developed is also generally applicable to the traditional doubly-excited wound rotor induction machine. The results presented have demonstrated good controller performance in the desired speed range for various loading conditions of the BDFRM prototype.