Direct torque control and space vector modulation-based direct torque control of brushless doubly-fed reluctance machines

This paper establishes the torque equation of brushless doubly-fed reluctance machines (BDFRMs) expressed by power winding or control winding (CW) flux vectors and the defined flux vectors generated by magnetic field modulation. On this basis, the direct torque control theory of BDFRM is established. The derivative expression of torque and CW flux are derived for accurately analysing the effect of CW voltage vectors and machine operation points on torque and CW flux. In addition, the space vector modulation-based direct torque control strategy of BDFRM is proposed, which can keep the switching frequency constant. The two methods are compared and analysed through experimental results.