Torque ripple reduction in DTC of single-phase open-circuit fault PM brushless

This paper presents a strategy to reduce torque ripple in direct torque control (DTC) of three-phase permanent magnet brushless (PMBL) motor having a winding open-circuit fault. An extra inverter leg is employed to supply voltage to motor neutral point during post fault operation. The zero-voltage vectors are utilized to reduce the torque ripple. Mathematic model of non-sinusoidal back-EMF PMBL motor is developed in which stator flux linkages and developed torque of the faulty motor are presented in a series function. To avoid the difficulty in variable estimation approximated models of stator flux linkages and developed torque based on fundamental component are established. Design of the proposed DTC is also described. The computer simulation shows that torque ripple can be reduced by the proposed method where zero-voltage vectors are utilized in the control scheme. Performances of the system with and without zero-voltage vectors in the scheme are presented and then validated by comparing with measured signals.