Mathematical Modeling of Direct Torque Control of BLDC motor

Direct torque control method for BLDC motor drives usually represents reduction in high ripples in the torque. The important characteristics observed in DTC is non-linear regulation of stator flux and torque within variables structure by hysteresis band controller. For particular sampling period Ts values of torque and flux are chosen for Hysteresis band. This would help to achieve average sampling frequency equal to constant switching frequency of switches. Abrupt ripples generates in quantities when control of flux and torque occurs at time in allowed limits. This means that voltage vectors are chosen to modify this quantity in time Ts within hysteresis band which would results in reduction in torque ripples. Here PI controller is suitable to adjust reference value responsible for sensitivity of speed error. The obtained simulation results shown where overshoot occurs in speed using PI controller and trajectory of stator flux represented in alpha-beta plane.