Improved duty cycle modulation direct torque control for dual three-phase PMSM with voltage vector online optimization

In this paper, an improved duty cycle modulation direct torque control is proposed for dual three-phase permanent-magnet synchronous machine, which aims to restrain current harmonics and reduce the ripples of torque and flux linkage. First, to restrain the current harmonics, 12 virtual voltage vectors (VVs) are employed as candidate vectors. Then, according to the deviations of torque and flux, the potential voltage vector set can be selected from the 12 virtual VVs. A cost function is employed to determine the optimal VV from the potential vector set. Next, the concept of torque deadbeat is applied to determine the duty cycle of VV and achieve the accurate adjustment of torque and flux linkage. This proposed method effectively reduces the torque and flux ripples and current harmonic. The simple structure of the conventional DTC is retained. The simulation and experimental results verify the effectiveness of the proposed method.