Direct Torque Control of PMSM using 12-sector and PWM Approach based on The Supplied Voltage Function

This paper presents a novel error level selector and switching voltage function to increase the control performance of the DTC-PWM approach. In the proposed control scheme, a three-phase inverter can supply a 12-voltage vector, which are the original six-voltage vectors and the combined voltage vectors. According to the error sign of the torque and flux, three-voltage vectors can be the candidate voltage vectors. Thus the proposed error level selector can determine the proper voltage vector among the three-voltage vectors to reduce the torque and flux ripple and to improve the dynamic response. In addition, the calculation of the dutyratio in the proposed DTC-PWM method is based on the actual d-q voltage functions, which can describe the output torque and flux characteristics according to the selected voltage vector. The proposed actual d-q voltage function is determined by the rotor position and selected voltage vector. The effective voltages in d-q axis of the selected voltage vector is approximated calculated by the pre-determined coefficients. Then, the PWM duty is determined by the flux error, torque error and the proposed actual d-q voltage function to reduce the torque and flux ripple.In order to verify the proposed method, the conventional DTC-PWM with 12-sector division method and the proposed method are experimentally compared. The compared experimental results show the effectiveness of the proposed DTC-PWM method.