Improved Sensorless Direct Torque and Flux Control of IPMSM based on On-line Parameter Estimation

This paper presents an improved direct torque and flux control of a sensorless control system with Interior Permanent Magnet Synchronous Motor (IPMSM). The estimation of torque and flux is enhanced by the real-time update of machine parameters including stator resistances, d- and q- axis inductance, permanent magnet flux linkage. The estimation of rotor speed and position is based on the measurement of current slopes at one zero- and two active-voltage vectors during every PWM cycle. The d- and q- axis inductances are estimated at PWM frequency based on those current derivatives and the DC bus voltage. The stator resistance and permanent magnet flux linkage which vary slowly due to temperature and aging factors are estimated based on the use of recursive least square technique. The numerical simulation and experimental study of the proposed methods show the effectiveness of the proposed parameter identification method and the improvement of estimated torque and flux of the sensorless control system.