Sensorless Direct Torque Control For Permanent Magnet Synchronous Motor

According to the mathematical model of permanent magnet synchronous motor (PMSM). direct torque control (DTC) in PMSM is represented systematically. The zero-voltage vectors, whose functions are keeping the output torque unchanged and reducing the torque ripple, are analyzed in details. Based on the scheme, the simulation model for PMSM DTC is set up using Matlab/Simulink. The simulation results show the dynamic response lime of the torque and speed only is several milliseconds, which verifies adequately the virtue of DTC and the effectiveness of the proposed strategy.In order to improve the system performances, the DTC based on space vector modulation (SVM) is proposed for PMSM, including space vector choice and modulation. The SVM DTC can dramatically improve the steady and dynamic performances. At the same time, the feasibility of sensorless operation for PMSM DTC is analyzed and a speed estimation scheme is proposed.To verily the feasibility of DTC. the conventional PMSM DTC experiment is made. A high speed digital signal processor (DSP) is used as a controller. The used intelligent power module (IPM) as inverter greatly decreases the bulk of system. The sensors of LEM Corporation are applied to the current and voltage detection, which increase the system sampling precision. The control software is designed in assemble language based on DSP TMS320LF2407. This software has realized functions of the stator phase current sampling, calculation of the phase voltage, observing stator flux and the output of switching signal, etc. As the driving signals of IPM are low active, the switching of space voltage vector is redesigned. The primary experiments of the open-loop and the closed-loop without load are completed. The obtained results are analyzed. The feasibility of system scheme is verified by simulation and experiments, which has established the foundation for the further research.