Direct torque control of permanent magnet synchronous motor drive with a sensorless initial rotor position estimation scheme

Direct torque control (DTC) can be applied to all AC machine drives. The synchronous motor torque control, based on DTC structure, permits to obtain high dynamic performances. DTC is a concrete solution to robustness and dynamic problems found in other control structures. In DTC scheme, the requirement of the continuous rotor position sensor and co-ordinate transformation is eliminated since all the calculation is done in stator reference frame. However; the DTC scheme requires the position sensor to determine the initial position of rotor at starting. Elimination of the shaft mounted position encoder is a very desirable objective in many applications as this sensor is often one of the most fragile components in the entire drive system. This paper presents the implementation of DTC to Permanent magnet synchronous motor (PMSM) with a sensorless initial rotor position estimation scheme. The requirement of sensor for the initial rotor position estimation can be avoided by impressing a high frequency voltage on the stator winding. The simulation results verify the effectiveness of the process.