Deadbeat direct torque control of permanent magnet synchronous motor based on reduced order stator flux observer

For the conventional direct torque control of permanent magnet synchronous motor, the flux and torque ripples are serious, and the inverter switching frequency is not constant. This paper proposes a deadbeat direct torque control scheme of permanent magnet synchronous motor. The error between the reference and actual flux amplitudes, and also the error between the reference and actual torques can be compensated accurately during a control cycle. So the flux and the torque can be controled in a deadbeat fashion. To solve this problem that permanent magnet synchronous motor direct torque control system requires the initial rotor position information to determine the initial value of the stator flux, the stator flux reduced order observer is constructed to eliminate the initial flux error. So the permanent magnet synchronous motor direct torque control system operation does not require the initial rotor position information. Finally a rotor speed identification method based on rotor flux is proposed, which is suitable for the deadbeat direct torque control algorithm and the stator flux reduced order observer. So the whole system can operate without any speed sensor.