A direct torque controlled interior permanent magnet synchronous motor drive incorporating field weakening

This paper presents a new control scheme for the wide speed range operation of interior permanent magnet synchronous motor (PMSM) drives, where both torque and stator flux linkage are directly controlled. The proposed scheme possesses some attractive features when compared to conventional current controlled drives. Current controllers followed by PWM or hysteresis comparators and coordinate transformation are not used. This eliminates the delays through these networks and offers the possibility of dispensing with the rotor position sensor for the electronic commutator, if the initial rotor position is known only approximately. The scheme incorporates all the usual control regimes such as the maximum torque per ampere operation in constant torque region, the flux weakening region, and operates the drive within the voltage and current limits of the motor/inverter. The control scheme has been verified by simulation and experimental tests with a prototype interior magnet motor. This paper describes the scheme in detail, followed by results of its implementation.