A DSP based instantaneous torque control strategy for interior permanent magnet synchronous motor drive with wide speed range and reduced torque ripples

An instantaneous torque control (ITC) method for interior type permanent magnet synchronous motors (IPMSM) is presented. The control scheme is based on the mathematical model of the motor and is applicable to the constant torque and field weakening operations. The theme allows the motor to be driven with maximum torque per ampere characteristic below base speed and it maintains the maximum voltage limit of the motor under wide field weakening and the motor current limit under all conditions of operation accurately. The ITC scheme is also shown to be very effective in suppressing the cogging and ripple torques produced by such motors due to stator slotting and nonsinusoidal air gap flux distribution respectively. These torque profiles are obtained from test runs of the drive under ITC and are used to augment the torque reference of the drive. The control scheme has been verified by experiments on an IPMSM which has nonsinusoidal back EMF and very high cogging torque.