Torque ripple minimization in direct torque control of a permanent magnet synchronous motor

The basic theory of direct torque control (DTC) for interior permanent magnet synchronous motors (IPMSM) was studied. A new approach to direct torque control of an interior permanent magnet synchronous motor was presented to decrease torque ripple. In order to improve the static and dynamic performance of the system, a fuzzy logic idea was introduced into the system. In the fuzzy direct torque control system, the flux error and the flux error change were both properly divided into several fuzzy subsets. The acting time of the selected voltage vector and reverse voltage vector were modulated based on fuzzy inference. A speed estimation scheme was integrated with the proposed DTC scheme in order to achieve a fully sensorless high-performance IPMSM drive. The scheme not only maintains constant switching frequency, but also reduces torque ripple, particularly at low speed. Simulation illustrates the operation and performance of the proposed fuzzy-logic-based controller.