Dynamic operation of carrier signal injection based sensorless, direct field oriented AC drives

This paper analyzes the dynamic operation of carrier signal based sensorless, field oriented AC motor drives. The effects of the harmonics introduced by the fundamental current transients at frequencies near the carrier signal frequency are first analyzed, then compensation based on a fundamental current observer is proposed. The utilization of such a fundamental current observer provides the possibility of modifying the analog to digital conversion process to increase the number of bits effectively containing spatial information and thereby substantially increasing the accuracy of the estimated rotor position or flux angle