Position estimation of IMSM using fundamental PWM excitation and its application in sensorless control

This thesis describes the development of Fundamental PWM Excitation (FPE) sensorless control method for an interior permanent magnet synchronous machine (IPMSM). The FPE is based on relating the measured incremental inductance to current derivatives for two or more adjacent PWM voltage vectors applied to the machine. In theory, this sensorless control method can work over a wide speed with lower current distortion, smaller current and torque ripples, power loss and lower acoustic noise compared to other saliency tracking sensorless control methods. However, the high frequency oscillations caused by parasitic effects when the switching devices change state prevent the immediate and accurate measurement of current derivatives. The measurement of current derivative cannot start until these high frequency oscillations die down. For very narrow voltage vectors, extensions are needed in order to have sufficient time for the accurate current derivative measurement after the high frequency oscillations disappear. Since the voltage vectors are extended, compensation schemes have to be implemented to minimize the undesirable effects which the extensions bring such as current distortion, torque ripples and acoustic noise. In this thesis, the high-bandwidth Anisotropic Magneto-Resistive (AMR) current sensors are used for estimating the current derivatives without the need of additional current derivative sensors. The advantage of high-bandwidth of the AMR allows the more accurate estimations of current derivative especially for machines with high inductances, like the IPMSM. Experimental results on current derivative estimation show that the AMR current sensor can achieve excellent performance.The implementation of FPE on IPMSM is more difficult compared to SPMSM because of the higher self and mutual inductances of this machine. The extension of FPE sensorless control method on IPMSM is described and analyzed in this thesis. The experimental setup, current derivative estimation methods, voltage vector extension and compensation schemes and sensorless control drive system have been developed for verifying the actual performance of FPE sensorless IPMSM drive. Experimental results show that FPE can achieve good performance in speed and rotor position estimation over a wide speed range