Sensorless control of permanent magnet synchronous machines with multiple saliencies

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The interest in surface mounted permanent magnet synchronous machines with concentrated windings (cwSPMSM) is increasing owing to their lower winding cost and the feasibility of more compact designs than the traditional ones with distributed windings. The elimination of mechanical sensors for rotor position measurement makes these drives even more competitive. Sensorless control of this machine type has got extensively attentions due to their promising properties. For the in series produced cwSPMSM, however, the sensorless control method has not yet been studied. This is because, firstly, they do not present significant magnetic saliencies, on which the traditional sensorless technologies using high-frequency signal injection are based; secondly, such machines show strong multiple saliencies, which cause large torque ripples using traditional sensorless control technologies; and thirdly, the saliency does not show constant properties with different excitation frequencies, for which no specific study has been carried out yet. The proposed study will provide a solution to this problem based on the sensorless concept by injecting revolving high frequency signals into the machine. As the starting point, a composition method will be realized, which removes the influence of the high order saliencies using the decoupling technology. On this basis, a combination method will be implemented, which, as the focus of this proposal, makes use of the information contained in different orders of the saliencies, in order to achieve increased accuracy. As a further step to extract even more information about the flux position, a multi-frequency injection method will be investigated based on the dependency of the saliency properties on different frequencies. In addition, the initial position detection for starting the machine from standstill will be also included in this study. Finally, based on the successful implementation of the proposed methods, the sensorless control of cwSPMSM in the full speed range will be realized combining with the traditional method based on back electromotive force.The results of this project will not only be directly applied on the studied machine type, but also provide new ideas and possibilities for the sensorless control of all kinds of machines with multiple saliencies.