Sensorless control of a permanent magnet synchronous machine with concentrated windings and short-cicuited rotor winding
Final Report Abstract
During the last 18 months all the work packages of this project are done. The research on the topic of short-circuited rotor windings for the improvement of the operating behavior led to new results. At first, a control algorithm for the encoderless position control was developed based on a 2-degree of freedom controller structure. Using this specific controller structure guarantees the independent adjustment of the reference tracking and disturbance rejection capabilities of the controlled system. Furthermore, two different methods for the encoderless control were implemented. At low speeds and standstill a signal injection method is used, which estimated the actual rotor position from the magnetic anisotropy, and at moderate and high speeds the back-EMF is used. The investigation of the signal injection method showed that considering the differential resistances instead of the differential inductances leads to strongly reduced position-sensing characteristics and accuracies. The reason is grounded on the very low signal amplitudes in that case. In a next step the additional losses caused by the signal injection and their influences on the efficiency and the power factor of the modified electric machine were investigated. The influence on the power factor is negligible, when the short-circuited windings are present on the rotor surface surrounding the surface permanent magnets. The overall losses increase in both cases of the signal injection method and the back-EMF method, if the short-circuited windings are present. Because of some additional higher harmonics in the air gap field the increase of the losses is higher in the case of the rotor with buried magnets in comparison to the rotor with surface-mounted magnets. This results also in stronger decrease of the efficiency. An influence on the transient operating behavior is not found. Finally, it was proved that the additional short-circuited windings surrounding the permanent magnets lead to an increase of the safe operating area of the machine in encoderless operation mode. Since the last 7 years the gained results in this research topic lead to the conclusion that in improvement of the magnetic anisotropy of electrical machines, which is essential for the encoderless position estimation using a signal injection method, is possible through analytical and numerical modelling methods. In the case of this research project this application of the named methods resulted in a practical solution for the issue at hand, the increase of the self-sensing capabilities of a permanent magnet synchronous machine. Especially the short-circuited windings can be mounted afterwards on the rotor of an industrially available machine. Therefore, the additional short-circuited windings will be an integral part of the state of the art concerning the encoderless and self-sensing control of electrical machines.
Publications
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“Resistance- and Inductance-Based Self-Sensing Control using Short- Circuited Windings on the Rotor of a SPMSM,” in IECON 2019 - 45th Annual Conference of the IEEE Industrial Electronics Society, 2019
C. Hittinger and I. Hahn
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“Short-Circuited Rotor Windings for Improving the Electromagnetic Saliency for Inductance- and Resistance-Based Self-Sensing Control,” in 2019 IEEE 28th International Symposium on Industrial Electronics (ISIE), Vancouver, BC, Canada, 2019, pp. 390–395
C. Hittinger and I. Hahn
