Sensorless control of a permanent magnet synchronous machine with concentrated windings and short-cicuited rotor winding

• Applicant: Professor Dr.-Ing. Ingo Hahn
• Subject Area: Electrical Energy Systems, Power Management, Power Electronics, Electrical Machines and Drives
• Term: from 2018 to 2020
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 407180108

Sensorless control has been investigated in research for many years. The goal is to gain the rotor position information on-line by direct available machine quantities without the requirement of additional measurement equipment. For higher speeds, this can be achieved by back EMF-methods, based on the induced voltage of the machine, whereas for small speeds and standstill, methods based on test signals are suitable. In this case, the evaluation of differential quantities (e.g. resistance and inductance) are necessary.The currently funded research deals with detailed investigations on the machine design for sensorless position estimation. A new concept, applying short-circuited windings (SC-windings) on the rotor, was developed and simulated analytically and with the finite element method. The simulation results were verified with the measurement results of an experimental setup. For investigating the qualification of this concept on practical applications, different SC-windings were applied to the rotor of an industrial synchronous machine with surface-mounted magnets. This setup was included on a test bench to perform dynamic measurements.In the following, a controller setup will be developed to perform the sensorless control over the total operating area. Especially, the focus should be put on the range where signal injection methods are used, as the advantages of the SC-windings will show up there.Additionally, an improved method for estimating the rotor position was developed. This method will be included in the controller setup. It evaluates a weighted combination of the differential resistance and inductance.Another key aspect is the influence of the SC-windings on the dynamic behaviour of the machine. As the SC-windings are configured to show the most significant damping effect at the test signal frequency, their influence can be neglected at stationary operation. During highly dynamical acceleration and speed reversion, the timely variation of the flux reaches high values, which could excite the SC-windings and, hence, damp the flux and, therefore, the dynamics. Another area, where the concept influences the machine’s behaviour, is at very high speeds. There, the fundamental machine frequency reaches high values that could excite the SC-windings as well. The investigation of this drawback is one of the main goals of the research on the test bench and on evaluating the performance for practical applications of the concept of SC-windings on the rotor.In the last section of this research proposal, the suitability of the concept will be proved on a rotor with integrated permanent magnets that already has an inherent electromagnetic anisotropy. The rotor will be designed in such a manner to reach the performance characteristics of the machine with surface mounted magnets. All measurements performed with the initial machine will be repeated for the setup with integrated magnets.

• DFG Programme: Research Grants