Research On 12/8 Bearingless Switched Reluctance Machine

Due to its simple structure and resilience to harsh operating conditions, the switched reluctance machine (SRM) has caused extensive concern over the recent years. The introduction of bearingless technology could fully take advantage of the high-speed ability of SRM. Meanwhile, the active control, over the unbalanced radial force between stator and rotor poles, is suitable for avoiding the vibration and noise in SRM. As the preferred implementation of power system for the more/all electric aircraft in USA, the high-speed switched reluctance starter/generator system has drawn more attention by scholars of all nations. Accordingly, the study of bearingless switched reluctance starter/generator will provide a solution for the future more/all electric aeroengine with the function of magnetic levitation. Moreover, the bearingless technology enhances the application of the switched reluctance generator (SRG) in the distributed power generation system, UPS, magnetic flywheel storage system, and electric/hybrid-electric vehicles.To aim at these two key techonologies in the starter/generator system, this dissertation focuses on the control scheme of the bearingless switched reluctance motor (BSRM) and the theory and implementation of the bearingless switched reluctance generator (BSRG).Based on the dual-winding BSRM, the modeling using Maxwell Stress Tensor method, the distributing design of two sets of windings, and the independent control of the average torque and the levitation force are proposed, respectively. Firstly, Maxwell Stress Tensor method is adopted to derive the mathematical models of instantaneous torque and radial force that can be used to design the current control algorithm. The derivation avoids the sophisticated deduction of the inductance matrix and partly considers the magnetic saturation, which can be referenced for machine design and offline analysis for motor characteristics. Secondly, in dual-winding bearingless motors, another winding is added in the stator to achieve the levitation function; hence, how to distribute the two windings becomes the key consideration for the machine designer. Therefore, the two-winding ampere-turn distribution is proposed for the machine design. Thirdly, in conventional control scheme of BSRM, both of the torque and the radial force are determined by main-winding and radial-force-winding currents. The current algorithm is complex and requires more digital memory resources. Therefore, an independent control is proposed for the average torque and the radial force. This method avoids the coupled control between the torque and the radial force, and simplifies the control algorithm of rotation and levitation. A set of levitation winding is added in dual-winding bearingless motors, which complexes the machine design and assembly. Hence, chapter 4 studies the single-winding technology of BSRM. Based on the radial-force mathematical model, the levitation control scheme is proposed for single-winding BSRM. The experimental results are included to verify the proposed bearingless strategy. The study of single-winding BSRM expands the theory of bearingless motors and provides a new approach for the application of BSRM.With the magnetic levitation and the generator being integrated, the BSRG is developed which is operated in a full-period generating mode. The concept of full-period stems from the latter half-period generation in the conventional SRG. In full-period generators, the mechanical energy is also converted into the electrical energy in the excitation region, which is why it is called"full-period generation". The theory of the BSRG is demonstrated based on the full-period generation. The inductance and radial-force models are also deduced. In addition, the excitation and generation currents are expressed in different regions via the winding-voltage equations. The flux-linkage-current curves are depicted in order to illustrate the energy conversion in the full-period generator. The radial-force control algorithm is proposed for the BSRG based on the derived radial-force model, which coordinately controls the output voltage and the levitation force. Finally, the proposed operation of BSRG is verified by simulation and experimental results.