The Study On Optimal Control Of Bearingless Switched Reluctance Generators

Bearingless switched reluctance motor (BSRM) integrates the functions of generation andlevitation. It not only inherits the advantages of switched reluctance motors (SRM), such as simplestructure, strong fault tolerance and resilience to harsh operating conditions, but also avoids vibration,noise and heat emission problems caused by mechanical bearings. With the objective of improvingoutput power, reducing the hardware cost and decreasing the difficulty of control, this paper study onthe optimal control of two BSRG——the full-period BSRG and the BSRG with the Adjacent ThreeExcitation-Windings Connected in Series.Based on the full-period BSRG, the expression of the generating current is derived underdifferent excitation regions according to the equations of the two windings. Accordingly, themathematical model of the output power is built in the excitation region. Then, the influences of theexcitation region on the output power in the excitation period and freewheeling period are analyzed.Finally, the method of selecting the optimized excitation region is proposed. In the guide of the theory,a series of experiments are carried out. The experimental results verify the proposed method.To overcome the disadvantage of full-period BSRG with the needing of power devices, a newexciting mode in which the adjacent three excitation-windings are connected in series is proposed inthis paper. The transient electric-circuit model is established and the induced potential is analyzed.After that, the energy conversion under different modes is illustrated combined with theflux-linkage-current curves. Then the mathematical model is derived, and the control strategy isproposed. The experimental results show that the proposed method is effective when the generator’sshaft is levitated.