Analysis And Design Of Three- Phase Switched Reluctance Machines Based On Biopolar-Excitation Control

Switched reluctance machine (SRM) has attracted extensive attentions due to its inherent advantages, including simplicity, robustness, excellent fault-tolerance, and being favorable for high speed operation. Especially during these years, as a brushless machine without permanent magnets, the SRM-based drive systems have accelerated developments due to the supply limitation and price fluctuation of rare-earth materials, which have been successfully employed in the applications of aerospace, traction and industrial systems. However, conventional SRM-based drive system adopt asymmetric bridge converters, resulting in bulky volumes, lacking of unified market standards, and high costs, and consequently, limit the widely applications of SRMs. To solve this problem, universal three-phase full-bridge converters instead of asymmetric ones are employed and the control strategies are modified from traditional unipolar currents into bipolar currents. Hence, the SRM under this new control strategy can be recalled as "Bipolar-Excitation Switched Reluctance Machine (BE-SRM). In this thesis, the working principle of the BE-SRMs is analyzed, and the winding connection methods and key design dimensions are optimized. Meanwhile, a prototyped BE-SRM with 12-stator-slots and 8-rotor-poles is manufactured and the experimental validations are carried out. In general, the work of this thesis lays a strong theoretical foundation for the further research and practical applications of bipolar-excitation switched reluctance machines.The contents and fruits of this thesis are as follows:(1) A comprehensive analysis of the basic principles of BE-SRMs is carried out and the voltage, flux-linkage, electromagnetic torque and mechanical movement equations of BE-SRMs are deduced. Then, the proper topologies and fundamental control strategies of BE-SRMs are proposed.(2) Based on 2-D static finite element analysis, electromagnetic performance of a three-phase 12/8 BE-SRM is analyzed firstly. Then, with the help of Maxwell/Simplorer a combined magnetic field-electric circuit co-simulation model is built to realize system-level simulations on BE-SRM-based adjustable-speed drive systems, where the operation principles of BE-SRMs are verified.(3) The influence of winding connection methods on the performance of BE-SRMs is investigated and the proper winding connection scheme is concluded. Furthermore, the optimizations of structural dimensions of the BE-SRMs are conducted.(4) A core loss model of BE-SRMs is proposed, which takes minor hysteresis loops and DC-bias in flux density waveforms into consideration. The flux distributions and core losses of the original and optimal BE-SRMs are compared in detail.(5) Based on a three-phase 12/8 SRM with unipolar excitation, a three-phase 12/8 bipolar-excitation SRM is manufactured and the static electromagnetic characteristics is measured.(6) The experiment platform of a 12/8 BE-SRM-based drive system is set up based on dSPACE1104. The main circuits and auxiliary circuits are designed and implemented. Extensive experimental measurements are carried out to the performance of the BE-SRM under four different winding connections comprehensively, and the results validate the theoretical analysis and FEA predictions.