Research On A Novel Stator Doubly-Fed Doubly-Salient Permanent-Magnet Machine And Its Control System

Doubly-salient permanent magnet machines (DSPMs), which are the combinations of switched reluctance machines and permanent magnet (PM) brushless DC machines, are becoming more and more attractive in electrical engineering because of their distinct features, such as high efficiency, high power density and simple structure, et al. However, similar to other types of PM brushless machines, the regulation of airgap flux is a research puzzle, as the PM excitation is difficult to realize field-weakening control. To meet this requirement, some methods were proposed in recent years, such as flux weakening by using mechanical actuators, split windings and hybrid excitation, et al. This thesis presents the design, analysis and control of a novel stator doubly-fed DSPM (DFDSPM) with true field controllable.Firstly, a new DSPM configuration, namely doubly-fed stator, is developed. Different from current DSPMs, an auxiliary airgap and a DC excitation winding are added aside the magnets. With the help of proper design of the reluctance of the auxiliary airgap, wide airgap flux regulating range is achieved by use of small DC excitation magnetomotive force (MMF). This novel design possesses the advantages of small excitation loss and effective field regulation, so the unique idea of this new configuration has applied and granted a patent.Secondly, a simplified equivalent magnetic circuit model of proposed DFDSPM is set up to illustrate the principle of operation, the relationship among the reluctance of the auxiliary airgap, the DC excitation MMF, and the airgap flux regulating range. The influences of different pole-arc coefficients and skewed rotors on the cogging torque and the commutation mode of DSPMs are analyzed. Then, a design concept of DSPMs is proposed, which includes that the rotor with the same pole-arc as that of the stator is skewed a half pole-arc. A six-state commutation mode for DSPMs is also presented. According to the feature of the magnetic field distributions of DFDSPMs, a unique design of block-combined stator structure with the magnets inserted at the side of the stator yoke is performed. Based on these, two prototypes with skewed and unskewed rotors are designed and built individually.Thirdly, to reveal the appealing characteristics of the DFDSPM, two-dimensional finite element method (FEM) is applied to analyze the static magnetic field distributions at different operational conditions such as different excitations, different rotor positions and different loads. The magnetic flux linkage, back EMF, the winding inductances as well as the...