| Synchronous reluctance motor (SRM) is a competitive candidate for the advanced high-performance AC variable-speed drives. The early version of SRM is equipped with a starting cage to generate the asynchronous starting torque. However, the rotor with such a structure has low saliency ratio and poor power factor. As the modified version, the so-called axially laminated anisotropic (ALA) rotor motor is proposed. The distinctive rotor lamination brings a lot of advantages, such as high saliency ratio, great power density, high power factor and efficiency, and so on. Actually, ALA rotor motor combines the advantages of induction motor, permanent magnet (PM) motor and switching reluctance motor, and becomes a potential alternative in various AC drive systems.In previous literature, the open-loop startup of ALA rotor motor is characterized as oscillation and asynchronous operation. To improve the dynamic stability, a mechanical damper is always required. But the employment of damper increases the complexity of the assemblage and reduces the number of available output shaft. Therefore, the direct torque control (DTC) is introduced to manipulate the operation of ALA rotor motor. Although many achievements have been reported in the research of DTC scheme used for induction motor and PM motor, the application to ALA rotor motor is firstly proposed. Compared with the counterparts, the DTC scheme applied to ALA rotor motor is featured with fast response of rotor flux and easy-to-control magnetic field.On the basis of the feature and principle of SRM, the mathematical model of ALA rotor motor inαβ0 coordinate system is established. Then various available control strategies for SRM are surveyed and their characteristics are highlighted. Based on the wide investigation, the background of DTC scheme is reviewed first. In succession, a comprehensive introduction to principle, development and prospect of such a technique is made. The difference of DTC schemes applied to PM motor and induction motor is underlined as well. It is noted that the control strategy used for these motors cannot be transplanted directly to ALA rotor motor regardless of the structural difference.To obtain the optimal performance, a novel DTC scheme customized for ALA rotor motor is proposed, i.e. discrete space voltage modulation (DSVM). By employing this technique, the torque and current ripple, especially at low speed, can be attenuated remarkably, on the condition that the switching frequency is unchanged. Furthermore, the online calculation of the duration of voltage vectors is avoided, hence the simplicity of the algorithm is maintained. The feasibility and validity of the proposed scheme is verified by simulation made with commonly used software Matlab.In order to make a validation of the theoretical analysis, an experimental investigation is implemented. A digital control system based on TMS320LF2407A is set up. The configurations on hardware as well as software are introduced in detail. Besides, a large number of experiments on startup, multi-step acceleration and normal-reverse rotation of four-pole ALA rotor motor are carried out. It is validated that the motor with the proposed DTC scheme has improved robustness and fast response.In addition, the experiment on two-pole prototype reveals that the proposed scheme has good flexibility to motors with different saliency ratios. The contrastive experiments on motor with and without mechanical damper reveals that the mechanical solution is not a necessity in close-loop operation. By utilizing the DTC scheme, the motor presents satisfactory startup performance and dynamic response. It implies that the DTC scheme may be the essential solution to the dynamic stability of ALA rotor motor.At the end of the dissertation, some suggestions aimed to future work are proposed.
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