Research On Characteristics For Doubly Salient Electrical Magnet Starter/Generator

With the prominent advantages of simple structure, high reliability, controllable excitation, easy regulation of the output voltage, the Doubly Salient Electrical-magnet motor(DSEM) has the potential to be the starter/generator. It is a new choice for the research field of integrated starter/generator and quiet suitable for the application filed of aviation and wind power generation. Therefore, the research on the Doubly Salient Electrical-magnet Starter/Generator(DSES/G) has important significance.The characteristics of starting, switching, generating process for DSES/G are analyzed in the dissertation. The main topics include the voltage variation of neutral point in the processes of starter and generator, the control method of excitation current in the starter mode, the transient characteristics of the switching process from starter to generator, parameters identification and control method design in the generator mode and fault diagnosis and tolerant control after the inverter faults.The starter and generator working principles are given by the magnet field and mathematic mode of the 6/4-pole DSEM. The research on the variation of the neutral point voltage and its influence on the system are conducted based on the simulation analysis by the subsection model of the pre-linear inductance. In the starting process, a novel current control method and windings design are proposed in order to reduce the influence of neutral point voltage on the winding current and output torque. A new eight-diodes rectifier is given in the generating process from the perspective of utilizing the neutral point voltage, and the load capacity of the generator can be greatly improved by the method.In the process of starting, the influence on excitation circuit by the induced voltage generated by phase-windings is given in order to get the conclusion that the excitation must be controlled in constant current control mode in order to stand the torque at constant torque starting process. A novel control strategy with the feed-back of the rectified three-phase terminal voltage is proposed to realize the field weakening, and it is compared to the advanced angle control method. It can be seen that the new method can effectively realize field weakening control for DSEM, and the speed range is greatly improved.It is concluded from the integrated modeling method of starting and generating process form DSEM and the operation of inverter that the transient process from starting mode to generating mode has three stages: energy feedback, capacitor discharge and voltage buildup. The relationship between the operational stages is analyzed in detail. The validity of the theory and simulation is verified by the experiment results. According to the nonlinear characteristics of DSEM generator, its open-loop transfer function is determined by the method of parameters identification. It simplifies the design of correction parameters by eliminating the consideration of the nonlinear characteristics. And the accuracy of correction parameters design is verified by two DSEM generators of different power ratings.Inverter is the weakness of the motor drives, hence it is necessary to study the fault diagnosis and fault tolerant control in order to improve the DSEM starter/generator's reliability. The fault classification of the inverter in the operating status after fault is described. The novel fault diagnosis algorithm based on software and hardware are proposed to diagnose the common open-circuit and short-circuit faults. Also the method of fault tolerance control after high-failure-rate single switch open-circuit faults and single bridge-arm open-circuit faults is proposed through reconstructing the full-bridge inverter by the four-switch three-phase topology. The proposed fault tolerant system provides compensation to maintain the performance of the driver after open-circuit faults.A digital experimental test-bed on DSP and CPLD for DSEM starter/generator is built to verify the theory and simulation analysis.