| Mobile capacitor charge power supply(CCPS)system develops with the goal of high power,miniaturization,and repetition frequency.With development of technology,the requirement of power density and reliablity is getting higher.Brushless doubly fed machine(BDFM)is a machine generated from cascade motor.BDFM has good reliability because it does not have brush and slip rings.So BDFM can be applied to be high voltage generator.At the same time,frequency of control winding in BDFM can be adjusted when speed declines so as to hold on the output voltage of power winding and keep the performance of repeating pulse unchanged.That is the ability which common machine does not have.So BDFM has great superiority and wide application prospect in CCPS system.CCPS system with BDFM is a complex system,cooperation relationship of magnetic field in BDFM and characteristic of capacitor load are complex.Research of BDFM in this system should be based on the studing in the characteristics of BDFM and capacitor load.This thesis reseaches on the basic theory of BDFM.Proceeding from the magnetic motive force of rotor winding,this thesis investigates relationship of inner magnetic field and the operation theory of BDFM.Focusing on the the application scenario —capacitor charge power supply system,this thesis does a brief analysis on the system composition and load characteristic.Thses analysis laies the foundation of research on the BDFM theory in CCPS system.Based on the analysis of inner magnetic field relationship,this thesis derived the physical model and established a novel synchronous—asynchronous series equivalent circuit model of BDFM.Based on this circuit model,characteristics under different operation mode is analyzed and corresponding analytical curves are drawn which reveals the operation mechanism of BDFM clearly.Combined with these characteristic curves,practical significance which circuit model and theoretical analysis taking to machine design and control theory is analyzed.Capacitor charging is a progress with equivalent load changing quickly.Especially at the begining of charging progress,great transient current and oscillating electromagnetic torque will generate in power winding because of nstantaneous short circuit.This thesis establishes mathematic models for two pole pair magnetic fields respectively.According to cooperationship between fields,coupling relationship between two subsystems is given.Through coordinate system transformation,Double dq mathematic model of BDFM is established.Based on this model,transient short-circuit mode of power winding is analysed and short-circuit current and transient reactance is got.Influence factor of short-circuit current is analysed which can be used to guide the machine design.With this mathematic model,control strategy of variable speed constant frequency generator is proposed to keep the power winding voltage constant when rotation speed declines.Corresponding simulation model is established in Simulink to verify the control strategy.Based on the above analysis to BDFM,this thesis studies on the machine design in detail(main diamension parameter,pole pair cooperation,winding design,et)and established an intact machine design theory for BDFM in CCPS system.With this design theory,this thesis design and manufacture a 30 kW prototype of BDFM in CCPS system.Detailed parameters of prototype are given.Based on these parameters,finite element model of prototype is established and performances of noload mode and charging mode are simulated.With this finite element model,control strategy of variable speed constant frequency generator is simulated to verify this strategy under finite element mode.At last,experimental platform is established,noload experiment and charging experiment are conducted.Experiment results show that this prototype designed reaches the design target.Little difference between simulation and experiment is compared,cooresponding element is analysed to guide the follow-up machine design. |
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