A Study On Doubly Fed Variable Speed Salient Pole Synchronous Machine And Its Excitation Control System

AC excited generator has many excellent characteristics, as its variable speed constant frequency, it may improve the stability of power system, it can not lose step even when operated in deep lead phase, it is especially applied in wind power generators and pumped-storage hydraulic power plant. As a new kind of AC excited generator, doubly fed variable speed salient pole synchronous machine adopt split salient pole and orthogonal winding. Variable frequency converter at rotor supplies the excitation winding. Its excellent characteristics mostly depend on the AC excitation system. Firstly, the fundamental principle of doubly fed variable speed salient pole synchronous machine is analyzed. The mathematical model in the synchronous reference frame is also established, and it will be the base of the research. The operation characteristic of the machine is analyzed. It shows that AC excitation capacity of induction motor depends on slip s of electric machines. With the variable speed of rotor, tracing maximal wind energy and optimum load regulation is realizable. Then stator flux oriented control is used to control active and reactive power of doubly fed variable speed salient pole synchronous machine. The simulation model is built on the software package of MATLAB/SIMULINK, and the simulation results indicate the validity of the excitation control. At last, the elementary excitation system made up of PWM converter and DSP is designed.