Design For System Of Vary Speed Constant Frequency To Connect Grid

With the rapid development of industrial modernization and the acceleration of the modern science and technology, VSCF system is more and more used in life. In the field of new energy power generation, such as wind power generation, waste heat power generation, most of the back-to-back double PWM converter be used to energy transmission. With the use of a large number of power electronic devices, it will bring a large number of harmonics into the entire power generation system and power grid. At present, most of the harmonics uppression at home and abroad is realized by passive filter such as L, LCL However, due to the motor and dead time effects, a large number of harmonics in the stator of the motor are also provided. These harmonics affect the efficiency of the motor power generation and heating, and even cause the motor damage.For motor stator harmonic suppression has become a problem in the application of VSCF system.First of all, two important topological structure in system of variable speed constant frequency (VSCF) were introduced in the paper and the direct drive permanent magnet wind power generation system was chosen as an example, then some common harmonic suppression strategies were introduced. In order to facilitate the analysis of the harmonic, this paper introduces a back-to-back PWM converter common control strategies. And the effect of the control strategy is verified by the simulation of MATLAB/simulink.Secondly, starting from the aspect of the motor and the control of the converter, this paper makes a deep analysis on the reason of the harmonic generation of the motor stator. Due to the manufacture of motor, the stator side will produce some torque of the Cogging, so as to bring the irregular harmonic. Due to the dead time effect of converter will bring a large number of harmonics of the rules, and the voltage of switching pipe will increase these harmonics and will improve the affect of these. These harmonics can be decomposed into a series of odd harmonics by Fourier, and the stator of the motor is connected to the Y, which is offset by the multiple sub harmonic of the three, and the harmonic content of the generator stator is obtained. The proposed conclusion is verified by MATLAB/simulink simulation. For these harmonics, first, the traditional proportional integral resonant controller, but it is found that the traditional proportional integral resonant controller bandwidth in permanent magnet synchronous generator of harmonic suppression is too small and poor stability by analysis of bode diagram. In order to solve these problems of the traditional proportional integral resonant controller, this paper presents an improved proportional integral resonant controller, system bandwidth and stability is greatly improved by Bode diagram, the value of the proportional integral resonant controller in engineer be enhanced.In five chapter, first the experimental platform of hardware selection and function are introduced detail; then the experimental platform of software process is analysed detail by the flow chart. Finally, the built experimental platform of the proposed control strategy was used to run the test and achieve the data.