Research On Variable-speed Constant-frequency Dfig Wind Power Generation's Main Controller Based On PLC

Wind power generation is a sort of inexhaustible and renewable resource. In the development of all kinds of renewable and new resources, the wind power generation has the great potential of scale production and the commercial development prospect.In variable speed constant frequency doubly-fed wind power generation system, the study of how to control wind power generator to run at optimal rotor speed, namely maximal wind power tracking ,turns into a available approach of enhancing variable speed constant frequency wind power generator operation efficiency. The control system of wind power generators is the core of generators, and has the close affinity with the other part of wind power generators, whose accurate control and perfect function affect the safety and efficiency of generators. Its control technology is one of the key technologies of wind power generators.Wind farms are usually located in remote areas even at the sea, and natural condition is poor, so it is necessary for the wind power generation to realize the automatic running, and that the control system is more reliable. However, the present domestic wind power control systems are mainly purchased from abroad, with poor universality and compatibility. Therefore, it has become a popular research topic to develop our own control system. Firstly,the variable speed constant frequency wind power generation theory and the system structure are analyzed in this paper. The relation between active and reactive power of DFIG, and the limits of the reactive power are studied. The idea of DFIG participating in wind power generation system's reactive power regulation is proposed. The procedure of maximal wind power tracking is studied. Then four maximal wind power tracking methods , which are wind turbine speed control method,tracking optimal power-rotor speed curve method,mountain climbing curve method and power sluggish loop compare method are mainly analyzed and compared. At last the tracking optimal power-rotor speed curve method is considered to be the best way to realize the maximal wind power tracking.The condition monitoring system's parameters, the monitoring positions and the monitoring ways are analyzed. For monitoring and fault diagnosis, research on vibration signals is focused on. The wavelet theory has a big advantage in analyzing the vibration signals. The evaluation standards are studied and the suggestion of the standards-choosing is presented.Based on the requests of main controller and the features of PLC, the PLC is selected to be the hardware to realize the main controller. The designs of main controller's hardware structure and software structure are presented.Based on the experiment plat of DFIG wind power generation system in the laboratory, the main controller is designed and the main functions are tested. The testing results prove the main controller is successful.