Research On Rotate Speed Control Of Variable Speed Constant Frequency Wind Turbine

For the purpose of economic, the grid connected wind turbine needs to capture maximum wind energy and provides electric power for grid as much as possible, but the off grid wind turbine receiving wind energy is limited by system and loads and superfluous electric power must be consumed through other ways. Therefore, the controlling purposes should be different according to different controlled objects. The key of wind turbine controlling is rotate speed controlling of wind turbine rotors. Rotate speed of wind turbine rotors is researched in this paper on the basis of the different controlling purposes of the grid connected wind turbine and the off grid wind turbine.To the grid connected wind turbine, the purpose of controlling it working at optimal tip speed ratio or about is to capture maximum wind energy. The grid connected wind turbines are mostly large-sized or middle-sized wind turbines. Their systems are complicated, have many uncertainties in inside and outside of system, and working circumstance usually changes. These factors increase difficulty of controller design. In this paper, model reference adaptive control method is adopted to control the kind of wind turbine for the first time on characteristic of adaptive control. System model of the connected grid wind turbine is developed. A controller is designed employing Lyapunov's stability theory. Simulation and analysis are performed under two kinds of different wind. Simulation results show that the control effectiveness to the variable speed constant frequency wind turbine working below rated wind speed is very good.To the off grid wind turbine, according to the difference of it and the grid connected wind turbine, a new control idea is developed from another perspective inthis paper, namely according to loads variety to control rotate speed of wind turbine rotors when power storage set is filled and the captured wind energy is more than that of the effective demand. Mathematical models of permanent magnet synchronous generator (PMSG) and rectifier of the off grid wind turbine system are developed. A controller is designed to realize the new idea. Three different working conditions are simulated and analysed. Simulation results show that the presented control idea is feasible and the control method is effective.