Research On Variable Speed Constant Frequency Wind Energy Generation Technology

Recently,the renewable energy such as wind power have been strongly encouraged because of environmental problem and shortage of traditional energy sources in the near future.Based on the tradional consrant speed constant frequency wind energy generation,this paper has a focus on the variable speed constant frequency wind energy convertion technonogy which using direct drive permanent magnet synchnonous generator and theory analysis and simulation are carried out in detail .First,variable speed constant frequency wind energy convertion theory is described in this paper ,then presents a review on the development of wind turbines control and the main types of generator and static converters used to interface variable speed wind turbines to the electric grid .Then discuss main circuit constructure and advantage of direct drive wind energy conversion system and introduce pitch-control method for wind power traction and electric power stability.Simply aerodynamic characteristic of the turbine is analysised and permanent magnet synchnonous generator math model is established .To convert the variable frequency electricity into utility grid, back to back four-quadrant PWM-VSI is used and three typies of control strategy is presented to capture the maximum wind energy and transmit energy.Then simulation is implemented to test the control strategy.In the following chapter a simple ac-dc-ac converter with a dc-dc boosting chopper is proposed to transmit the wind energy into electricity energy and two control strategy is presented. Research of maximum power extraction algorithm for inverter-based variable speed wind turbine system is going on in the last chapter.Main maximum power extraction algorithm is discussed and compared.A new MPPT control algoririthm is discussed to get fast and stable traking of maximum wind power in detail,then advanced hill-climb searching method has been developed for maximum wind power traction.