Simulation Research On Maximum Power Tracking Of Directly Driven Wind Energy System

Three-phase alternating current from the generatior directly charges the battery via uncontrollable rectifying, or through an inverter to supply the load in existing small-scaled wind power generation system. Because the wind power conversion process isn't controlled, it has a poor efficiency (0.3 around). But the maximum value of the power efficiency is 0.593 according to Betz' theory. If the wind turbine is always controlled to operate at the best tip speed ratio, the generating capacity per year can be improved by 20% to 30%.This paper focuses on maximum wind energy extraction strategies of variable speed turbine power generation systems for achieving the highest energy output. In order to provide user with three-phase electronical energy, a variable speed wind turbine requires a power electronic converter to convert a variable voltage and variable frequency source into a fixed voltage fixed frequency supply.The main results and work of this paper are as follows:Firstly, Base on the charicterestic analysis of wind power generation system components, including wind turbine, permanent magnetism synchronous generation (PMSG), rectifier and three-phase inverter, the first work of this paper is that the mathematical models are modeled by hand and then simulation models are modeld by the simulation software MATLAB/SIMULINK.Secondly, maximum wind energy extraction technology of the directly driven wind power generation system is analysised by simulation software on the base of the mathematical model. Speed control strategy is put out to realize the wind turben optimal operating, power efflcinency is improved to the maximum value (the largest C_p value of this paper is 0.46), and realize the aim of the maximum wind energy extraction below the rated speed. Although different wind turbine has differentλ-Cp characteristics, they all have a maximum value, and they have the same rules.Thirdly, when the wind speed supasses the rated speed (12m/s in this paper), the way of increase load torque of generation is adopt to limit the wind turbine's output power, making the wind power generation system run safely.Fourthly, when the generator reaches optimal run process, the fixed DC voltage is output by mean of controlling the rectifier, and suitable AC voltage by contraling the inverter.