| The integration of large-scale wind power into power system is one of the important changes in grid electric power sources in China.Based on the characteristics of wind resource and its distribution,large-scale wind power development mode with high concentration and long distance transmission is widely used in China which causes a high wind power penetration in some area and poses a serve challenge for the safe and stable operation of power system.Unlike traditional synchronous generator,the main stream commercial wind turbine is usually connected to grid by converter which has the characteristic of control flexibility.As a new kind of electric power source,the operation and control of wind turbine during grid fault and the analysis of power system with wind power integration have become the important technology challenge in wind power development.This paper deals with DFIG-based wind turbine(DFIG WT)and full scale wind turbine(FSWT)respectively and mainly focus on wind turbine converter rating constrain and the positive and negative sequence control of wind turbine is explored during grid serve asymmetrical faults.Then based on the above research results,the influence of wind turbine on grid voltage profile has been analyzed and some new phenomenon and problem has been brought out which possess an important meaning for the understanding of wind turbine when it conduct as power source and power system safety operation.Firstly,this paper outlines the dynamic models of DFIG WT and FSWT and analyzes the key point and solution of converter positive and negative sequence control with GE wind turbine model.Based on the further analysis of wind turbine converter constrain,the positive and negative sequence current control diagram and the controllable region of the two main commercial wind turbine is given.What's more,the limitation and division strategies of positive and negative sequence current is researched so that the wind turbine positive and negative sequence current control strategy which satisfy the control constrain is brought out and achieved.Secondly,based on the control strategy brought out above and by means of choosing typical simulation topology and setting different simulation scenes,with consideration about different limitation and division strategies of wind turbine positive and negative sequence current,on the one hand the applicability of the wind turbine positive and negative current strategy is verified in this paper,on the other hand the influence of wind turbine on grid voltage profile is summarized and some new problem which is different with traditional power system is also pointed out and the reason is analyzed.Finally,for a further research on the reason of the problem which is caused by wind turbine and different from traditional power system,this paper makes a summary about the differences of wind turbine and traditional synchronous generator from a unified view of equipment inside coupling and internal voltage when they both conduct as electric power source.The outcome is helpful for the understanding of wind turbine characteristics. |
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