Study On Transient Characteristics Of DFIG Wind Turbine Considering The PI Parameters Of Control System

The impact on power system regarding safe and stable operation is becoming gradually clear due to the integration of large-scale wind power. Especially its contribution to grid short-circuit current in the case of failure can not be ignored. The double-fed induction generator (DFIG) is the most widely used in farms, and the existing analysis methods fault characteristics are no longer applicable to the DFIG. A mature failure analysis methods and mathematical calculation model has not formed, which makes the relay setting calculation difficulties and threatens the safe operation of power system.Firstly, this paper analyzes the principle and mathematical model of a typical directional vector control strategy of doubly-fed machine, and established a space vector model. The simulation model is built in PSCAD software and the model operating characteristics under different generator terminals voltage dip levels are analyzed, verifying the feasibility of the model. Secondly, the double fed induction wind generator physical mechanism of the motor internal electromagnetic transient process is analyzed when terminal voltage drops. Using the method of mathematical analysis, when the grid occurred mild terminal voltage drop, the analytic expression of short-circuit current considering the current inner loop of DFIG rotor side converter control system is derived in detail. And study on the analysis of short circuit characteristics and its frequency components, the proportion of the size of the mechanism considering double loop of DFIG control system is expanded. Finally, using the resulting fault current model, analyze some factors such as the short-circuit time plant operation conditions, the structural parameters of the unit itself, the voltage drop on the influence of the short-circuit current. Both the time-domain simulation model methods and the field test verify the correctness of the expression.In this paper DFIG failure mechanism and transient characteristics are more in-depth study in the grid failure, based on simulation analysis calculation method extends in the direction of further failure mechanism and failure calculation method. And the fault characteristic of DFIG during mild generator terminals voltage dip is expanded. The proposed calculation method for the failure of DFIG which takes into crowbar protection circuit delay action account has clear physical meaning, more accurate results. And provide a theoretical support for the applicability of current relay principle in the study of large-scale wind power grid.