Research On The Voltage Stability Under The Influence Of The Control Strategy Of SVC In Wind Farm

With the increase of wind power penetration,the problem of voltage stability of-the wind power system is becoming more and more apparent.The frequently cascading trip-off accident of the wind turbines is proved to be one of the most serious voltage stability problem exposed in the wind power system.However,the researches on such issues still rest on the intuitive description and perception of the accident,which does not reach the essence of the problem.It is found that SVC acting as the dynamic var compensator does not play the role of dynamic reactive power regulator,analyzing the features of the wind turbine trip-off accidents under failure and non failure.To ease the problem of voltage stability caused by the control strategy of SVC,the analysis on the impact on the voltage stability of the system caused by SVC's control is developed in this thesis.Based on wind power integrated system in Zhangbei area,the mechanism analysis on high-voltage cascading trip-off accident of wind turbines under failure and non failure is developed,in which the formula of voltage-reactive power sensitivity is deduced.It put forwards that only to improve the low voltage ride through capability of the wind turbines could not avoid high voltage trip-off accident of wind turbines relying on the mechanism analysis.It is improving and regulating the control strategy of SVC the key point to solve the problem of voltage stability in the wind power system.The mechanism analysis between the system and different control strategy of SVC is developed,in which the point that whether the constant reactive power control on inductive branch and synthetically constant reactive power control of SVC could lead to over voltage of the system in extreme conditions is put forward.In contrast,inductively constant reactive power control of SVC is more practical,however,it is necessary to configure constant voltage auxiliary control for SVC considering the requirement of voltage stability of the wind power system.Considering the economy,voltage stability,and usability of the wind farm,the main-auxiliary coordinated control of SVC is raised,which could the switch between constant reactive power control on inductive branch and constant voltage control neatly.It could also decrease the risk of overvoltage of the system,and avoid the high-voltage trip-off accident of wind turbines.