The Effect Of Wind Power T-connected To Power Grid On Traditional Distance Protection And Countermeasures

With the increasingly exhaustion of traditional energy and the objective needs of environmental protection,it is inevitable that clean energy such as wind power generation gradually replaces traditional energy.When the single fan has high power,the installed capacity and the real capacity increase rapidly,and the power load is high,large-scale and high-capacity wind power is connected nearby by T-connection,which leads to the adaptability of the original distance protection,which can not meet the reliability requirements of the relay protection after the wind power grid connection.In order to solve this problem,this thesis proposes a solution from two dimensions of "point" and "line".The research content of this thesis mainly includes several aspects:(1)This thesis briefly introduces the basic concepts related to distance protection,theoretically analyzes the impact of wind power t connected to the bus of dual power system on the protection of the upstream,downstream and adjacent lower sections of the line,and carries out modeling verification.The results show that the impact of wind power integration on the distance section II is significantly greater than that on the distance section I.In extreme cases,the traditional distance protection will have maloperation,failure to operate and coordination It’s a difficult problem.(2)In view of the action judgment of wind power t connected to bus,based on "point",the paper proposes an adaptive distance protection scheme based on the inclination angle of transition resistance.Under the condition of unknown transition resistance,the angle relationship between the measurement impedance,short circuit impedance and R-axis is used to eliminate the influence of the transition resistance on the protection device,and the short circuit impedance can be tracked adaptively.The scheme is simple and effective,and it does not need to be modified.It has high economic and practical operability,which has certain guiding significance in field engineering.When wind power is connected to the line,an auxiliary criterion based on phase comparison of fault current component is proposed.It can accurately distinguish internal and external faults in the zone.It is less affected by fault type,fault point position,transition resistance,phase difference of power supply and grid connected capacity of wind power,which can make the protection device operate reliably.(3)Aiming at compound fault(short circuit of main circuit and defect of secondary circuit),a regional protection scheme based on multi-point information is proposed by means of "line" and using the protection information of all buses on the whole line.When the protection is started first and then the TV is disconnected,the distance protection will malfunction.The following protection strategies are proposed:according to the quadrant of each short-circuit impedance,the state information is summarized and uploaded to the regional host,and then the real fault interval is determined by the regional host logic to prevent protection malfunction.The scheme has low requirements for communication timeliness and hardware configuration of protection device,and does not need to modify the original distance protection device,so it has high economy and practical operability.Based on MATLAB / Simulink modeling and simulation,the correctness and effectiveness of the above protection scheme under various conditions are verified.