Study On Busbar Protection Performance Of 220kV Intelligent Substation With Doubly Fed Wind Farm Incoming Line

Doubly-fed induction generator(DFIG)has been greatly developed due to its many advantages,such as variable speed constant frequency(VSCF),decoupling control of active and reactive power,demanding for converter capacity is small and so on.However,after the large-scale doubly-fed wind farm is connected to the power grid,there is a big difference between the fault current characteristics of doubly-fed wind farm and the fault current characteristics of the conventional power grid,which affects the relay protection performance based on the conventional power supply setting to some extent.On the other hand,with the development of smart substation adopting IEC 61850 standard,the development process of power system relay protection technology from traditional protection to digital protection has been accelerated.The smart substation busbar acts as a node for carrying new energy access,ensuring its safe and reliable operation plays an important role in improving the reliable power supply and safe operation of the power grid.Therefore,it is very necessary to study the protection of smart substation busbar with doubly-fed wind farm access background.Studying the fault characteristics of new energy sources is an important basis for studying the relay protection of power systems.Because the DFIG adopts different control strategies,it will cause different fault characteristics.For this reason,the control strategies of grid-side and rotor-side converters and low voltage traversing strategies of doubly-fed units are studied,and the fault current characteristics of doubly-fed units are analyzed theoretically.Based on the wind farm equivalence theory,the simulation model of the doubly-fed wind farm is constructed based on RTDS,and the fault current characteristics provided by the doubly-fed wind farm are verified by simulation.In the research of smart substation busbar protection,the new technology adopted in intelligent substation and its influence on busbar protection are analyced.The principle of current sampling value differential protection used in busbar protection device of smart station is studied,and the of R and S values selection,the fuzzy zone discrimination and the factors affecting the correct operation of protection in sampling value differential protection are analyzed.Based on the above research,combined with the relevant relay protection test standards,the simulation model of 220 kV intelligent substation busbar protection with doubly-fed wind farm incoming line is built and simulated,the experimental results show that the current sampling value differential protection sensitivity is reduced under this background.In this paper,a busbar sampling value differential protection algorithm suitable for new energy background is proposed,and the feasibility of the algorithm is proved by RTDS simulation.In addition,taking the CSC150/E digital busbar protection device as an example,the closed-loop experimental principle of the busbar protection device is completed by means of the GTNET card in RTDS is introduced.Then the closed-loop test system of the busbar protection device with the doubly-fed wind farm access is constructed.The closed-loop experiment proves that the busbar protection device can operate correctly under the background of new energy access.