Research For Relay Protection Caused By Wind Power Connected To Grid

As a kind of clean and renewable energy,wind energy has the most mature technology,and it is one of power generation with largest development conditions and commercial development prospects.However,the topology of the distribution network will be changed when the wind power connects to power grid,which will make the setting and its correct action of original protection in distribution network change and cause tripping or malfunction and other issues that may lead to expanding fault or reducing the reliability of power supply,so that the distribution network can't operate with secure,reliable and stable state.Therefore,the study on problems of relay protection caused by wind power connected to distribution network has an important significance.A thorough study on the impacts of original overcurrent protection generated by the wind turbine connected to 10 kV distribution network was made in this paper,the main work was as follow:(1)The classification,the structure and working principle of the wind turbine was described,the network models of the wind turbine and simulation study of its fault characteristics was established.(2)The effects of wind power connected to the distribution network with the traditional co-ordination of overcurrent protection was theoretically analyzed in the paper.The main factors include location of wind power,capacity of wind power and line's length.(3)Taking squirrel-cage induction wind turbine as an example,PSCAD was used to build a simulation model that a wind farm connects to 10 kV distribution network;and short-circuit current waveform and the size of setting value in the distribution network with wind power compared to traditional one.In the model with wind power,different models by setting different fault locations,different capacity of wind power and different length of lines was respectively simulated and the foregoing theoretical analysis was verified,that is when the capacity of wind power increased to a certain extent,which will lead to malfunction at upstream of accessed point,problem of cooperation among each protection at downstream,so this couldn't guarantee the selectivity;on the other hand,increase of length would result in the malfunction of protection.(4)For the distribution network with wind power,a new method that Master-slave controlled Directional Pilot Protection applicable to power system with wind turbine was adopted.It theoretically showed that Relay Protection could realize the correct action and it was verified with a simulation.The main advantage of new protection scheme in this paper is that downstream fault of direction relay can be reacted by setting the positive direction of direction relay in both ends of line to oppositedirection,and there is no necessary to consider the location and the capacity that wind turbine connected to the distribution network,complex structure of grid,variation of operating mode and so on,which can effectively and speedy remove the fault to solve the problem of relay protection caused by wind power connected to distribution grid...