An adaptive current protection for distributed network with wind generators

With the integration of wind generators in the distributed network, the power flow and fault current characteristic have been changed. The negative sequence impedance of the doubly fed induction generator (DFIG) is quite different from the positive sequence impedance after the crowbar circuit is activated. This characteristic poses a big challenge on the operation of the protection system. Traditional setting principle for the current protection is based on the assumption that the positive and negative sequence impedances of sources are the same, which is not satisfied any more. The influence of this unique characteristic on the short-circuit current under different fault types and fault positions is analyzed and a correction factor is introduced to modify the setting values of the instantaneous overcurrent protection and time delay instantaneous overcurrent protection adaptively. Finally, simulated results using DIgSILENT PowerFactory demonstrate the validity of the proposed adaptive scheme for the current protection in the distributed network.