A Dynamic Reactive Power Control for DFIG Wind Turbines andIts Impacts on Distribution Protections

With the increasing penetration of distributed generations（DGs）into power grids，the fault ride-throughability of DG is attracting more and more attention.Recent grid codes require a DG to maintain its connection withthe grid during grid faults and to play an active role in the recovery of grid voltage.This paper chooses the doubly- fed induction generator（DFIG）as the typical wind turbine for study.Firstly，a dynamic reactive power controlstrategy is proposed to improve the fault ride-through characteristic of a DFIG.The contributions of a DFIG to thefault current under the dynamic reactive power control and the Crowbar control are analyzed and compared based onthe mathematical expressions and control behaviors.The impacts of a DFIG under two control strategies ondistribution protections are discussed.Studies show that although a DFIG under the dynamic reactive power controlprovides more fault current component than one under the Crowbar control，its impacts on distribution protectionsare acceptable.Finally，a10kV distribution network with a DFIG is simulated in PowerFactory DIgSILENT.Thesimulation results prove the correctness of above theoretical analysis