Concerns to the emerging grid codes for wind turbines´ LVRT in weak AC grid

Wind turbine generators (WTGs) are required to ride through grid faults due to the increasing wind power penetrations. The existing grid codes around the world concerning low voltage ride-through (LVRT) were designed under the assumption that wind turbine operates in strong AC grid. However, under weak AC grid condition, the secure operating area (SOA) of WTG has changed obviously. Thus the behaviors of WTG restrained by the existing grid codes during LVRT may put itself at the risk of instability in weak grid, which may lead to the WTGs´ disconnection from the grid and deteriorate the system transient stability after faults. The Limitations of WTGs´ SOA caused by weak grid during LVRT are studied in this paper. And the results are verified by time domain simulations in Simulink/MATLAB.