Influence factors on low-voltage operation characteristics of large-scale wind farms

Although the low voltage ride through (LVRT) capability is no longer a difficulty for most of the existing wind turbines, the low voltage operation characteristics of different wind turbines and reactive power compensation devices varies a lot. The LVRT capability test result of a single wind turbine is not equal to the performance of a whole wind farm during gird fault, especially when the wind farm is considerably large or the grid is weak. As a result, the influence factors on the low voltage performance of large wind farms need to be studied. In this paper, electromechanical transient simulation models of doubly fed induction generator (DFIG) wind turbine and direct-driven permanent magnet synchronous generator (D-PMSG) wind turbine were built in power system simulation software DIgSILENT/PowerFactory. The accuracy of the models was validated by comparing simulation results with test results. On the basis of the validated models, a 100MW wind farm was modelled with DFIG and PMSG wind turbines respectively, and the LVRT performance was compared. The interrelationship between the control characteristics of reactive power compensation devices and the overvoltage after fault clearance was analyzed. It is concluded that, when grid fault occurs, the reactive power characteristics and the overvoltage ride through capability of wind turbines as well as the behavior of the reactive power compensation devices are important factors that may affect the LVRT capability of a wind farm.