**5. Conclusions**

Given the increased penetration of wind power in the energy mix of current power systems, the need for public standard (i.e., generic) WT models to perform transient stability analysis is growing. IEC 61400-27-1, published in February 2015, defined four generic WT dynamic models able to be adapted to any particular WT vendor's commercial model. As it was published relatively recently, very few validation works with field data have been performed. Hence, TSO, DSOs, WT manufacturers and other stakeholders do not currently have evidence of the generic WTs' accurate response. The present work has validated three different generic WT topologies (type 3A, type 3B and type 4A) with six different actual variable-speed WTs from three manufacturers (Siemens–Gamesa, Senvion and ENERCON).

First, both IEC validation approaches, the play-back and the full system, were implemented, finding that when the play-back approach is used, the simulated voltage is identical to the measured voltage. In fact, when using the full system approach, the measured voltage experiences a slight hysteresis at voltage dip clearance, which cannot be represented by the simulations due to the lack of hysteresis in the transformer model.

Regarding the DFIG WT model validations, type 3B presented larger validation errors than type 3A, which is due to the crowbar protection system. In fact, the generic crowbar model implemented in type 3B is a simplification of a quite complex model.

Furthermore, the type 4 WT models provided a highly accurate response, for both active and reactive power, with respect to the three different type 4A WTs considered. In the case of the *ENERCON E-126* WT, a larger deviation between field and simulation was found, which was based on the particular representation of the current injection for this WT. In this sense, if a deeper voltage dip occurs, the active power results will be affected by the current limitation, which would yield a more accurate validation result.

**Author Contributions:** Conceptualization, A.H.-E., P.E.S. and E.G.-L.; methodology, A.H.-E., F.J.-B., P.G., S.F. and J.F.; software, J.L.S.-A., P.G. and S.F.; validation, A.H.-E., F.J.-B., P.G., S.F. and E.G.-L.; writing—original draft preparation, A.H.-E.; supervision, J.F., P.E.S. and E.G.-L.

**Funding:** This research was funded by the Spanish Ministry of Economy and Competitiveness and European Union FEDER, which supported this work under Project ENE2016-78214-C2-1-R, as well as the Agreement signed between the UCLM and the Council of Albacete to foster Research in the Campus of Albacete.

**Acknowledgments:** The authors would like to express their appreciation to the wind turbine manufacturers Enercon, Senvion and Siemens–Gamesa for their technical support, as well as to the rest of the members of Working Group 27 of IEC Technical Committee 88 in charge of the development of IEC 61400-27.

**Conflicts of Interest:** The authors declare no conflict of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, or in the decision to publish the results.
