# Ensuring Stable Operation of Wind Farms Connected to Distribution Networks
## 6 Conclusions  
In the event that the wind turbine does not comply with the requirements of the grid code of a particular country for stable operation under standard disturbances, it is necessary to implement technical measures at the wind farm and/or in the distribution network to reduce the depth of voltage dips and the duration of short circuit clearance.  
A methodology and an algorithm were developed to verify the parameters of the wind turbine LVRT characteristic to be set when connecting a wind farm to a distribution network to ensure their stable operation under various topologies and operating conditions. By utilizing these tools, one can check the settings of the LVRT characteristic for wind turbines under typical disturbances in the distribution network, analyze various technical solutions to prevent unnecessary shutdowns of wind turbines, and assess their effectiveness when designing a wind farm. This is crucial for the countries where the form of the voltage-time LVRT characteristic for wind turbines is not approved.  
Three operating zones were identified and described. Based on these, the recommendations were developed and presented to modify and adjust the settings of relay protection devices and automatic controls in the distribution network. These modifications aim to reduce the time it takes to clear short circuits.  
The efficiency of activation of the reactive current injection function at all wind turbines in the case of a short circuit in the distribution network has been proven, which makes it possible to increase the residual voltage at the inverter output from 0.028 \(U_{\text{nom}}\) to \(U_{\text{nom}}\), i.e., by 5-8 times, depending on the distance of the wind farm from the 220 kV substation. This allows preventing unnecessary shutdowns of wind turbines in the time range up to 0.2 s.  
Group and individual technical solutions are presented to ensure the stable operation of wind turbines under all types of standard disturbances, and their performance is assessed. The use of CLR allows increasing \(U_{\text{oper}}\) at the output of wind turbine inverters with a short-circuit elimination time of up to 0.9-1 s: from 8% \(U_{\text{nom}}\) to 25% \(U_{\text{nom}}\) (an increase of 213%) for three-phase short circuits; from 40% \(U_{\text{nom}}\) to 60% \(U_{\text{nom}}\) (an increase of 50%) for two-phase short circuits; and from 68% \(U_{\text{nom}}\) to 76% \(U_{\text{nom}}\) (an increase of 12%) for single-phase short circuits. The most effective technical solution involves making changes to the hardware of wind turbine inverters. However, in some cases, designers can use other technical solutions discussed in this article.  
Conceptualization, P.I. and A.S.; methodology, P.I. and S.F.; software, A.S.; validation, K.S.; formal analysis, P.I.; investigation, A.S., K.S. and S.F.; resources, P.I.; data curation, K.S. and S.F.; writing--original draft preparation, P.I. and A.S.; writing--review and editing, S.F. and K.S.; visualization, A.S.; supervision, K.S.; project administration, P.I.; funding acquisition, S.F. All authors have read and agreed to the published version of the manuscript.  
This work is supported by the Russian Science Foundation under grant 21-79-30013 in the Energy Research Institute of the Russian Academy of Sciences.  
Not applicable.  
The original contributions presented in this study are included in the article; further inquiries can be directed to the corresponding author.  
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.