**7. Conclusions**

This paper has presented the control of active and reactive power for a PV generator considering its capability curves variation applied in a large scale photovoltaic power plant. For this purpose, the current paper has presented the general configuration and control structure used commonly in a LS-PVPP. Then the active power control for a PV generator has been presented considering active power curtailment and active power reserves. Additionally, the control of reactive power was also studied under two different considerations: active power priority or reactive power priority taking into account the corresponding capability curves. Finally, DIgSILENT PowerFactory was used to simulate the control proposed under different conditions. From the control developed and the simulation some conclusions are presented.

The quick variation of solar irradiance affects not only to the active power response but also to the reactive power. When the solar irradiance is high, then the reactive power capability is reduced. Besides, this could disrupt the plant with quick variations of reactive power, this can be reduced with an appropriate control of the reactive power.

The modulation index and the dc voltage value play an important role on the point of operation of the PV generator when reactive power is injected. For an appropriate control the maximum modulation index can vary between 1 to 1.75 to comply grid code requirements.

The capability curves play an important role in the control of the PV generator when active and reactive power control are considered. These curves should be taken into account for each solar irradiance, ambient temperature, dc voltage and modulation index. The reactive power reference can be achieved by the consideration of these capability curves together with the control.

Considering the grid code requirements regarding the managemen<sup>t</sup> of active power, it can be stated that working with RPPT for a given reference helps to comply the basic requirements as power reserves and power curtailment. However, a deeper study on ramp rate control must be developed considering variable solar irradiance. In the case of reactive power, grid codes should also consider the behavior of the PV generator according to ambient conditions in order to set the limitations.

**Author Contributions:** Research concepts were proposed by A.C.-T. and O.G.-B. Manuscript preparation and data analysis were conducted by A.C.-T., M.A.-P., E.B.-M. The edition of the manuscript was performed by all the authors.

**Funding:** The work was conducted in the PVTOOL project. PVTOOL is supported under the umbrella of SOLAR-ERA.NET Cofund by the Ministry of Economy and Competitiveness, the CDTI and the Swedish Energy Agency. SOLAR-ERA.NET is supported by the European Commission within the EU Framework Programme for Research and Innovation HORIZON 2020 (Cofund ERA-NET Action, n<sup>o</sup> 691664). It also was funded by the National Department of Higher Education, Science, Technology and Innovation of Ecuador (SENESCYT).

**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.
