**7. Conclusions**

The work described in this paper focused on the effects clipping, caused by oversizing a PV array with respect to the power rating of its converter. An insight into the benefits and drawbacks in terms of annual plant factor and energy losses of this commercial practice is presented. An analytical model was used to predict the annual power loss due to clipping; the validation of the model was performed by comparing the predicted power, limited at the clipping level, with real data over a time horizon of one year sampled every minute. An ESS sizing strategy based on recovering annual clipping losses is proposed. The strategy uses a power and energy approach, which considers statistical data to select the best fitting ESS ratings. For the analyzed PV plant, the sizing method determined that a ESS of 600 kWh per central inverter enables the retention of 80% of energy that would be lost due to clipping. From a power perspective, each central inverter, rated at 1.4 MW, requires being retrofitted with a 200 kW DC-DC converter for the ESS to enable the aforementioned clipped energy storage. In relation to the EST, LiIon based BESS was selected to perform a validation of the ESS and control system due to comparison of several criteria (LiIon have 10 times higher energy density than FC, about half the cost of FES among other values). Simulation results at power electronics level of the ESS, the central inverter, the grid connection, and their control show that the selected ESS can be retrofitted to existing central inverters, and provide clipping energy storage while still performing properly (perform MPPT, store/deliver energy, retain a controlled DC link and inject energy to the grid with high power quality).

The proposed methodology and analysis can be applied to determine, depending on their plant measurements and parameters, the size of a ESS to retrofit their PV plant for clipping energy storage. This information is necessary to perform an economic assessment, and how it can impact the levelized cost of energy (LCOE), and assist in the decision-making process. In addition, the sizing methodology can be adapted to perform new analysis on other ESS applications such as: load shifting, power curtailment, frequency and voltage regulation, base load generation, capacity firming, etc., providing further value for the ESS to the retrofitting of a PV plant. Furthermore, provided the proper model and data, it can also be extended to other renewable energy sources, such as wind energy and ocean energy. **Author Contributions:** N.M. conceived, designed and applied the sizing methodology, and wrote the original draft; S.K. provided insight, resources, and supervision and reviewed the manuscript; P.Z. provided insight, resources, supervision and analysis; P.W. provided relevant key theoretical and technical suggestions and reviewed the manuscript; G.B contributed with mathematical modeling tools and insight; and F.G. provided experimental data, problem conceptualization and practical insight.

**Funding:** The authors gratefully acknowledge the financial support provided by FONDECYT 1191532, AC3E (CONICYT/BASAL/FB0008), SERC Chile (CONICYT/FONDAP/15110019), CONICYT-PCHA/Doctorado Nacional/2014-21141092, and PIIC of UTFSM.

**Conflicts of Interest:** The authors declare no conflict of interest.
