Impact of Calculation Assumptions on the Performance Ratio of Photovoltaic Power Plants: Influence of Discarding the Night Period and the Period of External Limitations
Abstract
The Performance Ratio (PR) measures the performance of photovoltaic plants by the ratio between the actual AC (alternating current) energy generated and the theoretical DC (direct current) energy, based on the influence of irradiation. This calculation can also be adjusted for temperature to better approximate reality. However, as it involves summarizing variables in averages and sums for a given period, the PR is the result of all the factors that can impact the period considered. Therefore, the purpose of this work is to demonstrate how the choice of assumptions for calculating the PR, especially those related to disposal periods such as: average night-time temperature, imported energy for night-time operation of absorption or injection of reactive power by inverters and power limitation by external requests can distort the actual performance of the photovoltaic system. This impact can generate misinterpretation of results when the objective is to obtain: a trend throughout the month, improvement of results after actions, achievement of a result target or comparison between two different plants.
Keywords
Photovoltaic Plant, Performance Ratio, Influence of Temperature, Power Limitation Period, Night Operation, Photovoltaic System Performance, Key Performance Indicator