Can Photovoltaic Plants Cause Voltage Flicker? – Field Measurement and Screening

Abstract

Renewable energy, especially photovoltaic (PV), plays an increasing role in distribution grids. Due to the variable nature of solar irradiance, there is concern that PV plants may cause power quality problems, such as flicker. This paper describes flicker measurement data from five PV plants ranging from 400 kW to 10 MW, over twelve to twenty-four months. Analysis is provided to estimate flicker contributions from these plants. The contributions were not significant, and results show flicker levels (grid voltage fluctuations) depend more on the PV output power levels than the output variability. We found that PV ramping is too slow to cause light flicker in cases measured. Even the relatively large PV installations do not contribute in a noticeable way because of relatively slow power output changes. Data from this analysis are used to define the PV variability, grid strength and relative plant size that define a borderline of cloud related impacts on feeder voltage fluctuation. This borderline is formulated as a practical flicker screen for PV plants depending on size and grid strength. It provides an easy way to check flicker potential at the time of application processing.