Cloud effects on distributed photovoltaic generation: slow transients at the Gardner, Massachusetts photovoltaic experiment

The Photovoltaic Generation Effects project was undertaken to verify that no serious consequences arise from the interconnection of distributed photovoltaic generation on electric power distribution systems. Here, slow transient responses at frequencies corresponding to fluctuations of photovoltaic generation resulting from the passage of clouds over the experiment site in Gardner, Massachusetts, are described. A statistical basis is developed extending the measured results to the entire area served by the distribution circuit in Gardner, as it might be both loaded and equipped with photovoltaic generation in the twenty-first century. Observations and analyses of the solar irradiance and photovoltaic system performance at a single point indicate that there are insufficient step changes in load levels to cause voltage flicker problems. Numerical techniques developed for interpolation of irradiance conditions over the experiment site are adequate for estimating the irradiance at intermediate points and times. The technique appears to be adaptable to extrapolation over larger areas