Decrease in Photovoltaic Power Output from Ripple: Simple General Calculation and the Effect of Partial Shading

The effect of voltage ripple on the power output of a photovoltaic panel is calculated and tested experimentally. Voltage ripple induces a much larger power reduction than would be predicted from a conventional small-signal model of the panel´s I-V characteristic, even with small ripple amplitude. A simple expression is provided to calculate power reduction from rms ripple voltage, for any ripple waveform shape. The effect of ripple on power output can be much more severe under nonuniform irradiance as can result from partial shading. The results are important for 1) consideration of double-line-frequency ripple in single-phase inverters; 2) high-frequency switching ripple with any power converter in a photovoltaic system; and 3) perturbations and tracking errors in maximum-power-point tracking systems.