A method for the determination of dynamic resistance of photovoltaic modules under illumination

Abstract

Dynamic resistance of solar cells and modules have been determined from a dark IV characteristic curve. In the determination, it is often assumed that series resistance R s is small and the shunt resistance R sh very large, their effects can be neglected. The resultant dynamic resistance can be called the external dynamic resistance R D . R D is normally taken to be the slope of the IV characteristic of a cell or a module. We present in this paper a new method to determine an internal dynamic resistance R d of a photovoltaic module based on one illuminated IV curve, taken into account finite series and shunt resistance. In the experiment, we measure illuminated and dark characteristics of a 4.5 Wp commercial X-Si solar module (9 V, 500 mA) at 25–27 °C, and calculate R d and R D . We see that R d and R D can be markedly different. Comparison is also made on the series resistance R s and shunt resistance R sh determined from single IV curve and two IV curve methods.