Evaluation of solar module equivalent models under real operating conditions-A review

A number of mathematical models are available to model the performance of solar modules under varying operating conditions. Most commonly recognized and used models include (a) the basic three-parameter model, (b) the five-parameter model, and (c) the seven-parameter model. The basic three-parameter model does not incorporate series and shunt resistance for IV curves. The five-parameter model incorporates the effect of series and shunt resistance, and the seven-parameter model further includes the additional effect of temperature and irradiance variation on solar cell parameters. While all these models reasonably predict IV profiles of solar modules at small variations from standard testing conditions (STCs), their performance in modeling the module performance at low irradiances and high temperatures is far from ideal. This work primarily reviews the accuracy of available models for various module technologies not only under STC conditions but also over a wide range of operating conditions. The accuracy of modeled results is quantified (with datasheet results) for 10 crystalline silicon (c-Si) based modules as well as 9 thin film module (TF) samples (commercial modules) at multiple irradiance conditions. The results show that the three-parameter model generally overestimates the power output both for c-Si and TF modules. The five-parameter model predicts TF technology more accurately compared to the other two available models, whereas the seven-parameter model is most accurate for c-Si module modeling under varying operations.