Estimation of Photovoltaic Cell Parameters Using Measurement Data of Photovoltaic Module String Currents and Voltages

Photovoltaic (PV) models play an important role in the simulation analysis and fault diagnosis of PV systems. The single diode model (SDM) is the most frequently used model in research and applications. There are numerous proposed methods to identify the SDM parameters. However, the characteristics of PV cells alter during the lifetime in normal operating environments; these variations may be due to degradation, faults, dust, weed, and so on. Therefore, it is crucial to estimate the actual parameters of the PV cells that represent those present state. The contribution of this article is to propose a method to estimate PV cell parameters on the basis of the measurement data regarding the currents and voltages of the PV module strings. A PV string model is described on the basis of the adaptive SDM for the PV cells in the system, and the parameters of each cell model are obtained by minimizing the difference between the measured string voltages and the string voltages computed by the model. The application of the proposed method to real data measured in a PV power plant is also presented to evaluate the proposed method.