Constrained optimisation approach for parameter estimation of PV modules with single-diode equivalent model

摘要

This study deals with estimation of five unknown parameters in single-diode equivalent model of photovoltaic (PV) modules. First, to simplify the problem, the unknown parameters are reduced to series resistance and diode thermal voltage. These two parameters have significant role for PV model identification. On the other hand, PV model has the least sensitivity to the choice of parallel resistance. Hence, an approximation is utilised for parallel resistance and large value is assigned to this electrical parameter. Thanks to the proposed approximation, a novel cost function is designed for the reduced model such that all of its optimum solutions remain in a small interval of the reduced model. A set of inequality constraints are defined to generate an almost convex optimisation problem with all solutions located in a very small set. The gradient update laws are developed to find the solutions in the tiny set forced by the constructed optimisation problem. The proposed estimation technique generates an accurate model for PV modules, especially at voltage values lower and equal to maximum voltage value.