FPGA-based real-time simulation of mismatched photovoltaic arrays

Abstract

This paper proposes an approach to the real time simulation of photovoltaic (PV) arrays that are subjected to mismatching conditions, e.g. partial shadowing. The method, which has been named Model by Zone (MbZ), adopts the best PV model depending on the operating conditions of the cells in the module: it switches among single-diode model (SDM), linear model and constant voltage model. An optimized digital hardware architecture exploiting parallelism of operations over a FPGA system is exploited to effectively implement the proposed model. It reduces the computation time and the use of hardware resources. The good trade-off between accuracy and computation time of the proposed technique has been demonstrated in two cases of study: by evaluating the long-term PV power production of a PV field subjected to dynamic shadowing conditions and by analyzing the model performance in a maximum power point tracking (MPPT) application. In the former case, the proposed approach improves the computation time by 182.5% with respect to methods that are available in recent literature, with a Relative Error (RE) at the Global Maximum Power Point (GMPP) lower than 0.39%. In the MPPT application, the proposed technique allows to achieve a MAPE of 0.0319% and 0.1892% in the string voltage and power calculation, respectively.