Digital Twin Design Framework for Photovoltaic Generation Systems Using FMU and Modelica

Digital twins (DTs) play an increasingly crucial role in enhancing the performance and reliability of renewable energy systems. This article introduces a standardised and open-source framework for developing DTs in photovoltaic generation systems using OpenModelica and the Functional Mock-Up Interface (FMI) standard. In contrast to existing applications, which often involve complex and costly tools for modelling, the proposed framework prioritises accessibility. Comprising three main components—OpenModelica, FMI, and the PyFMI Python library—the framework is both open-source and standardised. The process begins with OpenModelica modelling the photovoltaic system, followed by exporting it as a Functional Mock-up Unit (FMU) using the standardised interface of the FMI standard. Then, the PyFMI Python library enables the step-bystep execution of the model with dynamic inputs, enabling the parallel operation with the real system. A practical application of a DT generated with this framework is presented. Data from both the DT and photovoltaic system, including electrical and meteorological variables, is logged in the open-source Things-board database platform. The DT incorporates models of both the inverter and Photovoltaic (PV) array, operating concurrently with the real photovoltaic system. Finally, the results reveal a close alignment between real and simulated power, validating the functionality of the DT design framework.