Robustness Evaluation of Operational Methods for Off-grid Renewable Energy Systems Installed on Remote Islands

Installation of renewable energy can improve the economic and environmental performance of off-grid systems on remote islands. However, because renewable energy generation (e.g., photovoltaic generation) fluctuates with weather conditions, operating methods utilizing a battery energy storage system (BESS) and diesel generator (DG) should be considered. Previous studies have focused on operational control using mathematical optimization methods, which often consider a stable power supply, such as a DG operated all day. However, in the future, power is expected to be supplied only by inverter-based sources during some time periods for carbon neutrality. In such situations, these methods may not be robust to prediction errors. Moreover, no research has been conducted to evaluate the robustness of operating methods throughout the year, assuming actual operation. In this study, we propose event-triggered control methods where a BESS and DG are cooperatively controlled based on the state of charge (SOC) of the BESS to achieve a stable supply. Furthermore, in the proposed methods and mathematical optimization, operational parameters and plans were determined from prediction data and applied to actual data to quantitatively evaluate the robustness in actual operating conditions. Consequently, the results confirmed that the proposed methods have excellent robustness at any renewable energy rate. This is because the operation can be flexibly changed according to the SOC status even when the prediction errors are large. The proposed methods are simple to operate, achieve a stable supply, and can contribute to the penetration of renewable energy into offgrid systems.