Optimal Scheduling of Battery-Flywheel Hybrid Energy Storage System for Off-Grid Power System with Renewable Energy

The issue of climate change is a crucial reason for the expansion of renewable energy sources. The use of renewable energy sources such as wind power and photovoltaics must be considered. Deploying the right energy storage technology can help overcome problems such as intermittent renewable energy or power fluctuations in distribution. A hybrid energy storage system (HESS) includes two or more storage devices with complementary electrical charge/discharge characteristics to provide the required energy and power. There are two main complementary characteristics of energy storage systems: energy density and power density. Some energy storage devices have the characteristics of high energy density but low power density and vice versa. Therefore, HESS mainly consists of technologies that can complement each other in these aspects. Both flywheel energy storage (FES) and battery energy storage (BES) technologies combined as storage technologies to support the provision of intermittent energy. The optimal HESS scheduling for renewable energy systems consisting of PV and wind turbines using nonlinear programming. The approach in this paper is to plan the power-sharing for each energy storage system based on minimizing the total project cost, operation and maintenance (O&M) cost, and life cycle of each type of energy storage technology. The optimal power sharing of the two internal energy storage technologies in HESS achieve by considering the ramp rates of BES and FES.