Optimal power smoothing control for superconducting fault current limiter-magnetic energy storage system

•A novel criterion: available Smoothing Energy Capability is proposed for power smoothing.•A novel multi-input and multi-output fuzzy logic (FLC) is proposed for power smoothing.•An offline training and online implementation method is presented to optimize the FLC parameters. Optimal energy management is a major challenge for most energy storage systems (ESSs), which is especially a big concern for the superconducting fault current limiter-magnetic ESS (SFCL-MES). To prevent malfunction, the superconducting coil (SC) current of the SFCL-MES needs to be controlled strictly within a well-defined operational range. To optimally utilize the energy capability of the ESS while keeping the state of charge (SOC) within a safe range, a novel multi-input multi-output fuzzy logic controller (FLC), which adjusts both the filter time constant and the SOC regulator gains, is proposed for optimal energy utilization. The parameters of the FLC were further optimized offline by particle swarm optimization with real collected operational data. The optimized FLC has been successfully implemented on a 1MVA/1MJ prototype installed in a wind farm. The operational results of the prototype demonstrate the good performance of the proposed approaches.