Hierarchical multi-time-scale energy management system for secure and economic operation of islanded microgrids with GFM/GFL control

Abstract

The variability of renewable energy sources (RESs) and fluctuating load demands can cause power fluctuations in converter controllers, undermining energy management systems and posing security and economic risks. To address these challenges, this paper proposes a novel hierarchical multi-time-scale energy management system (EMS) to enhance the secure and economical operation of islanded microgrids under hybrid grid-forming (GFM) and grid-following (GFL) controls. The proposed methodology integrates GFM and GFL actions into the secondary and tertiary layers, each optimizing distinct objectives in a convex model to ensure secure and reliable economic power dispatch. Moreover, the proposed framework incorporates an energy management strategy for hybrid energy storage systems with high capacity and power density under different control operations, including unified renewable fuel cells (URFC), while adhering to real-time operational constraints. The secondary layer employs model predictive control (MPC) to address GFM power tracking discrepancies, ensuring short-term voltage and frequency regulation, while the tertiary layer uses mixed-integer linear programming to update power references based on economic and security constraints, particularly ensuring GFM margin compliance. The proposed framework’s effectiveness is validated through MATLAB/Simulink simulations and hardware-in-the-loop testing.