Energy management for grid-connected hybrid offshore wind-tidal storage power systems

Abstract

The increasing demand for renewable and sustainable energy solutions has intensified interest in hybrid offshore energy systems, particularly those combining wind and tidal power. This research focused on advanced energy management for grid-connected hybrid offshore wind tidal storage power systems, specifically focusing on South Africa’s coastal regions. Leveraging South Africa's abundant marine resources and addressing its growing energy needs, this study presents a comprehensive framework for efficient energy conversion and seamless grid integration of renewable sources, aiming to optimize power output and enhance grid stability. The primary aim was to develop and validate an advanced energy management system for such hybrid offshore systems, targeting improved renewable energy integration and enhanced grid reliability. South Africa faces the critical challenge of meeting increasing electricity demand while transitioning to sustainable and dependable renewable energy sources. The intermittent nature of offshore wind and tidal energy, combined with constraints of the existing grid infrastructure, underscores the necessity for optimized hybrid systems that ensure consistent power delivery and comply with regulatory standards. The study developed a hybrid system integrating offshore wind, tidal stream power, battery energy storage, and a diesel generator backup. A Fuzzy Logic Controller (FLC) was designed and implemented to dynamically manage power distribution based on real-time renewable inputs and battery state of charge, maximizing resource utilization and ensuring system reliability. Simulation results demonstrated over 70% utilization of wind power alongside a stable energy supply with total harmonic distortion maintained below 5%. Furthermore, a voltage-oriented control strategy employing a three-level H-bridge voltage source converter, supported by predictive control methods, was implemented to enhance grid interaction, reduce harmonic distortion, and improve transient response. This configuration effectively managed the variable outputs of high-capacity wind and tidal generators, resulting in improved power quality and system stability under fluctuating conditions. Economic feasibility was evaluated through software-based hybrid optimization models, revealing that combining tidal and wind power achieves a competitive levelized cost of energy. This approach highlights the potential of hybrid systems to accelerate South Africa’s transition toward a sustainable energy future. By addressing both technical challenges and regulatory requirements, this research offers a robust model for hybrid offshore energy systems and contributes valuable insights for integrating renewable energy in coastal regions worldwide.