Wave-to-grid hierarchical coordinated control with energy storage and management for point absorber wave energy converters

A major challenge in wave energy systems is their multidisciplinary nature, which to some extent hinders the development of effective holistic control strategies that simultaneously coordinate the mechanical and electrical subsystems, potentially improving the system's economic prospects. This paper presents a practical hierarchical coordinated control strategy for point absorber wave energy converters (WECs), designed to improve energy capture, manage energy storage, and ensure smooth power delivery to the grid. The system combines a reduced-order finite control set model predictive controller (FCS-MPC) at the actuator level with a supervisory energy management system (EMS) that coordinates a battery energy storage system (BESS) to smooth power output and extend battery life. An extended Kalman filter (EKF) estimates key mechanical variables using only electrical measurements, reducing sensor requirements and improving implementability. Simulation results under various irregular sea states show that the proposed strategy outperforms conventional resistive loading method, delivering approximately 8% more energy to the grid in the case of a fully developed very rough sea state, and up to 45% more energy in the case of a partially developed moderate sea state. It achieved an overall maximum efficiency of 77%, maximum capacity factor of 47%, and significantly reduces power fluctuations. The proposed energy management system (EMS) effectively enforced adaptive power curtailment to prevent battery overcharging and deep discharging, ensuring safe BESS operation within the 10%–90% state-of-charge range. Compared to a fixed grid power reference approach, the adaptive power dispatch capability of the proposed EMS delivered up to 22% more energy under low-energy sea states while maintaining system stability and safe BESS operation.