Research on dual-objective control of the wind-wave hybrid system with an aerodynamic-hydrodynamic-hydraulic-mooring coupled model

In the complex and changeable marine environment, the wind-wave hybrid system needs to control the hydraulic power take-off (PTO) system at appropriate times to improve wave energy capture and conversion efficiency or reduce the pitch motion response of the platform. Therefore, this paper establishes a simulation framework for a hydraulic PTO control system within a wind-wave hybrid system. This framework is based on aerodynamic-hydrodynamic-hydraulic-mooring coupled simulation and incorporates a hydraulic PTO controller. Moreover, a tracking control strategy based on the improved gray wolf optimizer (IGWO) algorithm is proposed to validate and apply this new framework, with the objectives of maximizing power output from the wave energy converters (WECs) array and minimizing the platform's pitch motion response. The results show that the IGWO control strategy demonstrates superior global search capabilities and tracking speed compared to the perturbation and observation, particle swarm optimization (PSO), salp swarm algorithm (SSA), and gray wolf algorithm (GWO). The IGWO control can effectively increase the output power of the WECs array or decrease the pitch motion response of the platform in different sea states. The IGWO control strategy also tracks faster than the PSO, SSA, and GWO control strategies after the sea state changes. Active pitch reduction effectively complements the limitations of passive methods, and active/passive synergistic control achieves the reduction of platform pitch motion across a broader wave period range, effectively improving the hybrid system's environmental adaptability.