A resource-constrained marginal-benefit batch maintenance framework for wind turbine fleets under degradation risk

Maintenance timing decisions for wind turbine fleets are crucial for ensuring operational safety and economic efficiency under limited maintenance resources. However, fleet-level maintenance scheduling remains challenging because multiple turbines may enter degradation-related maintenance windows concurrently, while degradation behaviors and economic consequences are heterogeneous. This paper proposes a dual-interval and marginal-benefit batch maintenance (DMBM) framework for wind turbine fleets under degradation risk and resource constraints. Firstly, a degradation-boundary-driven dual-interval formulation is developed to transform predicted degradation trajectories into decision-oriented maintenance intervals, where the degradation-constrained interval defines the latest admissible maintenance boundary and the executable interval determines the actual repair period. Secondly, a capability-risk-value decision model is constructed to quantify capability loss, degradation-induced risk, downtime loss, maintenance expenditure, fixed startup cost, and continued-operation revenue within a unified joint decision cost. Furthermore, fleet-level batch feasibility is modeled by considering interval overlap, time concurrency, cost sharing, and minimum crew requirements, while a marginal batching benefit mechanism is introduced to identify economically meaningful batches and avoid excessive aggregation. A SCADA-based case study demonstrates that DMBM can transform turbine-level maintenance preferences into executable fleet-level batch schemes and outperforms benchmark strategies in joint decision cost, batch organization, maintenance adequacy, resource demand, and time efficiency.