Multi-objective optimization of maintenance policy considering the impact of degradation of spare parts on the system

Wind power has emerged as a prominent method of new energy generation in recent years. As the efficiency of generator operation becomes increasingly critical, the maintenance of these generators has come into focus. Wind turbines are often located in areas with high wind availability, and establishing warehouses for spare parts storage at these sites can substantially decrease both maintenance time and costs. However, the longevity of these spare parts can be compromised by soft failures, such as corrosion, which diminish their service life. This paper explores a novel inventory management strategy designed to mitigate the effects of soft failures on spare parts and reduce overall system maintenance costs. It is noted that the degradation process of components during storage and usage follows different distributions of soft failures. Moreover, the transition probabilities between different system states are modeled using a semi-Markov decision process. The study aims to optimize the system’s inspection intervals and preventive replacement thresholds to minimize the average cost rate of the system.