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• A lifetime extension strategy for power module in wind energy system is proposed. • This strategy is based on the optimal effectiveness of the thermal management. • The effectiveness gives the choice criteria about temperature swing control target. • Each application of temperature control can improve as much lifetime as possible. • Disturbance on the regular operation of wind energy system is greatly reduced. The power module plays a vital role in the renewable energy conversion. But it is one of the most prone to fail components in the wind energy system. The thermal management has been proved to be a cost-effective mean to improve the reliability of wind energy system, but it has a dual nature. To balance the benefit and risk of thermal management, a lifetime extension strategy is proposed. This strategy considers the minimum junction temperature fixed to the lowest ambient temperature and the allowed maximum junction temperature determined by the predefined temperature swing. Then the related wind speeds of predefined temperature swing can be concentrated in a part wind speed area and the effectiveness of thermal management under each predefined temperature swing is calculated. The optimal effectiveness is chosen as a quantitative evaluation criterion to design the working range of thermal management and control target of junction temperature in a long time scale. As a benefit, the economic performance of thermal management is greatly improved in that each application of temperature control can reduce as much consumed lifetime of power module as possible. Case studies and experiments are presented for performance verification of proposed strategy. Results show that the consumed lifetime reduced by each application of temperature control is 6.04 × 10-3%. The expected lifetime of power module is extended from 7.55 years to 22.08 years which meets the target lifetime of wind power generation system (20 years). In addition, this method only needs to be applied in the specified working range where the wind speed is higher than 9.30 m/s. Thus, the disturbance on the system's normal operation is significantly alleviated. [ABSTRACT FROM AUTHOR]