The rapid development of wind energy in the power sectors raises the question about the reliability of wind turbines for power system planning and operation. The electrical subsystem of wind turbines (ESWT)

which is one of the most vulnerable parts of the wind turbine

is investigated in this paper. The hygrothermal aging of power electronic devices (PEDs) is modeled for the first time in the comprehensive reliability evaluation of ESWT

by using a novel stationary “circuit-like” approach. First

the failure mechanism of the hygrothermal aging

which includes the solder layer fatigue damage and packaging material performance degradation

is explained. Then

a moisture diffusion resistance concept and a hygrothermal equivalent circuit are proposed to quantitate the hygrothermal aging behavior. A conditional probability function is developed to calculate the time-varying failure rate of PEDs. At last

the stochastic renewal process is simulated to evaluate the reliability for ESWT through the sequential Monte Carlo simulation

in which failure

repair

and replacement states of devices are all included. The effectiveness of our proposed reliability evaluation method is verified on an ESWT in a 2 MW wind turbine use time series data collected from a wind farm in China.