In order to identify the faults of rolling bearing of wind turbines, the variational modal decomposition (VMD) was combined with two methods, including calculation order tracking (COT) and reversed sequence squared envelope spectrum (RE-SES), to carry out the envelope order analysis. The non-stationary signals in time domain were converted into stationary signals in angle domain by equal angle sampling. And the bearing fault characteristic information was obtained by envelope method. The results show that the modulation order of amplitude modulation signal can be extracted more effectively by VMD combined with RE-SES envelope order method. The VMD filter could make the fault feature order more prominent, and it is easy to identify the fault, and it provide reference for the fault diagnosis of rolling bearing of wind turbine under variable speed condition.
