The invention discloses a fault diagnosis method for an AC / DC charging equipment power device based on 
wavelet packet analysis, and the method comprises the steps: analyzing a charging equipment powermodule, and determining a 
fault class; obtaining output signals of the charging equipment 
power module under the normal condition and various fault conditions; carrying out the high-
low frequency decomposition of the output signals, carrying out the multilayer 
wavelet packet 
decomposition of the high-
low frequency signals obtained through 
decomposition, and carrying out the reconstruction of a 
wavelet packet decomposition coefficient; calculating the extracted 
signal energy at all frequency bands, carrying out the normalized calculation of the 
signal energy, and finally determining a centralized 
frequency band range of the 
signal energy; carrying out the power 
spectrum analysis of the reconstructed 
wavelet packet decomposition coefficient, determining the feature frequency and power spectrum value of a 
frequency band signal, comparing the comparison with the 
fault analysis, and determining the type of a fault; and carrying out the fault type coding of the type of the fault. The methodimproves the time-
frequency resolution of a signal, achieves the precise fault positioning through the spectrum features, and improves the precision of the fault diagnosis of the AC / DC charging equipment power device.