Real wavelet-domain modified phasor: Principle and applications in power systems

Wavelet transform is a new competitive tool to deal with power quality disturbances. Real discrete wavelet transform (RDWT) is simple, fast and non-redundant, but is regarded to be lack of phase information (PI). This paper presents three RDWT-based PI extraction methods and then develops a modified phasor Zw(n) in real wavelet domain to analyze single-frequency or narrow-band signal. Amplitude, frequency and phase of the signal simply relate to the phasor. Zw(n) can be used to separate, identify and quantify frequency disturbance, phase disturbance and amplitude disturbance at one time quickly. Demonstration examples are given. The modified phasor may have practical application in custom power and protective relays.