A novel time-frequency analysis of power system

In the past decade, with the rapid increase of large capacity load in the power system, the power-quality (PQ) disturbance has become a serious problem. In this study, a novel time-frequency analysis method, namely the null space pursuit-Hilbert transform (NSP-HT), is introduced to detect and identify the power-quality disturbance. The proposed method is an operational combination of the null space pursuit algorithm (NSP) and the Hilbert transform (HT). It decomposes a signal into many components according to their characteristics with NSP, and gets their instantaneous frequency at the same time. Then HT is employed to detect the instantaneous amplitude of each component. In the case studies considered here, some simulation experiments, including harmonics, interharmonics, voltage sag and voltage signal with changing frequency and amplitude of harmonics, will be investigated by using the proposed analysis method.