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The accuracy of unsteady-state disturbance analysis of power quality signals is reduced by the steadystate components with high amplitudes and energies.In this paper,a novel frequency-domain matching pursuits (FDMP) algorithm is proposed to estimate the parameters of the steady-state components and separate the unsteady-state disturbances from power quality signals.Firstly,the time-frequency atoms and redundant dictionaries are constructed according to the characteristics of power quality signal spectra.Secondly,the steady-state components and unsteady-state disturbances of power quality signals are decomposed by FDMP into two mutually orthogonal subspaces in Hilbert space.Furthermore,the expressions for parameters calculation of steady-state components have been derived.The experiments show that the relative errors of frequency and amplitude estimations of steady-state components are less than 2 × 10 -4 and 5 × 10 -3 respectively,and phase estimation errors are less than 1.6° under the existence of both interharmonics and unsteady-state disturbances.The steady-state components and unsteady-state disturbances are separated quickly and accuratelv.