The frequency change of the fault current signal and the decaying DC component contained in the signal will seriously decrease the accuracy and dynamic response speed of the phasor measurement algorithm based on Fourier transform algorithm. This paper proposes a strong tracking filter algorithm for dynamic phasor measurement considering the decaying DC component. Firstly

the decaying DC component is expressed by its second-order Taylor polynomial

and the decaying DC component and its first and second derivative are all added to the state variable vector. Then this paper establishes a nonlinear state space model of fault current including angular frequency and amplitude of the fundamental component and the decaying DC component

to reduce the estimation model error. In order to improve the ability of extended Kalman filter to fast track the system parameter mutation when the system reaches a steady state

the strong tracking filter is used to recursively estimate each state variable. The proposed method can effectively decrease the impacts of the decaying DC component on phasor estimation and has good dynamic response to time-varying fault current signals. Finally

the proposed algorithm is used to measure the numerical signal with noise and the fault simulation signal generated by ATP-EMTP. The test results verify the correctness and validity of the proposed algorithm.