Modified Dynamic Phasor Estimation Algorithm for the Transient Signals of Distributed Generators

In this paper, a modified dynamic phasor estimation method for protection relays is proposed to calculate the dynamic phasor of a fundamental frequency component with time-variant amplitude. The fault current is assumed to be the combination of a decaying dc offset, a decaying fundamental frequency component and harmonics with constant amplitude. The exponential functions of the decaying dc offset and fundament frequency component are replaced by Taylor series. Then, the LS (Least Square) technique is used to estimate the magnitudes and the time constants of decaying components. The performance of the algorithm is evaluated by using computer-simulated signals based on simple equations and fault current signals collected from DFIG wind farm model in MATLAB Simulink. The test results indicate that the proposed algorithm can accurately estimate the decaying amplitude and the time constant of the fundamental frequency component.