In order to have fast responding time of microprocessor-based protection
the halfcycle discrete Fourier transform (HCDFT) has been most widely used for fast computing the fundamental frequency component. However
when a fault occurs
both the voltage and current signals contain large harmonics and the decaying DC component during the fault duration. These abnormal components involved in measurements will significantly postpone the convergent speed of conventional HCDFT algorithm. In order to solve the problem
this paper presents a novel algorithm
which combines the constrictive bandpass filter and HCDFT. Combining the characteristics of decaying DC component has less influence on the real part of HCDFT and the advantage of low frequency and high harmonics can be restrained effectively by constrictive band-pass. Hence the proposed algorithm can calculate the fundamental frequency component more quickly. Simulation tests show that the filtering results of the proposed algorithm are better than that of the conventional algorithms.