Rapid extraction of fault current parameters for predicting the zero-cross point of the fault current is a premise in phase controlled interruption of fault current.In this paper

an improved half-wave Fourier algorithm is presented.By adding two extra sampling points and shifting data processing window twice

the algorithm can extract the initial value and time constant of the decaying DC component

and can also extract the amplitudes and phases of the fundamental wave and three-order wave to implement prediction of zero-cross point of fault current.Calculation and MATLAB simulation show that the improved half-wave Fourier algorithm can quickly realize zero-cross point prediction of fault current with errors less than ±1 ms.