Abstract: The phase-locked loop (PLL) is widely used to estimate the phase angle and frequency of gird voltage for distributed renewable energy resources. However, the grid background harmonics affect the accurate extraction of fundamental voltage leading to deviations of PLL. As the traditional delay signal cancellation (DSC) method had limited ability of suppressing odd harmonics, more cascaded DSC operators had to be used to eliminate all the harmonics in voltage which deteriorates system dynamic performance. In view of this, a fast DSC (FDSC) algorithm based on the vector triangle principle was proposed. It used three data samples with equal sampling interval that was the harmonics in third sample could be cancelled by the sum of the other two samples. The FDSC transfer function was derived and its parameters setting method was given. Theoretical analysis shows that it has a shorter filtering time, and better system performance than the traditional DSC method. The simulation and experimental results verify the advanced nature of the method.