The frequency estimation solutions based on the discrete phase locked loop (PLL) technology are widely applied in the intelligence electronic devices for power system. The PLL method cannot provide both the fast response and the good reliability under the system disturbance. In this paper, an improved frequency estimation solution is presented. Based on the angle characteristic of the positive sequence voltage, this method directly calculates the frequency deviation from angle difference of the continuous power cycles, without any iteration calculation. Unlike the discrete phase locked loop, which is a close-loop structure, the new method is based on an open-loop structure with the fixed sampling frequency. There is no interdependent between the calculation loops. Hence, the response time is shorter. Moreover, the 2 cycles hamming window is applied to reduce the interfaces and the angle jump detection based on the abnormal rate of change of frequency is also applied to improve the reliability of the solution. The theoretical analysis and Matlab simulations are performed. The results show the frequency estimation performance can meet the application requirements.

frequency estimation,frequency protection,frequency tracking