With the continuous access of high-power electronic equipment, electric vehicles and other loads in the user side, the frequency of power grid fluctuates. As one of the power quality parameters, higher or lower frequency has a negative impact on power system and users. Therefore, the accurate measurement of frequency is of great significance to the State Grid and users. In order to measure the frequency accurately, this paper proposes a frequency measurement method according to power quality monitoring technical specifications issued by the State Grid in 2017. Through the design of band-pass filter to filter out DC (Direct Current) component and high-frequency harmonic interference, along with the improved zero-crossing detection process, aim to judge the whole cycle wave number and its occupation time in ten-second time interval. Matlab is used to simulate the accuracy of the algorithm under different conditions. The results show that the error range measurement of frequency is far less than the accuracy level of class A and S power quality testing equipment. Therefore, this algorithm is feasible in the application of power quality monitoring terminal.
