A high-precision and wide-range method of frequency measurement in the new energy power grid connection

In the new energy power grid connection, frequency is an important indicator of power grid's operating state. The frequency in power system is easily affected by the access and exit of new-energy generators and appears large fluctuations, and thus it is essential to develop a measurement method that is highly precise and widely ranged. This paper initially introduced a variety of common methods of frequency measurement, and then proposed a high-precision and wide-range method of phase-difference frequency measurement which can switch the range of frequency measurement dynamically, ensuring the optimization of range and precision in the frequency measurement. This paper demonstrates the feasibility of the high-precision and wide-range method of frequency measurement theoretically and implements the method on an ARM embedded controller. In order to prevent frequency spectrum aliasing, this paper also designs an eight-order active low pass filter of Butterworth switched capacitor. The experimental results demonstrate that the method can achieve high precision in frequency measurement on occasions that frequency is constant, slowly growing and step changing and it can satisfy requirements of the frequency measurement in the new energy grid connected power system.