A Derivative Based Instantaneous Frequency Tracking Algorithm

Frequency is an important parameter for power system operation and protection. A frequency-tracking algorithm is presented for its fast and accurate measurement, which combines second derivative with linear approximation based on the sinusoidal characteristics of an AC signal and supplements a posteriori error processing. A Lagrange Polynomial-Fitting technique is used to calculate the second derivative, whilst an error compensation rate and a modifying factor are introduced to increase algorithm accuracy. The remainder of the fitting polynomial is analyzed, with the samples acquired in a half cycle data window filtered by equal ratios theorem to enhance the robustness, as well as the real time performance. Matlab simulation results show that the algorithm is suitable for instantaneous power system frequency tracking with high accuracy and a certain suppression of second harmonic interference.