A Practical Method for Harmonics Measurement based on Accurate Frequency Calculation

Traditional interpolation algorithms based on windowing FFT require large number of sample points, which usually means large calculation burden and more signal periods to be sampled; and the complexity of interpolation algorithm is dependent on window function. This paper gives detailed analysis of traditional interpolation algorithm based on windowing FFT. It introduces a practical frequency determination method, which only requires the number of sample points to satisfy frequency domain resolution requirement. The determination process is only to solve a simple linear equation and it has no relation with the adopted window function, thus makes possible the adoption of window function with better leakage suppression effect. The method has a similar accuracy as the traditional interpolation method but the calculation burden is notably reduced. Based on the proposed frequency tracking method, this paper develops a practical new harmonic measurement method. An example is given to demonstrate the feasibility of the proposed method.