An Improved Sub-harmonic Analysis Method Based on Negative Frequency Effects

摘要

Complex frequency signals are adopted for power harmonic analysis generally, whereas the actual measured signal is always a discrete cosine signal, which contains negative frequency components according to Euler's equation. Taking the negative frequency components into account, an improved multilayer DFT interpolation correction method is proposed based on negative frequency effects. The proposed method is applied to harmonic parameter identification, which can reduce spectral leakage by adding a window function, phase rotation and odd-point interpolation operation. Different frequencies and amplitudes of harmonics are analyzed. The results show that the proposed method has a higher accuracy when the analytical signal is mixed with low-frequency components, and the improved method gets more obvious advantages in sub-harmonic parameter estimation.