A spectral line curve fitting based algorithm for inter-harmonics measurement

The inter-harmonics produced by those power electronic devices leads to a more frequent occurrence of sub-synchronous oscillations (SSO). Many existing measuring methods are not suitable for the inter-harmonics measurement in the environment where plenty of power electronic devices exist. In this paper, a fast and precise measuring algorithm based on FFT and curve fitting is proposed to estimate the sub/super-synchronous harmonics. The windowing technique is used to reduce the spectral leakage firstly. Secondly, zero-padding is adopted to mitigate the picket-fence effect. Lastly, spectrum line curve fitting is applied to perform the inter-harmonic analysis. The simulation and experiment results indicate that the proposed algorithm is able to perform an accurate, real-time and anti-noise inter-harmonics estimation. Experiment results verify the accuracy and effectiveness of the proposed algorithm.