Accurate Measurement and Tracking for Subharmonics and Inter-harmonics

This article exhibits a simple and efficient technique to estimate and track the parameters of subharmonics and inter-harmonics in power systems. The estimation and tracking are realized using the maximum likelihood estimator associated with a spectral estimation technique to guarantee the convergence toward a global minimum. The proposed technique is easy to formulate and simple to implement in real-time applications because it has a good dynamic performance, and it is used to get the frequency, phase, and magnitude of the closely spaced harmonics, inter-harmonics and subharmonics. The proposed technique gives good results whether the harmonics' parameters are stationary or dynamic in a noisy or non-noisy environment. The proposed technique is compared to the adaptive notch filters and ESPRIT technique to justify its good performance. Finally, the presented technique is applied to the arc furnace current to extract its disturbances.