A non-intrusive method for real-time estimation of core flux for single-phase transformers

Estimating the core flux of transformers can extend their lifespans, improve power quality, and enhance the performance of power-electronic converters equipped with isolation transformers. However, existing flux-measurement methods either require access to the interior of transformers or offer limited applications. Accordingly, this paper proposes a non-intrusive method for real-time estimation of the core flux of single-phase transformers. The method also decomposes the core flux into its constituent AC and DC components and estimates the core-loss and magnetizing currents. The proposed method requires instantaneous current measurements from both sides of a transformer and its saturation curve. The exciting current is determined using the current measurements, and it is fed to the Extended Kalman Filter (EKF) to estimate the core flux. The proposed method is implemented in MATLAB and evaluated using EMTP-RV simulations and laboratory experiments. The evaluations confirm that the proposed method is able to estimate the core flux and its AC and DC components as well as the core-loss and magnetizing currents with appropriate accuracy.