Detection Method of the DC bias in Distribution Power Transformers

Non-linear loads such as AC drives switch-mode
power supplies and grid-connected converters can cause, besides
the generation of unwanted current harmonics, a DC current
component injection into the grid. This DC current component
can lead to magnetic saturation of the distribution power transformers, leading to higher current distortion and overheating.
This paper presents a method to detect the DC current
component flowing into the distribution power transformer with
a precise measurement of the DC voltage component at the
transformer winding. A magnetic sensor has been developed and
implemented in a closed-loop control system to achieve a high
sensitivity and guarantees a good linearity with a high rejection
ratio to grid voltage variations. Simulation and experimental
results confirm the effectiveness of the proposed approach.