Improving Current Transformer-based Energy Extraction from AC Power Lines by Manipulating Magnetic Field

This article presents a novel method to improve energy scavenging from ac power lines under magnetic saturation conditions. The extracted power level of a conventional magnetic energy harvester is limited by the maximum flux density of the magnetic core. When a magnetic core is clamped on ac power lines, the flux density in the core is proportional to the magnetic field strength around the power line. Choosing a high-permeability core has the advantage of harvesting more energy for a given primary current. The flux density in such a core could reach its maximum value when the magnetic field increases. In this scenario, very little energy can be harvested since flux density variation in the core is small. Here we introduce an artificial magnetic field by adding an additional control coil to manipulate the magnetic field of power lines. A power management circuit is employed to store the energy harvested by the control coil and feed it back to the harvester to generate a counter magnetic field. As a result, the core will not be easily driven into the saturation region; hence, more energy can be harvested. Experimental results show that the proposed energy harvester can harvest an average power of 283 mW on a 50 Hz 10 A_rms power line (2.34 mW/cm³/A_rms), which is increased by 45% compared with the device without the control coil. This new method could provide a promising solution for smart grid monitoring and other industrial sensing applications.