An enhanced energy harvesting method based on resonant current transformer for high voltage AC cable monitoring equipment

With the development of smart grid, a large amount of monitor equipment is employed to supervise the condition of power cable. Because of its convenience, extracting electric energy from cable via a current transformer is a promising technique used in power supply for these pieces of monitoring equipment. In this paper, an enhanced energy harvesting method based on current transformer in resonant state is proposed. In this method, a resonant capacitor is adopted to resonate with the equivalent magnetizing inductor of the current transformer. Therefore the reactive power on the inductor is compensated, thus the power harvested from the power cable is dramatically increased. Furthermore, the lower side diodes of the conventional rectifier are superseded by fully controllable switches. With the proposed control scheme and PI compensation, the output voltage can be regulated when the primary side current varies in a wide range. The method is verified by a 20W prototype.