An Effective Power Improving Method of Magnetic Field Energy Harvesters Using a Series-Connected Capacitor for Wireless Sensors in Smart Grids

The low power density of a magnetic field energy harvester (MFEH) limits its applicability. Conventional methods for improving power harvesting, e.g., increasing the volume of the magnetic core, cannot effectively increase the output power density of the MFEH and it increases the burden on the transmission lines. An in-depth investigation reveals that by adding an optimal series-connected capacitor before the rectifier, the output power of the MFEH can be maximized. By reducing the net voltage applied to the magnetizing inductance, the flux accumulation is slower, lengthening the energy harvesting time, and the output power is increased. Furthermore, the output power can be maximized with an optimal series-connected capacitor. The design method of the optimal series-connected capacitor is theoretically analyzed in this article, which is only related to the load characteristics. In addition, the proposed method has a simple structure and can effectively improve the system power density of the MFEH. An experimental prototype is constructed to verify the effectiveness of the proposed method, and the results agree well with the theoretical analysis. Compared with the conventional MFEH without a series-connected capacitor, the method presented in this article can increase the harvested power by approximately 50%.