An Energy Management Method for Magnetic Field Energy Harvesters Under Wide-Range Current in Railway Electrification Systems

The wide-range traction current brings great challenges to the stable operation of the magnetic field energy harvester (MFEH). Specifically, when the traction current is large, the core saturation increases, resulting in violent vibration of the magnetic core. When the traction current is low, the energy harvested by the MFEH is insufficient to power the load. To address these vital problems, an energy management method for MFEH is proposed to track the critical saturation point, i.e., the maximum power point in the unsaturated region. In this method, by regulating the equivalent load, the core voltage is controlled at the critical saturation voltage under different current levels. Moreover, the supercapacitor is employed to store excess energy at large currents, and the stored energy is released at low currents. Furthermore, a design procedure for the core and winding is proposed in this work, which can be used to adjust the critical saturation voltage of the MFEH. A laboratory prototype is built to verify the effectiveness of the proposal. The results show that the MFEH can operate at the critical saturation point and provide stable energy for the load under different current levels. This means that saturation suppression, maximum power point tracking, and energy management can be realized by applying the proposed method.