A Reconfigurable Rectifier-Based Power Improving Method of Free-Standing Two-Coil Magnetic Field Energy Harvesters Over a Wide Load Range

Free-standing magnetic field energy harvesters (FSMFEHs) have promising potential in charging sensors used in electrical power grids. The output power of the FSMFEH is highly dependent on the load resistance. However, the load resistance of the sensors varies over a wide range during the operation process. Therefore, a crucial challenge for an FSMFEH system is to maintain high output power over a wide load range. In this letter, an innovative reconfigurable rectifier-based FSMFEH system with two coils connected in parallel is proposed. First, a new structure of two identical coils in parallel is proposed in magnetic energy harvesting applications. Then, a reconfigurable rectifier with two operation modes is developed to incorporate the new coil structure. By switching between the full-bridge mode and the half-bridge mode according to the actual load demand, the proposed FSMFEH can maintain high output power over a wide load range. In addition, the mode transition can be easily achieved by shorting one of the diodes, leading to a simple and low-loss control. The effectiveness of the proposed FSMFEH system is verified based on a laboratory prototype. It is provided that the experimental result is consistent with the theoretical analysis. The output power can be maintained above 8.19 mW within the 50–1500 Ω range when the busbar current is 100 A.