An Energy Management Method Considering the Wide-Range Power Line Current Variation and Output Power Improvement for Free-Standing Magnetic Field Energy Harvester

Free-standing magnetic field energy harvesters (FSMFEH) have proven potential for powering sensors on power transmission lines. To realize the application FSMFEH, a key challenge is to satisfy the power supply requirements of sensors, i.e., the output power and the constant output voltage requirements. However, the output power and voltage of FSMFEH systems are highly dependent on the power line current, which typically varies over a wide-range. Therefore, the stabilized power supply to the sensor will be broken, and the optimal output power will not be maintained. To address these issues, an energy management circuit with dual-coil FSMFEH and bidirectional DC-DC is proposed in this work. Firstly, the influence of power line currents and the constant voltage output to the system are ana-lyzed. Then, the optimal operating modes of the system under different load conditions are clarified. Finally, the energy management strategies are presented based on the mode switching boundaries of the dual-coil system and the voltage control of the bidirectional DC-DC. Experimental results show that when the power line current varies from 30A to 500A, the output power can be improved from 0.6mW to 3.2mW at the minimum power line current, and from 195mW to 365mW at the maximum power line current.