Abstract：The free-standing magnetic field energy harvester (FSMFEH) has broad application prospects for powering self-powered sensors. However, due to its low output power, FSMFEH requires maximum power point tracking (MPPT) to increase its output and meet the sensor requirements. According to energy-acquisition principles, the maximum power points of harvesters for other energy sources differ from those of FSMFEH, whereas MPPT circuits based on the impedance-matching method suffer from complex circuitry and high power consumption. Furthermore, when commercial chips are used to perform MPPT on FSMFEH, issues such as low tracking speed and reduced tracking efficiency due to magnetic field fluctuations arise. Therefore, this paper proposes a fast-tracking method for the maximum power point of the FSMFEH based on the fractional open-circuit voltage (FOCV). Firstly, this paper analyzes the structure and equivalent circuit of the FSMFEH and discusses the influence of the quality factor Q on the maximum power point. Consequently, for FSMFEH under CCM, the maximum power point voltage VMPP and the peak open-circuit voltage Voc satisfy VMPP=0.39Voc. Secondly, this paper elaborates on the design principles of the maximum power point tracking method and describes the operation of the MPPT circuit. The working process was divided into two stages: sampling and energy acquisition. The working conditions of each component at different stages are analyzed, and the device selection criteria and the circuit's power consumption are discussed. Finally, experiments verify that the proposed method exhibits strong adaptability across a wide range of loads and spatial magnetic field variations. The MPPT method uses a power-supply coil to power the active device and an energy-harvesting coil to deliver power to the load. Thus, the sampling capacitor voltage can quickly reach Voc by periodically disconnecting the load, thereby enabling real-time sampling. After the load is connected, the output voltage is maintained near the VMPP through the comparator, thereby achieving MPPT. When the load changes, the MPPT circuit can remain at the maximum power point as long as the load requires less power than the output power. When the spatial magnetic field fluctuates, the MPPT circuit based on the proposed method can rapidly obtain the new Voc within 2 s and quickly maintain the output voltage near the new VMPP within a few seconds. The MPPT circuit has a high tracking speed, consumes only about 150 μW, and maintains a tracking efficiency above 91.8%. This paper provides a simple, efficient, low-power-consumption, and high-tracking-speed MPPT method for FSMFEH. In practical applications, the requirements of the load sensors and the spatial magnetic field conditions must be considered to optimize parameter settings and achieve long-term stable operation of the MPPT circuit.
郑力恺, 吕怡婷, 杨爱军, 荣命哲, 王小华. 一种非侵入式磁场能量收集器最大功率点快速跟踪方法[J]. 电工技术学报, 2026, 41(20): 7108-7120.
Zheng Likai, Lü Yiting, Yang Aijun, Rong Mingzhe, Wang Xiaohua. A Fast Tracking Method for Maximum Power Point of Free Standing Magnetic Field Energy Harvester. Transactions of China Electrotechnical Society, 2026, 41(20): 7108-7120.
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2026, Vol. 41 
