Wei Wang

In domino wireless power transfer (WPT) systems, inefficient magnetic energy circulation arises from complex coupling networks and redundant mutual inductance among resonators, which limits power delivery to downstream nodes, particularly in high-voltage insulator strings with multiple sensors. A magnetic coupling path reconfiguration strategy based on dynamic relay switching is proposed in this paper. By controlling the connection and disconnection of key nodes in the linkage, the target load operates under optimal coupling conditions, enabling controllable energy flow. Results show that, disconnecting node 2 can significantly enhance the downstream coupling strength, increasing load input power by 1.5–2 times, as verified in four- and five-coil structures. A feasible solution for long-term stable power supply to multiple sensors on high-voltage insulator strings is provided.

Accurate voltage–current phase-difference measurement is essential for power factor evaluation and condition monitoring in power delivery systems. Conventional synchronized measurement schemes generally require external time references, whereas non-intrusive voltage and current sensing links introduce additional phase shifts due to different coupling mechanisms and signal-conditioning circuits. To address these issues, this paper proposes a non-intrusive phase-difference measurement method for single-node power delivery monitoring without an external time reference. A unified internal sampling clock is adopted to ensure local temporal consistency between the voltage and current channels. Full-wave rectification and frequency-doubling phase mapping are introduced to convert bipolar AC signals into unipolar measurable signals and indirectly recover the fundamental phase difference. The Goertzel algorithm, together with the complex-ratio method, is employed for low-complexity single-frequency phase extraction and phase decoupling. A piecewise compensation model is further established to correct the additional phase shifts introduced by the sensing and conditioning links. Experimental results under steady-state power-frequency and thermal variation conditions show that the proposed method maintains a relative measurement error within 3%, demonstrating its feasibility for embedded power delivery monitoring applications.

With the ongoing digital transformation of power grids, massive deployment of `s (WMSs) at critical nodes of electrical equipment necessitates reliable self-powered solutions. To address the energy supply challenges for maintenance-free operation of these WMSs, electric field energy harvesting technology emerges as a promising method. However, the delayed development of this technology has resulted in an imbalance between existing ambient energy harvesters and the proliferating demand from ubiquitous WMSs. On this basis, a multiwinding electric field energy harvester (EFEH) with multichannel energy output is proposed in this article. Thus, an electrical isolation mechanism for multiload systems is established. Meanwhile, the energy extraction principles of multiwinding configurations in pulsed discharge EFEH are analyzed. Also, an electric field-electric energy conversion equivalent model is developed to characterize load energy coupling characteristics and allocation relationships under different discharge time-scales. Furthermore, a parameter configuration methodology is presented to achieve simultaneous discharge of multiple energy storage capacitors (ESCs). Finally, the humidity and temperature sensor, along with the tilt sensor, serve as the respective loads connected to each ESC. Experimental results demonstrate that premature discharge of any ESC in the multiwinding EFEH leads to unequal operational cycles across loads, which adversely affects energy superposition in other windings. These findings quantitatively validate the necessity and effectiveness of the proposed parameter configuration method in ensuring synchronized capacitor discharge.

Electromagnetic field energy harvesting technology has garnered significant attention for its ability to power monitoring sensors without batteries. However, the magnetic field energy harvester (MFEH), despite its high power density, suffers from unstable energy output due to line current fluctuations, while the electric field energy harvester (EFEH) provides stable performance but limited energy capacity. To address these problems, a high-reliability combination and handover method for electromagnetic energy harvesting across a wide current operating range is proposed in this article. By integrating a pulsed-discharge EFEH winding into the single-winding magnetic core of a traditional MFEH, self-adaptive switching of the magnetic core operating state is achieved through coupling interactions between the electric and magnetic field windings. Under high line currents, this method effectively mitigates core saturation depth and suppresses voltage spikes. Under low line currents, it disconnects the electric field harvesting capacitor and elevates the output voltage to the load, ensuring sufficient power delivery. Experimental results validate the effectiveness and feasibility of the proposed method for hybrid electromagnetic energy harvesting, core saturation suppression, and load output voltage regulation.

The high current measurement technology is of great significance for power systems, including protection and control, power metering, reliability diagnosis, performance evaluation of power equipment, and life prediction. Traditional toroidal current transformers are bulky and exhibit poor anti-saturation performance. Although the measurement range can be expanded by compensating circuits and increasing the number of winding turns, the problem of magnetic core saturation remains unresolved. Motivated by this challenge, a high-precision current measurement method based on magnetic field intensity inversion using a free-standing magnetic field energy harvester (FSMFEH) is proposed, significantly enhancing the anti-saturation performance of the current measurement with magnetic cores. Also, the magnetic field energy can be harvested by the current measurement to provide power for the current signal acquisition circuits without battery. Meanwhile, an ultralow-power energy management and parameter configuration methods for self-powered current measurement (SPCM) are proposed. Consequently, under normal room temperature conditions, the experimental results demonstrate that the SPCM can achieve current data acquisition without external power supply, with measurement accuracy within 1%.

With the intelligent development of smart power grids, the monitoring and maintenance of high-voltage transmission towers is subject to more stringent requirements. As an important part of the transmission tower, condition monitoring of insulators is critical for ensuring the safety of the power grid. However, existing traditional power sources, such as photovoltaic or wind energy, cannot reliably supply power to the battery modules. To solve this problem, a wireless power transfer and supply synchronization system (WPTS3) based on composite insulators is proposed in this paper, which can realize the reuse of the power consumption and energy transmission of a single load coil. Furthermore, a solution for multi-node wireless power transmission is provided that uses an almost constant current or constant voltage to provide multi-node power transmission under system characteristics. Moreover, to achieve a stable energy supply for multiple nodes over medium and long distances, a time-sharing load-launch linkage manipulation strategy that controls the resonant frequency of the system in a closed loop to achieve frequency switching under dynamic load changes is provided. Finally, the stability of the system is verified by building an 8-coil multi-node wireless power transfer (WPT) transmission network. Compared to traditional meter-level WPT systems, the time-sharing linkage of loads and synchronization of energy supply and transmission, while ensuring high transmission efficiency, are achieved. Interference is avoided to ensure the safety and stability of the power supply for the electrical equipment at each node.

With the rapid development of smart grids, abundant online monitoring sensors are installed at critical nodes of medium and low voltage power lines. To ensure reliable operation of these monitoring sensors, the power source problem needs to be solved urgently. The magnetic field energy can be captured and used as a stable energy source for online monitoring sensors. However, the single-phase magnetic field energy harvester (MFEH) tends to achieve low energy at low currents, and the output power is significantly influenced by load fluctuations. Motivated by these challenges, a three-phase distributed magnetic field energy harvester (TDMFEH) with transforms is proposed in this article. The power multiplier changes of the TDMFEH compared with the single-phase MFEH are further analyzed. Moreover, this article proposes an output power boosting control method under load fluctuations with single-phase and three phase joint energy harvesting, to achieve higher output power with a wide range of load connected. The experimental results demonstrate that the TDMFEH can achieve a maximum power ratio of 2.13 compared to an equal-volume single-phase MFEH. Besides, the output power can be enhanced with the switching between single-phase MFEH and TDMFEH when the load fluctuates.