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Domino-coils wireless power transfer (WPT) technology has emerged as an effective means of ensuring reliable power supply for online monitoring equipment in smart grid. Nonetheless, it encounters persistent challenges when integrating domino-coils into composite insulators, notably the issues of large coil size and low power transmission efficiency (PTE) over medium and long distances. In response, this article constructs a T equivalent model of domino-coils WPT system to deduce the optimal efficiency condition for any number of coils. Specifically, it is determined that PTE is maximized when the current ratio of nonadjacent coils equals the mutual inductance ratio of adjacent coils. Building upon this insight and considering practical constraints such as coil volume and transmission distance, an optimization model is formulated for single-layer domino-coils with uniform spacing under the optimal efficiency condition and given output power specification, which is subsequently determined using a particle swarm algorithm. Experimental validation is conducted utilizing a seven-coil system experiment platform, achieving an output power of 12.23 W and a PTE of 85.94% at a transmission distance of 50 cm. These findings demonstrate significant enhancements in PTE, coil volume reduction, and ease of integration into thin and uniformly distributed insulator.

Online temperature monitoring is important for ensuring safe operation of lithium-ion batteries (LIBs). As the battery impedance is related to the internal physical and chemical processes, some efforts have been made to realize sensorless temperature estimation based on the impedance characteristics of LIBs. Unfortunately, the existing impedance-based temperature estimation models are usually derived from pure battery cells, and the effect of peripheral circuit components of systems (e.g., resistors and capacitors) on measured impedance has not been considered. To fill the gap, this article investigates the effect of peripheral circuits (including filter circuits, balancing circuits, and line resistance) on the measured impedances. Taking a ternary lithium battery as a case study, it is found that the imaginary-part impedance at the frequency band of 100 Hz–1 kHz is almost not affected by the peripheral circuits. This can indicate the temperature variation of batteries, and it is independent of state of charge and state of health, which can be chosen as a thermal sensitive electric parameter (TSEP) of batteries. A similar conclusion can also be drawn for a battery with different types and packaging. Based on the obtained TSEP, a single-frequency impedance-based temperature estimation method is presented. Taking a dc/dc converter as a case study, experimental results demonstrate that the estimation method can be integrated into an interface converter for batteries, and the maximum estimation error is less than 5 °C.

Flexible output regulation and high efficiency are key requirements for wireless power transfer systems. However, it is a challenge to maintain high efficiency in wide output voltage range applications due to the limited regulation range of converters. To address this issue, in this article, two power transmission channels based on the LCC-LCC compensation network are used to improve system efficiency within a wide operation range. Multiple operation modes of two power channels are utilized to obtain multiple operation ranges with different optimal output voltages. Then, a multimode control strategy for two power channels is proposed to achieve optimal efficiency with different output voltage ranges. By properly switching the operation mode of these power channels, the system can always operate in an optimal range, thus the overall efficiency can achieve a high level even in not only heavy load, but also light load conditions. An experimental prototype with 100 to 420 V output voltage is constructed. Experimental results show that the proposed method can achieve an overall efficiency of 93.8% to 96.5%.

Accurate and rapid impedance measurement of high-speed train (HST) is crucial for small-signal stability analysis in the train-network system. Although using wideband disturbance can effectively reduce measurement time, its limited and inflexible spectral controllability will lead to inferior disturbance performance, compromising measurement accuracy, and potentially jeopardizing safety. To address this issue, this article proposes an HST impedance measurement approach based on adaptive multifrequency voltage disturbance. This approach enables precise control of the disturbance frequency band as well as adaptive adjustment of both disturbance frequency resolution and amplitude. First, an odd-even segmented frequency injection strategy is proposed to avoid the HST's frequency overlapping effect interfering with wideband impedance measurement. Then, an adaptive frequency resolution adjustment method is proposed to improve measurement accuracy in the frequency segments with heavy impedance fluctuation. Furthermore, a controllable multifrequency voltage injection device is designed for HST impedance measurement, which can inject desired wideband voltage disturbance whose spectrum energy is congregated at designated multiple frequencies with average amplitude. Particularly, the disturbance amplitude can be reduced automatically by adjusting the regulatory factor of modulated signal when capacitor voltage fluctuation exceeds the threshold, thereby enhancing measurement safety. Finally, the effectiveness of the proposed approach is well validated through real-time hardware-in-the-loop experiment.

To improve the power density of magnetic field energy harvesters (MFEHs) and supply stable voltage output, a maximum-power-point tracking (MPPT) method with constant voltage (CV) output for the MFEH in the saturated region is proposed. The proposed MFEH system consists of a bidirectional buck–boost converter connected with a supercapacitor and an active rectifier. The bidirectional buck–boost converter is employed for CV output control, and MPPT under CV output conditions is realized by controlling the conduction time of the active rectifier. Besides, the calculation formula for the optimal conduction time in the saturated region is derived, which is constant and does not vary with the primary current. Subsequently, the optimal coil turn design method of the MFEH under optimal conduction time control is proposed, which can be used to guide the design of the coil turns. An experimental prototype is constructed to verify the effectiveness of the proposal. Experimental results demonstrate that the output voltage can be maintained at 3.3 V, and CV output can be realized. Besides, compared to conventional methods, the output power of the MFEH with the proposed method at 50 Arms increases from 0.47 to 0.60 W, achieving a 27% improvement.

24 × 7 health monitoring of rotating shaft is very important for the safe operation of automotive axles. Wireless sensor power supply technology is one of the promising power supply means for monitoring systems. Since the radius of many rotation shafts is large up to 1 m, segmented coils are adopted to reduce the magnetic interference and power loss compared to single receiver coils, but this will lead to output voltage fluctuation causing the monitoring system failures. This letter proposes a fluctuation suppression method by a dc-side diode array and parameter optimization. Using multiple reverse parallel diode groups to connect the dc side of multiple receivers and the load, the diodes will be conducted when corresponding coils are activated, while those without induced voltage will not be conducted. In this way, the mutual inductance fluctuation as per different rotation angles can be greatly reduced. In addition, a detuned system has been designed, rendering the output gain insensitive to variations in mutual inductance, thereby enhancing the output stability. A prototype was built to verify the theoretical analysis. The experimental results indicate that the output voltage fluctuation is only 5.0%. The proposed method can achieve significant output stability without complex control and dedicated coil design.

Neutral sections (NSs) in electric railways cause train speed loss, transient overvoltage, and arcing, posing threats to the system's safe operation. Thus, this article proposes a wide-adaptable uninterrupted power supply system (WUPSS) for NSs. It enables trains to pass through NSs without power interruption, transient overvoltage, and arcing, under various operation scenarios. This WUPSS consists of two auxiliary transformers, two auxiliary inverters, and a back-to-back converter (BTBC), having a lower converter investment than existing schemes. Then, a multipoint current-based pantograph positioning method is designed to accurately detect the train pantograph position in NSs. On this basis, an event-triggered flexible power and voltage control method and an unequal active power division rule are proposed to calculate output power and voltage references for the inverters and BTBC. These methods aim to achieve power transfer in the transition zones and voltage transition in the virtual neutral zone while compensating for reactive power. Additionally, an output power-adaptive virtual impedance control scheme is designed for inverters to suppress the separation current between the train pantograph and the catenary. Finally, the feasibility and adaptability of the WUPSS under different operation scenarios, including single pantograph, double pantograph, double track, and different speeds, are demonstrated via hardware-in-the-loop tests.