In the DC subway system, sensors are widely used for operating condition monitoring, but their power supply problem remains prominent. To address this issue, this paper proposes a rail potential-based energy collector (RPEC). First, the formation mechanism and distribution characteristics of rail potential are analyzed, the rail-ground system is modeled as a Thevenin equivalent circuit, and an energy-harvesting equivalent circuit is constructed. To effectively achieve maximum power tracking, this paper combines the open-circuit voltage (OCV) method to propose a scheme using only a single-stage Buck topology. The scheme completes the three functions of OCV detection, optimal voltage maintenance, and energy transmission through pure voltage hysteresis control, featuring the advantages of a simple system structure, no need for additional measurement of other physical quantities, and high stability. Experimental results show that when the rail potential is in static or dynamic change conditions, the system can quickly update and stably track the optimal operating voltage within a 250-ms cycle, meeting the power supply requirements of sensors.

Sensors are used in the dc metro system for monitoring. Still, there is a problem of high costs using cable and battery power supply, while achieving self-powered technology through ambient energy harvesting is difficult on underground tracks. To address this issue, considering that the rail in the subway dc power supply system has a certain potential relative to the ground, this work proposes a subway rail potential-based energy harvester (RPEH). An energy harvesting equivalent circuit is constructed to analyze the output characteristic of the rail potential. To achieve maximum energy harvesting, the open-circuit voltage method is applied. However, the open-circuit voltage method requires disconnecting the energy harvesting device to obtain the open-circuit voltage. To significantly shorten the open-circuit monitoring time, this work designs an energy harvesting device based on a two-stage mosfet structure. In addition, the energy harvesting circuit fully utilizes low-power analog discrete components without relying on programmable controllers, thereby reducing system complexity and power consumption. The experimental results show that the RPEH can quickly track the optimal energy point under varying voltage levels and reduce the open-circuit detection time to less than 2 ms. It demonstrates that the proposed method can achieve maximum power point tracking, rapid response, and low power consumption, meeting the power supply needs of underground track sensors.

In an inductive power transfer (IPT) system, due to the presence of ferrite cores, changes in the air gap can alter the coil parameters (self-inductance and mutual inductance), leading to system detuning, resulting in efficiency degradation. To address this problem, an impedance self-adjustment method based on an integrated LCC-LCC topology with two variable inductors is proposed for IPT systems to enhance efficiency. Combined with the Second-Generation Nondominated Sorting Genetic Algorithm (NSGA-II) for system parameter design, the proposed method can mitigate secondary-side detuning and offer variable input impedance to realize wide-range zero-voltage switching (ZVS) of the inverter with phase-shifting (PS) control. The proposed method does not need additional components or complex controls. Experimental results show that with the air-gap variation from 30 to 60 mm (the self-inductance variation is 17.47%, and the mutual inductance variation is 80.91%) and the load variation of 50%, an accurate output is achieved with the PS control, and the system efficiency ranges from 92.6% to 94.23%. Compared with the traditional method, the maximum efficiency improvement is up to 16.92%.

To achieve a noncontact auxiliary power supply during low-speed operation of high-speed electromagnetic suspension (EMS) maglev trains while minimizing the weight of the coupling mechanism, this article proposes an integrated high-low speed auxiliary power supply system. During low-speed operation and station stops, two-phase transmitting coils are added to the stator slots to generate a high-frequency magnetic field, while the existing onboard collector coils are repurposed for harvesting high-frequency energy. To ensure efficient transmission of both low-frequency motional energy and high-frequency induced energy to the onboard electrical equipment, a hybrid high-low frequency energy coexistence circuit (HLC) is designed, which achieves full compensation of high-frequency energy while exerting minimal impact on low-frequency energy transmission. The proposed system has no impact on the train's original systems and requires no additional coils to be installed on the vehicle. To validate the feasibility and effectiveness of the proposed solution, a full-scale (1:1) prototype was developed and experimentally validated. Results demonstrate that a single power generation branch can consistently deliver over 600 W of output power, regardless of whether the collector coil is aligned with the stator tooth or slot.

Wireless sensors are widely deployed for the real-time monitoring of status in DC metro systems, and their long-term and stable power supply is the key to ensuring the reliable operation of monitoring systems. In view of the inherent potential that generally exists in metro rails relative to the ground, this paper proposes a self-power harvesting device (SPHD) for subway rail potential energy harvesting. Through the modeling and analysis of the metro power supply system, the output characteristics of rail potential are derived, and a corresponding Thevenin equivalent model is established to clarify the basic conditions for the system to achieve maximum power output. On this basis, a maximum power point tracking control method based on open-circuit voltage detection with a unipolar Buck topology as the core is designed to realize the efficient harvesting of rail potential energy. Simulation results show that the proposed SPHD can stably and accurately track the maximum power point at different rail potential levels with low self-power consumption, and can effectively meet the power supply requirements of sensors for metro track monitoring.

Inductive wireless power transfer technology is a highly promising solution for powering embedded sensors in the structural health monitoring of concrete infrastructures. However, during the dynamic movement of inspection vehicles, significant variations in coupling characteristics as well as changes in reflected impedance induced by special media such as special steel rebars ultimately result in insufficient power obtained by the sensors. To address this issue, this paper proposes a fast maximum power point tracking (MPPT) strategy based on a two-stage metal-oxide-semiconductor field-effect transistor (MOSFET) structure with open-circuit voltage as the detection basis. The proposed system achieves a 10-microsecond voltage detection speed and accurate clamping control. Results show that this strategy eliminates the problem of energy transmission interruption and significantly enhances the operational stability of the system; specifically, the output power of the system is increased by 34.1% under heavy-load mobile conditions.

In dynamic wireless power transfer systems, long segmented transmitter couplers facilitate simplified control and mitigate voltage fluctuations. However, dynamic capacitive power transfer (CPT) systems typically operate in the MHz range, where the high-frequency excitation wavelength is comparable to the dimensions of long segmented transmitter plates. This induces significant transmission line effects (TLE) in the system couplers, resulting severe electric-field inhomogeneity and even near-zero-field regions. These issues severely constrain the system's power transfer capacity and stability. This article develops a mathematical model for dynamic CPT systems accounting for the TLE in long segmented transmitter plates, and analyzes the electric-field distribution around transmitter plates as well as the receiver output characteristics. It also proposes an open-loop output voltage fluctuation suppression method based on switchable terminal reactance, along with a corresponding terminal reactance parameters optimization method and switching strategy. Integrated with the transmitter's DC-DC converter, it enables closed-loop control of output voltage. An experimental prototype was built with an operating frequency of 6.78 MHz, 10 m-long transmitter plates, and a system power of 30 W. Experimental results demonstrate distinct near-zero-power operation intervals in the output voltage without terminal reactance, with the voltage fluctuation rate approaching nearly 100%. Adopting the proposed method reduces the open-loop output voltage fluctuation rate to 30.1%, and implementing closed-loop control further decreases it to within 5%. The fluctuation trends and amplitudes of the system output voltage before and after using the proposed method are consistent with theoretical values, verifying that the proposed method realizes stable constant-voltage output across all segments of dynamic CPT systems.

In through-metal inductive power transfer (IPT), the three-loop equivalent circuit model is widely used to describe the eddy-current effect of the metal barrier. However, the model’s equivalent parameters are difficult to obtain directly because independent electrical test ports are unavailable. To address this challenge, this paper proposes a parameter-identification method based on multi-frequency impedance measurements. By measuring port-inductance variations over a narrow frequency band, the multi-parameter identification task is formulated as a nonlinear least-squares problem and solved using a physically constrained Levenberg–Marquardt (L-M) algorithm. Experimental results demonstrate that for five metal plates with different materials and thicknesses, the maximum relative errors in equivalent parameter identification are all below 0.02%. Furthermore, with the identified parameters applied for system optimization and compensation, the power transfer capability of all tested metal plates is significantly improved.

Powering sensors through non-perforated conductive barriers using Wireless Power Transfer (WPT), specifically Inductive Power Transfer (IPT), is challenging due to eddy current losses and structural constraints in industrial settings like gas pipelines. This study presents a novel 3 kHz IPT system using an LCC-series (LCC-S) compensation topology and compact multilayer helical (MLH) coils with iron powder cores to deliver robust wireless power through a 2 mm aluminum barrier with an 18 mm air gap. Finite element analysis (FEA) validates the design, showing enhanced coupling via distributed-gap cores. The LCC-S prototype achieves 0.79 W at 3.11% efficiency across a 20 mm TX-RX separation, sustaining 0.13 W at 30 mm lateral misalignment. Exceeding a benchmark series-series (SS) topology, it ensures miniaturization and barrier integrity, unlike systems requiring bulky coils or perforations. This study pioneers LCC-S at 3 kHz with misalignment analysis, enabling robust power for industrial Internet of Things (IoT) applications.

This letter proposes a nonresonant capacitive power transfer system for active biomedical implants that eliminates resonance dependency while maintaining physical isolation. By leveraging biological tissue as the dielectric medium in a four-plate coupler and drawing inspiration from Zeta converter topology, the system achieves parameter insensitivity and single-switch control. Theoretical analysis via state-space averaging confirms output voltage regulation solely through duty-cycle adjustment, independent of component variations. Experimental validation using 20 mm x 20 mm plates through 4-mm pigskin demonstrates 207 mW power transfer with 30.1% efficiency at 1 MHz with a simplified receiver circuit (1 diode/1 inductor/1 capacitor). The system maintains 3.7 V output under 150% load transients, 100% inductance variations, fat content change and issue bending.

To address the maintenance and wear issues of traditional power supplies in structural health monitoring for large-scale rotating machinery, this paper proposes a stable rotary inductive power transfer system utilizing double transmitter coils. By employing an LCC-S compensation topology and a multi-receiver parallel configuration, the system implements an "optimal energy transmission" mechanism. To mitigate mutual inductance fluctuations caused by shaft rotation, a "peak-valley complementary" coil layout is developed, where the angular displacement between transmitters is optimized to 1.5 times the receiver's span. Maxwell and Simulink simulations verify that this strategy suppresses mutual inductance fluctuations to within 6.3%, ensuring stable voltage output. This research provides a robust wireless power solution for passive sensing in marine propulsion and wind power systems.

The passive current sharing methods with coupled inductors for multiphase LLC converters typically cannot achieve interleaving operation, leading to high current ripple. To solve this problem, a coupled resonant inductor (CRI)-based topology is proposed with auto current sharing and interleaved operation. The proposed CRI topology is based on the switched-capacitor LLC converter (SCLLC), where the resonant inductors are moved out of the resonant tank and then combined into a coupled inductor. The improved coupled inductor method allows interleaving operation, achieving excellent current ripple cancellation effect while realizing auto current sharing. Besides, the partial power processing capability inherited from SCLLC reduces the losses in the coupled inductor. A 300W experimental prototype demonstrate that the current sharing error is within 4% across the load range of 5~25A. Besides, the prototype achieves a 56% reduction in output current ripple compared to a non-coupled implementation. Finally, the proposed topology maintains excellent efficiency performance (>96%) across the load range (5~25A), with a peak efficiency up to 97.5%.

In structural health monitoring systems, inductive wireless power transfer can periodically energize embedded sensors without physical contact. However, during dynamic motion, certain coupling configurations can cause the eddy current in the rebar at the receiver coil location to vanish, preventing the sensor from harvesting energy and reducing the system’s average output power. Based on the modeling analysis, a current-phase control method using DDQ transmitting coils is proposed. Simulation results indicate that the proposed approach not only extends the effective powering range but also increases the average transmitted power by 60.98% compared to the uncontrolled case.

This study introduces a novel three-end traveling-wave-based fault location (TW-FL) method for transmission lines to improve fault location accuracy and speed. Unlike traditional approaches, it eliminates the need for traveling-wave velocity and line-parameter measurements by analyzing current surges at three terminals and exploiting the time-of-arrival (TOA) of fault-induced waves to compute the fault location. For validation, the velocity implicitly derived from the TOA formulation was compared with its theoretical value, achieving an estimation accuracy of up to 99.96%, confirming the internal consistency and robustness. The model attained maximum and minimum fault location errors of 0.36% and 0.0803%, respectively, over 100 km from terminal P, demonstrating superior accuracy relative to existing models. Simulations conducted in PSCAD/EMTDC under various fault conditions verified its robustness, while validation of the WSCC 9-bus system confirmed its speed and reliability in improving grid performance and reducing power outage.

This paper proposes a 3-D omnidirectional wireless power transfer (WPT) system with multiple loads to satisfy the multi-directional charging misalignment condition in space. First, this work builds the equivalent circuit model of an omnidirectional multi-load WPT system, where the amplitude and direction of a magnetic vector can be regulated by adjusting the coil’s current. Second, the relationship between the synthetic magnetic vector and the system’s efficiency is analyzed under different misalignment conditions. Moreover, the current phase difference between transmitters should be set to 0° or 180° depending on the position of the multiple loads. Finally, the magnetic vector regulation method based on the gradient descent algorithm is proposed to realize maximum efficiency point tracking. A 72W prototype is built to validate the feasibility of the proposed method. The efficiency can be improved by 7.1% compared to without such a method.

In mechanical power transmission equipment, the power shafts are a common mechanical structure. It is not feasible to use traditional power supply methods to supply power from fixed power sources to rotating equipment. Capacitive power transfer (CPT) technology has the advantages of flexible and portable couplers and low eddy current loss, and these advantages are well suited to the power supply needs of equipment installed on rotating bodies. However, there are also some shafts with large diameters that can cause serious electromagnetic radiation and standby losses when using long receiving plates and a series of problems such as voltage drops caused by segmented couplers. Therefore, this article proposes a rotating segmented CPT system with low output voltage fluctuation based on three DC busbars; it establishes a mathematical model and equivalent circuit for the system's multiport capacitive coupling and achieves the superposition of adjacent rectified output voltages. Experimental results confirm that the system maintains a basically constant output voltage throughout the entire rotation process. In this process, the output voltage of the system drops from 47 to 41 V, with a maximum variation rate of 12.77%. The system output power reaches 82 W, and the peak efficiency achieves 84.97%.

For an inductive power transfer (IPT) system, stable power transfer is one of the most crucial abilities, but coupling variations can dramatically affect the system's output. This brief proposes a reconfigurable detuned S-LCC compensated IPT system with two discrete frequencies to mitigate power fluctuations due to coupling variations. The original detuned S-LCC topology can operate in one stable region. With the change of the primary capacitor and frequency, the equivalent ac load can be altered, which will create a new stable region. Therefore, the expected coupling range of the detuned S-LCC topology can be extended. First, a detuned S-LCC IPT system with two discrete frequencies is presented, followed by an analysis of the working modes. Then, a detailed parameter design process and switching control are introduced. Finally, a 140-W prototype was constructed to verify the validity of the proposed method. The experimental results demonstrate that the output power fluctuation of the proposed IPT system is less than 5% and the lowest efficiency can be improved from 91.5%% to 94%, with the coupling coefficient varying from 0.27 to 0.63. The proposed method does not need complicated control or dedicated coil design, and it can implement stable power transfer significantly.

Deep learning (DL)-based protection algorithms for power transmission lines require large volumes of operational data for accurate training. However, such data is often complex to access due to confidentiality, restrictions, and proprietary limitations. This paper proposes a synthetic data generation method that combines principal component analysis (PCA) with a conditional tabular generative adversarial network (CTGAN). PCA reduces the dimensionality of high-frequency time-series data, allowing CTGAN to operate efficiently while retaining essential statistical characteristics. The generated synthetic data shows strong correlation with real data and effectively augments limited datasets. Validation using an LSTM-based fault classification model demonstrated an improvement from 50.93% to 86.07% accuracy. Additional validation using sub-synchronous oscillation data demonstrates broader applicability. The proposed method is scalable and supports DL training in data-scarce scenarios.

This paper proposes an integrated topology with both wired and wireless outputs for automated guided vehicle (AGV) charging systems. The topology shares a primary-side bridge circuit and resonant network, achieving wired charging through a switched-capacitor converter and utilizing the resonant inductor as a transmitter coil for wireless charging. In wired charging mode, a phase-shifted and variable-frequency modulation strategy is adopted to regulate the output, enabling soft charging and reducing capacitor charge-sharing losses. In wireless charging mode, pulse-width modulation is employed to ensure precise alignment with battery charging curves. Detailed analyses of the equivalent circuits, steady-state operational waveforms, and zero-voltage switching (ZVS) conditions for both modes are presented. Theoretical analysis and numerical simulations validate the feasibility of achieving ZVS under varying load conditions, and a parameter design methodology is proposed. Simulation results based on a 400 W prototype demonstrate that the proposed topology achieves ZVS across a wide load range $(1 \sim 8 \mathrm{A})$, supporting both constant-current $(8 \mathrm{A})$ and constantvoltage $(50 \mathrm{V})$ charging phases for AGVs.