DC grids are recognized as a promising solution for next-generation power distribution systems due to their high efficiency and reduced energy conversion stages. Since modern electronic sources and loads operate with DC power, DC-DC converters serve as key components. In particular, non-isolated DC-DC converters are gaining attention due to their high efficiency and power density. However, the removal of galvanic isolation significantly lowers common-mode (CM) impedance, leading to increased leakage current and electric shock to users. To address these issues, a non-isolated three-switch converter topology is employed, which uses fewer switches while effectively suppressing CM currents. A low-frequency (LF) leakage current controller with a feedforward for enhanced transient response is developed, based on the CM equivalent circuit analysis. The operable range of the converter is analytically derived with consideration of the voltage fluctuations in both bipolar and unipolar DC grids. In addition, a hybrid pulse width modulation (PWM) scheme is introduced to suppress high-frequency (HF) CM currents, along with the DC CMV injection method to enhance the suppression performance. Experimental results in the bipolar and unipolar grids confirm that the proposed methods effectively suppress both LF and HF CM currents, ensuring the user safety. The 11 kW hardware prototype achieves a peak efficiency of 99.38% and reduces the rms leakage current by over 91.35% compared to the conventional designs.

Parameter identification-based control strategies are considered the preferred solution for achieving constant current and constant voltage charging control in communication-free inductive power transfer systems. However, identification errors in mutual inductance, load resistance and other parameters can affect control accuracy. To improve control accuracy and response speed, a communication-free control strategy based on neural networks and deep transfer learning is proposed. This strategy eliminates the need to identify parameters like mutual inductance and load resistance. Only a few measured data are required to train the network model offline, a trained model can online estimate output voltage/current will be obtained. By combining with a controller, constant voltage/current charging control can be achieved under conditions of real-time variations in mutual inductance and load resistance. The experimental results show that the proposed control strategy achieves a static error of only 1.5% and a response time of no more than 24ms. Compared to the parameter identification-based control strategy, the proposed strategy demonstrates lower static error, shorter response time, and a wider dynamic range.

Piezoelectric energy harvesting (PEH) efficiently converts ambient kinetic energy into electrical power, enabling sustainable and autonomous operation of low-power electronic devices. To optimize power extraction, maximum power point tracking (MPPT) methods are commonly employed. Conventional MPPT approaches, such as perturb-and-observe (P&O) and fractional open-circuit voltage (FOCV), typically rely on incremental power measurements or theoretical voltage estimations, but suffer from high power overhead, slow convergence, and circuit complexity. Duty-cycle-based (DCB) MPPT techniques partly overcome these limitations by regulating the rectifier's duty cycle at 50%, yet they still require a dedicated MPPT stage and large external capacitors, causing additional power loss and delayed convergence. To address these challenges, this paper presents a self-regulating bias-flip rectifier that inherently integrates rectification and MPPT into a single stage, eliminating cascaded energy losses and enabling rapid convergence to the maximum power point. Fabricated in a 0.18-μm CMOS process, the proposed rectifier achieves an end-to-end efficiency of 93%, MPPT efficiency of 98%, and provides a 7.7-fold improvement in energy extraction compared to conventional full-bridge rectifiers.

Grid-following (GFL) and grid-forming (GFM) inverters are usually synchronized with the phase-locked loop and the power synchronization control respectively, and they exhibit complementary characteristics on the grid strength adaptability. How to make the best of two synchronization approaches and endow the system with superior grid strength adaptivity and transient stability, remains a significant yet unsolved challenge. Based on their structural similarity and duality, this paper proposes a family of novel integrated synchronizations, which are in a symmetric and elegant form. The interaction between the integrated synchronization and other control parts is described by evolving the complex system into a simple single-input-single-output model. On its basis, comprehensive small-signal and transient stability analysis reveals that the proposed synchronization methods can ensure the robust operation of inverters and enhance their tolerance to severe faults.

According to the duality of inductive wireless power transfer (IPT) and capacitive wireless power transfer (CPT) in coupler and tuning method, an integrated coil is designed in this paper to constructs a compact hybrid wireless power transfer (HPT). The magnetic field coupling and the electric field coupling constructed by coils and plates share one energy transmission channel, which enhances the transmission power and energy density. The inductance of coils and capacitances of plates compensate for each other. The resonant frequency of integrated coils is adjusted to kHz. Additional tuning inductances and capacitances are eliminated to build a lighter self-resonance coupler. The stacked structure design of coils and plates enables compact integration and miniaturization of integrated coils. A 300W experimental platform was built, and some comparative experiments were conducted. Compared to the coupler of IPT, the self-resonance coupler has improved performance in transmission power, anti-offset, and over-coupling suppression. HPT performs better than CPT in transmission distance, transmission power, and transmission efficiency. It has some advantages in the medium-power application scenarios such as inspection robots and drones, which expect couplers to have a smaller volume, lighter weight, higher power density and better anti-offset.

Fatigue-induced delamination of the direct-bonded copper (DBC) solder layer is a critical and latent failure mode in multichip Insulated Gate Bipolar Transistor (IGBT) power modules. To address the challenge of online diagnostics, this letter proposes a novel method for monitoring solder degradation based on the temperature field of the copper baseplate. First, sparse temperature data are collected from a thermocouple array placed beneath the module. Then, a physics-guided Gaussian process regression (PG-GPR) model embedded with a 2D steady-state heat conduction equation via a Laplace kernel is constructed to reconstruct a high-resolution temperature field. Finally, the reconstructed field is converted into pseudo-color images and fed into an enhanced Tiny Vision Transformer (Tiny-ViT) network for degradation classification. Experiments conducted on eight customized IGBT modules with varying solder void ratios validate the approach. Compared with the average of bilinear and GPR interpolation baselines, the proposed PG-GPR reduces mean absolute error (MAE) by 34.2% and improves structural similarity index measure (SSIM) by 7.6%. The classification accuracy of solder degradation states reaches 99.75% with an inference delay of only 4.37 ms. These results show that using the baseplate temperature field as the diagnostic variable, together with physical priors and a lightweight vision model, enables accurate online monitoring of solder degradation. This method helps improve the safety and lifetime of high power devices.

In non-isolated three-level inverter applications, common-mode voltage (CMV) and the leakage current resulting from it will lead to potential safety hazards, and a decrease in system efficiency. Existing research on carrier-based modulation is generally featured by the tradeoff between CMV suppression and switching loss reduction. To address this limitation, an enhanced carrier-based discontinuous pulse-width modulation (ECB-DPWM) strategy is proposed for three-level inverters, using the T-type three-level inverter (T<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup>LI) as an example. The proposed strategy further reduces the CMV variation within each clamping region of DPWM to suppress leakage current. On this basis, the sector division is optimized, which introduces a novel clamping mode and incorporates transition regions to avoid abrupt CMV variation when switching between clamping regions. Meanwhile, the mechanism by which the proposed method achieves this suppression is revealed through a double Fourier decomposition of CMV. Finally, the feasibility and superiority of the proposed modulation strategy are validated through experimental results.

The excitation system (ES) of the Brushless Wound-Rotor Synchronous Starter-Generator (BWRSSG) plays a critical role in supplying field current for the main machine (MM), so effective online fault diagnosis for ES is necessary. In this paper, the waveform characteristics of the stator current of the main exciter (ME) under different faults in the ES are analyzed. And based on the average-value, periodicity and fluctuation rate of the stator current, an online diagnosis method for the electrical fault of the ES with DC excitation in the BWRSSG is proposed. The proposed method enables online diagnosis of the fault occurrence, fault localization, and fault type of the ES, including the ME stator/rotor windings, the rotating rectifier, and the MM field winding. Experimental results verified the feasibility and effectiveness of the proposed method.