The increasing penetration of inverter-based renewable energy systems requires grid-forming (GFM) inverters to maintain stable operation under fault conditions. However, their transient stability is significantly challenged when current-limiting mechanisms are activated, particularly when the power angle exceeds the unstable equilibrium point (UEP). To address this issue, an adaptive power-angle resetting (APAR) strategy is proposed to enhance post-fault recovery performance without relying on grid impedance information. The proposed method decouples the power-angle dynamics from the conventional power synchronous loop(PSL), enabling direct regulation of the power angle through an integrator resetting mechanism. Furthermore, the operating region is partitioned according to system states, and an adaptive adjustment scheme is developed to regulate the power angle under different fault conditions. And the Lyapunov energy-based stability analysis demonstrated that this proposed method can drive the system state to converge to stable operation point. Compared with existing approaches, the proposed strategy effectively suppresses post-fault oscillations, accelerates transient recovery, and maintains robustness under grid phase jumps. The effectiveness of the proposed method is validated through both simulation and experimental results.
The growth of electric vehicles (EVs) is driving new technological shifts, incorporating advanced control solutions in fast charging stations (FCSs) that expand their functionalities and provide greater operational flexibility. Specifically, these stations can operate as an uninterruptible power supply (UPS) to sustain critical local loads during grid contingencies. This paper implements a hybrid grid-forming (GFM) control approach for multifunctional FCSs capable of operating in both grid-connected and islanded conditions. Under this architecture, the system specifically addresses critical DC bus voltage overshoots resulting from reduced control bandwidth and sudden DC load variations. To mitigate these limitations, a DC-link direct compensation strategy is proposed. This parallel loop introduces a fast-acting current-injection mechanism that bypasses the slow inertia of the traditional droop branch, rapidly modifying the AC current reference to stabilize the DC bus. A comprehensive bottom-up modeling approach is detailed to support the control design. Experimental results for a 10 kW prototype validate the proposed method, demonstrating a significant 32.4 % reduction in DC voltage overshoot during load disconnection while ensuring stable, continuous operation across different grid scenarios.
Constant current (CC) DC power distribution is widely used in seafloor applications owing to its fault tolerance and high robustness. These systems are configured as daisy-chain networks, with discrete nodes drawing power in series. As the number of power nodes increases, particularly with the introduction of switching constant current to constant voltage (CC/CV) converters, system oscillation issues become increasingly prominent, and research in this system remains almost entirely unexplored. This paper establishes the impedance model for constant-current DC systems for the first time, which also incorporates the parasitic parameters of seafloor cables, providing a modeling basis for subsequent research. The impedance characteristics of each component are analyzed and summarized to support system stability analysis, rapid assessment, and oscillation suppression. In particular, the impedance features of shore-based DC current source assist in identifying the phase crossover frequency that trigger system oscillations. Also, a specific-band reduced-order compensated virtual impedance control method is proposed to suppress oscillations. The power-decoupled reduced-order compensation function eliminates the adverse effects of attached control loops and reduces the computational burden. Meanwhile, specific-band phase regulation is adopted to effectively enhance the compensation performance of virtual impedance. Finally, a 1 A multi-node constant-current DC experimental system is established, which verifies the accuracy of the model, the correctness of the stability analysis, as well as the effectiveness and scalability of the proposed control method.
This paper presents a model-driven electro-thermal design methodology for optimizing hybrid Totem-Pole Bridgeless power factor correction (PFC) converters employing both high-frequency SiC-MOSFETs and line-frequency silicon-controlled rectifiers (SCRs). The co-location of these dissimilar semiconductors on a shared thermal system induces complex electro-thermal interactions that conventional decoupled analysis fails to capture, thus hindering performance optimization. To address this, the proposed methodology utilizes a comprehensive, coupled electro-thermal model as an active design driver rather than a post-design verification tool. This approach enables a systematic, multi-objective optimization of component-level losses and the proactive management of thermal crosstalk between the SiC and SCR devices. Experimental results from a 3.3 kW hardware prototype confirm the methodology, achieving a competitive peak efficiency of 98.05%. Thermal measurements provide direct empirical evidence of the dominant thermal crosstalk from the heat-generating SiC-MOSFETs to the adjacent SCRs. Furthermore, the results reveal that significant temperature imbalances are governed by the physical component layout rather than by electrical symmetry. The primary contribution is a validated, system-level design principle: in a thermally-coupled hybrid converter, the junction temperature of a low-loss secondary device (the SCR) is governed predominantly by the efficiency of the adjacent dominant heat source (the SiC-MOSFET) rather than by its own dissipation. This shared-heatsink coupling is quantified with a closed-form coefficient, and the predicted temperatures are verified to within 8% of thermographic measurements.
As critical components in electromagnetic compatibility (EMC) filters, X2 film capacitors play an essential role in ensuring EMC compliance in power electronics. However, existing aging approaches are generally limited by selected-frequency measurements or incomplete aging-dependent parameter coverage, restricting wideband performance assessment. This paper proposes a wideband impedance degradation model for X2 film capacitors under AC electro-thermal-humidity stress, covering 20 Hz–110 MHz. Accelerated aging tests are conducted to characterize the impedance evolution and underlying degradation mechanisms. A lumped-parameter model is established by incorporating capacitance, equivalent series resistance, equivalent series inductance, and aging-dependent parallel insulation resistance, which is often neglected or treated as constant in existing aging models. The inter-sample degradation variability is statistically characterized using Weibull distributions and propagated through the impedance model via Monte Carlo simulation, generating percentile-based uncertainty bands. The model is applied to a CLC EMC filter, and the predicted differential-mode attenuation degradation is experimentally verified. Thermal analysis further shows that single-frequency characterization can substantially underestimate capacitor losses and thermal risk under wideband harmonic excitation. The proposed model supports aging-aware performance prediction and reliability-oriented design for EMI and EMC applications.
Current imbalance among parallel-connected power devices can lead to increased switching losses, aggravated thermal stress, and reduced reliability in high-power converters. This paper proposes a passive compensation circuit to mitigate transient current imbalance among parallel-connected power devices. The proposed circuit employs Rogowski coils to sense device current variations and modulate the gate currents during switching transients, thereby driving the device currents toward a closer match. The operating principle of the compensation circuit is analyzed using equivalent circuit models for both two-device and multi-device configurations. The analysis reveals that the induced electromotive forces generate gate extraction currents, forming a proportional-like feedback mechanism that acts on the device currents. Experimental validation is conducted using buck converter prototypes with two and four parallel-connected devices. Controlled current imbalance is introduced through threshold voltage mismatch and source parasitic parameter mismatch. Experimental results demonstrate that the proposed compensation circuit consistently reduces switching energy imbalance among parallel-connected devices. The proposed solution offers a fully passive approach for mitigating transient current imbalance, contributing to improved reliability in parallel device applications.
Due to the demand of simultaneously handling multiple objectives including current tracking, neutral point (NP) balancing and flying capacitor (FC) voltage balancing, the control of hybrid seven-level converter cascaded by three-level T-type converter and H-bridge (T2C-HB) is formulated as a multi-objective optimization problem (MOOP). Conventionally, model predictive control (MPC) applies weighting factors (WFs) to reformulate MOOP as a single-objective optimization problem. However, due to differences in the physical units of the objectives, WF selection typically relies on empirical trial-and-error. In addition, under varying operating conditions, constant WFs fail to adequately coordinate all control objectives, limiting the adaptability and system performance. To overcome this limitation, a reinforcement learning (RL)-based hierarchical MPC approach is proposed, replacing WFs with explicit admissible thresholds. Control objectives are hierarchically structured, and RL agent dynamically adjusts thresholds based on real-time deviations, achieving a trade-off in different control objectives. Both simulation and experimental results validate the effectiveness of the proposed approach.
Wide-bandgap devices impose severe constraints on gate driver isolation, adding extremely fast voltage transients to already stringent electrical requirements. This work introduces a bidirectional isolated communication strategy based on a single planar transformer. The approach relies on a simple push-pull circuit to generate customizable pulses. The associated protocol exploits pulse length and polarity to transmit control and fault signals, as well as additional feedback data such as module temperature. Bidirectional communication over a single channel inherently leads to message collisions, which are analyzed through simulation and mitigated by combining polarity alternation with an appropriate choice of pulse duration. Voltage transients impact is characterized and integrated into the decoding method. Reliable operation was demonstrated up to 300kV/μs without any failure. Partial discharge tests certify reinforced insulation up to 2.157kV, with creepage and clearance distances of 19mm. The system achieves a data rate of 350kB/s, a propagation delay of 470ns, and a jitter of 45ns. Compared with conventional solutions, the proposed approach uniquely combines a bidirectional protocol with planar transformer technology, allowing the design of a transformer with insulation thickness, creepage, and clearance adapted to specific application requirements.
In high-power converters, series-connected IGBTs exhibit dynamic voltage imbalance during turn-off, especially in the tail stage, leading to uneven voltage stress and energy dissipation. Although conventional RC snubber circuits are commonly used to suppress overvoltage during the tail stage, they introduce additional power dissipation and add design complexity. This article reveals that the tail-stage voltage deviation ΔVtail is fundamentally linked to the mismatch in residual tail charge Qtail and can be interpreted as an external manifestation of internal charge imbalance. Based on this insight, a stored-charge-regulated gate-delay control strategy is proposed, in which ΔVtail is used as the feedback signal for closed-loop delay adjustment. The proposed method indirectly regulates Qtail, improves stored-charge distribution, and enhances voltage sharing over the turn-off transient without using RC snubbers. Experimental results confirm that the proposed strategy maintains high effectiveness and adaptability across diverse operating conditions, even in the absence of RC snubber circuits. It effectively constrains the maximum ΔVtail to approximately 5%, thereby enhancing energy efficiency and system reliability, while enabling active voltage and energy balancing during the tail stage.
The thermal management of high-frequency magnetic components is an important design challenge in modern power electronics due to the drive toward higher power density. Traditional temperature monitoring methods, including invasive sensors and indirect thermal models, can be affected by electromagnetic interference or limited transfer across physical configurations. This work formulates steady-state ferrite-core temperature estimation as an inverse thermomagnetic sensing problem using a physics-aware vision transformer (PA-ViT). The synchronized open-circuit sensing-winding voltage and primary excitation current are reconstructed into dynamic $B$–$H$ responses and encoded as time-density hysteresis images (TDHIs). The Trajectory-Guided Attention Mask (TGAM) uses a deterministic trajectory-density mask derived from the TDHI to modulate the extracted visual features before tokenization, while cycle energy and excitation frequency are encoded into a separately formed physical token before fusion with the visual tokens. Under the controlled open-circuit magnetic-characterization condition, material-specific results are reported for TDK N87 and Ferroxcube 3C90, together with within-material evaluation on the corresponding Princeton MagNet subsets. On the self-built N87 test subset, PA-ViT yields a mean absolute error (MAE) of $1.22^\circ \text{C}$. Additional tests consider non-sinusoidal waveforms and additive white Gaussian noise (AWGN) synthetically applied to the measured signals, providing further evidence under the evaluated conditions.
This paper proposes a hybrid LC resonant circuit solution based on the active impedance module. Compared to passive resonant circuits with fixed resonant frequencies, which are prone to component parameter shift, the proposed hybrid LC resonant circuit can adjust the resonant frequency. It also maintains frequency stability under component parameter shift and different operating conditions. The paper further presents a control method for the resonant frequency and analyzes its impedance characteristics. Based on the proposed circuit solution and design process, a light-weight hybrid LC resonant circuit prototype is developed. To verify the hybrid LC resonant circuit, a 4000-W single-phase AC-DC converter test platform is constructed. Then, the feasibility of the proposed solution is verified in both steady-state and dynamic experiments.
Series partial power converters (S-PPCs) exhibit high efficiency in battery energy storage systems. Nevertheless, conventional topologies employing a fixed interconnection structure and unipolar switches are generally restricted to either step-up or step-down operation. Moreover, in the proximity of the unity-gain region, the duty cycle or phase-shift angle tends to approach its extreme boundaries, thereby aggravating the design challenges and substantially limiting the converter's voltage adjustment capability. To address these issues, a triple-active-bridge (TAB) based S-PPC featuring a differential series compensation architecture is proposed in this letter. By decoupling the voltage compensation requirement into two independent port voltages, the proposed strategy maintains the control variables away from zero, inherently bypassing the constraints of duty cycle or phase-shift angle. Consequently, the proposed topology achieves both the precise wide-range step-up/down regulation and the smooth mode transition. Experimental results from a 200-W prototype validate the proposed architecture, demonstrating excellent steady-state performance and an ultrahigh peak system efficiency of 99.4%.
A high-frequency common-mode (CM) resonance peak appears in the MHz range of the noise spectrum due to the impedance interaction between parasitic capacitances and inductances in power converters. Conventional suppression methods, such as increasing the filter inductance or adding a parallel RL damping branch, inevitably increase inductance and size, thereby increasing the suppression cost and reducing the power density of converters. The imaginary part of the magnetic core's complex permeability results in an equivalent resistance. This resistance exhibits a frequency-dependent characteristic, being relatively high at high frequencies while remaining low at low frequencies. Based on this characteristic, this letter proposes a simple and compact CM resonance damping method. First, the damping mechanism of the proposed method is analyzed. Then, the negative impact of the core's equivalent inductance on resonance suppression is evaluated, and the corresponding design method is further developed. Experiments on a 40-kW dc-dc converter verify the effectiveness of the proposed method and its advantages in reducing volume and weight.
This paper proposes a robust grid-forming (GFM) control method for grid-connected converters (GCCs) that ensures stable and satisfactory dynamic performance over a wide range of grid strengths. The proposed controller employs an observer-based synchronization method, which exploits available model information for analytical gain design, guaranteeing stable convergence of the load angle. Voltage magnitude control is incorporated to regulate the GCC as a voltage source, while an extended state observer (ESO) is introduced to improve active-power tracking accuracy under grid impedance uncertainty. Stability robustness is demonstrated through closed-loop pole trajectories under short-circuit ratio (SCR) variations from 1 to 10. The effectiveness of the proposed method is further validated experimentally on a 20 kVA power conversion system (PCS).
To improve the efficiency of the dual active bridge (DAB) DC-DC converters used for wide-voltage-range charging of electric vehicles (EVs), this paper proposes an efficient DAB converter based on the dual-transformers structure and H5 bridge circuit (DAB-DTH5). The DAB-DTH5 converter uses the leakage inductor of two transformers instead of the extra series inductor. Without requiring an extra component, it can operate in four operating modes with different equivalent turn ratio by controlling the switching state of the H5-bridge circuit. First, the topology, principles, and detailed circuit analysis of the proposed DAB-DTH5 converter are introduced. After mathematical modeling, the turn ratios of the two transformers are designed based on the criterion of minimizing the inductor rms current. The sectional windings are employed to increase the leakage inductor of both transformers. Second, a control scheme for the DAB DTH5 converter is designed, and it is compared with a conventional DAB converter in terms of inductor rms current and soft-switching range. Finally, the 1.5-kW experimental prototype validates the feasibility and superiority of the DAB-DTH5 converter. The experimental results demonstrate that the proposed DAB-DTH5 converter maintains transmission efficiencies from 95.0% to 98.4% under the voltage-gain range of 0.75 to 2.5.
This paper proposes a duplex active transient compensation circuit (DATCC) for data center power systems to enhance the transient response of point-of-load (PoL) power supplies. The proposed DATCC effectively mitigates the output voltage undershoot and overshoot of voltage regulator modules (VRMs) during load step-up and step-down transients. By employing an analog driving strategy and a dual-power-supply scheme, the circuit achieves an adjustable driving voltage, which enables flexible modulation of the compensation current required during transients. Furthermore, a time-domain model is established to provide theoretical guidance for the parameter design of the compensation circuit. To verify the feasibility of the proposed approach, a 14-phase, 337A interleaved buck converter prototype is constructed and tested with the DATCC scheme. Experimental results demonstrate that the proposed DATCC successfully reduces the output voltage undershoot by 43.36% and the overshoot by 64.77%.
The dc power flow controllers with wide-range current regulation have emerged as a promising solution to fulfill the power flow control demands of long-distance and high-voltage dc transmission. This paper presents a compact modular multilevel interline dc power flow controller composed of two arms and three resonant tanks. The proposed topology provides a wide current regulation range, which can be further extended through its modular structure and piecewise control. By adding the corresponding number of arms and series resonant tanks, the proposed topology can be flexibly extended to control the power flows of multiple lines. Owing to its series interline architecture, the proposed topology only needs to withstand a fraction of the nominal transmission voltage while handling the full rated current, thereby exhibiting good power regulation leverage. The proposed topology is suitable for high-voltage and wide-range current regulation applications as it exhibits modularity and scalability. The operation principle and control strategy are presented in this paper and validated through simulations performed in PSCAD/EMTDC and experiments based on a bench-scale prototype.
