Search Results (515)

This study establishes a field-measurement-based wideband modeling and station-level simulation framework for conducted high-frequency (HF) disturbance studies in modular multilevel converter-based high-voltage direct-current (MMC-HVDC) stations. Full-scale engineering-site frequency-response measurements are used to identify kHz-to-MHz terminal models of the arm reactor and the valve-side winding of the converter transformer. The arm reactor is fitted in the admittance domain by vector fitting and synthesized as a passive parallel network containing the main inductive path and multiple damped resistor–inductor–capacitor (RLC) branches. The transformer valve-side winding is represented by a Foster I/II hybrid $\pi$-type terminal network reconstructed from two single-phase port-impedance measurements. The validated equipment models are integrated into a representative Power Systems Computer-Aided Design (PSCAD) station model. A 2 ms valve-side source sequence, constructed from nearest-level-control switching instants and a parameterized switching-transient template, is applied in paired injection and zero-injection simulations. For the representative event, the source peak is 605.6 V. Over the first 4 $\mathsf{\mu }$s, the arm-reactor terminal reaches 972.6 V, while the direct-current (DC)-side, valve-side alternating-current (AC), and point-of-common-coupling (PCC) responses reach 534.2, 438.4, and 151.9 V, respectively. The corresponding peak changes relative to the source are $+4.11$, $-1.09$, $-2.81$, and $-12.01$ dB. The DC-side response contains a dominant damped oscillation near 0.61 MHz, and the AC/PCC transfer varies markedly across 0.2–2.0 MHz. In a separate control-identical comparison over the first 2.5 $\mathsf{\mu }$s, the field-identified and lumped models give DC-side peaks of 171.9 and 1.23 V and PCC peaks of 121.4 and 3.93 V under the same excitation. The framework connects field-identified equipment terminal behavior with station-level time-domain propagation analysis and provides a modeling basis for broadband resonance screening and conducted electromagnetic-interference (EMI) assessment. Full article

Three-level neutral-point-clamped (NPC) inverters are widely used in medium- and high-power drives and grid-connected applications due to their reduced device voltage stress, improved output power quality, and lower switching losses relative to conventional two-level topologies. Among the potential failure modes, clamping diode open-circuit faults are difficult to detect because the clamping diodes conduct only during the zero-voltage states, and their failure produces only subtle distortions in the phase current waveform. This paper proposes a fault diagnosis method for clamping diode open-circuit faults in three-level NPC inverters. The method is based on a current asymmetry index defined as the ratio of the per-cycle mean phase current to the per-cycle mean absolute phase current. During healthy operation, this index is approximately zero in all phases. A fault causes the index to deviate markedly from zero, while the polarity of this deviation identifies the failed diode. The method requires only phase-current measurements already available in the inverter control system. Consequently, no additional sensors, hardware modifications, or changes to inverter operation are required. Simulation results obtained for a 10 kW three-level NPC inverter demonstrate successful fault detection within approximately one to two fundamental cycles for open-circuit failures of both the upper and lower clamping diodes in all three phases. Full article

This paper presents the experimental validation of a high-frequency full-SiC railway auxiliary converter power module intended as a building block for modular multi-system railway auxiliary converters. The proposed architecture employs a unified SiC-based power conversion platform that integrates an active front-end single-phase PWM rectifier with a galvanically isolated high-frequency DC/DC stage operating at 90 kHz under zero-current switching (ZCS) conditions. Although the converter is designed for both AC and DC traction systems, this study focuses primarily on its operation under single-phase AC railway supply conditions, which are representative of practical applications. A hybrid bipolar–unipolar modulation strategy is used to reduce the RMS voltage stress on the input inductor while preserving controllability of the input current near the voltage zero-crossing regions. Special attention is given to operation under distorted railway supply voltages, which are common in real traction systems. The control structure combines a proportional–resonant (PR) current controller, harmonic compensators, feedforward voltage compensation, and MSOGI-based synchronization to ensure stable synchronization and low-input current distortion even under non-ideal conditions. Experimental validation was performed on a 10 kW laboratory prototype. The results demonstrate a peak efficiency of 98.4% and near-unity input power factor. Under heavily distorted supply conditions ${\mathrm{THD}}_{\mathrm{v}}>30\%$, the input current distortion remained below ${\mathrm{THD}}_{\mathrm{i}}=2.3\%$. Harmonic and STFT analyses confirmed the robustness of the proposed synchronization and current control structure. The obtained results indicate that the proposed high-frequency full-SiC converter topology is a promising solution for future modular railway auxiliary converters, offering high efficiency, reduced passive component volume, and high power density. Full-scale high-voltage validation under both AC and DC traction systems remains the subject of further work. Full article

The intensive development of electric vehicle (EV) technology, renewable energy systems, and stationary energy storage solutions has amplified the demand for advanced Battery Management Systems (BMS). The imbalance in cells within lithium-ion battery packs, due to manufacturing tolerances, varying aging, and thermal gradients, reduces available capacity, cycle life, and can cause thermal runaway. Active charge equalization with DC–DC converters has become a recent research focus among various balancing techniques because it has a better capability of redistributing energy. This paper gives a detailed study of converter-based cell-balancing topologies with a specific focus on the bidirectional flyback converter and the interleaved two-phase variant. Non-isolated topologies (buck–boost, Cuk converter topology, interleaved buck–boost) and isolated topologies (flyback, push–pull, dual-active bridge, LLC resonant) are compared concerning functional efficiency, component reduction, galvanic isolation, scalability, and bidirectional capability. The concept of soft-switching, including zero-voltage switching (ZVS) and zero-current switching (ZCS), and their circuit realizations are discussed. Advanced control models and artificial intelligence (AI) for the estimation of state-of-charge (SoC) and real-time optimization are mentioned. Thermal issues, scalability, reliability, and wide-bandgap semiconductor devices (SiC/GaN) are discussed. Full article

With the rapid development of DC grids, resonant DC circuit breakers (RDCBs) have become critical for fault isolation. However, existing RDCBs often suffer from severe energy mismatches, and components, including mechanical switches, resonant capacitors, and power electronic devices, suffer from excessive internal overvoltage during the current interruption process. To address these issues, a novel RDCB with a capacitor self-charging current excitation source (CES) is proposed in this paper. First, by controlling the charging process of CES by the fault current, the injected energy is matched with the commutation requirements, significantly reducing the transient recovery voltage (TRV) applied to the mechanical switch. Second, to suppress the voltage applied to the resonant capacitor, a metal oxide arrestor (MOA) should be connected directly in parallel with the resonant capacitor, avoiding overvoltage caused by the internal oscillation between the resonant inductance and the resonant capacitor. Furthermore, an anti-parallel magnetic core is designed for CES, ensuring dynamic current sharing among parallel IGBTs while maintaining a zero-inductance characteristic externally. Simulation results verify that the proposed RDCB reduces the peak TRV by at least 64% compared with existing RDCBs. Furthermore, the effectiveness of the proposed overvoltage suppression methods is validated, significantly improving the interrupting reliability. Full article

Stator winding reconfiguration technology has attracted increasing attention because it can modify the torque–speed output characteristics of motors online and extend the high-efficiency operating region. However, conventional winding switching methods suffer from several limitations, including long transient duration, typically at the millisecond level; difficulty in precise control; current interruption or asymmetric operation during the transient process; and the resulting torque loss and torque fluctuation. To address these issues, this paper first proposes a seamless winding switching method. The core idea is to complete the switching within the zero-vector interval of a single SVPWM period, thereby eliminating potential surge voltage without requiring a snubber circuit. The proposed method reduces the transient duration to only 5 μs, eliminates current interruption and current asymmetry, and suppresses the associated torque ripple. Furthermore, a deadbeat predictive control strategy is employed. By directly controlling the voltage vector, the proposed strategy enables fast and accurate current tracking within one sampling period after reconfiguration, thereby avoiding current overshoot, oscillation, and the corresponding torque and speed fluctuations. In addition, a voltage feedforward compensation method is proposed to pre-compensate the voltage applied during the PWM period in which the winding reconfiguration is performed, thereby preventing the application of voltage vectors that are inconsistent with the actual motor winding connection. With these three innovative measures, fast, smooth, and robust winding reconfiguration is achieved. The mechanisms and implementation procedures of the proposed strategies are described in detail, and their feasibility and effectiveness are verified through experiments. Full article

This paper presents a battery-aware control framework for a single-phase integrated battery charger (IBC) for electric vehicles, in which the traction system is reused as part of the charging hardware. The proposed charger consists of a stator-assisted bridgeless totem-pole power-factor-correction AC–DC stage and a bidirectional buck–boost DC–DC stage connected to a 48 kWh, 400 V lithium-ion battery pack. The battery pack is modeled using a lookup-table-based equivalent circuit model with state-of-charge- and temperature-dependent open-circuit voltage and impedance parameters. A conventional double-loop PI controller is used as the baseline, while the proposed strategy combines nonlinear model predictive control, an extended Kalman filter, and lookup-table-based battery parameterization to regulate charging current under electrical and thermal constraints. The system is evaluated under 7 kW, 230 V/32 A and 22 kW, 230 V/96 A charging cases using average-model simulations, switching-model transient simulations, and finite element thermal assessment of the induction motor stator. The average-model results show stable charging from 20% to 80% SOC, with charging times of approximately 275 min at 7 kW and 90 min at 22 kW. The EKF provides bounded battery state estimation, with maximum SOC estimation errors of approximately 1.3% and 2.0% for the 7 kW and 22 kW cases, respectively, while the core-temperature estimation error converges close to zero. The switching-model results confirm feasible duty-command behavior, bounded battery-current tracking error, and a representative DC-link ripple of approximately 8 Vpp. During grid-voltage reduction, the charging current is reduced to keep the grid-current envelope within the intended limit. FEM results show that charging-only motor temperatures remain low, reaching approximately 27.39 °C at 7 kW and 38.82–38.85 °C at 22 kW. The most critical charging-related thermal case occurs at 22 kW after one hour of full-load motor operation with a 40 °C initial condition, reaching approximately 92.32 °C. Overall, these simulation-based findings support the feasibility of the proposed NMPC–EKF–LUT framework as a battery-aware supervisory control strategy for single-phase IBC operation. The proposed controller improves constraint-aware, battery state-based decision-making, while switching ripple and motor thermal response are mainly governed by the power stage, feasible current trajectory, and initial thermal condition. Full article

Power-switch open-circuit (OC) faults distort electric-vehicle (EV) inverter phase currents and require fast on-board diagnosis for fault-tolerant control. Trajectory-image methods encode the $\alpha$–$\beta$ current-vector trajectory as a binary image and classify it with a convolutional neural network (CNN); however, the baseline uses $6.46\times {10}^5$ parameters and $3.31\times {10}^7$ multiply–accumulate (MAC) operations per inference, which is costly for motor-control microcontrollers (MCUs). Here, each one-cycle trajectory is represented by a 36-dimensional normalized angular sector-energy vector and classified by a compact two-stage multilayer perceptron. Sector accumulation averages zero-mean measurement noise in the representation, without relying on noise-augmented training. The locating stage uses $1.58\times {10}^4$ parameters and $1.56\times {10}^4$ MACs per inference, $97.55\%$ and $99.95\%$ fewer than the baseline CNN; the complete pipeline runs on a TI F28379D in $0.52$ ms. On measured resistive-load currents, both methods reach $100\%$ accuracy from 40 to 20 dB, whereas the proposed method remains more accurate at 15 and 10 dB, including under $88\%$ phase-current unbalance. A supplementary balanced $RL$-load experiment preserves $100\%$ clean accuracy, confirming MCU-executable diagnosis under a lagging power-factor load for embedded EV inverter protection. Full article

The main purpose of this study is to overcome the difficulty of maintaining high-quality zero-voltage switching (ZVS) in resonant converters over wide operating ranges. Conservative designs ensuring light-load ZVS inevitably generate excessive reactive current, causing severe circulating losses and body diode conduction under heavy loads. To resolve this intrinsic trade-off, this paper proposes an active closed-loop optimal ZVS control strategy utilizing a DC-biased variable resonant inductor. The core mechanism actively shifts the tank impedance to dynamically reshape the primary current. By integrating the primary current during each dead time, the real-time integrated charge is actively regulated to track an optimal reference limit defined by the switch parasitic capacitance and dc-bus voltage. Consequently, the variable inductor continuously regulates the tank current toward the optimal ZVS boundary, ensuring the parasitic capacitance is completely discharged just before the turn-on instant. Validations via simulation and a 192 W hardware prototype confirm the method’s efficacy. The strategy completely eliminates light-load hard switching and significantly suppresses heavy-load body diode conduction without compromising output voltage regulation. Compared to conventional active schemes, this approach achieves full-range optimal ZVS without requiring additional high-frequency switching devices, establishing a highly efficient shift from passive parameter design to active boundary tracking. Full article

High-frequency link inverters (HFLI) inherently suffer from voltage ringing, and the issue becomes more severe under non-unity power factor loads. Although active clamping circuits can effectively suppress the voltage ringing, they cause severe distortion in the output voltage and current waveforms under such loads. To address this problem, this paper proposes an improved modulation strategy with leakage energy feedback for active-clamped high-frequency link inverters (ACHFLI). In the proposed strategy, two secondary-side MOSFETs achieve zero-current switching (ZCS) turn-off, while the other two MOSFETs operate at low frequency throughout the entire line cycle. By feeding the leakage inductance energy back to the primary side, the voltage balance of the clamping capacitor can be better maintained under non-unity power factor loads, thereby mitigating the waveform distortion in the output voltage and current during the intervals when their polarities are opposite. A prototype with 48 V_in input, 110 V_o output, and 300 W rated power was built to verify the proposed strategy. Experimental results show that the modulation strategy alleviates the waveform distortion when the voltage and current have opposite polarities, and the total harmonic distortion (THD) of the output voltage is reduced by a maximum of 2.74%. Full article

The Four-Switch Buck-Boost (FSBB) converter has been widely used in airborne secondary power systems in recent years because of its excellent wide voltage regulation capability, its soft-switching characteristics and the fact that its polarity of input and output voltages are the same. However, when the FSBB converter adopts the quadrilateral modulation strategy to realize Zero-Voltage Switching (ZVS), its negative current, inductance parameters, and several time state variables all affect the efficiency of the converter. Aiming at the above problems, this paper proposes a fixed frequency control strategy for the sub-peak current, which reduces the number of sampling circuits and can calculate the control variables in real time by sampling only the input voltage and output voltage. Finally, a 500 W experimental prototype with a switching frequency of 200 kHz is built to verify the proposed control strategy. The experimental results show that the FSBB converter achieves a peak efficiency of 97.2% and operates stably under a wide input voltage range. Full article

To address head-end three-phase current unbalance and terminal power-quality deterioration caused by uneven three-phase load allocation in a low-voltage transformer area (LVTA), this paper proposes a DC-link-voltage-control-based phase-wise unbalanced power compensation strategy for a head-to-tail flexible interconnection structure embedded in the LVTA. The proposed structure consists of two three-phase four-leg converters sharing a common DC bus and connected to the head end and tail end of the LVTA, respectively. Different from conventional phase-wise compensation methods in which the DC side mainly acts as a power-transfer channel, the proposed strategy uses the DC-link voltage control of the head-end converter as the core of compensation power generation. Specifically, the outer DC-link voltage loop generates the total active compensation power, which is then allocated among the three phases according to the measured phase-power unbalance of the LVTA, thereby yielding the phase-wise compensation current references. Combined with phase-wise quasi-proportional-resonant current control, the compensation currents of different phase legs can be regulated without explicit positive-, negative-, and zero-sequence decomposition. Meanwhile, the tail-end converter adopts PQ control to support terminal power regulation and improve the terminal voltage quality of the LVTA. To provide a theoretical basis for the proposed method, a switching-cycle averaged model of the three-phase four-leg converter is established, and the leg-level phase-wise control characteristics are analyzed under the assumptions of a stiff DC link and symmetrical converter parameters. A control-oriented equivalent LVTA model is developed in MATLAB/Simulink. The proposed strategy is validated under steady-state unbalanced, RL load, load-disturbance, and equivalent feeder-impedance conditions. In addition, a conventional positive-, negative-, and zero-sequence compensation method is introduced as a benchmark for quantitative comparison. The simulation results demonstrate that the proposed method can effectively suppress the head-end three-phase current unbalance, maintain the DC-link voltage around its reference value, and improve the terminal voltage quality of the LVTA. Compared with the conventional sequence-component-based compensation method, the proposed strategy achieves effective unbalance mitigation while avoiding explicit sequence extraction and reducing the complexity of the compensation-current generation process. This study provides a feasible control framework for three-phase unbalance mitigation in flexible low-voltage transformer areas. Full article

Cell degradation in second-life battery packs introduces heterogeneous capacity and internal resistance mismatch, reducing the effectiveness of conventional balancing approaches and limiting available pack runtime. Although equal state of charge (SoC) does not necessarily imply equal usable capacity, SoC-based control remains attractive for runtime-oriented operation. This paper proposes a target-mean controller for heterogeneous reconfigurable battery packs under constant-bus constraints that aims to improve runtime and achieve the cutoff-defined theoretical maximum capacity utilization limit. Using only real-time cell SoC measurements and legal switching actions, the controller selects the configuration that best reduces deviation from the pack-average SoC while preferentially loading cells above the mean. The online action selection requires no active balancing hardware, no explicit capacity or state of health (SoH) estimation, and no offline optimization; experimentally measured capacities are used only for calibrated Coulomb-counting SoC estimation. Simulation results on a heterogeneous five-cell reconfigurable battery pack show that the proposed controller reaches the cutoff-defined 90% theoretical utilization limit in the full-initial-SoC cases, while also extending runtime and reducing switching activity by up to 11.75% relative to the comparison methods. Hardware validation on a five-cell prototype further confirms this trend, achieving 89.12% experimental utilization, zero final SoC spread, and higher delivered energy than both comparison methods. A stepped-load hardware test further achieved 88.19% utilization from current integration, corresponding to 97.99% of the cutoff-defined 90% theoretical limit. The results suggest that, for heterogeneous second-life packs, SoC-based reconfiguration control can achieve both runtime improvement and near-maximum utilization without the added complexity of explicit SoH-aware balancing. Full article

To address the issues of low voltage levels and insufficient reliability in dynamic regulation and voltage stabilization in existing high-voltage power supplies for electron-curtain accelerators, this paper presents a 150 kV/30 kW DC high-voltage power supply specifically designed for electron-curtain accelerators. The main circuit employs an LC high-frequency resonant topology and a step-up transformer with eight secondary windings, utilizing a parallel step-up and series output architecture to increase the output voltage level. During the charging phase, a dual-closed-loop frequency conversion scheme combined with duty cycle feedforward is employed to accelerate charging speed, while the voltage stabilization phase utilizes hysteresis burst control to improve accuracy. Simulation results indicate that the system can charge to 155 kV in 102 ms, with a voltage ripple less than 0.1%, a linear regulation of 0.01%, and a load regulation of 0.5%. Tests on a low-voltage prototype confirmed that the power devices can achieve zero-current soft switching, with a resonant current peak of 40 A and overall efficiency reaching 96%. The accompanying filament power supply can stably output 24 V/20 A, and the closed-loop voltage regulation is stable and reliable, providing technical support for the engineering application of high-voltage power supplies in high-power electron beam accelerators. Full article

The increasing adoption of electric vehicles (EVs) demands highly efficient bidirectional DC–DC converters capable of seamless energy transfer between the grid and vehicle batteries. This paper introduces a Fixed-Frequency Dual-Active-Bridge (DAB) resonant converter featuring four degrees of freedom, achieved through a combination of triple phase-shift (TPS) modulation and a current-controlled variable inductor (VI). The proposed control strategy aims to minimize conduction and switching losses by simultaneously managing reactive power, RMS current, and soft-switching conditions across wide variations in voltage and power. Unlike conventional phase-shift or variable-frequency modulations, the fixed-frequency operation maintains full zero-voltage switching (ZVS) for the two bridges, and zero-current switching (ZCS) in the bridge that is receiving energy, enhancing overall system reliability and control simplicity. The proposed converter is validated through simulations and experimental results from a SiC MOSFET-based 14 kW prototype operating at 122 kHz, demonstrating peak efficiencies above 97% under both charging and discharging modes. The experimental results confirm that the proposed DAB topology and modulation scheme significantly improve efficiency and controllability, making it a promising solution for next-generation on-board chargers and vehicle-to-grid (V2G) applications. Full article