This manuscript investigates a sigma–delta–based cycle-skipping modulation strategy for power regulation and current sharing in modular series resonant DC transformers. The method enables continuous power control without changing the switching frequency, duty cycle, or phase shift, making it suitable for DC transformer architectures that normally operate in a load-independent manner. A modified cycle-skipping approach is introduced to maintain magnetizing current during idle intervals, thereby preserving soft switching across the full operating range. The sigma–delta modulator replaces the fixed burst patterns of traditional cycle skipping with a noise-shaped pulse distribution that improves control resolution and mitigates low-frequency ripple. A practical implementation on an STM32 microcontroller is presented, including a lookup-table-based mapping of the sigma–delta bitstream to hardware burst-mode registers. Experimental validation on a 1-kW SRC-DCX prototype confirms accurate power regulation. Later demonstrated that, when extended to a dual-module IPOP configuration, the method achieves effective current balancing, with a peak efficiency of nearly 98%.

This work presents an efficiency-oriented modulation and morphing strategy for a three-phase three-level dual active bridge converter operating across both 800 V and 400 V electric vehicle battery systems. By reconfiguring the converter into a single-phase dual active bridge or a hybrid half-bridge/full-bridge structure at light-load, the proposed approach reduces current-invariant losses. A unified dual phase-shift framework is formulated to analytically model power flow and peak-current minimization across all three-level modulation variants, inner phase shift, duty-cycle control, and T-type zero-level modulation, demonstrating that all combinations produce equivalent voltage and current waveforms. Simulation efficiency maps are generated for all valid primary/secondary modulation pairs and indicate that inner and duty-cycle modulation achieve the highest efficiency across the full operating window. Hardware-in-the-loop experiments confirm stable three-phase-to-single-phase morphing and accurate power tracking between reference and measured power profiles for both voltage levels. The results validate that the proposed morphing strategy enables wide-range, auxiliary-free light-load operation suitable for next-generation EV charging architectures.

The paper proposes a novel dual-winding active magnetic energy harvester (D-AMEH), clamped around single power line conductor carrying AC currents with time-varying magnitude while supplying a constant power DC load via an uncontrolled rectifier (e.g., 24/7 aerial marker ball lighting). To allow continuous power flow to the load despite intermittent nature of power line current magnitude, an energy storage unit (rechargeable battery) is integrated into the system via an additional secondary winding, creating an AC-coupled, isolated hybrid energy system with completely decoupled battery and load voltages. The D-AMEH simultaneously harvests the maximum power from the current-carrying conductor and feeds the load with constant power, letting the battery to seamlessly match the difference between harvested and consumed power. Analytical expressions for system currents and voltages are developed, followed by conversion losses estimation. The revealed findings are accurately supported by experiments, demonstrating close matching with corresponding analytical predictions.

Voltage multiplier (VM) circuits are widely used in high-voltage DC power supplies. Traditional VMs are typically fed by sinusoidal voltages delivered by a resonant converter coupled with a high-voltage step-up transformer. This paper explores a transformerless solution, achieved by feeding the VM directly with the inverter's square wave output voltage. Although requiring additional multiplier stages to get the same output voltage level, this configuration simplifies the implementation and allows the elimination of the first smoothing capacitor, making it potentially suitable for size- and weight-sensitive applications. The performance and feasibility of the square-wave-fed hybrid VM are evaluated, and it is demonstrated that lower output voltage ripple and drop and better system dynamic response are achieved with this approach.

This paper presents a hybrid modulation technique combining phase shift control with sigma-delta based cycle skipping for asymmetrical bidirectional DC/DC converters. The proposed method enhances the light load efficiency while maintaining the precise power regulation through two independent control parameters. Unlike the conventional burst mode technique, the sigma delta approach enables continuous power regulation through dynamic cycle skipping modulation. Comprehensive numerical analysis validates the theoretical model, demonstrating significant efficiency improvements under light load conditions. Additionally, this technique establishes a foundation for talkative power converter applications, where the modulation pattern could enable simultaneous energy and data transfer without additional communication infrastructure.

With the increasing adoption of dc power distribution in both residential and commercial electrical installations, the demand for a universal power electronics interface between single-phase or three-phase ac systems and dc is becoming more critical. While 230 Vrms and 400 Vrms are standard on the ac side, 350 Vdc has emerged as the most established standard for buildings, following the NPR9090 and Current/OS protocols. In addition, besides adhering to standards, it is essential to provide reliable solutions capable of operating under faulty conditions. To address these needs, this paper proposes a universal interlinking converter (ac-dc). The proposed solution operates with both single-phase and threephase systems using a single hardware platform and remains functional under fault conditions, such as the loss of a phase or neutral wire. Furthermore, experimental results are presented to validate this proposal.

In many practical applications, such as electric vehicle charging and smart transformers, reverse power flow is significantly lower than forward power flow. Designing a full-rated bidirectional DC/DC converter in such cases leads to increased hardware costs. To address this, recent research has explored isolated topologies that support asymmetrical bidirectional power flow at reduced cost. This manuscript investigates an asymmetrical bidirectional DC/DC (AB-DC/DC) converter that integrates a partial-scale active bridge and a partial-scale diode bridge connected in parallel on the secondary side. Passive power sharing between these bridges is controlled by selecting appropriate coupling inductors, but practical magnetic tolerances cause power imbalances. To mitigate this, a novel modulation technique is proposed to enable active power sharing, allowing power transfer from the diode bridge to the active bridge. The study covers various operating regions, including discontinuous conduction mode (DCM), continuous conduction mode (CCM), dual-active-bridge (DAB) mode, and two hybrid regions, where the diode bridge operates in DCM and the active bridge in CCM. Closed-form power expressions and boundary conditions are derived for all modes. The proposed strategy is validated through simulations and experimental measurements on a hardware prototype, demonstrating consistent waveform behavior and confirming the feasibility of active power transfer from the diode bridge to the active bridge.

With the growing adoption of dc microgrids across various applications, the demand for flexible and adaptable power electronics solutions is becoming increasingly important. To address this gap in the literature, this paper presents a universal ac-dc power converter capable of integrating the ac power distribution with both unipolar (350 Vdc) and bipolar (± 350 Vdc) dc microgrids. Usually, such a converter is referred as a dc grid-forming or interlinking converter and is generally composed of two stages: an ac-dc rectifier and an isolated dc-dc. In this paper, a modification to the dc-dc stage is proposed to ensure full compatibility with different types of dc grids. The proposed converter is designed to operate with both single-phase and three-phase ac inputs, ensuring broad applicability with a single hardware solution. Additionally, a 5-kW prototype was used and experimental results were provided to validate the proposed approach.

This manuscript provides a detailed analysis of an asymmetrical bidirectional DC/DC converter operating across multiple regions. The converter features a partially scaled diode bridge and a partially scaled active bridge, connected in parallel on the secondary side, effectively integrating single- and dual-active-bridge topologies. A novel modulation technique enables active power-sharing control between the parallel-connected bridges, addressing challenges related to magnetic tolerances and asymmetrical power demands. By extending the approach beyond the discontinuous conduction mode, this study examines new boundary conditions-hybrid 1, hybrid 2, and continuous conduction mode-along with power transfer formulations for different operating regions.

This paper presents a comprehensive zero-voltage switching (ZVS) analysis of an interleaved current-fed dual active bridge (CF-DAB) converter under single-phase-shift control, targeting both bipolar and unipolar DC microgrids. Compared to conventional ZVS conditions, the presence of interphase inductors, either at the input or output bridges, enables an extended ZVS region, particularly under light-load conditions. This is important to increase the overall system efficiency, since in many applications, including DC microgrids, most of the time, such a converter operates at partial load. In addition, for unipolar DC microgrids and balanced bipolar systems, the interphase inductor currents may exhibit a DC offset or remain centered around zero, while under unbalanced load conditions, a DC offset is resulted. To cover both cases, analytical ZVS boundary expressions are derived for both scenarios: with and without DC offset. Experimental validation is conducted on a 300 W scaled-down prototype for the no-offset case, confirming that the CF-DAB can achieve reliable soft-switching over a wide voltage gain range with appropriate inductor design.

This paper investigates a cycle-skipping modulation technique based on sigma-delta modulation to improve the performance of series resonant converters, particularly those operating as a dc transformer. Compared to burst mode control, sigma-delta modulation provides a higher equivalent frequency at the output, which significantly reduces output voltage and current ripples. While dc transformer converters typically operate at a constant power with limited power regulation capabilities, the application of sigma-delta modulation enables effective power regulation. The proposed approach is experimentally validated on a 1 kW converter prototype operating at a switching frequency of 100 kHz. A peak efficiency of 98.4% and maintaining above 96% efficiency under light-load conditions has been achieved, with a 4 -point average efficiency of 97.47%, demonstrating its practicality and effectiveness.

This manuscript focuses on effective modulation techniques that enable the extension of soft-switching operations for a three-phase three-level dual active bridge under light-load conditions at both 400 V and 800 V, typical for electric vehicle batteries, without the need for auxiliary switches. The proposed methods take advantage of the high switch count typical of the three-phase three-level structure, allowing it to be reconfigured into a single-phase dual active bridge and a hybrid configuration composed of one half-bridge at the input and one full-bridge at the output with double transfer inductance. These reconfigurations significantly reduce the number of switching events, minimize current-invariant losses, and ensure zero-voltage switching turn-on for both the input and output bridges due to the unity voltage gain ratio at both 400 V and 800 V, resulting in enhanced efficiency during light-load operation.

This paper presents the discrete-time modelling and control of modular input-parallel–output-parallel (IPOP) dual-active-bridge (DAB) converters for electric vehicle (EV) charging. The proposed adaptive control system ensures adequate current-sharing among parallel modules while minimizing DAB current stress by adopting dual phase-shift modulation. Driven by the growing need for fast EV charging options, the paper highlights the importance of achieving top-notch control performance, especially with varying load conditions. Specifically, it introduces a discrete-time model for adjusting controller parameters adaptively, which simplifies the typically cumbersome manual tuning process associated with these systems. The proposed PI formulae are derived to satisfy specifications on the frequency domain as phase margin and the gain crossover frequency of the open loop gain transfer function, ensuring stability and robustness in operation. Moreover, the implementation of these formulae in discrete microcontrollers facilitates seamless PI autotuning for precise current, voltage, or power control. Notably, the proposed control strategy effectively mitigates current overshot issues commonly encountered during module engagement and shedding operations in modular EV chargers. To validate its efficacy, the proposed controller is evaluated through extensive testing and comparisons within the PLECS environment, particularly focusing on a two-module IPOP-DAB converter scenario, and including comparisons with classical offline model-based pole placement methodology. Furthermore, real-time hardware-in-the-loop experiments are conducted to confirm the feasibility and performance of the proposed controller under realistic EV charging profiles.

Understanding the effects of circuit element tolerances on power electronic devices is crucial for ensuring optimal performance and system reliability. Therefore, this paper explores the impact of magnetic tolerance in a parallel dual-output phase-shift full-bridge converter. Initially, a comprehensive analysis of power sharing among the individual legs on the converter’s secondary side is provided. Taking into account ±20% uniform tolerances in inductance, a rigorous mathematical derivation of the probability density function for the converter’s secondary-side leg power and for its partial-scale bridge power is provided. The outcomes of this derivation lead to a simplified triangular distribution for each leg, while an Irwin-Hall distribution for each bridge. These theoretical developments are further strengthened by numerical validation through extensive 30k PLECS simulations, incorporating randomized inductance parameters. The results of this validation process affirm the effectiveness of the adopted approach in accurately predicting power-sharing outcomes.

Achieving effective power sharing among paralleled power converters is challenging due to diverse component technologies, environmental conditions, diode working points, parasitic parameters, and component tolerances. These disparities can lead to uneven thermal stress and aging, negatively impacting component lifetime and reliability. To address these issues, this paper introduces a novel modulation strategy for parallel dual-output phase-shift full-bridge converters. This software-based power-sharing control technique leverages MOSFET control and allows power transfer from a parallel connected diode-bridge to the active-bridge on the secondary side of the converter providing an effective means to mitigate thermal stress. The approach can also enable a complete shutdown of the diode-bridge. Detailed analytical developments of the proposed technique are presented and validated numerically.

This paper presents a novel approach based on random variable algebra to study the neutral current ripple in three-phase four-wire split-capacitor inverters. The proposed method provides a more intuitive way of understanding and quantifying current ripple cancellations occurring on the neutral wire. Furthermore, thanks to its more straightforward approach, the extension over the whole modulation index range of neutral current ripple RMS in the case of interleaved PWM is presented. Finally, a comprehensive analysis of the neutral current ripple RMS in the case of unevenly displaced PWM carriers is also discussed. All the developments are validated by employing numerical results tested over various operating conditions.

Dual-active-bridge (DAB) converters have gained popularity primarily owing to their appealing features for electric vehicle (EV) charging and smart-grid applications. One among them is soft-switching commutation that comes inherently with the device control techniques. However, DAB converters lose the zero-voltage-switching (ZVS) commutation on either bridge for large output voltage variation, especially under light-load conditions. In this context, this paper provides insights into the behavior of the auxiliary inductor-based DAB converter in terms of ZVS operations. The integration of auxiliary inductors makes it paramount to study the RMS currents through the power switches to gain awareness about the effects on the converter performance. A graphical analysis proved useful in this direction. Finally, simulations are carried out over various operating conditions to validate the analytical developments.

This paper describes the preliminary analysis, design and implementation phases of a DC/DC boost converter dedicated to the Futura catamaran propulsion chain developed by the UniBoAT team at the University of Bologna. The main goal of the project was the reduction of the converter’s weight by eliminating the use of heat sinks and by reducing the component size, especially inductors and capacitors. The obtained converter is directly integrated into the structure containing the fuel-cell stack. The realized converter was based on an interleaved architecture with six phases controlled through the average current mode control. The design was validated through simulations carried out using the LT-Spice software, whereas experimental validations were performed by means of both bench tests and on-field tests. Detailed thermal and efficiency analyses were provided with the bench tests under the two synchronous and non-synchronous operating modes and with the adoption of the phase-shedding technique. Prototype implementation and performance in real operating conditions are discussed in relation to on-field tests. The designed converter can be used in other applications requiring a voltage-controlled boost converter.

This article proposes a dual-active-bridge control to support the fast synthetic inertial action in DC microgrids. First of all, the selection of the isolated DC/DC converter to link an energy storage system with the DC bus in a microgrid is analyzed and the advantages of the dual-active-bridge converter controlled by a single-phase shift modulation justify its selection. An active front-end can be then adapted to connect the DC bus with an AC grid. Secondly, this paper presents the design of a discrete PI controller for supporting fast synthetic inertial action. In particular, a discrete dual-active-bridge model based on the transferred power between both converter bridges, which overcomes the approximations of the output current linearization model, is proposed. Moreover, the article introduces a novel equation set to directly and dynamically tune discrete PI parameters to fulfill the design frequency specifications based on the inversion formulae method. In this way, during the voltage/power transients on the DC bus, the controller actively responds and recovers those transients within a grid fundamental cycle. Since the developed set of control equations is very simple, it can be easily implemented by a discrete control algorithm, avoiding the use of offline trial and error procedures which may lead to system instability under large load variations. Finally, the proposed control system is evaluated and validated in PLECS simulations and hardware-in-the-loop tests.