The isolated buck-boost current-fed (CF) series resonant converter with active clamping integrates low input current ripple, resonant soft-switching, and voltage spike suppression, thereby enhancing power conversion efficiency. While CF converters inherently operate in boost mode, achieving buck operation is crucial for applications that require a wide voltage gain range. To address this, various constant-frequency buck modulation methods have been proposed to regulate the step-down operation of CF-SRCs. This paper examines three buck control methods for an active-clamped CF series resonant converter: conventional Phase Shift Modulation (PSM), Hybrid Phase Shift Modulation (HPSM), and Single-Switch (1Sw) Buck Modulation. A comparative evaluation is conducted through theoretical analysis and experimental validation on a 350 W prototype, assessing efficiency, switching behavior, and voltage gain characteristics. The results confirm that 1Sw buck modulations achieve peak efficiencies while also highlighting key trade-offs in conduction losses and switching stress across the different modulation methods.

Wireless battery charging systems for electric vehicles (EVs) are convenient, safe, and flexible against environmental hazards. Resonant inductive power transfer (RIPT) is the most common method for EV battery charging applications. The inductive coil structure is a major component of the RIPT system, and misalignment between inductive coils is a key issue. This paper proposes an improved, misalignment-tolerant, novel dual orbirect inductive coil structure. The proposed coil structure is designed using finite element modeling (FEM) and investigates magnetic parameters such as self and mutual inductance at various horizontal and vertical misalignment distances. Finally, based on the FEM analysis, the RIPT system is designed for 1 kW, and simulations were carried out in MATLAB. The presented results show that the output voltage exhibits minimal variation across 50% misalignment range. The peak efficiency achieved at full load conditions is 96.2%.

This paper presents an alternative approach for efficient DC power distribution and voltage regulation in data centers. A switched-capacitor (SC) resonant DC-DC converter with differential power processing (DPP) is proposed, enabling servers to be electrically connected in series. This configuration inherently steps down the voltage from a higher-voltage DC bus. Voltage regulation for each server is achieved using SC half-bridge cells that process only the differential (mismatch) power between all servers, while the bulk power is transferred without active processing. It results in notably improved global system efficiency compared to conventional architectures. Additional features of the proposed converter include its simplicity due to open-loop operation, soft-switching capability, and tolerance to hot-swapping of servers. Here, the concept is demonstrated and validated through circuit simulations and experimental results considering a series-stacked server rack with four 12 V servers powered from a 48 V DC bus, delivering up to 600 W.

This paper presents a dual-input single-output (DISO) partial power converter (PPC) topology for efficient battery integration in DC microgrids. The proposed converter, based on a boost half-bridge architecture with secondary coupled two single-transformer, enables bidirectional power flow and high efficiency by processing only a fraction of the total power. Detailed analysis and case studies demonstrate effective decoupling of input ports under dynamic voltage and current variations. Additionally, the use of boost half-bridge circuits alleviates voltage stress on switches, allowing the use of lower-voltage-rated components. The DISO-PPC offers a compact, robust, and cost-effective solution for multi-source energy systems and seamless battery integration in dc microgrids. PSIM simulation studies validate the robust performance of the proposed converter under different conditions.

Extensive use of electric vehicles (EVs) requires a wider availability of charging infrastructure. Together with the penetration of renewable sources, like PVs, and other dc-native technologies, this creates a demand for developments in the field of dc distribution grids. This paper presents the concept of a universal bidirectional dc-dc converter that can be used as an off-board charger for electric vehicles (EVs). Thanks to the reconfigurable input stage, it can be suited for various types of uni- and bi-polar dc grids. The possibility to operate in four different modes allows for the reduction of the stresses on the components while providing a wide output voltage range. The concept is verified with a simulation model of a 3.3 kW charger with an output voltage range of 150…1000 V.

Series-resonant converters (SRCs) have gained attention for many applications, including power supply units, data centers, and smart transformers, due to their high and very flat efficiency curve. However, ideally, SRCs operate without voltage regulation, as implementing phase shift or frequency control can penalize the converter efficiency. This presents a significant drawback for certain applications such as dc buildings, nanogrids, and dc microgrids, where such converters must operate under droop control, resulting in a variable output voltage. To address this limitation and enable SRCs to operate under variable output voltage, this paper proposes a bidirectional partial power converter as a post regulator stage (P3R). The proposed converter is based on a current-fed topology, featuring fully controlled switches to allow bidirectional power flow and the capability to step-up or down the output voltage. Experimental results, showcasing the converter waveforms for a 5-kW prototype, are presented to evaluate the converter's viability for this application.

This paper proposes a hybrid phase shift control strategy for dual side inductor-capacitor-capacitor compensated inductive power transfer (IPT) system to achieve a wide output voltage regulation range. The first-order harmonic time domain model is used to compute the inverter output voltage. Then, models of system operation in constant voltage (CV) and constant current (CC) modes are developed to analyze the efficiency of the battery charging process. The designed controller loops are validated for a 1 kW MATLAB Simulink model. Results show that a maximum efficiency of 93.80% is achieved at full load conditions, and the proposed control strategy achieves zero voltage switching (ZVS) in more switches than the conventional control method.

Dual-active bridge (DAB) converters have gained significant attention in recent years, due to their high efficiency and excellent performance in medium and high-power applications. However, their performance is limited when a wide power and voltage range are required. One application example is the dc microgrid when DAB converters must operate with droop control to enable power balance and dc bus voltage regulation. When operating under droop control, the DAB converter efficiency can be penalized at low power, reducing the overall system efficiency. Being an open topic and not explained in current literature, this paper proposes for the first time to include the droop characteristic in the DAB converter analysis. The DAB converter efficiency is analyzed considering different factors, such as soft-switching conditions, circulating current, and dead-band insertion on droop control curves. Including the droop control as a new factor in the DAB converter design, a 5-kW prototype was built, and laboratory tested, evaluating different efficiency curves according to the selected droop curves.

Conventional full power dc-dc converters are processing the whole power flowing from the source to the load, which critically limits the overall efficiency of the system. Coming to the fact that the converter can perform the required functions by processing only the mandatory fraction of power, which is called power processing. In this paper, a Series Partial Power Converter (S-PPC). In order to get the full benefit of the S-PPC, the converter should process power less than 25% of the overall system power. Buck-Boost push-pull power converter is used in this paper with its modulation are proposed in this paper. The converter is modulated to ensure all switches are operating at soft-switching. Basic system analysis and system simulation are discussed in the paper

This paper compares the holdup time for different active-front end (AFE) dc grid-forming converters. AFE converters are required to perform an interface between the utility ac grid and dc microgrids in homes, offices, and other small-scale prosumer electrical installations (PEI). According to the current standards NPR 9090 and IEC 61000-4-11, AFE converters must provide isolation between ac and dc parts and ensure a minimum holdup time for the dc output side. Considering both requirements, two possible solutions are addressed and compared: a conventional dc-ac converter with a low-frequency isolation transformer and a two-stage ac-dc converter that includes a dc-dc stage with high-frequency isolation. To perform a comparative analysis of each solution, different scenarios are described and simulated in PSIM software.

This paper studies the transient behavior of a three-phase isolated bidirectional dc/ac converter operating as a rectifier. The purpose is to assess the viability of this converter for dc microgrid applications. A capacitor pre-charge method is developed to suppress inrush currents while charging the dc side capacitors during converter startup. The operation of the converter under grid fault transients is also studied, to assess the ability of the converter to maintain continuity of service to the dc microgrid in the case of grid undervoltage or loss of phase. A model of the converter was simulated on PSIM to validate the capacitor pre-charge method and grid fault responses.

This paper is presenting a new high-gain non-inverting buck-boost converter. The proposed converter has some distinct features such as high step up/down ability, low voltage and current stress on its switching devices. The voltage gain of the proposed converter is double of the traditional buck-boost converter and it is non-inverting. The three switches are operating synchronously. Although it has two inductors, the two inductors could be wounded on the same core due to similarity of the two inductors, and hence reduces the cost and size of the system. The overall efficiency of the system is promising due to the ability of selecting devices with low voltage drops. The steady state analysis of the system in both Continuous Conduction Mode (CCM) and discontinuous conduction mode (DCM) are presented in details. The system is simulated in MATLAB and results are discussed in detail through the paper. Experimental prototype is being build in the laboratory and hardware results will be presented in the final version.

Renewable energy sources like photovoltaic (PV) panels and battery energy storage are usually connected to the DC microgrids through dedicated full power DC/DC converters. Alternative to the conventional solutions is partial power converter (PPC) technology, where only a fraction of energy flow is handled by a DC/DC converter, and most of the energy flows from its source to a DC grid directly. PPC has several advantages over traditional full power converters: low power losses, lower cost, and higher power density. The proposed current-fed isolated full bridge buck-boost topology has shown excellent characteristics in PPC configuration, interfacing such nonlinear energy sources as PV panels. For experimental verification of PV partial power interface converter into a 350 V DC microgrid a 3.3 kW laboratory prototype with current-fed isolated full bridge buck-boost topology was designed, built, and tested. Experiments have proven the feasibility and benefits of PPC converter with proposed topology in DC microgrids.

Novel reconfigurable rectifier circuit is presented. It features three operating modes: full-bridge rectifier, voltage doubler rectifier, voltage quadrupler rectifier. After the rectifier topology is introduced, a case study dc-dc converter based on quasi-Z-source full-bridge topology is presented. An experimental prototype was assembled to verify concept feasibility. The assembled converter is suitable for the global maximum power point tracking owing to the wide input voltage range achieved. DC voltage gain theoretical expressions are verified experimentally, and measured efficiency is given.

This paper presents a novel soft-switching technique for the galvanically isolated impedance-source full-bridge DC-DC converters. It allows reducing the turn off losses of the inverter switches, which otherwise represent a significant portion of the total power loss in such converters. Zero-current switching is achieved by the introduction of the additional energy return interval provided by the secondary side switches in addition to conventional synchronous rectification. This operation allows to redistribute the transformer current from one pair of switches to another, thus decreasing the current in the switch pair to be turned off. The paper presents the generalized operation principle corroborated with the simulation and experimental verification of the proposed modulation method.

This paper discusses reliability issues of three different types of capacitors (ceramic, electrolytic and film) applied in the input side of an impedance-source photovoltaic (PV) microconverter having an ultra-wide dc gain range. The study considers a wear-out failure analysis based on a daily PV mission profile. The general operation and control principle are first described. Then the selection criteria of the capacitors are analyzed. Experimental measurements of capacitors temperature are translated into accumulated damage using their corresponding lifetime models. Finally, conclusions are drawn regarding the applicability of different capacitor technologies in impedance-source PV microconverters, where the film capacitor has the lowest damage.

This paper presents a novel asymmetric bidirectional isolated DC-DC converter topology with current source and voltage source terminals. The topology can be implemented in renewable, supercapacitor, battery and de microgrid applications. It features two bidirectional and two reverse-conducting switches in the current-source bridge side. Thanks to special control algorithm it provides soft switching of all semiconductors under wide range of operating conditions with low energy circulation. This is achieved without any dedicated snubbers or clamp circuits. The converter theoretical performance at various operating conditions is assessed and compared with other competitive solutions in terms of rms current stress on the transformer and semiconductors. Steady-state operation and design aspects of the converter are presented and verified experimentally with 500 W prototype.

Focus is on the design of a multiphase galvanically isolated quasi-z-source dc-dc converter based on the single-switch topology. A novel control approach uses phase shedding for input-parallel-output-series architecture to achieve a wide input voltage regulation range. Current ripples are analyzed to implement the quasi-Z-source network with discrete and coupled inductors. Proposed approach provides for modeling of the latter taking into account leakage inductances of the coupled inductors and interactions between cells and the wiring inductance. An experimental prototype rated for 300 W, capable of delivering the rated power within the input voltage range of 10 V to 60 V was used. Experimental results demonstrate the performance of the developed concept implemented with resonant currents in the isolating transformer. Influence of the voltage-dependent resonant capacitance on the converter operation was analyzed.

A new concept of shade-tolerant PV microinverter named Optiverter is capable of operating with both 60- and 72-cell PV modules. In order to ensure highly reliable operation of the Optiverter, this paper analyzes the wear-out failures of the Optiverter considering both 60- and 72- cells Si crystalline PV modules. The lifetime evaluation of the Optiverter also considers the impact of module degradation rates and different mission profiles into consideration. The evaluation results reveal that operating the Optiverter with a high-power PV module (i.e., 72-cell) results in a lower reliability performance compared with 60-cell PV module. This is mainly due to the higher power and thermal loadings of the power devices in the Optiverter with a 72-cell PV module. When considering the effect of module degradation, using the 72-cell PV module also lead to a higher deviation in the reliability prediction compared to the case without considering the degradation.

The focus of this paper is on power flow control in the asymmetric quad-active-bridge (QAB) converter and its limitations imposed by uneven values of parasitic elements in the isolation transformer. The QAB converter under study is intended for solid-state transformer applications in asymmetric configuration, where one of the ports is placed at the low voltage side and rated for the threefold power of the medium voltage ports. Significant imbalance between leakage inductance could be observed between them. The steady-state analysis of the asymmetric QAB converter and assessment of power losses using numerical simulation are provided. Experimental waveforms were obtained using a prototype rated for cumulative MV dc link of 2400 V and power of 30 kW.

In this paper magnetically integrated resonant single-switch quasi-Z-source DC-DC converter is evaluated as a candidate topology for the low-cost photovoltaic microconverter. The derivation of the topology and its basic operation principle are explained. Generalized design guidelines and experimental results of 250 W prototype are discussed for different realization approaches of the hybrid coupled inductor, which is the key component of the proposed topology.

This paper presents a novel bidirectional current-fed push-pull DC-DC converter topology with galvanic isolation. The control algorithm proposed enables full-soft-switching of all transistors in a wide range of input voltage and power with no requirement for snubbers or resonant switching. The converter features an active voltage doubler rectifier controlled by the switching sequence synchronous to that of the input-side switches. As a result, full-soft-switching operation at a fixed switching frequency is achieved. Operation principle for the energy transfer in both directions is described, followed by verification with a 300 W experimental prototype. The converter has considerably higher voltage step-up performance than traditional current-fed converters Experimental results obtained are in good agreement with the theoretical steady-state analysis.

This paper evaluates a modified single-switch galvanically isolated quasi-Z-source DC-DC converter intended as a topology for photovoltaic module-level power electronics applications. The operation principle of the converter is explained by the help of the steady-state analysis. To verify theoretical assumptions and evaluate the performance of the proposed concept, a 200 W experimental prototype of a photovoltaic microconverter was assembled and tested.

This paper discusses power losses in a current-fed DC/DC converter aimed for photovoltaic applications. Scenarios of the low voltage switch realization analyzed include a transistor with a series diode and two transistors in series. Both the high and the low voltage stage are designed with Si MOSFETs and GaN HEMTs to verify advantages of the new material in these applications. Semiconductor devices operate at soft-switching conditions, thus the study is focused on conduction and driving power losses. It appears from our calculations that GaN HEMTs show efficiency improvement of the soft-switching converter. Available GaN HEMTs belongs to the first generation of the commercially available devices. Future development of the GaN technology can greatly improve characteristics of the devices, which will result in superior performance over that of the Si.

This paper presents an evaluative comparison of Si- and SiC-based MOSFETs, operating in a qZS-derived step-up DC/DC converter. Special attention is paid to switching behaviour and power dissipation. A range of experiments was performed to determine an optimal di/dt value during transients to minimise overvoltages and dynamic losses. Additionally, some particular properties such as gate driver requirements, housing types and price are discussed.