Rui Wang

This article proposes a hybrid voltage level modulation (HVLM) strategy for a dual-transformer inductor–capacitor–inductor (LCL) immittance network resonant dual-active-bridge (DT-LCL INR DAB) converter to simultaneously optimize conduction and switching losses. The proposed HVLM strategy combines two modes to eliminate backflow power, reduce root-mean-square (rms) current, and achieve zero-voltage switching (ZVS). In the range of medium to full-load, the full half-bridge mode eliminates backflow power on both sides and reduces the rms current. Under light-load conditions, the half-bridge mode still achieves zero backflow power on the secondary side. In addition, the proposed scheme enables full-range ZVS operation for all switches. Compared with dual-phase-shift and enhanced dual-phase-shift strategies applied on a single-transformer LCL INR converter, the proposed method further reduces rms current, particularly under light-load. The effectiveness of the proposed method is validated through a 400 W experimental prototype.

This paper proposes a hybrid‐clamped three‐level series‐resonant dual‐active‐bridge (HC3L‐SRDAB) converter with an asymmetric pulse‐width modulation (APWM) strategy to improve efficiency. The HC3L‐SRDAB topology reduces the voltage stress of switches – , while the APWM strategy involves only two control variables, ensuring simple implementation. Furthermore, the APWM strategy extends the zero‐voltage switching (ZVS) range, achieving full‐range ZVS at and and maintaining ZVS above 16.7% of the normalized power at . To reduce conduction losses, the root mean square (RMS) current is minimized by solving an optimization problem with the Lagrange multiplier method. Converter operation and steady‐state behavior are analyzed using the fundamental harmonic approximation (FHA). A 400‐W prototype validates the proposed approach, confirming wide‐range ZVS, reduced current stress, and higher efficiency compared with the conventional EPS strategy.

This paper presents an enhanced triple‐phase shift (ETPS) modulation strategy for the inductor–capacitor–inductor (LCL) type resonant dual active bridge (DAB) converter. By analyzing the zero‐voltage switching (ZVS) conditions and operating modes using fundamental harmonic approximation (FHA), the proposed ETPS strategy adaptively adjusts the phase shift angles to ensure ZVS across the full operational range, particularly over a wide voltage conversion range. Furthermore, for both buck and boost modes, the total root‐mean‐square (RMS) current is minimized using the Lagrange multiplier method (LMM) to reduce conduction losses. Closed‐form analytical expressions for the optimal phase shift angles are derived to enable efficient power regulation. The effectiveness of the proposed strategy is validated through simulations and confirmed by experimental results, which demonstrate that the ETPS strategy consistently achieves ZVS under various load conditions and outperforms the conventional unity power factor (UPF)–triple‐phase shift (TPS) strategy in terms of efficiency.

In this paper, an isolated bidirectional three-level neutral-point-clamped dual-bridge series resonant converter (3L-NPC-DBSRC) is proposed for the wide-voltage range dc-dc applications in energy storage systems, which consists of a neutral-point-clamped (NPC) three-level bridge on the primary side, a LC-type series-resonant tank, and a full bridge on the secondary side. The proposed 3L-NPC-DBSRC is able to realize increased voltage gain and reduced harmonic components in the primary-side high-frequency-link voltages and currents. By using fundamental harmonic analysis (FHA), the steady-state operation principles of 3L-NPC-DBSRC are thoroughly analyzed in both forward and backward power-flow directions. Furthermore, a control algorithm based on globally optimal condition (GOC) is proposed for achieving zero-voltage switching (ZVS) in all switches and minimum root-mean-square (RMS) ac-link current, thus simultaneously reducing the switching and conduction power losses, and eventually resulting in high overall efficiency. Finally, to verify the effectiveness of the proposed 3L-NPC-DBSRC and its control method, both simulations and experiments are carried out on a designed example.

The DC-DC converter is a crucial component of an electric vehicle (EV) charger, and its performance is essential for the charging speed and driving range of EVs. Despite recent advancements in converter topology and modulation techniques, enhancing both switching and conduction losses in dual active bridge (DAB) converters continues to be challenging. This paper introduces a novel dual unbalanced modulation (DUM) for EV chargers. The DUM strategy, when combined with a CLCLC-type immittance resonant DAB (IRDAB) converter, can simultaneously reduce the switching and conduction losses. When the rated output power exceeds 25%, the DUM strategy operates in full-bridge mode, achieving zero-voltage switching (ZVS) operation of all switches, minimizing backflow power on both sides, and maintaining near-minimum root mean square (RMS) currents. For output power rated below 25%, the DUM strategy shifts to half-bridge mode. This mode slightly increases the RMS currents, yet it still ensures ZVS operation of all switches and minimum backflow power on both sides. Theoretical analysis and experimental results demonstrate that, when compared to conventional modulation strategies, DUM strategy maintains the highest efficiency across the entire load range.

This paper proposes an unbalanced duty cycle mod-ulation (UDCM) strategy to optimize conduction loss and improve the overall efficiency for dual-bridge resonant converter (DBRC). Steady-state analysis is performed using fundamental harmonics approximation (FHA), and the ZVS conditions are given. Further, the minimum current trajectory (MCT) is presented, which makes the converter operates with minimum resonant current. Moreover, the ZVS range is extended and the circulating current is well suppressed. The theoretical analysis and calculation are validated through simulation and experimental test.

This paper presents the operation, analysis, design, simulation, and experimental results for a proposed Dual-Transformer DC-DC Resonant Converter (DTRC). A three-arm bridge is employed on the input side and an H-type bridge is employed on the output side of the DTRC, and the two bridges are connected with two high-frequency (HF) transformers. By optimizing the ratio k of the two HF transformers, the proposed DTRC has a lower boundary power for losing zero-voltage switching (ZVS). That means the DTRC has a wider ZVS operation range and lower switching loss when compared with a traditional soft-switching pulse width modulation (PWM) resonant converter. The operation principle, power transfer, ZVS characteristics, and design procedures are analyzed in detail. Both simulation and experimental results prove the feasibility and superiority of the proposed Dual-Transformer DC-DC Resonant Converter.

To overcome the weakness of the narrow conversion gain of dual bridge resonant converter, a half-dual bridge resonant converter (H-DBRC) with voltage match modulation (VMM) is proposed and implemented for wide voltage range applications. The H-DBRC, including a full bridge on the primary side and a half bridge on the secondary side, is adopted to realize the bidirectional power flow and wide voltage operation. Owing to the synergy between the H-DBRC structure and VMM strategy, the converter can operate in full-bridge state and half-bridge state with maximized ZVS (zero-voltage switching) operation and minimized circulating current. The steady-state analysis is performed and the solutions for both forward and backward modes could be obtained uniformly by using the fundamental harmonics approximation approach. The soft-switching characteristics, implementation process and design example are analyzed in detail. Finally, to confirm the theoretical analysis and feasibility, both simulation and experimental verifications are demonstrated in this paper. Since the converter consistently achieves voltage-matching operation, the optimal ZVS range can be obtained when the voltage gain M is between 0.5 to 1. Moreover, the economic cost and control complexity are greatly reduced because only six switches are required in the converter.