Dual Bridge Series Resonant Converter Research Articles

Model and Control for Transient Process of Dual-Bridge Series Resonant Converter

Model and Control for Transient Process of Dual-Bridge Series Resonant Converter

Deep reinforcement learning-aided minimum current control for the DBSRC based on harmonic analysis method

Aiming to optimize the modulation efficiency for the dual-bridge series-resonant converter (DBSRC), this paper proposes an deep reinforcement learning (DRL) aided EPS (DEPS) modulation scheme for minimum current operation based on the harmonic analysis method. Using the deep deterministic policy gradient (DDPG) algorithm as an advanced DRL algorithm, the scheme obtains the optimized modulation scheme DEPS through offline training of the agent, which can adopt the extended-phase-shift (EPS) modulation scheme and consider the zero-voltage-switching (ZVS) constraints. Thus, the trained agent of the DDPG which likes an implicit function, can provide optimal phase shift angle for the DBSRC in real-time with the minimum current and soft switching performance in the continuous operation range. Compared with the existing EPS modulation schemes using First Harmonic Approximation (FHA), the DEPS modulation scheme has similar operational efficiency and performance of the converter, while also possessing the ability to obtain modulation angles in real-time based on environmental parameters. Finally, PSIM simulation verifies the effectiveness of the proposed optimization scheme.

Minimum Current Optimization of DBSRC Considering the Dead-Time Effect

In a dual-bridge series resonant converter (DBSRC) working at a high switching frequency, the dead-time effect is a serious issue. When the minimum current trajectory (MCT) method is applied, the inductor current cannot be minimized due to the dead-time effect, and the range of the soft switching is reduced. Considering the dead-time, this paper first presents a theoretical analysis of the transmission power and the soft-switching characteristics based on the fundamental harmonic approximation (FHA) approach. Then, a minimum current trajectory method considering the dead-time (MCT-d) is proposed to achieve the minimum inductor current by compensating for the dead-time. This method can extend the soft-switching range as well. Finally, the experimental results validate the theoretical analysis and the improvement of the converter’s efficiency.

Modeling with Beat Frequency Dynamics and Phase-Frequency Control Design for a Dual-Bridge Series Resonant Converter

Phase-frequency modulation is an effective soft-switching technique for a dual-bridge series resonant converter (DBSRC). In the literature, the DBSRC topology is investigated with phase-frequency control to increase the soft-switching region and to reduce the reactive power circulation in the high-frequency link. However, behavior of the circuit during transient was not addressed, especially when multiple input variables are involved. This article proposes a small-signal model for the DBSRC considering phase shift and switching frequency as the control parameters. The proposed model studies the dependence of the control variables. Therefore, a compensator design is proposed, which helps the two control loops to operate independently. Transient response of the DBSRC is extensively studied by providing a step load and a step change in output voltage reference. Proposed modeling accurately predicts the transient behavior of the circuit. The beat-frequency phenomenon, which is often found in resonant converters, can also be predicted in this model. The design of resonant tank parameters is also addressed in this article. Finally, the proposed model and the control method are verified in a 2.7 kW hardware prototype.

A SERIES RECONFIGURABLE STRUCTURE RESONANT CHOPPER FULLY SOFT-SWITCHED DUAL-ACTIVE-BRIDGE WITH DUAL TANK

Compared to the dual-active-bridge converter, the Double-bridge arrangement thunderous converter (DBSRC) can extend delicate exchanging run. To encourage broaden the soft-switching extend and progress the circuit execution, a modern DBSRC with double tank based on DBSRC is proposed in this paper. This modern converter highlights two thunderous tanks and a tapped transformer, and it can perform superior than the DBSRC by optimized tap coefficient x of the tapped transformer. Its operation guideline, voltage pick up, the soft-switching characteristics, and yield control are analyzed in detail, and compared with the DBSRC. Comes about appear that the pro-posed dual-tank topology has displayed higher voltage pick up, more extensive soft-switching locale, and bigger yield control than the conventional DBSRC when the tap-coefficient x is chosen sensibly. DC-to-DC bidirectional resounding converter to be utilized for bidirectional control exchange applications particularly battery charging discharging applications in electrical vehicles. Its similar to an LLC resonant converter, but on the secondary side of the circuit, an additional inductor and capacitor have been added to make the resonant network symmetric for operation in both forward and backward directions. The switches in the inverting step have zero voltage switching (ZVS). Under ZCS, the rectifier diodes on the secondary side also turn off. ZVS and ZCS reduce losses and enable high-frequency operation, resulting in smaller magnetic elements and filter capacitors, lowering size, weight, and volume while enhancing power density. INDEX TERMS—dual active bridge (DAB), dual-bridge series resonant converter (DBSRC), soft-switching, dual-tank, tapped- transformer, tap-coefficient

Bidirectional Series Resonant DC/AC Converter for Energy Storage Systems

This paper presents a novel bidirectional series resonant converter for energy storage systems (ESS). Conversion between a dc energy storage device and an ac grid has grown in importance because of the renewable energy generators and ESS used in microgrids, which usually use batteries or supercapacitors as storage devices in order to provide different services and improve the quality and reliability of the grid. This novel converter avoids the need to have two converting stages: one for converting the energy from the storage device to a regulated dc value, and the other for converting the regulated dc to the ac output. Conversion occurs via a modified dc/dc dual-bridge series resonant converter. The output bridge of the converter is attached to the input bridge through a resonant branch and a high frequency (HF) transformer, and it is also attached to the ac link through an output filter. Therefore, two ac power signals are mixed in the output bridge: a HF signal, which maintains the dc link capacitor voltage, and a low frequency power signal, which transfers energy to the grid. This paper details the different working modes of the converter and presents a 3000 W prototype that validates the design.

Model of DC/DC Dual-Bridge Series Resonant Converter in Buck and Boost Modes for Output Current and Commutation Timing Control

Model of DC/DC Dual-Bridge Series Resonant Converter in Buck and Boost Modes for Output Current and Commutation Timing Control

A Piecewise Control Strategy for a Bidirectional Series Resonant Converter

An energy storage system (ESS) plays an important part in a renewable energy generation system for stable and efficient power harvesting. To realize the function of an ESS, a bidirectional DC/DC converter with high power density and high efficiency is highly desired. In this paper, a high-frequency (HF) isolated dual-bridge series resonant converter (DBSRC) with a piecewise control strategy is proposed for an application with a wide variation of voltage gain. The proposed control strategy is based on dual-phase-shift modulation for a balance between complexity and flexibility. With this proposed control strategy, zero-voltage switching is kept for all switches on the low-voltage side and half of switches on the high-voltage side. Besides, there is no circulation energy on the low-voltage high-current side for full load operation. A step-by-step design procedure is also included to calculate the converter components and control parameters. Verification of the analysis and design are performed successfully through simulation and n experimental test. Comparisons with some existing control methods are also made experimentally, which highlights that the proposed control strategy is able to achieve comparable performance as the reported optimal current control with simpler calculation and implementation.

A New Dual-Bridge Series Resonant DC–DC Converter With Dual Tank

Compared to the dual-active-bridge converter, the dual-bridge series resonant converter (DBSRC) can widen soft-switching range. To further widen the soft-switching range and improve the circuit performance, a new DBSRC with dual tank based on DBSRC is proposed in this paper. This new converter features two resonant tanks and a tapped transformer, and it can perform better than the DBSRC by optimized tap coefficient x of the tapped transformer. Its operation principle, voltage gain, the soft-switching characteristics, and output power are analyzed in detail, and compared with the DBSRC. Results show that the proposed dual-tank topology has presented higher voltage gain, wider soft-switching region, and larger output power than the traditional DBSRC when the tap-coefficient x is selected reasonably. At last, a 1-kW prototype is built; experimental results verify the feasibility and advantages of the proposed dual-tank converter.

Isolated Bidirectional Grid-Tied Three-Phase AC–DC Power Conversion Using Series-Resonant Converter Modules and a Three-Phase Unfolder

Power-bidirectional converters are used to integrate energy storage with both dc and ac distribution grids. A modular bidirectional dc–dc converter system consisting of multiple dual-bridge series resonant converter (DBSRC) modules can be reconfigured to extend the system operating range. This paper proposes a modular three-phase ac–dc converter system by adding a line-frequency unfolder to series-connected outputs of two DBSRC modules. The DBSRC modules are controlled to output time-varying currents, which are then reconstructed into sinusoidal ac currents by the unfolder. Compared with a conventional two-stage system with a dc–dc converter and a two-level voltage-source inverter, the DBSRC–unfolder system has smaller dc-link capacitance, negligible unfolder switching loss, reduced line filter size, and faster dynamic response. The system operation and performance are verified on a 1-kW experimental prototype.

Performance Evaluation of a Semi-Dual-Bridge Resonant DC/DC Converter With Secondary Phase-Shifted Control

In this work, a unidirectional series-resonant dc/dc converter with a semi-dual-bridge structure is evaluated comprehensively. This converter can realize buck–boost conversion by means of the simple secondary phase-shifted control. With the variations of load level and converter gain, the converter may enter into different operation modes. Features of all possible operation modes and the boundary conditions among them are identified explicitly. Despite the differences between the modes, the steady-state solution for all modes with continuous resonant current could be obtained uniformly by using the fundamental harmonics approximation approach. Verifications of each operation modes are exemplified through experimental tests on a 300-W prototype converter. The measured efficiency can be maintained over 90% at low-load level when the input voltage is varied. Through comparison with reported topologies having similar structures, it is shown that this converter has lower circulation energy than a dual-bridge series-resonant converter. And the secondary arrangement of this converter is advantageous in terms of simpler driver circuit, no-risk of shoot-through fault, and low conduction loss.

An Isolated Bidirectional Integrated Plug-in Hybrid Electric Vehicle Battery Charger with Resonant Converters

Plug-in hybrid electric vehicles draw electricity from the electrical grid and store energy in their batteries. To increase charge availability for plug-in hybrid electric vehicles, on-board chargers can be used, which should be small in size and lightweight. In this article, an on-board bidirectional soft-switched battery charger is proposed that utilizes a phase-shift-controlled dual-bridge series resonant converter with isolation. The bidirectional characteristic of proposed charger makes it suitable for vehicle-to-grid operation (i.e., injecting power from the vehicle to the grid) in smart grids. A switching control scheme is also proposed to provide soft-switching operation for all semiconductor switches, resulting in high efficiency for the charger. In this structure, the conventional bulky capacitor of the DC link is eliminated. In addition, the proposed charger can integrate the hardware of the traction system; hence, the size of the whole charger–inverter system will be drastically decreased. The appropriate performance of the proposed charger is verified by simulation and experimental results.

Zero Voltage Switching Technique for Bidirectional DC/DC Converters

This paper proposes a zero voltage switching (ZVS) technique for bidirectional dc/dc converters. The dc/dc unit considered consists of two distinct bidirectional dc/dc cells paralleled at both input and output and whose two input bridges are coupled by means of passive inductive branches. A multiangle phase-shift modulation method is proposed which simultaneously achieves bidirectional power control, power sharing, and ZVS of all the electronic devices over the full power range without the need for auxiliary switches. Simulation and experimental results are reported for a 2.4 kW dc/dc unit consisting of two paralleled 1.2 kW bidirectional dual-bridge series resonant converter cells.

Minimum Current Operation of Bidirectional Dual-Bridge Series Resonant DC/DC Converters

This paper discusses the steady-state operation of phase-shift modulated dual-bridge series resonant converter (DBSRC) intended for dc/dc power bidirectional control over a wide range of input and output voltages. The analysis, developed here for the most general case of three independent phase-shift control angles, demonstrates the existence of minimum current trajectories in the 3-D control space along which the DBSRC cell can deliver any admissible power level with minimum tank circulating current. At nonunity conversion ratios, minimum current operation prevents the DBSRC output bridge from experiencing severe hard-switching losses, substantially reducing the effort normally required by auxiliary zero-voltage switching assistance circuitry, and outperforming the efficiency of conventional one-angle modulation approaches especially at light load. The developed approach is validated via computer simulations and experimental tests on a 1-kW DBSRC prototype. Tests performed at a nonunity voltage conversion ratio indicate a marked light-load efficiency improvement with respect to the conventional one-angle modulation, confirming the importance of the minimum current operation when the converter is expected to operate with programmable output voltages or under wide input voltage variations.