Soft-switching Bidirectional DC-DC Converter Research Articles

Modular high conversion ratio soft-switching DC-DC converters with extended multi-ports structure for multi-energy storage systems interconnection

This paper focus on the advanced multi-energy storage systems interconnection by DC smart grids with high efficiency and high compactness. A non-isolated modular high conversion ratio bidirectional soft switching DC-DC converter and its extended multi-ports structure are proposed in this paper. In each power module of the converter, an auxiliary zero-current transition (ZCT) cell is integrated to achieve the zero-current turn-on and turn-off for all semiconductor devices. Therefore, the switching losses are reduced greatly and the efficiency is improved considerably. The presented converter is suitable for the small and medium power scale interconnection in smart DC grids, and can realize the flexible multi-energy storage system interaction owing to its extended multi-ports structure. Besides, various control schemes are adopted to optimize the control system of this converter, which can improve the performance on energy interaction. The operation principles and design considerations are discussed in details and a 5 kW experimental prototype is constructed to justify the validity of the theoretical analysis.

Analysis of a novel soft switching bidirectional DC-DC converter for electric vehicle

A bidirectional converter (BDC) designed with high voltage gain and it is incorporated with the soft-switching operations to the insulated gate bipolar transistors (IGBTs). The main dual operating characteristics of this converter are boost and buck modes respectively. In order to achieve the reduced switching losses and improved efficiency, the main IGBTs are operated at zero current (ZC) while the IGBTs commutating from turn-on to turn-off state. The ZC turn-off operation is obtained with the aid of soft- switched cell, which consists of resonant inductor (Lr), capacitor and additional IGBTs. In this work, the design simulation analysis for high-gain BDC was performed by 70/300 V power system with the maximum 800 W output power under the operating frequency of 50 kHz. The efficiency for the high-gain soft-switched BDC was obtained as 96.5% when it is operating in boost mode and efficiency of 97% was achieved for the buck mode operation. The simulation evaluations of the above said converters were performed by using MATLAB/Simulink.

A Soft-Switching Bidirectional DC–DC Converter With High Voltage Gain and Low Voltage Stress for Energy Storage Systems

In this article, an interleaved soft-switching bidirectional dc-dc converter (BDC) with high voltage conversion ratio (VCR) and low voltage stress is proposed for battery charging/discharging applications. A built-in transformer (BT) is integrated into conventional half-bridge BDC and three-level structure to achieve high VCR and reduced voltage stresses simultaneously. The feature of BT is that the balanced magnetic flux exists in the magnetic core, which allows for small size of the magnetic core. The current ripple in the battery side is reduced by adopting the interleaved structure. Moreover, the voltage-matching on both sides of the BT is realized by the adjustment of the duty cycle. As a result, even if the battery voltage changes, the BT always operates under the highest efficiency condition. Besides, by employing phase-shift control, power flow can be regulated monotonously. Soft-switching of all the switches within a wide range of battery voltage is obtained by employing the optimal design. The operational principles, characteristics, and design considerations are analyzed in detail. Experimental results from the BT-BDC prototype of 1-kW, 40-60 to 400 V verify the effectiveness.

A Soft-Switched Bi-directional DC-DC Converter for a BLDC motor based Electric Vehicle

A Soft-Switched Bi-directional DC-DC Converter for a BLDC motor based Electric Vehicle

A new nonisolated soft switched DC-DC bidirectional converter with high conversion ratio

ABSTRACT In this paper, a new soft switching bidirectional DC-DC converter with high conversion ratio is proposed. In the proposed converter, soft switching condition is provided with only one auxiliary switch for both directions, which simplifies the structure of the converter. The switching in boost mode is under ZCS condition and in buck mode is under ZVS condition. In the proposed converter, all diodes turn off under ZCS condition; therefore, losses related to diodes reverse recovery are eliminated. The control of the auxiliary switch is complementary to the main switch; thus, complex control circuit is not required. The voltage stress of the switch in boost mode is reduced extremely due to high voltage gain. The proposed converter is analysed, and to confirm the theoretical analysis, a 200-W prototype is implemented and the results are presented. Consequently, the efficiency of the proposed converter at full load is 97.5%.

Soft Switching of Full-Bridge DC-DC Buck Converter

The conventional Bidirectional Full-bridge dc -dc converter is inefficient and may not be practical for the low power applications. This paper specifies an efficient DC-DC Converter that avoids power losses by using soft switching techniques like Zero Voltage Switching and Zero Current switching. The soft switching of Bidirectional Full-bridge DC-DC Converter operates as a buck converter when the power is positive and as a boost converter when the power flow is negative. Applications of soft switching Bidirectional Full-bridge DC-DC Converter are uninterrupted power supplies (UPS), distribution Systems, battery charger circuits, telecom power supplies, computer power systems. Detailed analysis of the converter is carried out in buck mode to obtain relations between the power circuit parameters. Based on the analysis, control schemes are described to operate the converter. The proposed full bridge DC-DC converter is simulated in Buck mode using MATLAB /SIMULINK.

Bidirectional Resonant DC-DC Converter for Microgrid applications

This paper presents a non-isolated bidirectional soft-switching dc-dc converter for DC microgrid energy storage synchronization. To assist the soft switching of switches and diodes, the LCL resonant circuit is applied and an input end half-bridge boost converter is enforced. Using the voltage doubler circuit introduced on the output side, a voltage gain of 2X is achieved. Through the non-isolated circuit, the total voltage gain is obtained. The capacitive divider halves the voltage on the greater hand. The circuit performs a high frequency ripple of low output voltage. Diodes guarantee zero voltage Turn ON for switches and zero current turn ON and turn OFF during buck / boost operation Although no internal snubber circuits are available, the circuit ensures low voltage stress across semiconductor systems.

Soft Switching Bidirectional DC-DC converter for Hybrid Electric Vehicle Applications

Soft Switching Bidirectional DC-DC converter for Hybrid Electric Vehicle Applications

Non-isolated stacked bidirectional soft-switching DC-DC converter with PWM plus phase-shift control scheme

In this paper, a non-isolated stacked bidirectional DC-DC converter with zero-voltage-switching (ZVS) is introduced for the high step-up/step-down conversion systems. The extremely narrow turn-on and/or turn-off duty cycle existing in the conventional bidirectional buck-boost converters can be extended due to the stacked module configuration for large voltage conversion ratio applications. Furthermore, the switch voltage stress is halved because of the series connection of half bridge modules. The PWM plus phase-shift control strategy is employed, where the duty cycle is adopted to regulate the voltages between the input and output sides and the phase-shift angle is applied to achieve the power flow regulation. This decoupled control scheme can not only realize seam-less bidirectional transition operation, but also achieve adaptive voltage balance for the power switches. In addition, ZVS soft-switching operation for all active switches is realized to minimize the switching losses. Finally, a prototype of 1 kW operating at 100 kHz is built and tested to demonstrate the effectiveness of the proposed converter and the control strategy.

A State Space Modeling of Non-Isolated Bidirectional DC-DC Converter with Active Switch

In this paper, analysis, design and implementation of non-isolated soft-switching bidirectional DC-DC converter with an active switch are described. The proposed topology gives the output voltage as twice as the input voltage and enhances the efficiency up to 94.5% and 92.9% for boost and buck mode operation by proper selection of the duty cycle. Soft switching can be achieved at both steps up and step down operating modes. Small signal analysis based on state space averaging and transfer functions have been presented in detail for the proposed converter. Finally, the feasibility of the desired converter is confirmed to mat lab simulation and investigational results.

Soft-Switching Bidirectional DC-DC Converter Using a Lossless Active Snubber

A soft-switching bidirectional dc-dc converter using a lossless active snubber is proposed in this paper. In the proposed converter, zero-voltage-switching (ZVS) of main switches is achieved by utilizing an active snubber which consists of auxiliary switches, diodes, an inductor, and a capacitor. Although conduction losses associated with additional components increase, switching losses are significantly reduced due to the ZVS operation of main switches. Therefore, total efficiency is improved. Moreover, there is no reverse-recovery problem of the intrinsic body diodes of the switches. To verify the ZVS of the main switches and efficiency improvement of the proposed bidirectional dc-dc converter, theoretical analysis and experimental results from a 200 W prototype are discussed.

High Gain Soft-Switching Bidirectional DC–DC Converter for Eco-Friendly Vehicles

This paper proposes a nonisolated soft-switching bidirectional dc-dc converter suitable for high step-up and step-down applications. The proposed converter can achieve zero voltage switching turn on of all switches and zero-current-switching turn off of some switches in continuous conduction mode in both forward and reverse modes. An optimized switching strategy is presented to minimize switch current rating and achieve soft switching in wider range. An intermediate switching pattern is introduced to carry out seamless mode change. Experimental results from a 5-kW prototype are provided to validate the proposed concept.

Analysis of a Novel Soft Switching Bidirectional DC-DC Converter

In this paper, a novel bidirectional DC-DC converter employing soft switching technique was proposed. Compare to conventional bidirectional converters, the main switches of proposed converter are operated without switching losses. Moreover, auxiliary switches are used, and the switches are operated under zero voltage switching (ZVS) and zero current switching (ZCS) condition. To verify the validity of the proposed converter, mode analysis, design procedure, simulation and experimental results are presented.

High-efficiency bidirectional DC-DC converter with coupled inductor

This study presents a novel soft-switching bidirectional dc-dc converter with a coupled inductor. Transformer-based circuit topologies are commonly employed in conventional bidirectional converters and soft-switching techniques, including zero-voltage switching (ZVS) or zero-current switching (ZCS), are frequently applied to mitigate switching losses. Unfortunately, the use of more than four switches and several diodes in these transformer-based schemes increase production costs and reduce conversion efficiency. This work presents a coupled-inductor bidirectional converter scheme that utilises four power switches to achieve the goal of bidirectional current control. The high step-up and step-down ratios enable a battery module current with a low-voltage level to be injected into a high-voltage dc bus for subsequent utilisation. Experimental results based on a 24 V/200 V 800 W prototype are provided to verify the effectiveness of the proposed bidirectional converter. Since the voltage clamping, synchronous rectification and soft-switching techniques are utilised in the proposed circuit topology and the corresponding device specifications are adequately fulfilled, the proposed converter can provide highly efficient bidirectional power conversion in a wide range on the low-voltage side.

A Nonisolated Bidirectional ZVS-PWM Active Clamped DC–DC Converter

Power electronic converter systems for applications such as telecom, automotive, and space can have dc voltage buses that are backed up with batteries or supercapacitors. These batteries or supercapacitors are connected to the buses with bidirectional dc-dc converters that allow them to be discharged or charged, depending on the operating conditions. Bidirectional dc-dc converters may be isolated or nonisolated depending on the application. A new soft-switched bidirectional dc-dc converter will be proposed in this letter. The proposed converter can operate with soft switching, a continuous inductor current, fixed switching frequency, and the switch stresses of a conventional pulsewidth modulation converter regardless of the direction of power flow. These features are due to a very simple auxiliary active clamp circuit that is operational regardless of the direction of power flow. In the letter, the operation of the converter will be discussed and its feasibility will be confirmed with experimental results obtained from a prototype.