Skip to main content
Top

2019 | Book

High-Frequency Isolated Bidirectional Dual Active Bridge DC–DC Converters with Wide Voltage Gain

Authors: Deshang Sha, Guo Xu

Publisher: Springer Singapore

Book Series : CPSS Power Electronics Series

insite
SEARCH

About this book

Written by experts, this book is based on recent research findings in high-frequency isolated bidirectional DC-DC converters with wide voltage range. It presents advanced power control methods and new isolated bidirectional DC-DC topologies to improve the performance of isolated bidirectional converters. Providing valuable insights, advanced methods and practical design guides on the DC-DC conversion that can be considered in applications such as microgrid, bidirectional EV chargers, and solid state transformers, it is a valuable resource for researchers, scientists, and engineers in the field of isolated bidirectional DC-DC converters.

Table of Contents

Frontmatter
Chapter 1. Introduction
Abstract
This chapter presents a brief introduction focusing on the applications and classifications of bidirectional DC–DC converters, review of the control methods for dual active bridge control, and key issues of DAB converters. Bidirectional power flow, galvanic isolation, and wide voltage gain range are necessary for some applications such as energy storage system, automotive applications, SST-based DC fast charger. To achieve wide ZVS ranges and low current stresses for the conversion stages of these applications, the topology candidates and the corresponding power control methods have been a challenge in both industry and research communities. This chapter provides a basic foundation for the whole work, and it gives the goal of this book which is to provide valuable knowledge, advanced control methods, and practical design guides for the high-frequency isolated bidirectional dual active bridge DC–DC converters with wide voltage gain.
Deshang Sha, Guo Xu
Chapter 2. Unified Boundary Trapezoidal Modulation Control for Dual Active Bridge DC–DC Converter
Abstract
The unified boundary trapezoidal modulation (TZM) control utilizing fixed duty cycle compensation and magnetizing current design for dual active bridge DC–DC converter is proposed in this chapter. The fixed duty cycle compensation and magnetizing current design are firstly introduced to achieve the zero-voltage switching (ZVS) of the power switches, which cannot be ensured with the conventional TZM control. As a result, all the power switches of dual active bridge DC–DC converter can achieve ZVS and four switches can be turned off with very low current. Besides, based on the revealed power transfer characteristic, the power control variables including the duty cycles and phase shift ratio can be unified without look-up tables or operation region division. With the proposed boundary TZM control, circulating current losses can be reduced and non-active power is significantly suppressed according to the mathematic analysis, resulting in decrease of the conduction loss. A 1.6 kW laboratory prototype is built to verify the theoretical analysis and effectiveness of the proposed control.
Deshang Sha, Guo Xu
Chapter 3. Hybrid-Bridge-Based DAB Converter with Wide Voltage Conversion Gain
Abstract
This chapter proposes a voltage match (VM) control for hybrid-bridge-based dual active bridge (DAB) converter in wide voltage conversion gain applications. With the addition of an auxiliary half-bridge circuit, the topology becomes an integration of a half-bridge and a full-bridge DAB converter. Unlike other PWM generation method for DAB converters, this converter utilizes four-level voltage at one port of the transformer to obtain matched voltage waveforms within the range of twice the minimum conversion gain. Wide conversion gain, decoupling of the two power control variables, and wide zero-voltage switching (ZVS) ranges can be achieved with the proposed voltage match control. Full load ranges of ZVS for the six main power switches can be achieved, and the two auxiliary switches can also operate in a wide ZVS range. In addition, the power control is done only using two control variables and its implementation is very simple, only needing a divider and a conventional voltage regulator. These characteristics and benefits of the proposed control are verified by experimental results from a 1 kW converter prototype.
Deshang Sha, Guo Xu
Chapter 4. Dual-Transformer-Based DAB Converter with Wide ZVS Range for Wide Voltage Gain Application
Abstract
Dual-transformer-based dual active bridge (DAB) converter with wide ZVS range for wide voltage conversion gain application is derived and studied in this chapter. The phase shift control is adopted for this converter with minimum power switches employing half-bridge output, and a control law is proposed to achieve wide ZVS range. With the proposed method, four switches of the converter can achieve full range of ZVS. The other two switches can achieve full-range ZVS under positive power flow, while slightly reduced ZVS region under reverse power flow. Unlike the methods employing three control degrees of freedom, the proposed method only utilizes two decoupled control variables, making the controller easy to be implemented. In addition, the design of turns ratios for the two transformers under the proposed control is also optimized based on the gain ranges and conduction loss. The effectiveness of the converter with the proposed control is verified by experimental results from a 1 kW prototype.
Deshang Sha, Guo Xu
Chapter 5. Blocking-Cap-Based DAB Converters
Abstract
Blocking-cap-based dual active bridge (DAB) converter with wide voltage conversion gain is studied in this chapter. The DC blocking capacitor, which is used for avoiding the DC flux bias in the transformer of conventional DAB converter, is utilized to achieve better performance under wide voltage gain range. By changing PWM generating method under different voltage input, the converter can work in half-bridge and full-bridge mode correspondingly with presented hybrid control. To simplify the PWM generating method, the duty cycles of primary and secondary bridges are fixed as 50%. The power transfer characteristics, ZVS region, and RMS current are analyzed and are compared with the DAB converter using single-phase shift (SPS) control. The theoretical analysis and conclusion of the converter with the hybrid control are verified by experimental results from a 1 kW prototype.
Deshang Sha, Guo Xu
Chapter 6. Three-Level Bidirectional DC–DC Converter with an Auxiliary Inductor in Adaptive Working Mode for Full-Operation Zero-Voltage Switching
Abstract
This chapter proposes a three-level bidirectional DC–DC converter with an auxiliary inductor for full-operation zero-voltage switching (ZVS) in high-output voltage applications. The auxiliary inductor is connected across the middle node of the split flying capacitors and the center tap of the secondary winding in the transformer. In this topology, the outer and inner switches in the three-level stage can generate two independent 50% duty-cycle square waveforms, which is used to control the current in the auxiliary inductor to extend ZVS range from no loads to full loads condition. Considering the phase shift angle in three-level stage, the ZVS range of the converter is analyzed, and the modulation trajectory to maintain the full-operation ZVS range with low conduction loss is proposed. A flowchart implementation can guarantee the seamless transfer in different working modes. Then, the conduction loss in the proposed converter is compared with the previous three-level bidirectional solution, which illustrates that the conduction loss in the proposed converter only increases in light loads. Finally, the experimental results verify the theoretical analyses and ZVS performance across the whole power and voltage range, and the efficiency curves demonstrate the efficiency improvement.
Deshang Sha, Guo Xu
Chapter 7. A Current-Fed Dual Active Bridge DC–DC Converter Using Dual PWM Plus Double Phase Shifted Control
Abstract
A double PWM plus double phase shifted (DPDPS) control is proposed for current-fed dual active bridge (DAB) bidirectional DC–DC converters. With which the circulating current during the non-power transfer stage can be minimized. The mode analysis of the current-fed bidirectional DC–DC converter using the proposed control strategy is given. The comparison concerning the peak current and RMS current for transformer windings and switches is made by using the conventional PWM plus phase shifted (PPS) control and the proposed DPDPS control. The mode analysis of the proposed control strategy and comparison between PPS control and the proposed control are given. With the proposed DPDPS control, the converter has lower conduction loss, lower peak current, and higher efficiency. A 1 kW prototype is built to verify the proposed topology employing the proposed DPDPS control.
Deshang Sha, Guo Xu
Chapter 8. High Efficiency Current-Fed Dual Active Bridge DC–DC Converter with ZVS Achievement Throughout Full Range of Load Using Optimized Switching Patterns
Abstract
For current-fed dual active bridge bidirectional DC–DC converters, all the possible switching patterns are summarized in view of the combinations of both side PWM duty cycles and phase shift angle. A control strategy is proposed for the current-fed dual active bridge converter to operate with the optimized patterns. The equivalent duty cycle of the secondary side is smaller than that of the primary side by a fixed value, which is optimized based on the soft switching achievement and the circulating current minimization. The closed-loop control is easy to be implemented since there are only two independent variables, one-side duty cycle and the phase shift angle. With the proposed control, zero-voltage switching (ZVS) can be achieved for all power switches throughout full range of load even at no load condition. The typical working modes with the proposed control are given. The optimal design of the system parameters including the fixed time delta and dead time is illustrated. The effectiveness of the proposed control is verified by the experimental results of a 1 kW laboratory prototype.
Deshang Sha, Guo Xu
Chapter 9. A ZVS Bidirectional Three-Level DC–DC Converter with Direct Current Slew Rate Control of Leakage Inductance Current
Abstract
A high-frequency isolated bidirectional three-level DC–DC converter is proposed for high-voltage applications. Direct current slew rate (DCSR) control of leakage inductance is proposed to minimize conduction loss and current stress in facing the load variation, the mismatch of turns ratio and circuit parasitic parameters. The mode analysis and the disadvantages of conventional PWM plus phase shift (PPS) control are addressed while these disadvantages can be dealt with the proposed control. Comprehensive comparison between conventional PPS control and the proposed DCSR control are made within the designed low-voltage side (LVS) voltage range. Besides, the implementation of the proposed DCSR control is also given. With the proposed DCSR control, lower conduction loss, lower peak current, lower voltage spike over switches can be obtained in spite of the turns ratio mismatch, load variation, and system parasitic parameters. Zero-voltage switching (ZVS) can be achieved for all power switches in spite of the power flow direction. The effectiveness of the proposed DCSR control on the proposed topology is verified by simulation and experimental results.
Deshang Sha, Guo Xu
Chapter 10. A Bidirectional Three-Level DC–DC Converter with Reduced Circulating Loss and Fully ZVS Achievement for Battery Charging/Discharging
Abstract
A high-frequency isolated bidirectional three-level DC–DC converter is proposed for battery charging/discharging applications. To reduce the circulating loss, a double PWM plus double phase shifted control employing voltage matching control is proposed. ZVS for all power switches can be obtained even at no-load condition by employing the magnetizing inductance. The mode analysis is given to illustrate its working principle. The system parameter design criterion is given in view of the efficiency improvement and ZVS achievement for all switches. A detailed comparison of RMS value and peak value of the leakage inductance current is made with the voltage matching control and mismatching control, respectively. The effectiveness of the proposed control for the DC–DC converter is verified by experimental results of a 1 kW three-level prototype.
Deshang Sha, Guo Xu
Chapter 11. A Current-Fed Hybrid Dual Active Bridge DC–DC Converter for Fuel Cell Power Conditioning System with Reduced Input Current Ripple
Abstract
In this chapter, a novel current-fed hybrid dual active bridge DC–DC converter is proposed, which is suitable for low-voltage fuel cell power conditioning system. The high-frequency input current ripple can be reduced to minimum because the input-side switches are always switched at 50% duty cycles in spite of the fuel cell voltage and the load variation. Notch filter is used in the voltage feedback path to reduce the low-frequency input current ripple when interfaced with a single-phase inverter load. All of the power devices can achieve zero-voltage switching on by the proposed control strategy. The mode analysis, the operation principle, ZVS conditions, and parameter design are given in this chapter. A 1 kW prototype has been fabricated to verify the effectiveness of the proposed converter and control strategy.
Deshang Sha, Guo Xu
Chapter 12. Dynamic Response Improvements of Parallel-Connected Bidirectional DC–DC Converters
Abstract
Parallel-connected modular current-fed bidirectional DC–DC converters are used for the AC motor drive system powered by batteries with low voltage and wide voltage range. The input current ripple can be reduced significantly by employing interleaving technology not only for individual module but also for all the modules. A current-sharing control strategy is applied for the constituent modules. Double pulse width modulation plus double phase shifted control with equal duty cycles for one module can minimize the circulation loss and avoid non-active power issue. Factors affecting dynamic performance are investigated based on the small-signal modeling. The leakage inductance value is optimized in view of system reliability and better dynamic performance. Besides, to improve the dynamic performance further, feed-forward control employing optimized feed-forward coefficient based on the small-signal analysis is implemented. A 4 kW prototype composed of two bidirectional DC–DC converters is built to verify the effectiveness for the proposed control strategy in AC motor drive application with fast regenerative braking.
Deshang Sha, Guo Xu
Metadata
Title
High-Frequency Isolated Bidirectional Dual Active Bridge DC–DC Converters with Wide Voltage Gain
Authors
Deshang Sha
Guo Xu
Copyright Year
2019
Publisher
Springer Singapore
Electronic ISBN
978-981-13-0259-6
Print ISBN
978-981-13-0258-9
DOI
https://doi.org/10.1007/978-981-13-0259-6