Dual Active Half Bridge Research Articles

Design and Optimization of High-Gain Bidirectional DC–DC Converter for Electric Vehicles

To better leverage and cope with the characteristics of low-voltage electric vehicle battery pack, this work optimizes the design of on-board bidirectional DC/DC converter. Based on the dual active half-bridge (DAHB) converter, combined with partial switch sharing, a high gain bidirectional DC/DC converter is proposed. This converter has 48-V and 24-V output voltage levels, and the multiple voltage levels, which are often required by new energy vehicles, are able to reduce the number of on-board converters. The theoretical part of this work analyzes the design process of the converter, and in parallel, establishes the mathematical models of transmission power, soft switching, current stress and reactive backflow loss. Under the condition of high gain, the system has good soft switching characteristics and low reactive backflow loss. In the experimental part, a prototype with an input voltage of 400V is built under an operating frequency of 100 kHz. The voltage of the two output ports is stable and a peak efficiency of 94.7% is achieved. The experimental results verify the validity of the theoretical analysis.

A Low-Cost Battery-Balancing Auxiliary Power Module With Dual-Active Half Bridge Links and Coreless Transformers

Redistributive balancing brings many benefits to electric vehicles, such as increased range and more uniform cell degradation. Despite previous analyses suggesting a 17-36% extension of battery lifetime, the cost of such systems has prevented the technology from being adopted in practice. This study proposes a simplified topology for battery-balancing auxiliary power modules with reduced magnetic material to achieve cost-friendly solutions without sacrificing functionality or balancing modes. The proposed system consists of a dual-active half bridge, halving the number of switches needed compared with the conventional dual-active bridge. In addition, the transformer core material is removed and a coreless transformer is used to provide isolation and energy transfer. Both changes reduce the cost of redistributive balancing. The topological modeling differs from cored transformer circuits as the coupling of the coreless transformer is weaker. The coupling coefficient is now used in an updated model that includes transformer currents and output powers. These, along with the balancing modes, are analyzed then experimentally verified. The proposed models can guide the selection of MOSFETs and the design of the coreless transformer. An analytic projection shows up to a 22% cost reduction compared with similar topologies.

A Closed-Loop High-Frequency Current Shaping Method to Achieve Trapezoidal Transformer Current in a Current-Fed Dual Active Half-Bridge Converter for Minimum RMS Current and Wide-Range ZVS

This article proposes the use of primary and secondary side duty ratio control along with the phase shift control in a current-fed dual active half-bridge (DAHB) converter to achieve trapezoidal transformer current, which results in zero voltage switching (ZVS) of all the switches and minimum rms current even at light loads, for a wide range of input voltage. The high-frequency transformer current is directly sensed at specific transition instants by a delay-adjusted sampling strategy to be used as control variables in a current control structure. This is better because the voltage control of capacitor voltages would have required more expensive sensors. A simple and accurate small-signal model of the converter is developed, and the relevant transfer functions are derived. The controller design details are provided. Finally, experimental results on a 1-kW laboratory prototype demonstrate the effectiveness of the closed-loop duty ratio control in achieving trapezoidal transformer current resulting in improved efficiency and ZVS of the switches, compared to a simple phase shift control.

Half-Bridge Lithium-Ion Battery Equalizer Based on Phase-Shift Strategy

The energy flow is step-by-step among Lithium-ion-battery when an equalizer based on the buck-boost converter is adopted, resulting in a long energy transmission path and low equalization efficiency. First, a Lithium-ion-battery equalizer based on the dual active half-bridge is studied in this paper. Second, the key parameters of the energy flow between cells in the same group and cells in different groups in the equalizer are analyzed. Third, a phase shift control strategy is put forward according to the analysis results. The equalizer with the proposed control strategy not only can realize the energy flow between cells in the same group and different groups but also work at high frequency. Therefore, the transformer can be designed to be small in size and light in weight, greatly reducing the volume and weight of the equalizer. A prototype of the dual active half-bridge equalizer with four lithium batteries was managed. The experimental results show that the proposed Lithium-ion-battery equalizer based on phase shift control has good equalization performances.

Dual-Active-Half-Bridge Converter With Output Voltage Balancing Scheme for Bipolar DC Distribution System

Conventional dual-active-bridge dc–dc converters require a dedicated voltage balancer or feedback control when they are used for a bipolar LVdc distribution system. This article proposes a dual-active-half-bridge (DAHB) converter with voltage balancing. The proposed converter is composed of a conventional DAHB converter with an additional inductor and capacitor voltage balancer (LCVB). The LCVB is added between the transformer and the output of the DAHB converter. Although the LCVB increases the switch current, it can balance the two output voltages without additional active switching device and feedback control under unbalanced load conditions. In addition, compared with the conventional DAHB converter, the LCVB can increase the zero-voltage-switching range of the DAHB converter and has no detrimental effect on the operation modes and performances. A 2.8-kW prototype was built and tested to verify the performances of the proposed converter.

Minimum current stress operation of dual active half-bridge converter using triple phase shift control for renewable energy applications

With the development of renewable energy, dual active half bridge (DAHB) has been widely used in renewable energy systems. For the purpose of reducing the damage caused by excessive current stress and improve the operation performance of the DAHB, this article proposes an optimized strategy of minimum current based on the Karush–Kuhn–Tucker (KKT) method. The expressions of current stress corresponding to each mode are analyzed through mathematical derivation. Then the optimal solution of duty ratios are solved through KKT method. The proposed strategy decreases the current stress and improves the operation conditions compared to conventional single phase shift (SPS) and dual phase shift (DPS). Finally, simulation results conducted to validate the effect of proposed strategy.

Bidirectional EV charger with ancillary power quality capabilities

This paper presents a bidirectional electric vehicle (EV) charger with ancillary power quality (PQ) capabilities in grid-to-vehicle (G2V), vehicle-to-grid (V2G) and vehicle-to-home (V2H) applications. The proposed configuration consists of a five-level (5L) neutral point clamped (NPC) converter in cascaded with a dual-active half bridge (DAHB) DC-DC converter. The proposed cascaded control strategy used for regulating the common DC bus voltage as well as for compensating the grid current harmonics and the reactive power through the 5L-converter is based on a performant proportional-resonant (PR) compensator. By applying the single-phase-shift (SPS) technique to the DAHB converter, the battery power flow is accurately regulated. A detailed study with exhaustive tests and simulation results obtained in MATLAB-SimPowerSystems for a full-scale power system based on a Nissan Leaf´s battery validate the fairly good performance of the proposed configuration and control strategies. The main achievements of this work are: 1) the system’s stability is maintained even during fairly abrupt changing conditions, 2) in steady state of the G2V/V2G operation modes, the total harmonic distortion (THD) of the grid current remains below 3% while the power factor (PF) is kept at unity, 3) the reactive power demanded from the grid is zero in spite of feeding a highly nonlinear load, and 4) when a power outage occurs, the transition to the V2H mode is seamless and the home load is uninterruptedly supplied with a very low-distortion output voltage from the 5L-converter.

Hybrid Input-Series–Output-Series Modular DC–DC Converter Constituted by Resonant and Nonresonant Dual Active Bridge Modules

Possessing the capability to handle high voltage, the bidirectional input-series–output-series (ISOS) modular dc–dc converter is suitable for use in dc grids. Regarding topology selection of the constituent modules, the open-loop controlled series-resonant dual active bridge (SR-DAB) converter exhibits superior efficiency performance and the advantage of simple control. However, it has no regulation capability. Aimed to reap the advantages of SR-DAB and achieve flexible control, this article presents a hybrid ISOS converter composed of SR-DAB and nonresonant phase-shift controlled dual active bridge (PS-DAB) modules. The SR-DAB modules process most of the power to ensure high-efficiency conversion, whereas the PS-DAB is responsible for flexible control. At the output stage of the ISOS system, embedded nonisolated resonant dual active half-bridge (NR-DAHB) converters are integrated between every two adjacent modules without adding any switches. The transformer property of the open-loop controlled SR-DAB and NR-DAHB circuits facilitates natural voltage sharing at both the input and output sides. The hardware experiment has been conducted to verify the operating principles and performance of the proposed ISOS system.

Scalable architecture of DC microgrid implemented with multi‐input multi‐output converter

In this study, modelling, implementation, and control of a hybrid renewables-based, scalable DC microgrid using multi-input multi-output dual active half-bridge (DAHB) converter is presented. The proposed microgrid architecture exhibits superiority and enhanced functionality in comparison to the existing conventional architectures in terms of the reduced number of converters for each resource integration, modularity, scalability, and bidirectional power flow capability, and local maximum power point tracking for each renewable resource. The proposed architecture is significant in terms that only a single converter is responsible for the whole operation of the DC microgrid. A dual half active bridge acts as a central hub for power processing while multiple renewable energy resources can be integrated through isolated input and output ports. The proposed microgrid is analysed for power flow, and the control scheme for different voltage and power-sharing scenarios is designed. The proposed architecture of the microgrid is simulated on the Power-SIM simulator, and a simplified hardware prototype is implemented in the laboratory with satisfactory results.

Design of an Isolated Bidirectional DC–DC Converter With Built-in Filters for High Power Density

This article aims to realize an isolated dc-dc converter with high power density, high power efficiency, and low noise performance. Although a dual-active-half-bridge (DAHB) converter can achieve high efficiency, it requires input and output low-pass filters to suppress the operational ripple current and switching noise. Owing to the volume of the filters, a DAHB converter cannot be implemented with high power density. This article presents a design theory for a novel isolated bidirectional dc-dc converter with built-in filters. The proposed converter is derived from a DAHB converter and can eliminate the input and output filters via split windings and tank capacitors; the principle of elimination is based on LC low-pass filter function and zero-ripple-current operation. As the number of transistors, capacitors, and magnetic cores of the proposed converter are equal to those of the DAHB converter, the application of the proposed converter allows volume reduction by eliminating the filter components at the input and output ports. Theoretical equations are derived to design a power flow control function and a filter function simultaneously. Finally, prototypes of a DAHB converter and the proposed converter are constructed for comparison. The results demonstrate that the input port noise of the proposed prototype is lower than that of the DAHB prototype by 10 dB (peak) over 1 MHz, and the proposed approach can achieve a significant improvement in efficiency.

A Unified State-Space Modeling Method for a Phase-Shift Controlled Bidirectional Dual-Active Half-Bridge Converter

In certain applications of phase-shift (PS) controlled dual-active half-bridge (DAHB) extended dc–dc converters, the duty cycle is not fixed at 50%. The existing state-space modeling methods are only suitable for modeling such a converter in two PSs directions separately, which results in a positive-PS model and a negative-PS model. This is inconvenient for study the converter operation where the PS direction changes online, such as in the energy storage applications. Hence, a unified approach is very desirable to include the two PS directions into a single model. However, this is very challenging for non-50% duty cycle. The current-fed dual half-bridge (CF-DHB) converter is one typical example of such converters. For the CF-DHB converter, this article proposes an approach for the bidirectional PSs unification. The approach is named the ‘conjugate PSs superposition technique.’ A basic modeling method is also proposed based on the approach. A single model built by the method can be utilized for both positive and negative PSs, even with a non-50% duty cycle. A large-signal model and a small-signal model are established. Simulations and experiments are used to validate the PSs unification approach and the modeling method.

Analysis, Design, and Implementation of DC–DC IBBC-DAHB Converter With Voltage Matching to Improve Efficiency

The interleaved bidirectional buck–boost converter dual active half-bridge (IBBC-DAHB) dc–dc converter consists of two converters IBBC and DAHB and a coupled inductor. The IBBC-DAHB converter has significant features such as low ripple current at the low-voltage side, low current stress on the input inductors, voltage stress across the switches less than the high-voltage side, high voltage gain, and zero-voltage soft switching. The converter offers high efficiency using phase-shift modulation when it operates at a nominal design operating point. However, the efficiency decreases due to high circulating current, high current stress, and limited soft-switching range when the source and load voltages deviate from their nominal values. This paper employs both duty cycle and phase-shift modulation methods to improve the above mentioned shortcomings using voltage matching for the DAHB converter. The proposed converter is analyzed and a 500-W experimental prototype with 40–60 V input voltage and 400 V output voltage under 100 kHz switching frequency is implemented to verify the theoretical results. The maximum efficiency of 97.15% is achieved at 60 V and 400 W. A flat efficiency characteristic for the converter is derived by the proposed control method, where the efficiency at 20% of nominal load is 91% and much higher than the phase-shift control, which is 70.8%.

Fully ZVS, Minimum RMS Current Operation of the Dual-Active Half-Bridge Converter Using Closed-Loop Three-Degree-of-Freedom Control

This paper discusses how duty ratios of the primary and secondary half-bridge legs of a dual-active half-bridge converter can be used in conjunction with phase-shift control to operate the converter with the least possible transformer rms current at a given power. Following introduction of all possible operational modes arising due to such three-degree-of-freedom control, results from a numerical-optimization-based approach are used to identify the best mode. Using information gleaned from careful observation of simulation results corresponding to the minimum current trajectory in this mode, key insights regarding circuit conditions to be satisfied for optimal operation are obtained. This information is used to propose the framework of a 3-D modulation strategy, which results in globally minimum rms current operation and is remarkably also found to satisfy the necessary conditions for zero-voltage-switching operation of all devices. The proposed strategy is implemented through closed-loop control and, hence, does not have the demerits associated with a lookup-table-based approach involving offline precomputation of optimal duty ratios. Simulation and experimental results on a 625-W laboratory prototype demonstrate the significant efficiency advantages of the proposed modulation scheme compared to simple phase-shift (1-D) control or 2-D asymmetric control, particularly at light loads in applications with widely varying voltage ratios.

Power Supply Redundancy Design of Aircraft's Electric Braking Electro-Mechanical Actuation System

In this paper, a power source redundancy-optimization approach for aircraft electrical brake electromechanical actuation system was proposed. The PWM plus phase-shift (PPS) control method was introduced in Dual active half bridge, which limited the amplitude of transform's leakage inductance current, thus expanding the fluctuation range of input voltage. Then, the voltage gain formula was deduced. By analyzing the leakage current under different phase shift in one period, the average power and root-mean-square (RMS) value of leakage current can be compared. Then, the optimum modulation range of phase shift can be obtained. By analyzing the soft-switching operation in this range, all switches can realize zero-voltage-switching (ZVS). To ensure the output voltage stability and voltage balance across the leakage inductance, a closed loop control method is designed. Finally, a prototype of 28V/270V-1kW was built to verify the theoretical analysis and calculation.

Minimum-RMS-Current Operation of Asymmetric Dual Active Half-Bridge Converters With and Without ZVS

This paper presents a comprehensive steady-state analysis of asymmetrically operated dual active half-bridge (DAHB) dc–dc converters, i.e, DAHB converters operated with a non 0.5 duty-ratio. Such asymmetric operation presents an additional control handle, which may be used to optimize converter performance. The different possible modes of operation are introduced followed by detailed analysis of active power and rms current variation and zero-voltage-switching (ZVS) performance in each mode. Using this information, closed-form expressions corresponding to two control strategies are derived which minimise rms value of transformer current at a given power with and without ZVS operation. The accuracy of the theoretical predictions are verified using numerical optimisation approaches and also through matlab Simulink-based simulations. Finally, experimental results on a 625 W laboratory prototype are presented which validate the discussed ideas. Both simulation and experimental results indicate that the proposed strategies potentially offer significant efficiency advantages compared to simple square-wave control, especially under light-load conditions for converters operating with nonunity effective voltage conversion ratios.

High Step-Up/Step-Down Soft-Switching Bidirectional DC–DC Converter With Coupled-Inductor and Voltage Matching Control for Energy Storage Systems

A soft-switching bidirectional dc–dc converter (BDC) with a coupled-inductor and a voltage doubler cell is proposed for high step-up/step-down voltage conversion applications. A dual-active half-bridge (DAHB) converter is integrated into a conventional buck-boost BDC to extend the voltage gain dramatically and decrease switch voltage stresses effectively. The coupled inductor operates not only as a filter inductor of the buck-boost BDC, but also as a transformer of the DAHB converter. The input voltage of the DAHB converter is shared with the output of the buck-boost BDC. So, PWM control can be adopted to the buck-boost BDC to ensure that the voltage on the two sides of the DAHB converter is always matched. As a result, the circulating current and conduction losses can be lowered to improve efficiency. Phase-shift control is adopted to the DAHB converter to regulate the power flows of the proposed BDC. Moreover, zero-voltage switching (ZVS) is achieved for all the active switches to reduce the switching losses. The operational principles and characteristics of the proposed BDC are presented in detail. The analysis and performance have been fully validated experimentally on a 40–60 V/400 V 1-kW hardware prototype.

Common-Duty-Ratio Control of Input-Parallel Output-Parallel (IPOP) Connected DC–DC Converter Modules With Automatic Sharing of Currents

Input-parallel output-parallel (IPOP) connected converter systems allow the use of low-power converter modules for high-power applications, with interleaving control scheme resulting in smaller filter size, better dynamic performance, and higher power density. In this paper, a new IPOP converter system is proposed, which consists of multiple dual-active half-bridge (DAHB) dc-dc converter modules. Moreover, by applying a common-duty-ratio control scheme, without a dedicated current-sharing controller, the automatic sharing of input currents or load currents is achieved in the IPOP converter even in the presence of substantial differences of 10% in various module parameters. The current-sharing performance of the proposed control method is analyzed using both a small-signal model and a steady-state dc model of the IPOP system. It is concluded that the equal sharing of currents among modules can be achieved by reducing the mismatches in various module parameters, which is achievable in practice. The current-sharing performance of the IPOP converter is also verified by Saber simulation and a 400-W experimental prototype consisting of two DAHB modules. The common-duty-ratio control method can be extended to any IPOP system that consists of three or more converter modules, including traditional dual-active bridge dc-dc converters, which have a characteristic of current source.