Dual Active Bridge DC-DC Converter Research Articles

Modelling and compensation of dead time in three-phase dual-active bridge DC-DC converter

ABSTRACT With growing decentralized power generation, medium-voltage (MV) dc-dc converters are becoming increasingly important. A three-phase dual-active bridge (DAB3) is a promising topology for high-power MV applications. The semiconductor devices used in such converters at multi-megawatt level tend to be slow in switching. Hence, a considerable dead time between switching instants is required to avoid shoot-through in phase legs. This dead time forces the current to commutate to the freewheeling diodes and introduces a current dependence of the phase voltages. In this work, the effects of dead time on the operation of DAB3 are analysed in detail. The derived analytical expressions are used in the control development to compensate for the effects of dead time and hence achieve superior control performance. Measurements are carried out on a small-scale laboratory prototype to validate the derived operational modes and the effectiveness of the proposed dead time compensation.

A Simple Phase-Shift Modulation Using Parabolic Carrier for Dual Active Bridge DC–DC Converter

The power transfer of a dual active bridge (DAB) dc-dc converter is not linearly proportional to the phase shift between the two active bridges. When the DAB converter controller receives the power reference, the phase shift needs to be obtained by either solving a quadratic equation online or looking up from a table. The online calculation method is computationally inefficient. The lookup table method has only limited operating points. In addition, when using interpolation to find missing operating points from the table, the control accuracy will be reduced. This letter proposes a simple phase-shift modulation using a parabolic carrier. The proposed method converts the power command into phase shift by modulation. Therefore, the solving of the quadratic equation can be eliminated. The Verilog results are provided to verify the proposed parabolic carrier. A case study of DAB with sinusoidal ripple current charging concept is provided to demonstrate the advantage of the proposed method.

Optimal Strategy of Triple Phase Shift Transient DC Bias for Dual Active Bridge DC-DC Converter

Under the traditional phase shift control, dual active bridge DC-DC converter (DAB) has a transient bias on the inductance current when the phase shift ratio changes suddenly, which leads to increase in the current stress of switch tubes and even unidirectional saturation of the transformer. All those will affect the stable operation of the converter. This paper focuses on quantifying the transient DC bias model on the control of triple phase shift when phase shift ratios change, and then the strategy proposed by the paper can eliminate the DC bias within one switching period and reduce current stress and response time by adjusting the drive signal during the transient transition process. Finally, the proposed strategy is verified by simulation results from Matlab/Simulink software.

Robust Feedback Linearization Control for DAB Converter feeding a CPL

Cascaded converters are used to satisfy the different voltage levels that loads need. Instability problems in cascaded systems may occur due to the interaction of Point-of-Load (POL) converters. POL converters exhibit the important characteristic of almost-perfect regulation at the output terminals independent of the input perturbations. However, such characteristic reflects at the input terminal as a constant power load (CPL). CPL exhibits incremental negative resistance behavior causing undesired oscillations and a high risk of instability in interconnected converters. In this paper, the cascaded converter system consists of a Dual Active Bridge (DAB) DC-DC converter that maintains a regulated DC voltage on the intermediate bus and a POL DC-DC Buck converter that acts as a CPL. Aiming to ensure system stability and effectively mitigate oscillations effects in a cascaded system, this paper proposes a Robust Feedback Linearization Control to regulate the intermediate DC bus voltage. Simulation tests are performed by using a MATLAB/Simulink simulator to show the robustness and effectiveness of the proposed controller. The simulation results show that the proposed control approach ensures robust control performance and stability with a minor performance degradation compared to a Robust Control approach, Feedback Linearization Control approach, and Classical Control approach.

Improved TPS control for DAB DC–DC converter to eliminate dual‐side flow back currents

In this study, the essential reason for causing the dual-side flow back currents in the isolated dual active bridge (DAB) DC-DC converter is originally revealed first. It is because the polarities of the AC side output voltages of the two H-bridge converters in DAB converter are not able to be always kept the same as that of the inductor current in the conventional modulation strategies. An improved triple-phase-shift (ITPS) control is proposed according to the analysis results to ensure that the dual-side flow back currents are eliminated, and all of the power switches achieve soft switching in the entire power range. The detailed experimental results of the ITPS control validate its validity and feasibility.

Research on Transient DC Bias Analysis and Suppression in EPS DAB DC-DC Converter

During excitation and demagnetization phase for the superconducting magnet, in dual-active-bridge (DAB) converter based power supply, a dc bias may occur in high-frequency transformer and thus lead to the faults. In this paper, an improved transient extend-phase-shift (TEPS) control strategy is proposed to suppress the dc bias without any additional hardware. Unlike the traditional extend-phase-shift (EPS) strategy, the voltages of the transformer are asymmetrical for half a period after changing phase-shift and then remain symmetrical. This makes it take half a switching period for the current of transformer to reach the steady state, and then eliminates the dc bias. The experiment verifies the performance on dc bias suppression. This method provides a good theoretical and experimental basis for the EPS DAB DC-DC converter to realize the optimal control for excitation and demagnetization system in high-field superconducting magnet power supply (SMPS).

Leakage Inductor Current Peak Optimization for Dual-Transformer Current-Fed Dual Active Bridge DC–DC Converter With Wide Input and Output Voltage Range

A current-fed dual active bridge dc-dc converter using dual transformers is proposed for the energy storage system and electric vehicles, which is suitable to be used in wide input and wide output voltage range bidirectional power flow applications. Optimized switching pattern and the coupling relationship among all the controlled variables have been explored in order to minimize the leakage inductor current peak and rms value in spite of the load and voltage conversion gain variation, which can reduce the current stress in switches and conduction loss. Furthermore, wide ZVS range can be achieved. The preferred optimized working modes and real-time closed-loop implementation by employing the proposed control strategy are given. The ZVS conditions for each switch are discussed in detail. The turns ratio design is also demonstrated. The effectiveness of the proposed method is verified by the experimental results of a 1-kW prototype.

Performance comprehensive optimization of dual active bridge DC-DC converter based on triple phase shift control

Performance comprehensive optimization of dual active bridge DC-DC converter based on triple phase shift control

Operation of Current-fed Dual Active Bridge DC-DC Converters for Microgrid

Dual Active Bridge (DAB) is an isolated bidirectional DC-DC converter, which comprises two full bridge converters linked through a high frequency transformer. It has low stresses and permits high frequency performance because of the soft-switching. All the switches in the converter achieves the turn ON & OFF during Zero Voltage Switching (ZVS) and Zero Current Switching (ZCS) to minimize switching loss. Generally, DAB is classified as two types, namely, voltage-fed and current-fed variants. At light load conditions, soft-switching is not realized in case of voltage-fed DAB topologies. The application of current-fed DAB converters is to reduce the losses at the time of switching under light load conditions and improves the efficiency. This paper describes the various topologies of voltage-fed and current-fed DAB used for different applications in microgrid and fuel cell energy generation system by using the simulation. The performance of voltage-fed and current-fed DAB with snubber-less converters are also demonstrated and their effectiveness are validated.

Dual Active Bridge DC-DC Converter based Wide Dimming Range LED Driver With High-Speed Turn-Off for High-Brightness LED Floodlight

Dual Active Bridge DC-DC Converter based Wide Dimming Range LED Driver With High-Speed Turn-Off for High-Brightness LED Floodlight

Development of T-type Dual Active Bridge DC-DC Converter with Switching Operation Mode Over Wide-Voltage-Operation Range

Development of T-type Dual Active Bridge DC-DC Converter with Switching Operation Mode Over Wide-Voltage-Operation Range

Modeling and Optimization of Dual Active Bridge DC-DC Converter with Dead-Time Effect under Triple-Phase-Shift Control

Dead-time effect has become an apparent issue in high-switching-frequency high-power dual active bridge (DAB) DC-DC converter. This paper gives a detailed analysis of phase-shift errors effect caused by dead time, including output voltage offset, soft-switching failure, optimal scheme failure, etc. Phase-shift errors effect will invalidate traditional analyses of optimal control and mislead the design of DAB converter. To overcome these drawbacks, various operating modes and an accurate transmission power model incorporating dead time under triple-phase-shift (TPS) control are developed. On this basis, an optimal TPS incorporating dead time (TPSiDT) scheme is further proposed to minimize the current stress, while guaranteeing soft-switching operation by using Lagrange multiplier method (LMM) and Genetic Algorithm (GA). The novel transmission power model can provide accurate power flow computation to avoid phase-shift errors. Therefore, in practical applications, the minimum current stress and soft-switching operation can be guaranteed, and the efficiency of DAB converter can be improved. Finally, the experimental results verify the feasibility of the proposed TPSiDT scheme.

Circulating Current and ZVS-on of a Dual Active Bridge DC-DC Converter: A Review

Dual active bridge (DAB) dc-dc converters have several attractive features including auto-adjust bidirectional power flow, wide voltage gain range, and zero voltage switching (ZVS)-on capability. Various applications based on DAB including solid-state transformer in power grids and traction, energy storage system, and electric vehicle on-board chargers have been proposed by academics. Nevertheless, industrial applications based on DABs are still seldom mainly due to the circulating current and loss of ZVS problems under certain load and voltage gain conditions. There is an intensive research effort underway to solve these problems recently. This paper presents the state-of-the-art view in the cause of circulating current and loss of ZVS and surveys the solutions to these problems.

A Stability Analysis of Output Voltage Control for DAB DC-DC Converter with Discrete Time Model

This paper presents a stability analysis of a closed loop controlled dual active bridge (DAB) dc-dc converter. At first, a discrete time model of a DAB dc-dc converter considering dead time effects is developed. Then, the stability of the output voltage control for DAB dc-dc converter is analyzed. Finally, the theoretical results are verified with a circuit simulator.

Dual Active Bridge DC-DC Converter with Tunable Dual Pulse-Width Modulation for Complete Zero Voltage Switching Operation

Dual Active Bridge DC-DC Converter with Tunable Dual Pulse-Width Modulation for Complete Zero Voltage Switching Operation

A Comprehensive Optimization Control of Dual-Active-Bridge DC–DC Converters Based on Unified-Phase-Shift and Power-Balancing Scheme

This paper presents a comprehensive optimization control scheme to improve efficiency and dynamic response of dual-active-bridge (DAB) dc-dc converters. Unified-phase-shift (UPS) control is widely used to increase the efficiency of DAB dc-dc converters by minimizing the peak current, but dynamic performance of the converters needs to be further enhanced. In this paper, to gain superior dynamic performance of DAB dc-dc converters, an equivalent power-balancing (PB) model is employed, which is capable of predicting dynamic behavior of converter output voltages due to input voltage fluctuation and load disturbance. And then, combining the UPS control and the PB control, a comprehensive UPS and PB (UPS-PB) scheme is proposed to improve the efficiency and dynamic performance simultaneously. This work also includes the detailed inductance parameter sensitivity of the proposed UPS-PB scheme and a zonal voltage control strategy to further improve dynamic responses of the output voltage under the start-up process or a large step change of the output voltage reference. Moreover, the variant of UPS-PB scheme for constant power load is analyzed in the experimental part. Finally, experimental results have verified the excellent performance of the proposed UPS-PB scheme and correctness of theoretical analysis in this work.

Control Techniques of the Auxiliary-Resonant Commutated Pole With Special Regards on the Dual-Active Bridge DC-DC Converter

Control Techniques of the Auxiliary-Resonant Commutated Pole With Special Regards on the Dual-Active Bridge DC-DC Converter

Multi-Objective Optimization Control for the Aerospace Dual-Active Bridge Power Converter

With the development of More Electrical Aircraft (MEA), the electrification of secondary power systems in aircraft is becoming more and more common. As the key power conversion device, the dual active bridge (DAB) converter is the power interface for the energy storage system with the high voltage direct current (HVDC) bus in aircraft electrical power systems. In this paper, a DAB DC-DC converter is designed to meet aviation requirements. The extended dual phase shifted control strategy is adopted, and a multi-objective genetic algorithm is applied to optimize its operating performance. Considering the three indicators of inductance current root mean square root (RMS) value, negative reverse power and direct current (DC) bias component of the current for the high frequency transformer as the optimization objectives, the DAB converter’s optimization model is derived to achieve soft switching as the main constraint condition. Optimized methods of controlling quantity for the DAB based on the evolution and genetic algorithm is used to solve the model, and a number of optimal control parameters are obtained under different load conditions. The results of digital, hard-in-loop simulation and hardware prototype experiments show that the three performance indexes are all suppressed greatly, and the optimization method proposed in this paper is reasonable. The work of this paper provides a theoretical basis and researching method for the multi-objective optimization of the power converter in the aircraft electrical power system.

English

English

A Galvanic-Isolated Grid-Connected fuel cell single phase AC power generation system with LCL filter

Fuel cell system is a promising alternate way of power generation from clean, green fuel such as Hydrogen with almost zero emissions. It can be a primary power or an aiding power to the grid during instability. Grid connected fuel cell systems experience double line frequency ripples from the inverters which affect the life of fuel cells. The current ripples are to be limited within 15% for safe operation of the fuel cells. This paper presents design of a dual active bridge DC-DC converter to step up the low voltage DC output from fuel cell to a high voltage DC with galvanic isolation and a PLL based grid synchronized single phase PWM inverter with dq reference frame grid current control suitable for fuel cell systems. Extended Symmetrical Optimum method is used for optimal tuning of the PI controllers. An LCL filter is designed for effective ripple attenuation in the grid current with active damping of the resonance in the region of stability. MATLAB/Simulink ® is used for the design and is verified with a 1kW Horizon PEM fuel cell system. The power is exported to the grid with measured THD i of 1.7% in the grid current with reactive power injection by simple phase shift modulation control. The maximum overall system efficiency is measured to be 85%.