Feedback and Feedforward Control of Dual Active Bridge DC-DC Converter Using Generalized Average Modelling

This paper discusses an expansion method of zero voltage switching (ZVS) operation range in a dual active bridge (DAB) dc-dc converter using a three-level neutral-point-clamped (NPC) inverter topology. A DAB converter consists of two active bridges connected through a high-frequency transformer. A drawback of a conventional DAB converter is that ZVS operation range is limited. This paper presents a novel control strategy for the proposed DAB converter using a three-level NPC inverter to expand the range of the conventional ZVS operating mode. In addition, the effectiveness of the proposed scheme for the DAB converter is verified through simulations and experiments.

This paper proposes a unified phase shift control strategy for optimized transient current response of dual active bridge (DAB) dc-dc converters. Conventional phase shift control for DAB converters may cause dc offset in the high-frequency-link inductor current during transients, which may lead to magnetic flux saturation and excessive current stress on the switching devices. The proposed phase shift method can eliminate the transient current offset during both unidirectional and bidirectional power flow changes in a unified form. Experimental results are provided to verify the theoretical analysis.

Compared to single-phase dual active bridge (1p-DAB) DC-DC converters, three-phase dual active bridge (3p-DAB) DC-DC converters have advantages such as high single machine power, high power density, small filtering capacitance, and are more suitable for high-voltage situations. Therefore, they have good application prospects in DC transmission and industrial high-power DC-DC converters. However, under traditional single-phase shift (SPS) control, especially in the low power range, there is a large reactive current and severe soft switch loss. This article adopts an asymmetric modulation strategy for its larger reactive power, which reduces its reactive power in the low power range with more degrees of freedom and improves the efficiency of power transmission. Taking current stress as the optimization objective, the KKT algorithm is used to solve, and the corresponding analytical solution is ultimately obtained. Finally, a simulation is built by using MATLAB software to verify the feasibility of the proposed solution.

Aimed at the input parallel and output parallel (IPOP) dual-active bridge (DAB) dc-dc converters, this paper proposes an unbalanced-power-distribution scheme (UPDS) that considers the practical parameter deviation between DAB converters for minimizing the total backflow power. Firstly, combined with the characteristics of extended-phase-shift (EPS) control, the popular balanced-power-distribution scheme (BPDS) cannot achieve minimum backflow power due to the parameter deviation. In this regard, UPDS is established by detailed mathematical derivation, dividing the system operation into three sections. Simulation model and two-parallel DAB converters protype were built, and the results substantiated the validity of the theoretical analysis and the effectiveness of the proposed method.

The dual active bridge (DAB) converter is widely used in different fields, such as electric vehicles, distributed power generation system, energy networks. it also can be introduced in railway applications to implement power electronic transformers, bidirectional battery chargers etc. The DAB converter is usually designed combining with series resonant to reduce the switching off loss. Nevertheless this will make it hard to achieve the zero voltage switching on of the primary power semiconductor at light load, especially when voltage conversion ratio is far away from one. Besides, the dead-time has great effect to the soft switching implementation. The voltage polarity reversal and voltage sag phenomena etc. are caused by the dead-time effect. This paper provides a precise mathematical transmission power model considering the resonant and dead-time effect respectively. A comprehensive theoretical analysis of the dead-time effect on the series resonant DAB converter is presented. By improving the dead-time, the soft switching rang is increased and the efficiency will be improved at light load. The experimental results are provided to verify the theoretical analysis.

The dual active bridge (DAB) DC-DC converter is the core link of a power electronic transformer (PET). With the development of PETs toward medium- and high-voltage applications, more DAB modules are adopted. However, conventional Electromagnetic Transient (EMT) simulation for a multi-switch circuit is quite time consuming. In this paper digest, a modified constant admittance method has been developed for modeling of an isolated DAB. By reducing the expense of admittance matrix reconstruction and related iterative operation at switching instant, the simulation efficiency has been improved significantly, and the new model becomes more suitable for a real-time simulation algorithm. Meanwhile, time domain simulations are given, which show that the proposed method can keep the same accuracy as the conventional model.

Dc-dc converters can be found in different kinds of electric vehicles (EVs), Their main function is to accommodate voltages and currents to the motor or other EV systems requirements. The use of wide-bandgap (WBG) devices can improve the efficiency of silicon-based power converters, qualifying also for higher switching frequencies. In this article the features of a dual active bridge (DAB) converter are studied. The high voltage side of the DAB is implemented with Silicon Carbide (SiC) MOSFETs. For the low voltage side two types of devices are used: either Gallium Nitride (GaN) enhancement high-electron-mobility transistors (e-HEMTs) or SiC MOSFETs. The influence of switching frequency and output power on the efficiency are evaluated. The parallel connection of GaN devices is proposed to overcome the device current limits and thus increase the overall DAB converter output power. A feedback controller has been designed to reduce the effects on the output voltage of load changes. The DAB converter evaluation has been realized by using MATLAB/Simulink and PLECS software.

This paper presents the design of new highfrequency transformer isolated bidirectional dc-dc converter modules connected in module-cascaded solid state transformer (SST). A phase-shift dual active bridge (DAB) converter is employed to achieve high-frequency galvanic isolation, bidirectional power flow, and zero voltage switching (ZVS) of all switching devices, which leads to low switching losses even with high-frequency operation. Bidirectional DC-DC converter is crucial to the power transmission in SST. The proposed DAB converter consists of two three-leg bridges and a high-frequency transformer with winding shunting taps. Furthermore, the commutation inductance connected in series with the transformer in the conventional DAB converter is integrated into the transformer windings, thus, enjoying smaller volume and higher power density. By changing the number of primary winding turns, leakage inductance, which is the key parameter in the energy transfer process of DAB converter, can be adjusted on a large scale, enabling the possibility of reducing loss over wide load range. Additionally, time-sharing circuit topology and operation mode are adopted to adapt to the output power by detecting the output current as the feedback. As a result, the efficiency at both light and heavy load can be significantly improved compared with the conventional DAB converter, and, therefore, high efficiency over wide load range and high power density can be achieved. Besides, the additional bridge arm structure along with a flexible control scheme provides possible high-level fault tolerance. Finally, the simulation results on a 2-kW DAB converter module switching at 10kHz are presented to validate the theoretical analysis.

DC-DC Dual Active Bridge (DAB) converters can potentially be used as an interface between DC micro-grids and battery packs of PHEVs/EVs. This paper focuses on presenting a new method to achieve Zero Voltage Switching (ZVS) for all the switches in DAB converters. This is done by initially extracting the ZVS criteria, which corresponds to different operating conditions (bus voltage and power level). Then, a Look-Up-Table (LUT) is created that is compliant with the derived ZVS region. The LUT can be used in the control system of DAB converters to achieve ZVS for a wide range of operating conditions. Simulation and Experimental results are provided to validate the effectiveness of the proposed method.

Recently, the bi-directional dc-dc converter has been focused on because of the huge demand for diversification of power supply network including battery. The dual active bridge (DAB) dc-dc converter is one of the most popular circuits for bi-directional applications because of its simple structure. However, power efficiency at light load is the intrinsic problem of a bi-directional DAB DC-DC converter. In this paper, the simple solution with digital operation for the problem is proposed and experiments are performed with 1kW system. This method can reduce a switching surge without other circuits such as snubber and improve power efficiency at light load. Therefore it can reduce loss of switching surge, and improve power efficiency. From the results, 37% maximum power efficiency improvement at light load is confirmed. Furthermore, this method is capable for control in the conventional method in the heavy load range. Consequently, it is possible to reduce the switching surge and realize high power efficiency in a wide load range.

This paper proposes a practical and economically viable MVDC bidirectional DC-DC isolator required for interface of grids to Microgrid (MG), MG to MG and integration of large scale renewable energy sources to the grid. The proposed MVDC bidirectional isolator can also be used in MVDC to HVDC series/parallel taps and other MV interconnections that need galvanic isolation. Dual active bridge (DAB) DC-DC converter based isolator is a suitable solution for achieving isolation and bidirectional power flow in medium voltage applications. Three level, three phase DC-DC converter topology with series connected Gen 3 10kV SiC MOSFETs is used to implement the proposed DAB converter to obtain a 24kV DC bus. The design specifications of proposed DAB converter is described in detail. Large signal modelling for the three level and three phase DAB converter with a non-linear transformer model is presented. Finally, experimental results for a single phase half bridge DAB and full Bridge DAB converter operating at 2.5kV DC bus is presented.

The cooperative triple-phase-shifted modulation (CTPS) for the isolated dual-active bridge (DAB) DC-DC converter has the advantages of zero dual-DC side flow back currents and best current characteristics. However, the mathematical model and corresponding closed-loop control configuration of the DAB converter driven by CTPS are not presented so far. In order to solve this problem, in this paper, the average state space model of the DAB converter driven by CTPS is established for the first time. It is proven that the DAB converter driven by CTPS is a zero-order system and it is not necessary to construct an inner inductor current closed-loop control loop in the entire closed-loop control configuration of DAB converter. Furthermore, the average power model is derived. Two control strategies based on the resulted average power model when the DAB converter is connected to DC microgrid or a pure resistive load are proposed to realize the precise control of the transfer power or the output voltage, respectively. The detailed experimental results verify the correctness of the established mathematical model and the closed-loop control strategies.

This Dual-phase-shift (DPS) mode of operation can significantly increase the effectiveness of an isolated bidirectional DC-DC converter when compared to typical single-phase-shift control. This paper discusses the power flow and their relation with the phase shift ratios and condition for maximum power transfer. Detailed switching characteristics of dual active bridge DC-DC converter under dual phase shift mode of operation is discussed. The dual-phase-shift control technique gives two degrees of freedom i.e. inner phase shift and outer phase shift ratio when it comes to controlling the transmitting the power and developed voltage across the load and improving the dual active bridge converter's performance. The model of converter under dual phase shift mode is simulated in MATLAB SIMULINK.

This study proposes an optimization approach based on metaheuristic algorithms to improve the control performance of a bidirectional dual active bridge (DAB) DC-DC converter. DAB converters are widely preferred in many applications due to their high efficiency, flexible control, and bidirectional power transfer capabilities. However, accurate determination of controller parameters is critical for achieving efficient energy transfer and minimizing losses. In this study, the DAB converter is controlled using proportional-integral (PI) and fractional-order proportional-integral (FOPI) controller structures. The controller parameters are optimized using Dandelion Optimization (DO), Particle Swarm Optimization (PSO), and Grey Wolf Optimization (GWO) algorithms, with the Integrated Time-Weighted Absolute Error (ITAE) employed as the objective function. In addition, the effects of circuit parameter selection on system efficiency are investigated. The results provide a comparative evaluation of the three algorithms and confirm the effectiveness of metaheuristic optimization in improving DAB converter control performance, contributing a comprehensive perspective to the existing literature.

This paper proposes a transmission power error compensation method for a Dual Active Bridge (DAB) converter with a three-level operation when a DC-bus is varied. The nonlinear transmission power error due to a dead-time is compensated by designing a zero current period to be longer than the dead-time using the three-level operation because the nonlinear transmission power error occurs when an inductor current reaches zero during the dead-time. The proposed method adjusts a zero-voltage period according to the variable DC-bus voltage in order to design the zero current period for compensating the non-linear transmission power error. In addition, the three-level operation is controlled to reduce a circulating current in order to reduce RMS value of the inductor current. The validity of the proposed method is confirmed by a 1.9-kW prototype. As the experimental results, the transmission power error is reduced from 49% to 3.5%.