Direct Power Based Control Strategy for DAB DC-DC Converter With Cooperative Triple Phase Shifted Modulation

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 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.

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.

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.

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.

The dual active bridge (DAB) converter achieves relatively high efficiency and high power density. Therefore, it is widely used in ac–dc–ac converters to provide electrical isolation between the input and output. However, the single-phase converter inherently exhibits significant low-frequency voltage ripple in the DAB topology. Traditional control strategies focus on reducing voltage ripple and optimizing the capacitor size by transferring fluctuating power through the DAB converter. This method leads to higher magnetic component and switch currents, as well as a larger transformer size. To suppress these effects, this article proposes a constant power transmission (CPT) control for the DAB converter. The proposed CPT control dynamically adjusts the modulation width of each operating cycle by tracking the input–output voltage fluctuations in real-time through the control variables. This ensures constant power transfer in the DAB converter. Compared to traditional methods, the proposed control strategy reduces both the RMS and peak-to-peak values of the inductor current, thereby reducing the size of the converter and improving system efficiency. Simulation and experimental results confirm that the CPT control effectively reduces the peak-to-peak and RMS values of the inductor current by 40.7% and 18.8%, respectively, reduces the transformer size by 21.4%, and increases the efficiency by 1.1%.

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.

With some electrical advantages, such as high-power density and electric isolation, dual active bridge (DAB) dc-dc converter has been widely studied and applied for high power isolated dc-dc applications. However, as a converter with zero-value centered inductance current feature, the output power of DAB converter is coupled with circuit parameters, especially input voltage, which limits transferred power range. To weaken the coupling between output power and input voltage, a Buck-Boost DAB (B2DAB) dc-dc converter with large input voltage range is presented in this paper, and a hybrid control method combining direct power control for DAB dc-dc stage and peak-valley current control for Buck-Boost stage is proposed for fast dynamic performances. Finally, simulation results have verified the excellent performance of the B2DAB dc-dc topology and corresponding control strategy, and correctness of theoretical analysis in this work.

The small-signal approximations which are generally used in the DC-DC converters provide the limited range of operation which is around the steady-state point. However, if the ripples are large, this approximation is generally not true for which the generalized average modelling is better to capture the effects of other harmonic components along with the DC component. Here, the author has employed the generalized averaging technique including the input and output side parameters using the feedforward and feedback control on the dual active bridge converter. The inductor current is alternating and to capture the behaviour of system parameters, the generalized average modelling is done. It is found that the input parameter will also affect the overall dynamics and using MATLAB/Simulink tool the overall analysis is validated.

Dual Active Bridge (DAB) Converter and PushPull Converters are mainly used for Conversion of power with large cycles per second. Dual active bridge converter consists of couple of full bridge converters linked through a transformer. Two way power flow capacity, high power density, high proficiency, soft switching, less number of passive elements and galvanic separation are the important characteristics of DAB pulling in industry. The push-pull converter is utilized as DC-DC converters are reasonable for low and medium power application. High efficiency, low switching loss and high power density are the important characteristics of this converter. By increasing the switching frequency, it results in the reduction of complexity of the circuit. However the switching loss increases as the switching frequency is increased. In this paper, the study is focused on a comparative analysis of DAB converter and Push-Pull converter.

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.

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.

This article proposes a single-stage three-phase AC-DC converter composed of a SWISS converter and two Dual Active Bridge (DAB) converters connected in parallel at the output. The input current relationship between the SWISS and DAB converters is analyzed, and the optimal triple-phase-shift (TPS) control of the DAB converter is introduced to achieve the unity power factor for the entire load power. Under optimal TPS control, zero voltage switching (ZVS) and minimal current stress can be achieved. Based on the optimal working modes of TPS control, the analytical expression is derived to describe the relationship between the phase-shift angle and the input current of the DAB converter. A dual-loop control strategy is proposed to achieve good power quality and output regulation. The ranges of working modes and the control variables under different load power conditions are analyzed, demonstrating the adaptability of this strategy to a wide range of load powers. The design of the series inductor and the calculation of losses are discussed, and the loss distribution under different power conditions is presented. Finally, the proposed control strategy is applied to a 1.6 kW three-phase single-stage DAB-based SWISS converter with 200V/50Hz input line voltage and 200V output voltage. The experimental results validate the feasibility and effectiveness of the control strategy.

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.

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.