This article classifies, describes, and critically compares different modeling techniques and control methods for dual-active-bridge (DAB) dc–dc converters and provides explicit guidance about the DAB controller design to practicing engineers and researchers. First, available modeling methods for DAB including reduced-order model, generalized average model, and discrete-time model are classified and quantitatively compared using simulation results. Based on this comparison, recommendations for suitable DAB modeling method are given. Then, we comprehensively review the available control methods including feedback-only control, linearization control, feedforward plus feedback, disturbance-observer-based control, feedforward current control, model predictive current control, sliding mode control, and moving discretized control set model predictive control. Frequency responses of the closed-loop control-to-output and output impedance are selected as the metrics of the ability in voltage tracking and the load disturbance rejection performance. The frequency response plots of the closed-loop control-to-output transfer function and output impedance of each control method are theoretically derived or swept using simulation software PLECS and MATLAB. Based on these plots, remarks on each control method are drawn. Some practical control issues for DAB including dead-time effect, phase drift, and dc magnetic flux bias are also reviewed. This article is accompanied by PLECS simulation files of the reviewed control methods.

In a dual active bridge (DAB) dc-dc converter, modulating the phase shift ratios can suppress reactive power and increase efficiency under non-unity voltage gain conditions. Derivation of the optimal shift ratios to achieve the minimum reactive power is challenging as a DAB can operate in four different scenarios (forward/backward, buck/boost) and each scenario has five operating modes. This paper firstly introduces a transformation that different DAB operating scenarios (forward/backward, buck/boost) can be equivalent to each other, then only optimization of one scenario (forward/buck) is required. Next, for the five modes in forward/buck scenario, based on a graphical method, this paper proves that each operating point of Mode 1, 2 and 5 can be mapped into that of Mode 3 with lower conduction losses, and only two modes (Mode 3 and 4) require detailed analysis. The optimization process of these two modes are derived step by step. Global optimal phase shift signals that minimizing the reactive power under four different DAB operating scenarios (forward/backward, buck/boost) are presented. A simple table and control block diagram are presented for practical implementation of global reactive power minimization control. Experimental comparison with other modulation schemes verifies the efficiency improvement of the proposed control method.

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.

Pulsed-Power-Loads (PPLs) are becoming more common in medium-voltage naval DC micro-grids. To reduce their impact on the electrical system, energy storage elements can be installed. For optimal performance the interface converters need to have fast dynamics and excellent disturbance rejection capabilities. Moreover, these converters often need to have a voltage transformation capability and galvanic isolation since common energy storage technologies like batteries and super capacitors typically operate at relatively low voltages. In order to address these issues a Dual-Active-Bridge converter with a Moving Discretized Control Set Model Predictive Control (MDCS-MPC) is proposed in this paper. The controller has a fixed switching frequency, which allows straightforward filter design. The operating principles of the MDCS-MPC are introduced in this paper with the development of a cost function that provides stiff voltage regulation. Resonance damping and sampling noise resistance have been achieved by an adding additional term in the cost function. This paper presents an assessment of the performance of the proposed MDCS-MPC and comparisons with other control methods. Experimental validation from a 300V/300V 20kHz 1kW Dual-Active-Bridge converter are also presented to verify the theoretical claims.

A three-phase modular multilevel dc-dc converter is proposed and analyzed for power electronic transformer (PET) applications. Similar to a dual active bridge converter, the proposed converter comprises two three-phase inverters/rectifiers, coupled via a medium frequency (MF) transformer. The modular multilevel converter structure is used in the medium-voltage side to meet the high-voltage requirements and to reduce the dv/dt stress on the MF transformer. The frequency of the voltage through MF transformer (isolation frequency) is the same as the switching frequency of the power semiconductor devices, and zero-voltage switching-ON can be achieved for all the devices. With only one three-phase MF transformer, the proposed topology can greatly simplify the transformer design compared with the existed input-series output-parallel dc-dc converter structures for PET applications. A dual-phase-shift method is presented to control the output power and to balance the submodule capacitor voltages. Simulations and experimental results are provided to validate the theoretical analysis.