Three-phase dual active bridge (3p-DAB) dc-to-dc converters are typically avoided in low-power applications especially for wide voltage and power ranges. Even so, the 3p-DAB do offer a means to reduce filter costs and volume. The aim of this study is to propose the triangular and trapezoidal modulation for the 3p-DAB to address the problem of poor partial load efficiency. The proposed modulation schemes were compared with two conventional DAB concepts. It was found that the efficiency of the 3p-DAB increased substantially. Moreover, the 3p-DAB showed a considerably lower filter volume than that of the single-phase dual active bridge converter (1p-DAB). In conclusion, a modulation strategy combining the two proposed modulation schemes with the phase-shift modulation is ideal, because they boost efficiency and take most benefit from the inherent low filter volume. Ultimately, the three-phase dual active bridge may offer a promising solution to miniaturize galvanically isolated dc-to-dc converters for electric vehicles.

Enhanced Modulation Strategy for a Three-Phase Dual Active Bridge—Boosting Efficiency of an Electric Vehicle Converter

Full-order small-signal modelling and dynamic analysis of zero-voltage-switching (ZVS) phase-shift bidirectional DC-DC converters is studied. A general modelling method is proposed to develop the discrete-time average model. This full-order model takes into account the leakage inductance current and the resonant transition intervals in order to realise ZVS. Both the leakage inductance current and the resonant transition intervals are the key to accurately predict the dynamic behaviour of the converter. A control-to-output-voltage transfer function is derived for the dual active bridge DC-DC converter, which is taken as an example to illustrate the modelling procedure. Experimental results confirm that the new model correctly predicts the small-signal frequency response up to one-third of the switching frequency and is more accurate than the previously presented models.

Full-order averaging modelling of zero-voltage-switching phase-shift bidirectional DC-DC converters

This paper presents the configuration and control methods for a building block module suitable for application in a fully modular, AC-DC, DC-AC and DC-DC power conversion architecture, where the modules can be connected in any combination of series and parallel connections and support bidirectional power flow. The advantages of the proposed configuration, which is a combination of AC PWM full bridge stage and a dual active bridge based isolated DC-DC stage, are explained. The control implementations and average models of the building block module are discussed in detail. Analytical, simulation and experimental results are presented that confirm the feasibility of the fully modular power conversion approach with the proposed building block module.

Building Block Converter Module for Universal (AC-DC, DC-AC, DC-DC) Fully Modular Power Conversion Architecture

This paper presents predictive current-mode control for a single-phase high-frequency transformer-isolated dual-active bridge dc-to-dc converter. The predictive control algorithm increases the bandwidth of the current loop of the converter which enables tracking of the current reference within one switching cycle. The paper further demonstrates that the application of the predictive control algorithm can remove transient dc offset from the current in high-frequency isolation transformer within one switching cycle. Direct control of the converter current protects the transformer from saturation even at transient conditions. The control algorithm has been implemented on an experimental setup and transient tests have been performed to validate controller performance. Since the predictive control algorithm is dependent on the measured value of the leakage inductance of the transformer, a compensator has been implemented to improve the parameter insensitivity of the proposed controller.

A Digital Predictive Current-Mode Controller for a Single-Phase High-Frequency Transformer-Isolated Dual-Active Bridge DC-to-DC Converter

The dual active bridge (DAB) converter attracts more and more attentions thanks to its advantages over the other isolated dc-dc converters, such as soft-switching, immunity to parasitic inductance, less circuit components and less component stress. Rectangular (also named as phase-shifted) modulation method on DAB has been widely studied and but other two proposed modulations (trapezoidal and triangular methods) have much less applications. Due to the characteristics of the modulation principles, one of these three methods outperforms the other two in certain operating ranges from system efficiency point of view. This paper summarizes the properties of three modulation methods and optimizes the combined use of three modulations on a DAB converter (12V/360V, 1 kW and 25 kHz) in order to obtain the best system efficiencies over full converter operating range. A validated loss model is utilized as the analyzing platform, based on which the optimal operating ranges of three modulations are determined.

Mustansir Hussainty Kheraluwala

Papers

High-power high-frequency DC-to-DC converters