Abstract
The isolated dc-dc converters with middle inductive AC links dc-dc converter have been extensively studied in modern energy conversion applications for safety and reliability, especially those featuring intermediary inductive ac-link (I <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> ACL) configurations such as full-bridge dc-dc converter and dual-active-bridge (DAB). However, up to now, the dynamic equivalence in these I <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> ACL type converters has not been systematically revealed. To fill such a gap, in this paper, the existing I <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> ACL isolated dc-dc converters are reviewed thoroughly, including unidirectional type and bidirectional type. Then, the general current transferred features of these two groups are analyzed, respectively, and the transferred current during the transient process is just influenced by the middle inductance little. So, the I <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> ACL isolated dc-dc converter can be regarded as the first-order converter. Based on the discovered general characteristic, a unified fast-dynamic direct-current (FDDC) control scheme is proposed for improving the dynamic performance of these I <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> ACL isolated dc-dc converters. Such a scheme can also facilitate the uniform control design for existing or emerging new topologies with the same electrical equivalence. Moreover, the specialized design principles of the PI parameters in the unified FDDC control method are also presented. Finally, to verify the universality and feasibility of the proposed general FDDC control strategy, both simulation and experiment results are presented with demonstration examples, e.g., full-bridge type, DAB-type, and the three-phase DAB type dc-dc converters.
Highlights
Isolated dc-dc converters have been extensively applied in modern industrial applications such as metro vehicles [1], electric vehicles [2]–[4], data center [5], and grid systems [6]–[9], etc
Real-world projects can be found like the auxiliary power supply of a metro vehicle system shown in Fig. 1, where the isolated dc-dc power conversion stage is employed to replace the traditional line-frequency for lower cost, smaller size, and less acoustic noise [1]
Based on the power or current transferring characteristic of I2ACL dc-dc converters previously, a general fast-dynamic direct-current (FDDC) control method will be proposed for this type of converters, which can be employed to deal with the variations of the input voltage and the load condition
Summary
Isolated dc-dc converters have been extensively applied in modern industrial applications such as metro vehicles [1], electric vehicles [2]–[4], data center [5], and grid systems [6]–[9], etc. The same elementary cells can be modularly implemented in the power converter stage with much easier scalability regarding power and voltage ratings In such a way, the inherent dc-fault blocking capability can be acquired naturally since the intermediary ac power stage is embedded in the isolated dc-dc stage [12]–[13]. HOU ET AL.: UNIFIED FAST-DYNAMIC DIRECT-CURRENT CONTROL SCHEME FOR INTERMEDIARY INDUCTIVE AC-LINK ISOLATED DC-DC CONVERTERS. Up to now, such electrical equivalence has not been discovered in the isolated dc-dc converter research field, let alone the unified fast-dynamic control method. To fill such a gap, in this paper, a thorough overview of existing isolated dc-dc converters is presented. Based on different criterion, isolated dc-dc converters can be classified into different types such as resonant/nonresonant dc-dc converters [14]–[15], voltage-source/currentsource/impedance-source dc-dc converters [16], etc
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