Dynamic Optimization for Dual-Active-Bridge-Based DC-DC Converter Systems

  • Author / Creator
  • With the development of renewable energies, such as wind energy and solar energy, the dc power system becomes a promising candidate to manage and transfer the re-newable energy source, which stimulates the study of the dc-dc converters in the past decades. Among various dc-dc converters, the dual-active-bridge (DAB) dc-dc con-verter is regarded as one of the most promising candidates for the dc power conver-sion due to merits like isolated, high-efficiency, bidirectional, and ultrafast dynamic characteristics. Except the DAB dc-dc converter, there are some other isolated dc-dc converters such as full bridge dc-dc converter, three-phase DAB dc-dc converter, etc. They nor-mally have similar dynamic characteristics as the DAB dc-dc converter featuring in-termediary inductive ac-link (I2ACL) configuration. However, they are rarely investi-gated in existing literature, especially for better dynamic control performance. To fill such a gap, the dynamic equivalence between the DAB dc-dc converter and other I2ACL isolated dc-dc converters is revealed with the thorough overview of the existing I2ACL topologies in this work. Further, a unified fast-dynamic direct-current control scheme is proposed for significantly improving the dynamic performance of these I2ACL isolated dc-dc converters. With this predetermined analysis, the dynamic con-trol schemes for the DAB-based dc-dc converter systems can be easily extended to other I2ACL converters with the same configurations.The single DAB dc-dc converter has been extensively investigated, but its modular-ized converter systems such as input-parallel output-parallel (IPOP), input-independent output-parallel (IIOP), in-put-parallel output-series (IPOS), and input-series output-parallel (ISOP) configurations have been seldomly covered in the exist-ing research. Particularly, it is emergent to improve the dynamics, e.g. the input-voltage disturbance, the load-condition change and the power sharing disturbance. In this work, the advanced dynamic controls for these modular DAB dc-dc converter sys-tems are proposed, featuring the flexible power sharing control performances with fast-dynamic responses. Moreover, to realize the reliable operation of these DAB-based systems, the hot swap operations are presented. To ensure the desired power sharing performance, the circuit-parameter estimating methods are proposed for these DAB-based converter systems.This work expands scope of the application of the DAB-based converter system in the partial power processing (PPP). Different from the existing literatures focusing on embedding renewable energy source into the strong ac system, this work proposes a PPP converter system, which can realize the independent control of the renewable energy source and the stabilization of the total dc bus. Combining with DAB module, the DAB-based PPP converter system is proposed. Then, as one of the important func-tions, the stabilization of the total dc bus should be further improved for this DAB-based converter system. In detail, a high-robustness control strategy is proposed to realize the fast-dynamic control, and the operation when one renewable energy source is out of work is also presented. Notably, the renewable energy should feature the current output and the limited output-voltage regulation such as PV, fuel cell and wind turbine with ac-dc conversion. By using the PV as an example, the effectiveness of the novel system is verified with following results: 1). The maximum power point tracking of the PV panels can be realized by using the existing method. 2). By using the proposed high-robustness control scheme, the total dc-link voltage can maintain at its desired value when the irradiance of PV panels, the voltage of the battery and the load condition are changed, and even when the PV panel is heavily shaded.

  • Subjects / Keywords
  • Graduation date
    Spring 2022
  • Type of Item
  • Degree
    Doctor of Philosophy
  • DOI
  • License
    This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.