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Contribution to Stability Analysis and Stabilization of DC Microgrids: Application of the Concept of Passivity

Abstract : This dissertation focuses on dealing with the stability issues of DC microgrids, especially in electrified transportation applications. The main objective of this dissertation is to solve problems and find improvements related to the stability analysis and stabilization of DC microgrids. In the applications under consideration, stability is still a key issue in the design of DC microgrids. These systems, mainly consisting of multiple cascaded and/or parallel converters and LC filters, can suffer from instability, even when individual converters are stable alone. Moreover, DC microgrids in electrified transportation applications may have a time-varying structure, with highly flexible subsystems and operating modes. Both sources and loads can switch their operation patterns, or even join or quit the microgrid in a plug-and-play manner. This feature makes it difficult to conduct the stability studies, and puts forward higher requirements for controller design. To consider the aforementioned issues, the concept of passivity is studied in this dissertation. Indeed, the general stability study is established using the passivity concept which ensures that a microgrid is stable as long as all its components meet the passivity conditions and are interconnected to each other under certain conditions. In this way, the stabilization objective is localized to avoid investigating the whole microgrid, thereby offering immunity against system variations. Initially, a branch of Passivity-Based Control (PBC), i.e. the Interconnection and Damping Assignment Passivity-Based Control (IDA-PBC), is applied to two typical DC/DC converters. This is achieved by designing an adaptive interconnection matrix to establish internal links in Port-Controlled Hamiltonian (PCH) models and to generate a unique control law. Then, the stabilization of DC microgrids is achieved by developing a modified IDA-PBC at the subsystem level. The instability effects caused by the LC filter, and also caused by the interaction between subsystems are taken into account in the controller design. Moreover, a nonlinear observer is added to the PBC controller to solve the effect caused by parameter and model uncertainties. Afterward, a passivation strategy is proposed to stabilize DC microgrids. This is achieved by developing a PBC controller that preserves the passivity property from the interconnection perspective. All the proposed PBC theory and estimation technology can guarantee the large-signal stability of the DC microgrid. In addition to these theoretical backgrounds, the proposed control methods are validated by extensive simulation, experimental, and Hardware-in-the-loop (HIL) results.
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Submitted on : Wednesday, November 25, 2020 - 9:40:12 AM
Last modification on : Wednesday, November 3, 2021 - 7:56:32 AM

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  • HAL Id : tel-03022970, version 1


Shengzhao Pang. Contribution to Stability Analysis and Stabilization of DC Microgrids: Application of the Concept of Passivity. Electric power. Université de Lorraine, 2020. English. ⟨NNT : 2020LORR0121⟩. ⟨tel-03022970⟩



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