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Title: Impedance control and stability of DC/DC converter systems
Author: Zhang, Xin
ISNI:       0000 0004 5991 7171
Awarding Body: University of Sheffield
Current Institution: University of Sheffield
Date of Award: 2016
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Cascaded DC/DC converter systems (or 'cascaded systems') have instability problems; i.e., although the subsystems may work well individually, the whole system may be instable due to the impedance interaction among these subsystems. To solve this problem, a family of impedance-based stabilisation methods are proposed in this thesis. First, parallel-virtual-impedance (PVI) and series-virtual-impedance (SVI) control strategies are proposed to stabilise cascaded systems via shaping the load input impedance. Theoretically, the PVI or SVI control strategy connect a virtual impedance in parallel or series with the input port of the load converter so that the magnitude or phase of the load input impedance can bemodified within a very small frequency range. Therefore, with the PVI or SVI control strategy, the cascaded system can be stabilised with minimal compromise of the load performance. Then, based on the PVI and SVI control strategies, adaptive-PVI (APVI) and adaptive-SVI (ASVI) control strategies are proposed by introducing an adaptive mechanism to change the impedance. With the APVI or ASVI control strategy, the load converter can be stably connected to different source converters without changing its internal structure. It is also shown that the ASVI control strategy is better than the APVI control strategy and can make the cascaded system more stable. Moreover, a minimum-ripple-point-tracking (MRPT) controller is proposed and utilised to solve the potential problem of the ASVI control strategy. Finally, a source-side SVI (SSVI) control strategy and a VRLC damper are proposed to stabilise the cascaded system with better source performance or input filter performance, respectively. All the proposed stabilisation and control methods are validated by extensive experimental results.
Supervisor: Zhong, Qing-Chang ; Wei, Hua-Liang Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available