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Stability of series-connected DC-DC converters


E. Zvizdic

Semester Thesis, HS12 (10266)

In this thesis we investigated and analyzed stability issues related to distributed DC power systems. While it is very dicult to destabilize a DC-DC buck converter with a resistive or constant current load, dynamical loads such as constant power loads usually cause stability issues. Large part of this thesis deals with the so-called 'negative resistance in- stability' caused by constant power loads, which are a common occurrence in distributed power systems. Issues that arise are typically tackled using impedance criteria, however these can only be studied once there is some information available about the load, and they are usually too conservative. The setup observed in this thesis was a pair of coupled buck converters (i.e a source converter loaded with a regulated DC-DC converter), where each of them is separately regulated with state feedback. Most applications assume a resistive load when designing a controller for a buck converter, which is generally not a good idea for this kind of a setup. Therefore, we analyzed the drawbacks of this approach, and proposed assuming a constant power load when designing the controller for the source converter. This turned out to be a much better solution, as it is able to stabilize a larger range of loads and is therefore way more robust.

Supervisors: Joe Warrington, Sébastien Mariéthoz, Manfred Morari


Type of Publication:

(13)Semester/Bachelor Thesis

J. Warrington

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% Autogenerated BibTeX entry
@PhdThesis { Xxx:2013:IFA_4462
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