Vu, Tue T.
(2014)
Non-linear Dynamic Transformer
Modelling and Optimum Control Design
of Switched-mode Power Supplies.
PhD thesis, National University of Ireland Maynooth.
Abstract
With recent advances in semiconductor manufacturing and computational technology, digital
control systems have grown to a relatively mature stage, and will soon become a viable replacement
for their analogue counterparts in the design of isolated and non-isolated DC-to-DC converters in
general, and
yback converters in particular. Inspired by this possibility, the thesis adopts the
first-ever digital control design in the field for wide-operating range
yback converters, based on a
low-cost microcontroller.
Accurate transformer modelling is a necessary exercise for the study of the
yback converters
as well as for model-based controller design. Therefore, a non-linear dynamic model, which allows
an accurate representation of both linear dynamics and non-linear core behaviour in a practical
transformer, is proposed. The parameters of the proposed transformer model are obtained using
time-domain system identification based on experimental data. In order to reduce the round-of
error typically occurring in the collected time-domain data, a method which is based on adjusting
the value of the current sensing resistor is also adopted.
To facilitate control design, a control-oriented model is developed based on the full converter
model through a simplification step. As demonstrated in the thesis, the control-oriented model is
able to preserve the bulk of the full converter model fidelity, critical for a control design step, while
at the same time requiring a significantly shorter execution time for simulation when compared
with the full converter model. For the purpose of implementing isolated-feedback control within a
low-cost microcontroller, a magnetic sensing principle, which can operates in both continuous and
discontinuous conduction modes of the
yback converter, is developed. The proposed sensing principle
is also based on the bias winding voltage of the
yback transformer to estimate the converter
output voltage; however, the sampling instant is chosen at the point where the secondary current
is known, instead of the knee point where the secondary current is zero. The implementation of
the proposed sensing technique, based on analogue circuitry and a microcontroller, is also studied.
Finally, optimum digital control for a wide-operating range
yback converter is developed and
implemented. The control architecture is purposely designed to perform a variety of tasks, including
efficiency optimisation, magnetic sensing, and valley switching operation, in addition to
the main task of regulating the output voltage. Three different methods for synthesizing optimum
compensators, based on mixed-sensitivity H1 robust control theory, gain-adaptive predictive functional
control (GAPFC) theory, and gain-adaptive quantitative feedback theory (GAQFT), are also
studied. In order to improve the performance of the robust controllers, parametric variations of
the
yback converter models are minimized before applying the robust control. Two possibilities
for reducing converter parametric model uncertainty, based on adapting the converter open-loop
gain and varying the sampling rate of the digital controller, are also demonstrated.
| Item Type: |
Thesis
(PhD)
|
| Keywords: |
Non-linear Dynamic Transformer
Modelling; Optimum Control Design; Switched-mode Power Supplies; |
| Academic Unit: |
Faculty of Science and Engineering > Electronic Engineering |
| Item ID: |
5615 |
| Depositing User: |
IR eTheses
|
| Date Deposited: |
15 Dec 2014 12:03 |
| URI: |
|
| Use Licence: |
This item is available under a Creative Commons Attribution Non Commercial Share Alike Licence (CC BY-NC-SA). Details of this licence are available
here |
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