Control Techniques for DC-DC Buck Converter with Improved Performance

By: Biswal, MousumiContributor(s): Maity, Somnath [Supervisor] | Panda, Anup Kumar [Supervisor] | Department of Electrical EngineeringMaterial type: TextTextLanguage: English Publisher: 2011Description: 108 pSubject(s): Engineering and Technology | Electrical Engineering | Power ElectronicsOnline resources: Click here to access online Dissertation note: Thesis (M.Tech (R))- National Institute of Technology, Rourkela Summary: The switched - mode dc - dc converters are some of the most widely used power electronics circuits for its high conver sion efficiency and flexible output voltage. These converters used for electronic devices are designed to regulate the output voltage against the changes of the input voltage and load current. This leads to the requirement of more advanced control methods to meet the real demand . Many control methods are developed for the control of dc - dc converters. To obtain a control method that has the best pe rformances under any conditions is always in demand. Conventionally, the dc - dc converters have been controlled by linear voltage mode and current mode control methods. These controllers offer advantages such as fixed switching frequencies and zero steady - state error and gives a better small - signal performanc e at th e designed operating point. But under large parameter and load variation , their performance degrades . Sliding mode (SM) control techniques are well suited to dc - dc converters as they are inherently variable structure systems. These controllers are r obust concerning converter parameter variations, load and line disturbances. SM controlled converters generally suffer from switching frequency variation when the input voltage and output load are varied. This complicates the design of the input and output filters. The main objective of this research work is to study different control methods implemented in dc - dc converter namely (linear controllers, hysteresis control, current programmed contro l, and sliding mode (SM) control ) . A comparison of the effects of the P WM control lers and the SM control on the dc - dc b uck converter response in steady state, under l ine variations, load variations is performed . iv The thesis shows that, in comparison with the PWM controllers , the SM control provides better steady - state response, better dynamic response, and robustness against system uncertainty disturbances. Also the h ysteretic control led converters response to disturbances and load change right after the transient take place and they give excellent transient performance. It does not require the closed loop compensation network and results with a lesser component count and small size in implementation. Hence, hysteretic control is considered as the simplest and fastest control meth od. The dc - dc buck converter employing current h ysteresis control scheme is given in thesis . The result shows that h ysteresis control converters have inherently fast response and they are robust with simple design and implementation. A hysteretic curr ent control technique for a tri - state buck converter operating in constant switching frequency is designed and its behavior is studied by making the use of essential tools of sliding mode control theory because dc - dc buck converter is a variable structure system due to the presence of switching actions. The principle of operation of tristate dc - dc buck converter is explained. The converter response is investigated in the steady - state region and in the dynamic region. The problem of variable switching frequ ency is eliminated without using any compensating ramp.
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Thesis (Ph.D/M.Tech R) Thesis (Ph.D/M.Tech R) BP Central Library
Thesis Section
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Thesis (M.Tech (R))- National Institute of Technology, Rourkela

The switched
-
mode dc
-
dc converters are some of the most widely used power electronics
circuits for its high conver
sion efficiency and flexible output voltage. These converters used for
electronic devices are designed to regulate the output voltage against the changes of the input
voltage and load current. This leads to
the requirement of more advanced control methods
to
meet the real demand
. Many control methods are
developed
for the
control
of
dc
-
dc converters.
To
obtain a control method that has the best pe
rformances under any conditions is always in
demand.
Conventionally, the dc
-
dc converters have been controlled by linear voltage mode and current
mode control methods. These controllers offer advantages such as fixed switching frequencies
and zero steady
-
state error and gives a better small
-
signal performanc
e at th
e designed operating
point. But
under large parameter and load variation
, their performance degrades
.
Sliding mode
(SM)
control techniques are well suited to dc
-
dc converters as they are inherently variable
structure systems. These controllers are r
obust concerning converter parameter variations, load
and line disturbances. SM controlled converters generally suffer from switching frequency
variation when the input voltage and output load are varied. This complicates the design of the
input and output
filters.
The main objective of this research work is to study different control
methods implemented in dc
-
dc converter namely (linear controllers, hysteresis control, current
programmed contro
l, and sliding mode (SM) control
)
.
A comparison of the effects
of the P
WM
control
lers
and the SM
control
on the
dc
-
dc
b
uck converter response in steady state, under l
ine
variations, load variations
is performed
.
iv
The thesis shows
that, in comparison with the
PWM controllers
, the SM
control
provides
better steady
-
state response, better dynamic response, and robustness against system uncertainty
disturbances.
Also the h
ysteretic control
led
converters response to disturbances and load change
right
after the transient take place and
they give excellent transient performance. It does not
require the closed loop compensation network and results
with a lesser
component count and
small size in implementation.
Hence,
hysteretic control is considered as the simplest and fastest
control meth
od. The dc
-
dc buck converter employing current h
ysteresis control scheme is
given
in thesis
.
The result shows that h
ysteresis control converters have
inherently fast response and
they are
robust with simple design and implementation.
A hysteretic curr
ent control technique for a tri
-
state buck converter operating in constant
switching frequency is designed and
its behavior is studied by making the use of
essential tools
of sliding
mode control theory because dc
-
dc buck converter is a variable structure
system due to
the presence of switching actions.
The principle of operation of tristate dc
-
dc buck converter is
explained.
The converter response is investigated in the steady
-
state region and in the dynamic
region.
The problem
of
variable switching frequ
ency is eliminated without
using
any
compensating ramp.

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