MODELING AND SIMULATION OF CLOSED LOOP CONTROLLED
INTERLEAVED THREE SWITCH BUCK CONVERTER
FED DC DRIVE
K.NARASIMHA RAO
Professor of Instrumentation Technology, BMS College of Engineering, Bangalore 560019
Abstract- This paper deals with modeling and simulation of interleaved buck converter fed DC drive. A new interleaved
buck converter with three switches is proposed. Three pulses with a phase shift of 1200 are applied to reduce the ripple in the
output. This reduces the ripple in the armature current. Therefore the torque ripple is also reduced. Open loop and closed
loop controlled drive systems are modeled using the blocks of Simulink and the results are presented.
Index terms- Buck Converter, interleaved, low switching losses and switching stresses.
In [8]–[10], three-level buck converters are
introduced. The voltage stress is half of the input
voltage in the converters. However, so many
components are required for the use of IBC. In [11],
an IBC with a single-capacitor turnoff snubber is
introduced. Its advantages are that the switching loss
associated with turn-off transition can be reduced,
and single
coupled inductor implements the
converter as two output inductors. However, since it
operates at discontinuous conduction mode (DCM),
all elements suffer from high-current stress, resulting
in high conduction and core losses. In addition, the
voltages across all semiconductor devices are still the
input voltage. In [12], an IBC with active-clamp
circuits is introduced. In the converter, all active
switches are turned ON with zero-voltage switching
(ZVS). In addition, a high step-down conversion
ratio can be obtained and the voltage stress across the
freewheeling diodes can be reduced. However, in
order to obtain the mentioned advantages, it requires
additional passive elements and active switches,
which increases the cost significantly at low or
middle levels of power applications. In [13], an IBC
with zero-current transition (ZCT) is introduced to
reduce diode reverse recovery losses. The ZCT is
implemented by only adding an inductor into the
conventional IBC.
However, in spite of these advantages, the converter
suffers from high current stress, because the output
current flows through each module
in a
complementary way. And it still has the drawbacks of
the conventional IBC. An IBC with two winding
coupled inductors is introduced in [14] and [15]. The
converter has the following advantages. Since it
operates at continuous conduction mode (CCM), the
current stress is lower than that of DCM IBC. The
voltages across all semiconductor devices can be
reduced by adjusting the turn ratio of the coupled
inductors, which allows that although it operates with
hard switching, the switching losses can be reduced.
Additionally, a high step-down conversion ratio can
also be obtained.
I. INTRODUCTION
In applications where non isolation, step-down
conversion ratio, and high output current with low
ripple are required, an interleaved buck converter
(IBC) has received a lot of attention due to its simple
structure and low control complexity [1]–[6].
However, in the conventional IBC shown in Fig. 1,
all semiconductor devices suffer from the input
voltage, and hence, high-voltage devices rated above
the input voltage should be used. High-voltage-rated
devices have generally poor characteristics such as
high cost, high on-resistance, high forward voltage
drop, severe reverse recovery, etc. In addition, the
converter operates under hard switching condition.
Thus, the cost becomes high and the efficiency
becomes poor. And, for higher power density and
better dynamics, it is required that the converter
operates at higher switching frequencies. However,
higher switching frequencies increase the switching
losses associated with turn-on, turn-off, and reverse
recovery. Consequently, the efficiency is further
deteriorated. Also, it experiences an extremely short
duty cycle in the case of high-input and low-output
voltage applications.
To overcome the aforementioned drawbacks of the
conventional IBC, some pieces of research for
reducing the voltage stress of a buck converter and
several kinds of IBCs have been presented until now.
Proceedings of SARC-IRF International Conference, 12th April-2014, New Delhi, India, ISBN: 978-93-84209-03-2
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Modeling And Simulation of Closed Loop Controlled Interleaved Three Switch Buck Converter FED DC Drive
In the Fig 2, a two stage IBC, which is suitable for
the applications where the input voltage is high and
the operating duty is below 50%, is proposed. It is
similar to the conventional IBC, but two active
switches are connected in series and a coupling
capacitor is employed in the power path. The two
active switches are driven with the phase shift angle
of 1800 and the output voltage is regulated by
adjusting the duty cycle at a fixed switching
frequency. The features of the proposed IBC are
similar to those of the IBCin [14]. Since the proposed
IBC also operates at CCM, the current stress is low.
During the steady state, the voltage stress across all
active switches before turn-on or after turn-off is half
of the input voltage [16] – [19]. Thus, the
capacitive discharging and switching losses can be
reduced considerably. The voltage stress of the
freewheeling diodes is also lower than that of the
conventional IBC so that the reverse-recovery and
conduction losses on the freewheeling diodes can be
improved by employing schottky diodes that have
generally low breakdown voltages, typically below
200V. The conversion ratio and output current ripple
are lower than those of the conventional IBC.
III. SIMULATION RESULTS
DC input voltage is shown in Fig. 3a. The switching
pulses for M1, M2 and M3 are shown in Fig. 3b.
They are shifted by 1200. The switching pulse for M1
and output voltage are shown in Fig 3c. The
switching pulse for M2 and output voltage are shown
in Fig 3d. The voltage across the capacitor CB is
shown in Fig. 3e. The waveforms of output voltage
and current in switch2 are shown in Fig. 3f. The
waveforms of iL1 and iL2 are shown in Fig. 3g. DC
output current and voltage are shown in Figs 3h and
3i respectively. The DC output voltage Is 33V and the
output current is 17 Amps.
The proposed IBC is described in Section II in detail.
The relevant analysis results are presented in Section
III. The performance of the proposed IBC is
confirmed by the simulation results of prototype
converters with 150–200V input, 33 V/17A output in
Section III. The conclusion is made in Section IV.
The above literature does not deal with three switch
IBC. This work proposes three switches for the
control of output voltage. The Simulink models are
open and closed loop controlled IBC fed DC drives
are also not present in the literature. This work
develops Simulink models for open and closed loop
controlled three switch IBC systems.
Fig. 3a. DC Input Voltage
II. INTERLEAVED BOOST CONVERTER
Interleaved boost converter structure is similar to a
conventional IBC except three active switches in
series and a coupling capacitor employed in the
power path. The pulses given to the switches are
displaced by 1200. Three switch interleaved buck
converter system is shown in Fig.3.
Fig. 3b. Switching pulses to M1, M2, M3
Proceedings of SARC-IRF International Conference, 12th April-2014, New Delhi, India, ISBN: 978-93-84209-03-2
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Modeling And Simulation of Closed Loop Controlled Interleaved Three Switch Buck Converter FED DC Drive
Fig. 3h. DC Output Current
Fig. 3c. Switching Pulse to M1 and Voltage between the drain
and source
Fig. 3i. DC Output Voltage
Three switch interleaved buck converter fed DC
servo drive is shown in Fig. 4a. The separately
excited DC motor is used as the load. Scopes are
connected to display the speed and torque. DC input
voltage is shown in Fig. 4b. The input voltage is 150
Volts. Speed response is shown in Fig. 4c. The speed
increases and settles at 330 rpm. The torque decreases
and settles at 2 N-M.
Fig. 3d. Switching Pulse to M2 and Voltage between the drain
and source
Fig. 3e. Voltage across the capacitor CB
Fig. 3f. Output Voltage and Current
Switch2
Fig..4a. Three switch interleaved buck converter fed DC servo
drive
Fig. 3g. Waveforms of iL1 and iL2
Fig. 4b. DC input voltage
Proceedings of SARC-IRF International Conference, 12th April-2014, New Delhi, India, ISBN: 978-93-84209-03-2
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Modeling And Simulation of Closed Loop Controlled Interleaved Three Switch Buck Converter FED DC Drive
Fig. 6b. Input Voltage
Fig. 4c. Speed response
Fig. 4d. Torque response
Fig. 6c. Speed Response
CONCLUSION
Three switch interleaved buck converter fed DC
servo drive is successfully modeled and simulated
using Matlab simulink. The circuit models for open
loop and closed loop systems are developed and they
are used for simulation. The switching losses and
stresses are reduced by soft switching. The closed
loop system is able to regulate the speed. The torque
ripple is minimized by using the proposed three
switch interleaved buck converter system. The
interleaved three switch buck converter system is a
viable alternative to the exiting converters since it has
reduced ripple and improved speed regulation.
Fig. 5a. Open loop System with step change at the input
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Fig. 5b. Input Voltage
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Proceedings of SARC-IRF International Conference, 12th April-2014, New Delhi, India, ISBN: 978-93-84209-03-2
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Modeling And Simulation of Closed Loop Controlled Interleaved Three Switch Buck Converter FED DC Drive
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Dr. K.Narasimha Rao has
obtained his B.Tech , M.Tech and Ph.D. He has 26
years of teaching experience. He is currently a
Professor in the Department of Instrumentation
Technology, BMS College of Engineering,
Bangalore, India. His research interests include
modeling, design and control of Power converters,
soft switching power converters, resonant converters,
electric drive systems, Digital signal processing and
Biomedical Engineering..
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Proceedings of SARC-IRF International Conference, 12th April-2014, New Delhi, India, ISBN: 978-93-84209-03-2
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