International Journal of Modern Engineering Research (IJMER)
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Vol.2, Issue.2, Mar-Apr 2012 pp-197-201
ISSN: 2249-6645
Three-Phase Five-Level PWM DC–DC Converter Using
H-Bridge
E.Bhasker1, M.Kiran Kumar2
*(Student, Department of Electrical and Electronics Engineering, KL University, India)
** (Assistant Professor, Department of Electrical and Electronics Engineering, KL University, India)
Abstract- A three-phase dc–dc converter based on the
threephase neutral point clamped (NPC) commutation
cell is proposed, which is intended for use in applications
where the energy from a medium dc bus voltage needs to
be processed. In this paper, all six continuous conduction
modes (CCMs) are described, presenting the main
waveforms and equations. For the discontinuous
conduction modes the main equations are also provided
for a complete converter characterization. Finally a Hbridge is proposed to get five levels.
Keywords: - DC–DC converter, neutral point clamped
(NPC), three-phase transformer.
I. INTRODUCTION
Recently, there has been increased interest in three phase
dc–dc conversion for high-power applications [1]–[10]. The
major reason is that three-phase dc–dc converters can
achieve lower power component current stresses and also
considerably reduce input and output filter requirements,
when compared to single-phase topologies [3], [4].
Moreover, three phase high-frequency transformer can
handle higher power levels than single-phase ones, although
they have the same size. All these characteristics make the
use of three-phase dc–dc converters a very attractive
solution when high power density and high efficiency are
required.
Some solutions use three-phase resonant converters
where soft-switching can be achieved, thus increasing the
converter efficiency. On the other hand, the number of
power components and also the converter volume are
increased due to the addition of reactive power elements.
Other promising solutions are the non resonant softswitched three-phase converters. These combine the
advantage of a reduced number of power components, due
to the use of non resonant converters, with reduced
switching losses by means of soft-switching techniques.
A non resonant hard-switched three-phase dc–dc
converter was published in [1], and its circuit is shown in
Fig. 1(a). It is composed of a three-phase inverter connected
to the primary side of a three-phase highfrequency transformer. The secondary side of the
transformer feeds a three-phase rectifier, and the output
stage of the converter is composed of an L–C filter and the
load. The concept of resonance applied to the three-phase
dc– dc converter can be observed in the converter proposed
in [5], which is depicted in Fig. 1(b). This converter can
operate under zero-voltage-switching (ZVS) or zero-currentswitching (ZCS) conditions, with the drawback of using
three additional capacitors to achieve the desired resonance.
Fig. 1. Previously reported three-phase dc–dc converters: (a)
non resonant
Hard-switched [1]; (b) resonant soft-switched [5]; (c) non
resonant soft switched [6]; (d) non resonant with active
clamp [7]. Non resonant soft-switched three-phase dc–dc
converters were also proposed in [6] and [7], and their
circuits are shown in Fig. 1(c) and (d), respectively. The
converter depicted in Fig. 1(c) can achieve ZVS for all
switches and control the output voltage by means of an
asymmetrical PWM. Therefore, upper and lower
commutation cell switches are subjected to different current
stresses.
II. PROPOSED THREE-PHASE DC–DC
CONVERTER
The circuit of the proposed three-phase three-level
pulse width- modulated (TPTL-PWM) dc–dc converter is
shown in Fig. 2. Basically, it is composed of a neutral point
clamped (NPC) inverter connected to the primary side of a
three-phase high-frequency transformer, the secondary side
of which is, in turn, connected to a three-phase rectifier.
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International Journal of Modern Engineering Research (IJMER)
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Vol.2, Issue.2, Mar-Apr 2012 pp-197-201
ISSN: 2249-6645
Diodes D1–D12 are intrinsic to switches S1–S12 and D13–
D18 are clamping diodes. One important characteristic of
this converter is that the inductance is placed between the
inverter and the rectifier stage. Therefore, the leakage
inductance of the transformer T may be used in favor of the
converter operation, and inductors Lin are added to the
circuit whenever the value of the leakage inductance is not
sufficiently large. Capacitor Co comprises the purely
capacitive output filter, which is an attractive solution due to
the reduced ripple produced in current io . Resistor Ro
represents the load fed by the converter
Fig. 2. Proposed three-phase three-level PWM dc–dc
converter
Fig. 3. Three-phase transformer and the equivalent symbol
used for its Representation.
III. PRINCIPLE OF OPERATION
Due to publication space limitations, only the
continuous conduction modes (CCM) will be described
herein. For discontinuous conduction modes (DCM) only
the resulting equations will be provided. A given operation
mode is classified as discontinuous if there is no current
flowing through the inductor Lin during at least one
operation stage. Otherwise, the mode is considered to be
continuous. In this paper, all six CCM operation modes will
be described and mathematically analyzed. Each operation
mode is composed of 18 operation stages. However, the
analysis of three stages is sufficient to generate all linearly
independent equations that completely describe a given
operation mode, due to PWM and converter symmetry.
During the analysis, all components will be treated as ideal.
are turned on during the first stage. When current ia
becomes positive this stage ends.
2) Second stage (t1 , t2)—At the time instant t = t1 the
value of current ia becomes positive, therefore S1 and
S2 assume this current. Moreover, diodeD20 is blocked
andD19 starts conducting. This stage ends when switch
S1 is turned off.
3) Third stage (t2 , t3)—After S1 is blocked, diode D13
starts conducting in order to maintain current ia
flowing. At the time instant t = t3 switch S10 is turned
off and the third stage ends.
B. CCM Mode 2
For a duty cycle interval of 1/3 ≤ D < 2/3 there are two
possible operation modes in CCM. One of them is described
in this subsection. Fig. 5 shows three operation stages for
this mode.
1) First stage (t0 , t1)—At the time instant t = t0 switch S3
is turned off and diodes D1 and D2 start conducting.
Diodes D20, D22, and D23 are conducting in the bridge
rectifier. As soon as switch S8 is turned off this stage
ends.
2) Second stage (t1 , t2)—Blocking switch S8 implies that
diode D16 starts conducting to guarantee the continuity
of current ib. Both S1 and S2 must be turned on during
the first or the second stage, in order to achieve ZVS
turn-on for these switches. At time t = t2 the direction
of current ia is reversed and the second stage ends
3) Third stage (t2 , t3)—Since the ia value has become
positive, this current starts flowing through switches S1
and S2 . In the bridge rectifier, the blocking of diode
D20 occurs, and D19 starts conducting. This stage
persists until switch S10 is turned off.
C. CCM Mode 3
Mode 3 is the second possibility of converter
operation for the duty cycle interval of 1/3≤ D < 2/3 in
CCM. As provided in the previous modes, three operation
stages are shown in Fig. 6.
1) First stage (t0 , t1)—Starts when switch S3 is turned
off, and therefore diodes D1 and D2 assume the current
ia. In the bridge rectifier, diodes D20, D22 and D23 are
forward biased. It is important to note that ZVS turn-on
is only achieved if switches S1 and S2 are turned on
during the first stage. When t = t1 the current ia
becomes positive and the first stage ends.
A. CCM Mode 1
In CCM, whenever the duty cycle is within the interval 0
≤ D< 1/3, the converter operates in mode 1. Three operation
stages for this mode are shown in Fig. 4.
1) First stage (t0 , t1)—Starts when S3 is turned off. Since
current ia has a negative value, the diodes D1 and D2
start conducting. In the bridge rectifier diodes D20,
D22, and D23 are conducting. The condition of ZVS
turn-on for S1 and S2 is only achieved if these switches
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ISSN: 2249-6645
Fig. 5. Three operation stages for mode 2.
2) Second stage (t1 , t2)—At time t = t1 switches S1 and
S2 start conducting the current ia . Therefore, the diode
D20 blocks and D19 starts conducting. As soon as
switch S8 is turned off the second stage is finished.
3) Third stage (t2 , t3)—In order to guarantee the
continuity of current ib , diode D16 starts conducting
when switch S8 is turned off. The third stage will
persist until switch S10 is turned off.
Fig. 4. Three operation stages for mode 1
C. CCM Mode 4
The three remaining continuous conduction operation
modes are observed when the converter operates with duty
cycle values within the range of 2/3 ≤ D ≤ 1. One of them is
called mode 4 and is described in this section. Three
operation stages for this mode are depicted in Fig. 7.
1) First stage (t0 , t1)—When switch S3 is turned off the
first stage starts. At this moment, diodes D1 and D2
assume the current ia . The diodes D20, D21, and D23
are forward biased in the bridge rectifier. The stage
ends when current ib changes its signal.
2) Second stage (t1 , t2)—The second stage begins when
the direction of current ib is reversed and it starts
flowing through switches S7 and S8 . Therefore, the
blocking of the diode D21 occurs and D22 starts
conducting. This stage finishes when switch S9 is
turned off.
3) Third stage (t2 , t3)—After switch S9 is blocked, diode
D17 starts conducting, beginning the third stage. It is
important to note that ZVS turn-on condition for S1 and
S2 is only achieved if these switches are turned on
during the first four operation stages. When switch S10
is turned off this stage ends.
D. CCM Mode 5
Mode 5 is another possible operation mode when the
converter operates with duty cycle within the range of 2/3 ≤
D ≤ 1. Fig. 8 shows three operation stages for this mode.
1) First stage (t0 , t1)—Begins when switch S3 is turned
off. Thus, current ia starts flowing through diodes D1
and D2 .In the bridge rectifier, the diodes D20, D22,
and D23 are in conduction. At the time instant t = t1 ,
switch S9 is turned off and this stage ends.
2) Second stage (t1 , t2)—With the blocking of S9 the
diode D17 starts conducting. The condition of ZVS
turn-on for S1 and S2 will only occur if these switches
are turned on during the first or the second stage. As
soon as current ia becomes positive the second stage is
finished.
3) Third stage (t2 , t3)—After the direction of ia is
reversed switches S1 and S2 assume this current.
Moreover, the diode D20 is blocked while D19 starts
conducting. At the time instant t = t3 switch S10 is
turned off and this stage ends.
E. CCM Mode 6
The last CCM operation mode to be described is mode 6. As
for the last two modes the duty cycle is within the range of
2/3 ≤ D ≤ 1. Three operation stages for this mode are shown
in Fig. 9.
1) First stage (t0 , t1)—At the time instant t = t0 the switch
S3 is turned off and diodes D1 and D2 assume the
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International Journal of Modern Engineering Research (IJMER)
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Vol.2, Issue.2, Mar-Apr 2012 pp-197-201
ISSN: 2249-6645
current ia . Diodes D20, D22 and D23 are conducting in
the bridge rectifier. This stage ends when current ia
becomes positive.
2) Second stage (t1 , t2)—As the direction of current ia is
reversed switches S1 and S2 start conducting.
Therefore, the blocking of diode D20 occurs and D19
starts conducting. It is also important to note that S1 and
S2 must be turned on during the first or the second
stage, thus ZVS turn-on is achieved for both switches.
The second stage persists until switch S9 is turned off at
the time instant t = t2 .
3) Third stage (t2 , t3)—After the blocking of switch S9
the diode D17 starts conducting to guarantee the
continuity of current ic . When switch S10 is turned off
this stage finishes.
Fig. 7 Inductor Current
Fig.6 shows the diode clamped inverter output voltage. Fig.
7 shows the inductor current and Fig.8 shows the switch
voltage.
III MATLAB/SIMULINK MODEL
Fig. 5 Matlab/ Simulink Model
Fig. 8 Voltage across the switch
Fig. 5 shows the Matlab/Simulink model of three level diode
clamped DC to DC converter.
Fig. 9 Switch Current
Fig. 6 Diode clamped inverter output voltage
Fig. 10 DC output voltage
Fig. 9 shows the switch current and Fig. 10 shows the DC
output voltage.
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ISSN: 2249-6645
DC to DC converter is proposed and simulation results are
presented.
V REFERENCES
[1]
[2]
[3]
Fig. 11 Three phase H-Bridge DC to DC converter
Fig.11 Shows the Matlab/Simulink model of proposed DC
to DC converter. In the proposed converter a H-bridge is
used.
[4]
[5]
[6]
[7]
[8]
Fig. 12 Five level PWM output
[9]
[10]
R. Prasad, P. D. Ziogas, and S. Manias, ―Analysis and
design of a threephase offline DC–DC converter with
high frequency isolation,‖ in Proc. IAS, 1988, pp.
813–820.
P. D. Ziogas, A. R. Prasad, and S. Manias, ―A threephase resonant dc/dc converter,‖ in Proc. IEEE
Power Electron. Specialists Conf., 1991, pp. 463–
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R.W. A. A. De Doncker, D. M. Divan, and M. H.
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pp. 63–73, Jan./Feb.1991.
A. K. S. Bhat and R. L. Zheng, ―A three-phase seriesparallel
resonant
converter-analysis,
design,
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three-phase DC/DC converter for high-power
applications,‖ in Proc. IEEE Power Electron.
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D. S. Oliveira and I. Barbi, ―A three-phase ZVS
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power current-fed DC/DC converter with active
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T. Song, H. S. H. Chung, S. Tapuhi, and A. Ioinovici,
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Fig.13 DC output Voltage
Fig.12 shows the Five level PWm output and Fig. 13 shows
the corresponding DC output.
IV CONCLUSION
A three-phase three-level PWM dc–dc converter was
proposed. Theoretical analysis results for both CCM and
DCM operation were presented, allowing a complete static
characterization of the proposed converter through its output
characteristic graph. In this paper a new five level H-Bridge
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