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TRANSACTION ON ELECTRICAL AND ELECTRONIC CIRCUITS AND SYSTEMS, VOL. 4(21), PP. 124-127, DEC., 2014.
Multi-Output Converter Design with two Regulated Output
and Minimized System Harmonic
Behroz Bashiri , and Amin Shahbazi 
Abstract: DC converters with multiple outputs have long
been used extensively in research and history. They produce a
DC voltage with different supply voltage levels. In this paper,
advantages and disadvantages of each method with different
topologies are reviewed, from different perspectives such as
cost of implementation, the performance of the transducer in a
separate set of outputs, the complexity of control theory,
analog or digital control circuit implementation complexity. It
can be seen that each of them contains an impressive number
of harmonic sources. Integrated steel and iron melting
industry utilize large electric Arc furnaces. SVC can be used
along with the Arc furnaces to compensate the reactive power
requirements and improve the efficiency. In other parts of the
industrial centers various kinds of AC and DC motors are
utilized along with their own controls, which inject comparable
amount of harmonics in complex networks. Petrochemical and
chemical industries need DC supplies for their electrical and
chemical processes. Hence there is a need to the DC power
supplies which use large rectifiers producing a large amount of
network harmonics. These harmonics will be efficiently
compensated by the proposed architecture. In this section, to
evaluate the performance of sophisticated multi-output
converters, the simulation will be discussed. Depending on the
nature of each transducer and its key details and its magnetic
components, the simulations will be performed in SIMULINK
or OrCAD environment.
Keywords: Multi-Output Converter, Regulated Output, Minimized
System Harmonic
1
1.
INTRODUCTION
Multilevel converters are divided into three categories of
floating capacitor, diode clamp, and H Bridge (Cascade).
Among them, Cascade Converter is taken into consideration
due to the smaller number of semiconductor devices, as well
as its modular structure. So far, different methods are
proposed for controlling Cascade converter in inverter and
rectifier modes in which the method proposed in [i-man]
has attractions such as the regulation of DC voltage and
reducing flow harmonics. Harmonics are sine waves that
frequencies are integer multiples of the fundamental
frequency of the networks. These sine wave networks are
added to the original wave network and change it to the
wave. Non-linear ions are such as adjustable speed drives,
electronic ones used in fluorescent lamps and CFLs,
saturable equipment, welding rectifiers of electronic power
supplies are the main sources of harmonics.

Email: [email protected]
Nonlinear ions are usually the odd harmonic generations
and are face the third, fifth and seventh and eleventh
harmonics in the network. Third harmonic and its multiples
rarely emerge and higher harmonics than the ninth are not
significant. Only the fifth and seventh harmonics are
important.
Harmonic has many effects on network and also
consumers. These disorders will cause transformers, cables
and motors overheat and relays act unexpected and
measuring the voltage and current measuring devices
measure incorrectly. Voltage harmonics increase iron losses
in transformers and in the engine also they cause excessive
heating of the rotor and also moments throbbing. Harmonics
are harmful for sensitive ions, there are several ways to
reduce or eliminate harmonics. Harmonics become shorter
through the filters connections and are not allow passing
into the system or distribution network of consumer.
Another Harmonic elimination method is to use isolation
transformers or reset the system capacitors. It can also be
done by isolate transformers or and resetting the system
capacitors.
2.
DISCUSSION
A. Cascade Converter Concept
The conversion is made of H-N series connection. The
number of levels generated in the network is equal to 2N +
1. The H convertors are connected to each other from the
AC terminals. For example, if three H exchangers are used,
the voltage on the network will have 7 levels. The H
exchanger is called a class, which has a DC output. Each
output load is shown by a resistance in Fig. In this way, the
DC output voltages are equal, while the loads can be
different. AC transformers' flow is the same, because they
are connected in series and since power is equal to the
average cell AC voltage multiplied by the AC flow, AC
voltage of each cell will have a determiner role in cell
power. Several strategies have been proposed to control the
converter Cascade. All these methods challenge is for
balancing the DC voltages. Especially when load of the
same DC class are not equal, DC voltages will be divergent.
Consider the case in which all cell loads are the same, i.e.
DC power of cells are the same. The DC voltage will be the
same for all cells, because the AC power cells are equal. If
for any reason, one of the cell loads is increased, the DC
output power of the cell will increase without increasing the
AC power input. DC voltage of the cell will start to decline.
Finally, becomes the unstable converter. Consequently, a
RECEIVED: 15, NOV., 2014; REVISED: 25, NOV., 2014; ACCEPTED: 20, DEC., 2014; PUBLISHED: 25, DEC., 2014.
BASHIRI et al.: MULTI-OUTPUT CONVERTER DESIGN WITH TWO REGULATED OUTPUT AND MINIMIZED SYSTEM HARMONIC.
control system is required to stabilize at the new value of
AC voltage when DC power changes in a cell until AC
power become equal to DC power of the cell and the DC
voltage is stabilized.
System presented at reference [1] consists of two parts
that the first area can be seen in Figure 1-1. VC1 and VCN
are output voltages of DC, and the VC voltage shows source
voltage. If the DC voltage is less than the source value, the
adapter must receive much flow of the network to charge
the output capacitor. Therefore, a proportional-integral
controller (PI-Type) determines the current demanded
network domain. The domain is multiplied to a sinusoidal
same-phase network to produce AC flow. This command is
shown by Iin * in Fig. Iin * is subtracted from Iin again
until the AC is controlled. The other controller is used for
forming a network flow. The output of the controller is the
∗
voltage AC (𝑉𝐴𝐶
) command.
Fig. 1. part control system proposed in [1].
The second part of the system [1] has the task of
regulating the DC voltage. For this purpose, the command
voltage 𝑉∗𝐴𝐶 is divided into same sections. "Voltage
region, K is as in Figure 2, and is defined according to
the 𝑉∗𝐴𝐶 as follows:
125
short. In PWM mode, for the period, S1 and S4 keys and for
the rest S2 and S3 keys are turn on.
Fig. 3. Operational conditions of each cell.
The second part of the control system that is responsible
to make DC voltage outputs the same shown in Figure 4.
According to this figure, the first DC voltage is raised from
V1 to VN and then one of four positions of +1, -1, 0, or PWM
for each cell is selected according to the K value and polarity
∗
of Iin and 𝑉𝐴𝐶
. For example, when Iin and 𝑉∗𝐴𝐶 both are
positive and the fourth area is the source voltage, the first,
second and third cells are in the +1 position, fourth cell
makes PWM wave, and the remaining cells don’t produce
any voltage. The AC voltage of the converter can be obtained
from the sum of the voltage of the cells and stay in region IV
the same as the source voltage. The main point is that in this
way, the first to third cells with the lowest DC voltages has
charged, and fifth cells above with the highest voltage will
receive no power. The cell voltages become closer and avoid
divergence.
(𝐾 − 1). 𝑉𝐶 < |𝑉∗𝐴𝐶 | < 𝐾𝑉𝐶
Fig. 2. Definition of the voltage K area.
Fig. 4. The second part of the control system proposed in [1].
Kth zone is when the source voltage is between K (K-1)
VC and KVC. So in K zone, the minimum numbers of cells
are required for the reference voltage equal to K.
In this method, each cell in each switching cycle can be
functioned in one of four positions of +1, -1, 0, or PWM.
Position+1 are two switches off keys as S1, S2, S3 and S4
thus will produce + VCi voltage in AC cell terminals. In
situation -1, two keys of S3 and S2 are turned on and the
voltage is -VCi. In state 0, the switch keys of S1 and S3 or S2
and S4 are turned on and AC terminal in this state will be
3.
SIMULATION OF CASCADE
CONVERTER
Cascade converter and described controller are
simulated in the Simulink field and schematic is shown in
Figure 5.
TRANSACTION SERIES ON ENGINEERING SCIENCES AND TECHNOLOGIES (TSEST) ©
TRANSACTION ON ELECTRICAL AND ELECTRONIC CIRCUITS AND SYSTEMS, VOL. 4(21), PP. 124-127, DEC., 2014.
126
up1
dow n1
[duty1]
in
up2
dow n2
Vac
dow n1
Vdc
up2
AC1
dow n2
PWM1
up1
[duty2]
in
dow n1
up2
dow n2
up1
[duty3]
in
dow n1
up2
dow n2
[Vdc1]
i +
-
100
AC2
HB1
L
up1
Vac
[vac2]
dow n1
Vdc
[Vdc2]
up2
AC1
dow n2
PWM2
current and voltage phase difference to zero and thus the
power coefficient of Cascade Converter is a unit.
[Iin]
[vac1]
up1
50
grid
AC2
0
HB2
up1
Vac
[vac3]
dow n1
Vdc
[Vdc3]
up2
AC1
dow n2
PWM3
-50
AC2
HB3
-100
0.4
0.405
0.41
0.415
0.42
0.425
0.43
0.435
0.44
-K-
Fig. 7. Seven-level current waveform and (AC) voltage obtained by
simulation [1].
[Vdc2]
-K-
1
s
[iac_ref]
Saturation1
Ki
[Vdc3]
Grid Phase
NVc
[vac_ref]
[iac_ref]
In1
Out1
PR1
[iac]
In1
vac_ref
Duty1
[duty1]
[Vdc2]
vdc2
Duty2
vdc3 Balancer
[duty2]
[Vdc3]
Saturation [Vdc1]
vdc1
Out1
PR3
[Iin]
iac
Duty3
[duty3]
clk
clk
Fig. 5. Simulink simulation of the control system in [1].
Simulation results are shown in Figures 5 to 7. In Figure
6, before t = 0.3s, the first and third cell loads are 20 ohm
and second cell is 120 ohm. Although there is a significant
difference between the loads, each of three has been well
established in source voltage V30. At the moment t = 0.3s,
the second cell load is increased to 20 ohms. Although load
increasing shows the voltage drop, the controller is well
able to return voltages to the source. At t = 0.6s again the
second cell is reduced to 120 ohms and also the DC voltage
is returned to the desired value.
The limitations of this method are as follows
 All cell voltages must be equal.
 The number of used keys is relatively high.
Voltage drop on the inductor L in cascade converters,
(Figure 5), is very small because of the low frequency
impedance of the inductor. Therefore the network domain
and voltage phase are equal to the harmonics domain and
voltage phase of the inverter. If the difference is large, the
magnitudes current passes the inductor and damage the
inverter devices. Where the sum of the base DC voltage is
lower than the peak network voltage, the inverter is not able
to produce voltage the same as domain and the flow control
is lost and the converter becomes unstable. This is shown in
Figure 8. In this figure, the DC voltage command for each
capacitor is V30. Thus, the collected will be V90. Peak
value of the voltage is V71 and the converter works in a
sustainable way. At t = 0.5ms, the DC voltage command
decreases from V30 to V20 and becomes unstable.
35
30
25
Vdc
Kp
[Vdc1]
20
Vdc1
15
Cell2 Load Step
10
0.4
Cell2 Load Step
0.45
0.5
0.55
0.6
Time (sec)
0.65
0.7
0.75
0.8
vdc (v)
Fig. 8. DC base voltage instability when voltage command Vdc is less than
the amplitude of the peak.
V
dc2
4.
V
dc3
0.2
0.3
0.4
0.5
time (sec.)
0.6
0.7
0.8
Fig. 6. DC voltage obtained from the simulation [1] Under Changing Test
(three voltages are equal to 30 V and are shown separately for better view).
Figure 7 shows a seven-level voltage and flow from
network. Stable is voltage and waveforms are very close to
the sinus. Proportional-resonant controller has reached
CONCLUSION
Simulation results are shown in Figure 6 and 7. In
Figure 6, before t = 0.3s, the first and third cells are with a
20 ohm load and second cell load is 120 ohm. Although
there is a significant difference between the loads, each of
three voltages has been well established at the source V30.
At the moment t = 0.3s, the second cell is increased to 20
ohms. Although the effect of increasing the voltage drop
can be seen, the controller is well able to return to the
TRANSACTION SERIES ON ENGINEERING SCIENCES AND TECHNOLOGIES (TSEST) ©
BASHIRI et al.: MULTI-OUTPUT CONVERTER DESIGN WITH TWO REGULATED OUTPUT AND MINIMIZED SYSTEM HARMONIC.
reference voltage. At t = 0.6s second cell again is reduced to
120 ohms and the DC voltage is returned to the desired
value. Network flow has the minimal distortion. Harmonic
effects are reduced somewhat in this convector.
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Cite this work as:
Behroz Bashiri, and Amin Shahbazi, "Multi-Output
Converter Design with two Regulated Output and
Minimized System Harmonic," TSEST Transaction on
Electrical and Electronic Circuits and Systems, Vol.
4(21), Pp. 124-127, Dec., 2014.
TRANSACTION SERIES ON ENGINEERING SCIENCES AND TECHNOLOGIES (TSEST) ©