Implementation of a Voltage Multiplier based on High Step-up Converter using FLC

109 International Journal for Modern Trends in Science and Technology
Volume: 2 | Issue: 06 | June 2016 | ISSN: 2455-3778IJMTST
Implementation of a Voltage Multiplier based
on High Step-up Converter using FLC
Dhanraj Soni1
| Ritesh Diwan2
1PG Scholar (Power Electronics), Department of ET&T, RITEE, Raipur, C.G., India.
2HOD, Department of ET&T, RITEE, Raipur, C.G., India.
A Front end of the Photovoltaic Solar Panel is been proposed based on Step-Up Converter. The use of
distributed energy resources is increasingly being pursued as a supplement and an alternative to large
conventional central power stations. The specification of a power electronic interface is subject to
requirements related not only to the renewable energy source itself but also to its effects on the power-system
operation, especially where the intermittent energy source constitutes a significant part of the total system
capacity. Implementing a voltage multiplier module, an asymmetrical interleaved high step-up converter
obtains high step-up gain without operating at an extreme duty ratio. The voltage multiplier module is
composed of a conventional boost converter and coupled inductors. An extra conventional boost converter is
integrated into the first phase to achieve a considerably higher voltage conversion ratio. The two-phase
configuration not only reduces the current stress through each power switch, but also constrains the input
current ripple, which decreases the conduction losses of metal–oxide–semiconductor field-effect transistors.
In addition, the proposed converter functions as an active clamp circuit, which alleviates large voltage spikes
across the power switches. Finally, the simulation circuitry with a 40V input voltage and 230V output voltage
is operated to verify its performance analysis with respect to the Fuzzy Logic Controller. The highest
efficiency is 97.75%.
KEYWORDS: Boost/fly-back converter, high step-up converter, photovoltaic system, voltage multiplier
module, Fuzzy Logic Controller.
Copyright © 2016 International Journal for Modern Trends in Science and Technology
All rights reserved.
I. INTRODUCTION
As conventional sources of energy are rapidly
depleting and the cost of energy is rising,
photovoltaic energy becomes a promising
alternative source. Among its advantages are that
it is: 1) abundant; 2) pollution free; 3) distributed
throughout the earth; and 4) recyclable. The main
drawbacks are that the initial installation cost is
considerably high and the energy conversion
efficiency is relatively low. To overcome these
problems, the following two essential ways can be
used: 1) increase the efficiency of conversion for the
solar array and 2) maximize the output power from
the solar array. With the development of
technology, the cost of the solar arrays is expected
to decrease continuously in the future, making
them attractive for residential and industrial
applications. The state-space-averaging method [9]
is widely used to derive expressions for
small-signal characteristics of pulse width
modulated (PWM) converters [9], [10]. However,
this method is sometimes tedious, especially when
the converter equivalent circuit contains a large
number of elements. To obtain the models of dc/dc
converters, the principle of energy conservation is
used in this paper to derive the model and transfer
function for the system [11]. The models are
especially convenient in analyzing complicated
converter topologies and for including parasitic
components.
Figure 1 Typical PV System
ABSTRACT

Implementation of a Voltage Multiplier based on High Step-up Converter using FLC
The increasing number of renewable energy
sources and distributed generators requires new
strategies for the operation and management of the
electricity grid in order to maintain or even to
improve the power-supply reliability and quality. In
addition, liberalization of the grids leads to new
management structures, in which trading of energy
and power is becoming increasingly important. The
power-electronic technology plays an important
role in distributed generation and in integration of
renewable energy sources into the electrical grid,
and it is widely used and rapidly expanding as
these applications become more integrated with
the grid-based systems.
Figure 2 Integrated fly-back boost converter
Modifying a boost fly-back converter, shown in
Fig. 2(a), is one of the simple approaches to
achieving high step-up gain; this gain is realized
via a coupled inductor. The performance of the
converter is similar to an active-clamped fly-back
converter; thus, the leakage energy is recovered to
the output terminal [12]. An interleaved boost
converter with a voltage-lift capacitor shown in Fig.
2(b) is highly similar to the conventional
interleaved type.
Figure 3 Proposed Voltage Multiplier Circuit
The advantages of the proposed converter are as
follows:
1.The converter is characterized by a low input
current ripple and low conduction losses, making
it suitable for high power applications.
2.The converter achieves the high step-up voltage
gain that renewable energy systems require.
3.Leakage energy is recycled and sent to the output
terminal, and alleviates large voltage spikes on
the main switch.
4.The main switch voltage stress of the converter is
substantially lower than that of the output
voltage.
II. LITERATURE SURVEY
Photovoltaic systems normally use a
maximum power point tracking (MPPT) technique
to continuously deliver the highest possible power
to the load when variations in the isolation and
temperature occur. It overcomes the problem of
mismatch between the solar arrays and the given
load. A simple method of tracking the maximum
power points (MPP’s) and forcing the system to
operate close to these points is presented. The
principle of energy conservation is used to derive
the large- and small-signal model and transfer
function. By using the proposed model, the
drawbacks of the state-space-averaging method
can be overcome. The TI320C25 digital signal
processor (DSP) was used to implement the
proposed MPPT controller, which controls the
dc/dc converter in the photovoltaic system. [1],
[13].
The use of distributed energy resources is
increasingly being pursued as a supplement and
an alternative to large conventional central power
stations. The specification of a power electronic
interface is subject to requirements related not
only to the renewable energy source itself but also
to its effects on the power-system operation,
especially where the intermittent energy source
constitutes a significant part of the total system
capacity. In this paper, new trends in power
electronics for the integration of wind and
photovoltaic (PV) power generators are presented.
A review of the appropriate storage-system
technology used for the integration of intermittent
renewable energy sources is also introduced. [2]
A substantial increase of photovoltaic (PV)
power generators installations has taken place in
recent years, due to the increasing efficiency of
solar cells as well as the improvements of
manufacturing technology of solar panels. These
generators are both grid-connected and
stand-alone applications. We present an overview
of the essential research results. The paper
concentrates on the operation and modeling of
stand-alone power systems with PV power
generators. Systems with PV array–inverter
assemblies, operating in the slave-and-master
modes, are discussed, and the simulation results

obtained using a renewable energy power system
modular simulator are presented. These results
demonstrate that simulation is an essential step in
the system development process and that PV power
generators constitute a valuable energy source.
They have the ability to balance the energy and
supply good power quality. It is demonstrated that
when PV array–inverters are operating in the
master mode in stand-alone applications, they will
perform the task of controlling the voltage and
frequency of the power system. The mechanism of
switching the master function between the diesel
generator and the PV array–inverter assembly in a
stand-alone power system is also proposed and
analyzed. [3]
III. PRINCIPLE OPERATION
The proposed high step-up converter with
voltage multiplier module is shown in Fig. 3(a). A
conventional boost converter and two coupled
inductors are located in the voltage multiplier
module, which is stacked on a boost converter to
form an asymmetrical interleaved structure.
Primary windings of the coupled inductors with NP
turns are employed to decrease input current
ripple, and secondary windings of the coupled
inductors with Ns turns are connected in series to
extend voltage gain. The turn’s ratios of the
coupled inductors are the same. The equivalent
circuit of the proposed converter is shown in Fig.
3(b), where LM1 and LM2 are the magnetizing
inductors, LK1 and LK2 represent the leakage
inductors, S1 and S2 denote the power switches, Cb
is the voltage-lift capacitor, and n is defined as a
turn’s ratio NS/NP
The proposed converter operates in
continuous conduction mode (CCM), and the duty
cycles of the power switches during steady
operation are interleaved with a 1800 phase shift;
the duty cycles are greater than 0.5. The key steady
waveforms in one switching period of the proposed
converter contain six modes, which are depicted in
Fig. 4, and Fig. 5 shows the topological stages of
the circuit.
Stage A [t0, t1]: At t=t0, the power switches S1 and
S2 are both turned ON. All of the diodes are
reversed-biased. Magnetizing inductors LM1 and
LM2 as well as leakage inductors LK1 and LK2 are
linearly charged by the input voltage source Vin.
Stage B [t1, t2]: At t=t1, the power switch S2 is
switched OFF, thereby turning ON diodes D2 and
D4. The energy that magnetizing inductor LM2 has
stored is transferred to the secondary side charging
the output filter capacitor C3. The input voltage
source, magnetizing inductor LM2, leakage inductor
LK2, and voltage-lift capacitor Cb release energy to
the output filter capacitor C1 via diode D2, there by
extending the voltage on C1.
Stage C [t2, t3]: At t=t2, diode D2 automatically
switches OFF because the total energy of leakage
inductor LK2 has been completely released to the
output filter capacitor C1. Magnetizing inductor LM2
transfers energy to the secondary side charging the
output filter capacitor C3 via diode D4 until t3.
Figure 4 Operating Stages of the Proposed Converter
Stage D [t3, t4]: At t=t3, the power switch S2 is
switched ON and all the diodes are turned OFF.
The operating states of modes 1 and 4 are similar.
Stage E [t4, t5]: At t=t4, the power switch S1 is
switched OFF, which turns ON diodes D1 and D3.
The energy stored in magnetizing inductor LM1 is
transferred to the secondary side charging the
output filter capacitor C2. The input voltage source
and magnetizing inductor LM1 release energy to

Implementation of a Voltage Multiplier based on High Step-up Converter using FLC
voltage-lift capacitor Cb via diode D1, which stores
extra energy in Cb.
Stage F [t5, t0]: At t=t5, diode D1 is automatically
turned OFF because the total energy of leakage
inductor LK1 has been completely released to
voltage-lift capacitor Cb. Magnetizing inductor LM1
transfers energy to the secondary side charging the
output filter capacitor C2 via diode D3 until t0.
The operation principle analysis and the
steady-state waveforms of the high step-up
ZVT-interleaved boost converter have been
discussed in [9]. Compared with the proposed
converter, the full-bridge dc–dc converter is also
employed commonly as a similar first stage in the
PV system. However, for the high step-up gain
applications, the large current ripples of the
primary-side switches increase the conduction
losses, and the secondary-side diodes need to
sustain a high voltage stress. Moreover, as a buck
type converter, a large turns ratio of the
transformer is necessary to obtain a high step-up
gain, which induces a large leakage inductance
and large commutation energy on the primary-side
switches. Therefore, the design of the transformer
is difficult and the converter’s efficiency is
impacted. Furthermore, the resonant-mode
converters such as LLC, LCC, and higher order
element converters are studied and developed,
which are attractive for potential higher efficiency
and higher power density than PWM counterparts.
However, most of resonant converters include
some inherent problems, such as electromagnetic
interference (EMI) problems due to variable
frequency operation and reduced conversion
efficiency due to circulating energy generation.
Moreover, to make practical use of the resonant
converters, the required precise control waveform
and difficult over current protection increases the
design complexity of the whole system [11].
IV. DESIGN CONSIDERATIONS
Figure 5 Simulink Diagram using FLC
Figure 6 Solar Panel & MPPT (P & O)
V. FUZZY LOGIC CONTROLLER
In this section, the fuzzy control fundamentals will
be outlined first, and then, the key point of
self-tuning PI-like fuzzy controller (STFC) will be
briefly reviewed. Afterward, the modified design of
the proposed STFC will be described in detail. A
basic FLC system structure, which consists of the
knowledge base, the inference mechanism, the
fuzzification interface, and the de-fuzzification
interface, is shown in Fig. 7. Essentially, the fuzzy
controller can be viewed as an artificial decision
maker that operates in a closed-loop system in real
time.
Figure 7 Basic Structure of Fuzzy Logic Control System
It grabs plant output y(t), compares it to the
desired input r(t), and then decides what the plant
input (or controller output) u(t) should be to assure
the requested performance. The inputs and
outputs are “crisp”. The fuzzification block
converts the crisp inputs to fuzzy sets, and the
de-fuzzification block returns these fuzzy
conclusions back into the crisp outputs. Inference
engine using if-then type fuzzy rules converts the
fuzzy input to the fuzzy output.

Table 1 5x5 Based Rule
VI. RESULTS
Figure 8 Boost Converter DC Output
Figure 9 Inverted AC Output
Figure 10 THD (2.25%)
VII. CONCLUSION
According to the proposed model using Fuzzy
Logic Controller maximum harmonics has been
reduced along with the minimization of the settling
time as well as Total Harmonic Distortion of 2.25%
with an efficiency of 97.75%. Thus, the proposed
converter is suitable for PV systems or other
renewable energy applications that need high
step-up high-power energy conversion.
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Implementation of a Voltage Multiplier based on High Step-up Converter using FLC

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Implementation of a Voltage Multiplier based on High Step-up Converter using FLC