An Efficient Photo Voltaic System for Onboard Ship Applications

Shashidhar Kasthala et al. Int. Journal of Engineering Research and Applications www.ijera.com
ISSN: 2248-9622, Vol. 6, Issue 2, (Part - 1) February 2016, pp.75-81
www.ijera.com 75|P a g e
An Efficient Photo Voltaic System for Onboard Ship Applications
Shashidhar Kasthala*, Krishnapriya*, Rajitha Saka**
*(Faculty of ECE, Indian Naval Academy, Ezhimala, Kerala-670310)
** (Department of Electrical & Electronics, Gurunanak Institutions Technical Campus, Hyderabad)
ABSTRACT
In this paper a high efficient photovoltaic system is proposed for onboard ship applications which convert the
lower voltage obtained from solar modules to higher voltage required by the ship service loads. In a typical
photovoltaic system only step-up /boost converter is used due to which the converter has to operate in extreme
duty ratio, resulting in increase of switching losses and thus decreasing the overall efficiency. But in this paper
the conventional boost converter is used with interleaved inductors and capacitors. The poposed system stores
the energy in inductors and thus reduces the stress in the switches (Without allowing the total voltage to appear
across the switch). The simulation is designed using MATLAB/Simulink with an Input voltage of 40-V to
achieve a output voltage of 300-380 V. The developed simulation results are compared for output powers of
500W and 1kW
Keywords - Photovoltaic system, renewable energy sources, interleaved boost converter, voltage multiplier
module.
I. INTRODUCTION
Currently, the diesel engines, is considered has the
most viable and reliable option for ship propulsion
and auxillary power generation. But the complication
with the extensive usage of this technology is
emmision of gases like CO2, NOx, SOx and other
organic chemicals. The shipping industry is estimated
to produce 3% of global emmission of CO2, this
includes the mechant ships, combat ship and cruise
ships [7][8]. As a solution to this, extensive research
is being carried out world wide in implementation of
renewable energy sources for Ship propulsion and
other Ship service loads. The renewable energy,
primarily solar and wind energy sources can be
considered as an alternative energy source for main
propulsion and auxillary power requirements of a
ship though there are some inherent limitations for
these renewable energies due to their intermittent
nature [4].
The electrical load on board ship can be
classified into propulsion loads and service loads.
With the present day solar technology and with the
typical characteristics of propulsion drives, the solar
energy has a primary source of energy may not be a
feasibile option for medium or large ships but can be
used for small size ships. For large size ships, the
solar energy can be used to cater only the selected
laods so as to mainatin the continuity of electrical
supply. The solar energy on board ship can be
connected to the vital loads viz. Combat systems,
mobility systems, fire systems etc [1]. Fig. 1 shows a
typical photovoltaic system catering the service loads
of the ship which consists of a solar module, a step-
up converter, a controller, a battery set, and an
inverter.
Fig. 1 Typical photovoltaic system Theoretically, the
conventional step-up converters, such as the boost
converter and fly-back
converters, cannot achieve a high step-up conversion
and high efficiency because of the resistance of the
elements or leakage inductance [2]-[4]. The answer
to this problem a modified boost–fly-back converter
is proposed in this paper.
As compared to the conventional circuit, losses
are less in an asymmetrical interleaved converter for
a high step-up and high-power application. But the
asymmetrical interleaved converter circuit is
complicated. One of the simplest approaches to
achieve high step-up gain is by using the Modified
boost–fly-back converter as shown in Fig. 2(a). Here
the gain is realized by using a coupled inductor. The
performance of the converter is similar to an active-
clamped fly-back converter in which the leakage
RESEARCH ARTICLE OPEN ACCESS

energy is recovered to the output terminal [5][6]. An
interleaved boost converter with a voltage-lift
capacitor is shown in Fig. 2(b). It is similar to the
conventional interleaved type converter. It obtains
extra voltage gain through the voltage-lift capacitor,
and reduces the input current ripple, which is suitable
for power factor correction (PFC) and high-power
applications.
Fig. 2 (a) integrated fly-back–boost converter
structure.(b) Interleaved boost converter with a
voltage-lift capacitor structure.
In this paper, an asymmetrical interleaved high
step-up converter is proposed with PV system having
voltage multiplier module. The turns ratio of coupled
inductors are designed to extend the voltage gain, and
a voltage-lift capacitor is used to offer an extra
voltage conversion ratio. The system designed here
stores the energy in inductors and thus reduces the
stress in the switches (Without allowing the total
voltage to appear across the switch).
II. OPERATING PRINCIPLE
The proposed high step-up interleaved inductor
capacitor converter with voltage multiplier module is
shown in Fig. 3. A boost converter withinterleaved
capacitor and inductor makes the system
asymmetrical. Number of winding in primary is Np
and that of secondary is Ns.
Fig. 3 The proposed converter.
Fig. 4 Waveforms for the proposed converter .
Primary windings of the coupled inductors
are employed to decrease the input current ripple, and
that of secondary windings are used for extend
voltage gain. The turn’s ratios of the coupled
inductors are the same .In the circuit 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 equal to Ns /Np.
The proposed system operates in continuous
conduction mode (CCM).The power switches during
the steady state operation are interleaved with a 180◦
phase shift; the duty cycles are greater than 0.5.
The steady state waveforms in one switching
period of the proposed converter have six modes,
which are depicted in Fig. 4, and the different modes
of operations are explained in detail in Fig. 5. In the
circuit the PV system is represented by a DC voltage
source.
2.1 Mode 1 [t0, t1]: In mode 1, when t=t0 both the
switches S1 and S2 are turned ON. So voltage drop
across the switches VDS1 and VDS2 are zero. Diodes
D1 to D4 are reverse biased. Hence capacitors are not
charged. But the magnetizing inductors Lm1 and Lm2
as well as leakage inductors Lk1 and Lk2 are linearly
charged by the input voltage source Vin. Therefore
current flowing through the iLk1 and iLk2 starts
increasing. The operation is described in fig 5 (a).

Fig.5 Operating modes (a) Mode 1 (b) Mode 2
2.2 Mode 2 [t1, t2]: When t=t1, the power switch S2 is
switched OFF, thereby diodes D2 and D4 are forward
biases. The energy stored in the magnetizing inductor
Lm2 now transferred to the capacitor Cb. In this mode
iLk1 is increasing since the power switch S1 is on. Also
C2 is charging through D2 and C3 is charging through
D4.The current flowing through the magnetizing
inductor Lm2, leakage inductor Lk2, and then voltage-
lift capacitor Cb releases the energy to
the output capacitor C1 through the diode D2, there by
extending the voltage on C1.
2.3 Mode 3 [t2, t3]: At the end of t2 the capacitor Cb
discharges completely and diode D2 is reverse biased
automatically. Hence current through that capacitor
icb is zero. In mode 3, the power switch S2 is switched
OFF, S1 is ON as in the previous mode. In this mode
of operation, C1 is charged completely using the
energy released from the Cb through D2.Since D2 is
reverse biased capacitor C2 also discharges
completely. Magnetizing inductor Lm2 transfers
energy to the secondary side charging the output
filter capacitor C3 through the diode D4 until t3.
Fig 5: (c) Mode 3. (d) Mode 4
2.4 Mode 4 [t3, t4]: At time t=t3, the power switch S2
is switched ON and all the diodes are reverse biased.
The operation of mode 4 is similar to that of mode
1. Diodes D1 to D4 are reverse biased. But the
magnetizing inductors Lm1 and Lm2 as well as leakage
inductors Lk1 and Lk2 are linearly charged by the
input voltage source Vin. Fig 5 (c) and (d) explains
the mode 3 and 4.
Fig 5: (e) Mode 5. (f) Mode 6
2.5 Mode 5 [t4, t5]: At t=t4, the power switch S1 is
switched OFF, which forward biases the diodes D1
and D3. D3 is on due to the fully charged C1 capacitor.
The capacitor C2 is charging from the fully charged
capacitor C1. The input voltage source and
magnetizing inductor Lm1 release energy to voltage-
lift capacitor Cb through diode D1, which stores extra
energy in Cb. Since the Cb is charging through D1 the
polarity is changed. Hence the icb direction is
reversed.
2.6 Mode 6 [t5, t0]: At t=t5, the 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.
III. STEADY-STATE ANALYSIS
The transient characteristics of circuitry are
disregarded to simplify the circuit performance
analysis of the proposed converter in CCM and some
formula and assumptions are as follows:
1. All the components are ideal.
2. Leakage inductors Lk1 and Lk2 are neglected.
3. Voltage VCb,VC1,VC2, and VC3 are considered to be
constant because of infinitely large capacitance.
3.1 Voltage Gain and other voltage equations:

3.2 Voltage stresses on semiconductor
components:
IV. SIMULATION RESULTS OF THE
PROPOSED CONVERTER
Fig 6 shows the simulation circuit of high step
up converter with voltage multiplier. Simulation is
done using MATLAB simulink.
Fig 6 simulation circuit of high step-up converter
with a voltage multiplier module with PV
The input voltage is taken from a PV panel and
the power switches Sw1 and Sw2 are Power
MOSFETS. The converter components used and
parameter values are give in TABLE 1.
Parameters Notations Values
Magnetizing
inductances
Lm1,Lm2 133µH
Leakage
inductances
Lk1, Lk2 1.6µH
Turns ratio Ns/Np 1
Capacitors Cb,C2,C3 220 µF
Capacitors C1 470µF
TABLE 1: Converter parameters
Fig 7 shows the gate pulses G1 and G2, voltage
across the power switches Sw1 and Sw2. Switch Sw1 is
ON during Mode 1 to 4. Mode 5 and 6 Sw1 is OFF.
During mode 2 and 3the switch Sw2 is off, and in
other modes it is turned ON. Fig 7 shows the gate
pulses and voltage across the switches for 0.5 kW
and fig 8 gives the same response for 1kW.
Fig 7 gate pulses & voltages across the switches
Sw1& Sw2 for 0.5kw power
In Fig 9 the measured input current, different
leakage input current and capacitor current for 0.5kW
are shown. When the switch Sw1 s on, iLk1 is
increasing from zero and when t=t3 it iLk1 is
maximum, after that it starts to decreases and when
t=t5, current flowing through the leakage inductor
iLk1 again reaches zero.

Fig 8 gate pulses & voltages across the switches
Sw1& Sw2 for 1kw power.
Fig 9 Measured waveforms of Iin, ILK1, ILK2 and Ic
for 0.5kw power
Fig 10 Measured waveforms of Iin, ILK1, ILK2 and Ic
for 1kw power
In Fig 10 leakage current and measured input
current, different leakage input current and capacitor
current for 1kW. When the switch Sw2 s on, iLk2 is
increasing from zero and when t=t0 it iLk2 is
maximum, after that it starts to decreases and when
t=t3, current flowing through the leakage inductor
iLk2 again reaches zero. t.
Fig 11. Measured waveforms of D1, D2, D3 and D4 for
0.5kw power
Fig 12 Measured waveforms of D1, D2, D3 and D4 for
1kw power
Fig 11 shows measured current waveforms of
D1,D2,D3,D4 for 0.5kW.In mode 1 all are reverse
biased ,hence no current flows through the circui
In Fig 12 it shows the different diode current at
1kW.In mode 2 D2,D4 are on where as in mode 3 and

mode 4 D4 is on the rest is off. In mode 5 D1 and D3
are on where as in last mode D3 is On.
Fig 13 Waveforms of Vcb, Vc1, Vc2 and Vc3 for 0.5kw
power
Fig 13 and 14 represents the voltage across
different capacitors. In mode 2, each capacitor starts
to charging, and Cb starts to discharge. At t=t3, Cb and
C2 are fully discharge and again when t=t4, capacitors
C2 and Cb will again start to charge.
Fig 14 Waveforms of Vcb, Vc1, Vc2 and Vc3 for 1kw
power
In Fig 14 gives the different capacitor current at
1kW power. Fig 15 and 16 compares the input,
output power at 0.5 kW and 1kW.The voltage stress
over the power switches are restricted and are much
lower than the output voltage. These switches of low
on-state resistance MOSFET, can be selected. The
full-load efficiency at Po = 1000 W is 96.1%, and the
efficiency at Po = 500 W is 96.8%.
Fig 15 Waveforms of Pin, Po and %n for 1kw power
Fig 16 Waveforms of Pin, Po and %n for 0.5kw
power
V. CONCLUSION
This paper has presented the topological
principles, steady-state analysis, for a designing an
efficient photovoltaic system that can be used for
onboard ship applications. The converter proposed in
this paper provides a efficient high step-up
conversion through the voltage multiplier module and
voltage clamp feature. Due to the low conduction
losses and high efficiency, the proposed converter is
suitable for onboard ship high power applications like
blasting compressors, assault systems, radar
communications etc.
REFERENCES
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Books:
[7] Future Ship Powering Options, Exploring
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