Transformer Less FPGAControlled 2-Stage IsolatedGrid Connected PV System
Dogga Raveendhra, Saad Faruqui and Parvesh Saini,“Transformer Less FPGA Controlled 2-Stage Isolated Grid Connected PV System”, 2014 Power and Energy Systems: Towards Sustainable Energy (PESTSE 2014)
Presented By
ANOOP S
M1 EEE
ROLL NO 5
CONTENTS• Introduction
• Conventional system
• Proposed topology
• PV module
• Boost Converter based MPPT Charge controller
• Neutral Point Clamped Inverter
• Conclusion
• References
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Introduction
• Photovoltaic systems convert light energy to
electrical energy
• Grid connected PV systems are becoming a major
part of distribution systems.
• PV systems use galvanic isolation for protection from
dc leakage current.
• New inverter topology to eliminate dc leakage
current is proposed.
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Conventional PV system
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Leakage current in three phase full bridge inverter
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Proposed System
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• Array of solar cells
• DC/DC converter which converts variable DC
output from PV module to fixed DC
• Inverter to convert DC to AC
• Neutral point clamped inverter is used
• 1st stage : dc-to-dc conversion
• 2nd stage : dc to ac conversion without isolation
transformer
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PV Module
• Crystalline silicon is the most widely used PV material
• Solar energy energizes electrons in semiconductor
material which results in flow of electrons
• A number of solar cells are combined to form an
array or a PV module.
• Solar cell can be realized as a current generator
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Boost Converter based MPPT Charge Controller
• MPPT or Maximum Power Point Tracking is an
algorithm that is included in charge controllers used
for extracting maximum available power from PV
module.
• Maximum power depends on solar irradiation and
temperature of solar cell.
• Boost converter steps up the input voltage
magnitude to a required output voltage
magnitude.
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Neutral point clamped inverter
• Multilevel inverter
• Suitable for medium and high level voltage
• As the number of levels are increased switching
frequency will be reduced
• It can be connected directly to the grid
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Topology of neutral point clamped inverter
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S1 and S2 ON
VRO= 𝑉𝑑𝑐2
S3 and S4 ON
VRO= −𝑉𝑑𝑐2
S2 and S3 ON
VRO= 0
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Phase Voltage of NPC inverter
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Firing Scheme of Switches
S1 S2 S3 S4 VRO
1 1 0 0 +𝑉𝑑𝑐
2
0 1 1 0 0
0 0 1 1 −𝑉𝑑𝑐
2
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Gate pulses generated from FPGA
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Line voltage waveforms
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Leakage current elimination
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Advantages of NPC inverter
• Leakage current will be eliminated since mid point
of capacitors is connected to ground.
• Better waveform quality.
• Harmonic elimination.
• Less error between actual and ideal waveforms.
• The power devices and the DC-link capacitors have
to stand only one half of the DC-link voltage.
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PV system20
Conclusion• Transformer less photovoltaic systems are smaller in
size and petite in weight.
• Usage of neutral point clamped inverter eliminates
the danger of DC leakage current.
• The total harmonic distortion is much less compared
to that of conventional inverters
• Size of filter is reduced as THD is low
• Overall cost of the PV system is reduced.
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References• Dogga Raveendhra, Saad Faruqui and Parvesh Saini,“Transformer Less FPGA
Controlled 2-Stage Isolated Grid Connected PV System”, 2014 Power and
Energy Systems: Towards Sustainable Energy (PESTSE 2014)
• Y. Xue, K. e. Divya, G. Griepentrog, M. Liviu, S. Suresh, and M. Manjrekar,
"Towards next generation photovoltaic inverters," in Froc. iEEE Energy
Converso Congr. Expo., 2011, pp. 2467-2474
• Raveendhra, D.; Pathak, M.K.; Panda, A, "Power conditioning system for solar
power applications: Closed loop DC-DC convertor fed FPGA controlled diode
clamped multilevel inverter," Electrical, Electronics and Computer Science
(SCEECS), 2012 iEEE Students' Conference on, vol., no., pp.l,4, 1-2 March 2012
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QUESTIONS…??
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THANK YOU
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