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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