Main Title

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THE IMPACT OF BoBC IN OFF-SHORE WIND ENERGY
CONVERSION SYSTEM
PRESENTED BY E. SHEEBA PERCIS Dr.M.G.R University
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Abstract
Offshore windfarms is an emerging technology in
the wind energy conversion system. For onshore
wind farms high voltage overhead lines are used
for transmitting power from the wind farm to the
grid. However this option is not possible in the
case of an offshore windfarm as large part of the
distance to connection point must be covered by
submarine cables. The application of high
voltage dc (HVDC) transmission for integrating
large scale and/or off-shore wind generation
systems with the electric grid is attractive in
comparison to extra high voltage (EHV) ac
transmission due to a variety of reasons like
efficiency, economics etc. In the case of HVDC
transmission a converter is connected between the
wind farm and the utility grid. Even though CSCs
and VSCs are widely used for the realization of
large HVDC systems, as an alternative approach
Bridge of Bridge converter (BoBC) is introduced
recently. In this work the performance of the VSC
and BoBC are compared and analyzed. The
simulation is done using PSCAD/EMTDC software.
Compared with the onshore wind farms, the
offshore wind farms have access to significantly
better wind energy resources and hence offer
larger energy generating capability. Therefore
offshore wind farms are gaining importance and
the BoBC proves to be better than the VSC for
similar applications.
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Paper Publication

• Sheeba Percis, L. Ramesh, Dr. S. P. Chowdhury,
  Dr. S. P. Chowdhury. The Technical Impacts
  prediction of Small Scale DG in Low Voltage
  Distribution Networks International Conference
  on Renewable Energy , Anna University Chennai
  ,India ,August 2010 , Page 20-25.
• Sheeba Percis, L. Ramesh, Impact of BoBC in
  Off-shore Wind Energy Conversion System , IEEE
  and IET International Conference on Computer
  Communication (ICCCET 2011) ,National College of
  Engineering , Tirunelveli, India ,March 2011,Page
  50-56.
•  Sheeba Percis,Detection of flaws in rolling of
  steel sheets using Image processing, National
  Conference on Future challenges and Budding
  Intelligent Techniques in Electrical
  Electronics Engineering (NCEEE 2010), Sathyabama
  University,Chennai ,India , April 2010, Page
  78-81.
•  

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OUTLINE OF PRESENTATION

• Introduction
• Literature review
• Methodology
• Results and Discussion
• Conclusion

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INTRODUCTION

• Wind - Promising renewable energy
• resource.
• Wind energy conversion systems
• sustainable energy.
• Off-shore WECS are better than on-
• shore WECS.
• Long distance transmission HVDC
• stands ahead of HVAC.

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LITERATURE REVIEW

• Limited availability of onshore sites and better
  off-shore wind conditions are the driving force
  for off shore WECS.
• With a HVDC system power flow can be controlled
  rapidly.
• Development availability of power electronic
  devices is the underpinning technology for
  integration of large wind farms with electricity
  grid.
• VSC based HVDC transmission is a good solution
  for connection of large off-shore sites over long
  distances.
• The BoBC has proved to be advantageous than CSCs
  VSCs in terms of efficiency and economics.

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METHODOLOGY
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System Design
STAGE I Design of VSC STAGE II Design of
BoBC STAGE III Realization of HVDC
system SOFTWARE USED PSCAD/EMTDC
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Voltage Source Converter
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Features Of VSC

• Consists of six arms with series connected
  sub-modules.
• Fully controlled switches accompanied with
  anti-parallel diodes are used.
• Bi-directional current flow is obtained.
• Operated in four quadrants.
• Control of real and reactive power is possible.
• A dc bus capacitor is used to provide stiff dc.
• PWM is used.

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Bridge Of Bridge Converter
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Features of BOBC

• Has six arms with sub-modules connected in
  series.
• Sub-modules are stand alone power converters.
• Any number of sub-modules can be connected and
  desired voltage rating is obtained.
• Instead of PWM if discrete voltage steps are used
  low harmonics and switching losses are achieved.

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TESTED RESULTS
Output voltage of VSC
Output voltage of BoBC

• For an input of 0.44kV, the VSC gives an output
  of 0.3369kV.
• Q15.799 kVAR
• For an input of 0.44kV, the BoBC gives an output
  of
• 0.432kV.

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AC Side Reactive Component - VSC
Q15.799KVAR
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Realization OF HVDC System
HVDC SYSTEM USING VSC
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HVDC System Using BoBC
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Output With HVDC System
Output of HVDC-BoBC
Output of HVDC-VSC
The efficiency of the HVDC-BOBC is 87 percent and
hence the HVDC system using BOBC is more
efficient than the system using VSC.
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Comparison

• In VSC, RC networks are needed for voltage
  sharing. BoBC does not demand this.
• In VSC, the number of series connections are
  restricted due to the RC networks. BoBC is not
  affected in this manner.
• AC side reactive components.
• Fault tolerance.
• During fault, energy stored in dc bus capacitance
  of VSC feeds the fault.
• BoBC is comparatively less costly and more
  efficient.

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CONCLUSION

• Off-shore WECS is an emerging solution for green
  energy.
• As distance becomes longer, AC has technical
  limitations.
• Based on PSCAD/EMTDC simulation results BoBC is
  found to be better than VSC in performance.
• BoBC based HVDC off-shore WECS is highly
  efficient and cost effective.

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REFERENCES

• Daniel Ludois and Giri Venkataramanan, An
  examination of AC/HVDC Power Circuits for
  Interconnecting Bulk Wind Generation with the
  Electric grid,energies 2010,vol 3,1263-1289,ISSN
  1996-1073.
• Sheng Jie Shao and Vassilios G. Agelidis,
  Review of DC system Technologies for Large Scale
  Integration of Wind Energy Systems with
  Electricity Grids,Energies 2010,3,1303-1319,ISSN
  1996-1073.
• Juiping pan, Reynaldo Nuqui, Le Tang and Per
  Holmberg, VSC-HVDC Control and Application in
  Meshed AC Networks
• S. K. Chaudhary, R. Teodorescu and R. Rodriguez,
  Wind Farm Grid Integration Using VSC Based HVDC
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• S. M. Muyeen, R. Takahashi, T. Murata, and J.
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• S. M. Muyeen, Member, IEEE, Rion Takahashi,
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  IEEE, Operation and Control of HVDC
  connected Off-shore wind farm, IEEE Transactions
  on Sustainable Energy, Vol. 1, No. 1, April 2010.
• Christian Feltes, Holger Wrede, Friedrich W. Koch
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  Connected to the Grid through VSC based HVDC
  Transmission, IEEE Transactions on Power
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• Hermann Koch and Deitmar Retzman, Connecting
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  3, March 2009.

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