FRACTIONAL FREQUENCY TRANSMISSION SYSTEM
By Nihas k
M080394EE
CCIP
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TOPICS
Introduction 3
Why Fractional Frequency..? 4
Structure and its Implementation 9
Experimental setup 15
Other advantages 17
Conclusion 19
References 20
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Introduction
Different approaches for Improving Power Transmission* HVDC* FACTS
Uses lower frequency (50/3 Hz) Designed for long transmission Conventionally voltage is raised Specially useful for hydropower
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Why Fractional Frequency ?
Q is total reactive
power flow
and, X= 2πfL
X 100ΔV%=QX—V2
1. Better Voltage Regulation
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2. Receiving End Voltage At No Load(Ferranti Effect)
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3. Improved Stability
Pmax
= V2/X
Where, Pmax (stability limit) is the
maximum power a stable transmission line
can carry
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4. Lesser Voltage Fluctuation
∂U1/∂P2* = U
2Sin βl
∂U1/ ∂Q2* = U
2Sin βl
Fluctuation is smaller when βl is small
βl is phase coefficient is given by,
β= 2πf
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5. Power angle CharacteristicsPower angle, δ is given by
tanδ = P2* tanβl/(1 + Q2*tanβl)
For P2*= 1 & Q2* = 0(surge impedance loading)
δ = βlδ is an indicator of transmission stability
6. Thermal Limit
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Structure of FFTS
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Blocks
1. Hydroelectric Generatora) Low rotational velocity, suitable for low frequency
b) Only change is in the No. of poles
c) Cost &efficiency remains constant
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Blocks
2. Transformer
* More expensive than 50 Hz transformer
* Larger cross sectional area because of low frequency
3. Frequency Multiplier
* Saturable Core Transformer Type
* Power electronics based. (Cycloconvertor)
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Magnetic Frequency Changer
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Cycloconvertor Circuit
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Cycloconvertor Control System
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Experimental Setup
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Experiment on FFTS
Modeling ratio
* Voltage Ratio: 1000:1(500kV:500V)
* Impedance Ratio: 10:1
* Power Ratio:10002/10=105:1(10MW:1KW)
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Other advantages
Corona Losses
Eddy current loss
Hysteresis loss
Skin effect
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Conclusion Efficient approach to overcome inherent
difficulties of conventional systems Multiply increasing transmission
capability and remarkably improving operating performance
Has economic profits Feasibility study for a project from west
to east china underway Work like analysis of transient & dynamic
stability, improvement of efficiency, restraint of harmonics still needs to be done
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References Wang Xifan, Cao Chengjun, Zhou Zhichao,”
Experiment on Fractional Frequency Transmission System,” IEEE transaction on Power System, vol. 21, no.1, Feb 2006
X. Wang & X Wang, “ Feasibility Study of Fractional Frequency Transmission System,” IEEE transaction on Power System, vol.11,no.2,pp. 962-967,May 1996.
X. Wang , “Fractional Frequency Transmission System,” Proceedings of IEE, Japan, Jul. 1994
B.K. Bose, Modern Power Electronics and AC Drives. Prentice-Hall 2002
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THANK YOU