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