In The Name of GOD SIMULTANEOUS VOLTAGE CONTROL OF SEVERAL LOADS ON FEEDERS OF A DISTRIBUTION...

In The Name of GOD

SIMULTANEOUS VOLTAGE CONTROL OF SEVERAL LOADS ON FEEDERS OF A

DISTRIBUTION SUB-STATION USING

FUZZY MODELING AND FUZZY OPTIMIZATION

A. Ebrahimi A. Zolfaghari S.Mohseni

Electrical and Comp. Eng. Department

Isfahan University of Technology, IRAN

Barcelona 12-15 May 2003

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Scope of this paper

• A new algorithm for simultaneous voltage control of several loads located on various feeders of a distribution sub-station

• Using Fuzzy Modeling and Fuzzy Optimization

• According to actual limitations

Barcelona 12-15 May 2003

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Usual Methods for Load Voltage Regulation

• Using Automatic switched shunt capacitors.

• Using Dynamic voltage regulators.• Using A.V.R. & Tap Changer Systems at

Distribution Substations.

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Limitations:

• Variation of loads and their power factor • The loads are distributed along the feeder • High voltage drop during peak and over voltage

during off-peak hours• Different behaviors of various loads• Different sensitivity of loads to voltage deviations• ِِ��At last but not least : No Remote Controlled

Switch and no Monitoring Systems are usually available

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There is an Optimization Problem!

Max : D = Min [i1 (Vi ) , i2 (Vi )]

S.T. : VA = Vi + Ri Ii COS Øi + Xi Ii SIN Øi

VAmin VA VA

max

For all i =1, 2,…, n

D is the decision fuzzy set defined as the intersection of fuzzy sets i

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Why Fuzzy Modeling

& Optimization?

• Fuzzy nature of loads and voltage variations

• Approximate data and rare of information

• No measurement and monitoring systems are available at most load points

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The Proposed Algorithm

• By FLP and some approximations:

VA = Vi + Ri Ii COS Øi + Xi Ii SIN Øi

• VA is the magnitude of low voltage side of transformer at sub-station

• Vi is the voltage of load i

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Triangular Membership Function

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WhyTrapezoidal membership functions?

• Representing a more realistic modeling for flexible constraints.

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Especial loads &

Their Priority in Voltage Regulation

• By priority factors (i ) multiplied to membership functions

• Decreasing acceptable bound of membership function

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Case Study

• A distribution sub station with 4 radial feeders• Loads assumed constant and at the end of feeders• Using triangular and trapezoidal membership

functions for voltage fuzzy sets• Using several priority factors

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• A symbolic view of the test system

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CONCLUSIONS

• Simultaneous voltage control of loads located at several distribution feeders

• Priorities for especial loads considered

• Useful and applicable in systems without remote controlled switches and monitoring system

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Thanks For Your Attention

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