AN UNDER FREQUENCY LOAD SHEDDING SCHEME FORHYBRID AND MULTI AREA POWER SYSTEMS

PRESENTED BY

AJAY PRAKASH SINGH

PSE 152603

EEE NIT WARANGAL

UNDER THE GUIDANCE OF

SREE B. NAGU

INTRODUCTION

What is under frequency load shedding scheme (U.F.L.S)

Need of U.F.L.S scheme

Previously used scheme (Adapted U.F.L.S) & related issues

Problem Statement Of U.F.L.S scheme

Simulation with Hybrid Power System & its Analysis

Simulation with Multi Area Power System & its Analysis

Conclusion

NEED OF U.L.F.S SCHEME

U.F.L.S WILL MAINTAIN

FREQUENCY WITHIN

PERMISIABLE LIMIT

IN CASE OF INTER CONNECTED OR

ISOLATED P.S

IN CASE OF FAULT

• IN CASE OF SOURCE AND LOAD CONNECTION & DISCONNECTION SYSTEM PAPAMETER VARIES

• MOREOVER OUTPUT OF DG’S ALSO CHANGE DURING LOAD SHEDDING PROCESS .

• EFFECT IN PERPORMANCE AND RELIABILITY DECREASES

• ISSUES

RESULTS IN

HOW TO CONTROL FREQUENCY

• In case of worst possible contingency results in highest initial rate of decay in

frequency.

• Amount of load shed ensures that frequency further do not fall below.

• So we need to determine, number and size of shedding, It is done by hit and

trial method.

• Its not a trivial task it has too be done very precisely and accurately otherwise

results in undesirable damage black outs and serious cost .

• For this few schemes are there-

1. ADAPTIVE U.F.L.S SCHEME

2. NOVEL U.F.L.S SCHEME

ADAPTIVE U.F.L.S & ITS ISSUES

• Power deficit is calculated bases on frequency derivative (at the time of disturbance)

• Its advantage is we don’t have determine worst possible contingency

• Calculated amount of load is shed based of power deficit.

• If power deficit is occur due to gen. outage and islanding of power system

• P cal < P actual . …...… … ………………………………

• Amount of load shed do not have a linear relation with power deficit …

• New frequency U.F.L.S technique is based on frequency second derivative

• Calculation of second derivative is very tedious …… …………

• In hybrid P.S power is not constant we require a scheme independent of .

Parameter . . .

disadvantage

U.F.L.S SCHEME

• U.F.L. S scheme uses fre. first derivative , only one parameter that effect power

deficit is H

• In first step estimated H is used, & in next step updated H will be used

• power deficit is Cal by swing equation

• Since this scheme is based on fre first derivative it will account for all the sudden

change of power due to DG’s.

Pd =2Heq f'Hz /t = t0

fN

ADVANTAGE

• Independent of system parameter………………………………………………………………………• Consider changes in generated power during load shedding …………………………………………...

Cal power deficit (Pd)

start

SPECIFY THE LOAD TO BE SHED

If Fo-Fk/fo

*100>=T.LS(k)

UPDATE INERTIA & POWER DEFICIT FOR NEXT STEP

If F > 0

IfF < 48.4

Shed all the remaining loads shedding steps

Stop

no

yes

yes

no

SIMULATION WITH HYBRID POWER SYSTEM & ITS ANALYSIS

SCENARIO 1 : ISLANDING HYBRID POWER SYSTEM

SCENARIO 2 : DECREASE IN SUN IRRADIANCE DURING L.S

SIMULATION WITH HYBRID POWER SYSTEM & ITS ANALYSIS

SCENARIO 3: INERTIA CONSTANT VARIATION

SIMULATION WITH HYBRID POWER SYSTEM & ITS ANALYSIS

SCENARIO 4 : IN CASE OF WIND TURBINE OUTAGE

SIMULATION WITH MULTI AREA POWER SYSTEM & ITS ANALYSIS

BLOCK DIAGRAM OF MULTI AREA P.S

IN CASE OF FAULT ALL FREQUENCY VARY AND FLUCTUATE BUT Fcoi IS SMOOTHLY VARRY

SIMULATION WITH MULTI AREA POWER SYSTEM & ITS ANALYSIS

IN CASE OF POWER DEFICIT IN AREA 1 ,THERE IS STEP CHANGE IN Fcoi & FI BOTH CAN BE USED TO ESTIMATE POWER

TO MAINTAIN POWER SYSTEM STABILITY DERIVATIVE OF Fcoi IS USED SINCE IN IS NOT VARRYING FAST

.

SIMULATION WITH MULTI AREA POWER SYSTEM & ITS ANALYSIS

IN CASE OF POWER DEFICIT FREQUNCY RESPONSE SHOWS THAT SCHEME IS SUCCESSFUL

EFFECT OF CHANGE IN ‘H’ ON U.F.L.S SCHEME : ‘H’ IN INCRESE BY 50%

• .

SIMULATION WITH MULTI AREA POWER SYSTEM & ITS ANALYSIS

EFFECT OF CHANGE IN ‘H’ ON U.F.L.S SCHEME : ‘H’ IN INCRESE BY 50%

EFFECT OF CHANGE IN SYSTM PARAMETER ( R,D,Tg,Tt)

CONCLUSION

An U.F.L.S scheme for a hybrid distribution system including PV,

FC, DEG, and BESS was proposed.

Under frequency load shedding scheme is successful in

determination of load shed and maintain the frequency within

limit for various scenarios for hybrid and multi area power system.

REFRENCES

U. Rudez and R. Mihalic, “Monitoring the first frequency derivative to

improve adaptive under frequency load-shedding schemes,” IEEE Trans.

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for islanded microgrids,” Int. J. Elect. Power Energy Syst., vol. 62,

pp. 599–607, Nov. 2014.

J. J. Ford, H. Bevrani, and G. Ledwich, “Adaptive load shedding and

regional protection,” Int. J. Elect. Power Energy Syst., vol. 31, no. 10,

pp. 611–618, Nov./Dec. 2009.

U. Rudez and R. Mihalic, “A novel approach to under frequency

load shedding,” Elect. Power Syst. Res., vol. 81, no. 2, pp. 636–643,

Feb. 2011.