www.ijsret.org 699 International Journal of Scientific Research Engineering & Technology (IJSRET), ISSN 2278 – 0882 Volume 3, Issue 3, June 2014 Performance of Automatic Generation Control in an Interconnected Power System under Deregulated Environment Ramandeep Kaur 1 , Sirdeep Singh 2 (Associate Professor) 1 (Department of Electrical Engineering, BGIET (Sangrur), INDIA) 2 (Department of Electrical Engineering, BGIET (Sangrur), INDIA) ABSTRACT In this paper the Automatic Generation Control (AGC) in interconnected power system under deregulated environment to control the tie line power of the interconnected hydro-thermal power system in which thermal reheated turbine is used . All four areas have different number of GENCOS, DISCOS and TRANSCOS. A DISCO can individually and multilaterally contracts with a GENCO for power requirements and these transactions are done under the ISO supervision. After deregulation, the bilateral contract on the dynamics of automatic generation control (AGC), DPM has been used. The control strategies guarantees that the steady state error of frequencies and inadvertent interchange of tie-lines power are maintained in a given tolerance limit. The study is carried out on IEEE 75-bus system. The performances of the controllers are simulated using MATLAB/SIMULINK package. Keywords - Automatic Generation Control(AGC), GENCO, CPF, DISCO, DPM, TRANSCO. I. INTRODUCTION The automatic generation control (AGC) is a technical requirement for the proper operation of an interconnected power system. Automatic generation control is very important in power system operation and control for supplying sufficient and reliable electric power with good quality. In cases of area load changes and abnormal conditions, such as mismatches in frequency and scheduled tie-line power flows between areas can be caused. These mismatches are corrected by controlling the frequency. To attain zero steady state error and to maintain the system frequency constant, a control scheme is needed. Here study of the four area restructured power system is done in which each area has its own automatic generation controller (AGC) which maintains the tie line power and system frequency constant by varying the generation according to the area control error (ACE). The AGC varies the set position of generators of that area, which minimize the average time of ACE (Area Control Error). II. RESTRUCTURED POWER SYSTEM A deregulated electricity market comprises of many players such as generator owners (GENCO‘s), load supply entities (DISCO‘s), and transmission owners (TRANSCO‘s). Each market has an independent grid operator, known as the ISO (independent system operator), responsible for the day-to-day and, long- term operation of the power system. Restructured power system is needed which is basically divided into three parts GENCOs (generating companies), TRANSCOs (transmission companies), and DISCOs (distribution companies). The GENCOs generates power and DISCOs have freedom to have contract with any generating company for the sake of power trading. To visualize the contracts between GENCOs and TRANSCOs, the concept of DISCO participation matrix (DPM) is used. DISCO participation matrix is in the form of rows and columns where row represents number of GENCOs and columns represents number of DISCOs. In a deregulated system GENCOs sell power to DISCOs at competitive price and hence, DISCOs have various options for the transaction of power from any of the GENCOs of its own area or different area. In each area, an automatic generation controller (AGC) supervises the tie line power and system frequency, also computes the net change in the generation required which is related to the area control error (ACE) and changes the set position of the generators with in that area due to which net average time of ACE is at minimum. Fig.1. Configuration of power system under deregulated environment.
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699International Journal of Scientific Research Engineering & Technology (IJSRET), ISSN 2278 – 0882
Volume 3, Issue 3, June 2014
Performance of Automatic Generation Control in an Interconnected PowerSystem under Deregulated Environment
Ramandeep Kaur1, Sirdeep Singh2(Associate Professor)1(Department of Electrical Engineering, BGIET (Sangrur), INDIA)2 (Department of Electrical Engineering, BGIET (Sangrur), INDIA)
ABSTRACTIn this paper the Automatic Generation Control (AGC)in interconnected power system under deregulatedenvironment to control the tie line power of theinterconnected hydro-thermal power system in whichthermal reheated turbine is used . All four areas havedifferent number of GENCOS, DISCOS andTRANSCOS. A DISCO can individually andmultilaterally contracts with a GENCO for powerrequirements and these transactions are done under theISO supervision. After deregulation, the bilateralcontract on the dynamics of automatic generationcontrol (AGC), DPM has been used. The controlstrategies guarantees that the steady state error offrequencies and inadvertent interchange of tie-linespower are maintained in a given tolerance limit. Thestudy is carried out on IEEE 75-bus system. Theperformances of the controllers are simulated usingMATLAB/SIMULINK package.
The automatic generation control (AGC) is a technicalrequirement for the proper operation of aninterconnected power system. Automatic generationcontrol is very important in power system operationand control for supplying sufficient and reliableelectric power with good quality. In cases of area loadchanges and abnormal conditions, such as mismatchesin frequency and scheduled tie-line power flowsbetween areas can be caused. These mismatches arecorrected by controlling the frequency. To attain zerosteady state error and to maintain the system frequencyconstant, a control scheme is needed. Here study of thefour area restructured power system is done in whicheach area has its own automatic generation controller(AGC) which maintains the tie line power and systemfrequency constant by varying the generationaccording to the area control error (ACE). The AGCvaries the set position of generators of that area, which
minimize the average time of ACE (Area ControlError).II. RESTRUCTURED POWER SYSTEM
A deregulated electricity market comprises of manyplayers such as generator owners (GENCO‘s), loadsupply entities (DISCO‘s), and transmission owners(TRANSCO‘s). Each market has an independent gridoperator, known as the ISO (independent systemoperator), responsible for the day-to-day and, long-term operation of the power system. Restructuredpower system is needed which is basically divided intothree parts GENCOs (generating companies),TRANSCOs (transmission companies), and DISCOs(distribution companies). The GENCOs generatespower and DISCOs have freedom to have contractwith any generating company for the sake of powertrading. To visualize the contracts between GENCOsand TRANSCOs, the concept of DISCO participationmatrix (DPM) is used. DISCO participation matrix isin the form of rows and columns where row representsnumber of GENCOs and columns represents numberof DISCOs. In a deregulated system GENCOs sellpower to DISCOs at competitive price and hence,DISCOs have various options for the transaction ofpower from any of the GENCOs of its own area ordifferent area. In each area, an automatic generationcontroller (AGC) supervises the tie line power andsystem frequency, also computes the net change in thegeneration required which is related to the area controlerror (ACE) and changes the set position of thegenerators with in that area due to which net averagetime of ACE is at minimum.
Fig.1. Configuration of power system underderegulated environment.
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700International Journal of Scientific Research Engineering & Technology (IJSRET), ISSN 2278 – 0882
Volume 3, Issue 3, June 2014
In DPM diagonal element shows the local demand.The demand of one region discos value to anotherregions GENCO value is shown by the off diagonalelement. The actual and scheduled steady state powerflows on the given tie line is:-ΔPtie i-j, schedule = [ Demand from genco of area iby disco of area j –Demand from genco of area j bydisco of area i ]The tie line error is given by:-ΔPtiei-j, error = ΔPtiei-j, actual - ΔPtiei-j, schedule.The tie line error disappear the steady state error.The ACE signal given to the ISO is:-ACEi = Bi Δfi + ΔPtiei-j, errorΔfi is change of frequency of area „i‟ andBi is frequency Bias factor of area „i‟Genco1(scheduled) = (0.2+0.1)*0.01 = 0.03 puGenco2(scheduled) = (0.2+0.4)*0.01 = 0.06 puGenco3(scheduled) = 0 puGenco4(scheduled) = (0.1+0.2)*0.01 = 0.03 puGenco5(scheduled) = (0.1+ 0.2 + 0.3)*0.01 =0.06 puGenco6(scheduled) = (0.2 +0.4 +0.3)*0.01 = 0.09 puGenco7(scheduled) = 0 puGenco8(scheduled) = 0 puGenco9(scheduled) = (0.1 +0.3 +0.4)*0.01 = 0.08 puGenco10(scheduled)=(0.2)*0.01=0.02puGenco11(scheduled)=(0.2+0.3+0.2+0.5+0.5)*0.01 =0.17 pu
Genco12(scheduled)=(0.2 +0.1+ 0.2+0.2+0.5)*0.01 =0.12 puGenco13(scheduled)=(0.2+0.3+0.2+0.2+0.2+0.2+0.1)*0.01=0.14puGenco14(scheduled) = 0 puGenco15(scheduled) = 0 puThe schedule tie line powers are:-∆Ptie1-2,schedule=-(0.2x0.1+0.1x0.1)+(0.1x0.1)= 0.02pu∆Ptie1-3,schedule = -(0.1x0.1) = -0.01pu∆Ptie1-4,schedule= [(0.2x0.1+0.2x0.1+0.2x0.1)+(0.3x0.1+0.3x0.1)]+(0.4x0.1)=-0.08pu∆Ptie2-3, schedule = 0.2x0.1 = 0.02pu∆Ptie2-4, schedule=0.3x0.1 + [(0.2x0.1+0.1x0.1+0.2x0.1) -(0.2x0.1+0.2x0.1)] = 0.06pu∆Ptie3-4,schedule=-(0.5x0.1+0.2x0.1+0.2x0.1) = 0.09puA. Bacterial foraging optimization techniqueIt is recently developed technique, named as Bacterialforaging optimization (BFO) which has been projectedby Passion based on a bacteria. The BF techniquedependent on the deportment of E.coli bacteria whichis found in the human intestine. The bacterial foragingoptimized the controller gains and other parameters.In simulation work the parameter for coding is to beS=20, Nc=8, Ns=3, Nre = 15, Ned=2, Ped=0.80.D(attr.)=0.003, W(attr.) = 0.04, H(repellent)=0.003,W(repellent)= 10 and P=10 considered.
= (Δ )2 + (Δ )2}B. Result And AnalysisThe simulation is carried out on Four-Areainterconnected deregulated system. The PI controller isimplemented with and without bacterial foragingtechnique. In this, tie line power of the system iscompared. The simulation result are shown in fig(3) tofig(23). Using Simulink/MATLAB formulation theoptimum AGC controller gain value, representing thescheduling of generators, tie line power exchange aredone. With the help of BF algorithm value of Ki isobtained, which is applied to AGC in interconnectedfour area system under the deregulated environment.
C. Tie-line power comparison of different areas
Fig.3. Del Ptie1-2 with and without BF controller
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701International Journal of Scientific Research Engineering & Technology (IJSRET), ISSN 2278 – 0882
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Fig. 4. DelPtie1-3 with and without BF controller
Fig. 5. DelPtie1-4 with and without BF controller
Fig. 6. DelPtie2-3 with and without BF controller
Fig. 7. DelPtie2-4 with and without BF controller
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Fig. 8. DelPtie3-4 with and without BF controller
Fig. 9. Del Pg1 with and without BF controller
Fig. 10. Del Pg2 with and without BF controller
Fig. 11. Del Pg3 with and without BF controller
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703International Journal of Scientific Research Engineering & Technology (IJSRET), ISSN 2278 – 0882
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Fig. 12. Del Pg4 with and without BF controller
Fig. 13. Del Pg5 with and without BF controller
Fig. 14. Del Pg6 with and without BF controller
Fig. 15. Del Pg7 with and without BF controller
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704International Journal of Scientific Research Engineering & Technology (IJSRET), ISSN 2278 – 0882
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Fig. 16. Del Pg8 with and without BF controller
Fig. 17. Del Pg9 with and without BF controller
Fig. 18. Del Pg10 with and without BF controller
Fig.19. Del Pg11 with and without BF controller
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705International Journal of Scientific Research Engineering & Technology (IJSRET), ISSN 2278 – 0882
Volume 3, Issue 3, June 2014
Fig. 20. Del Pg12 with and without BF controller
Fig. 21. Del Pg13 with and without BF controller
Fig. 22. Del Pg14 with and without BF controller
Fig. 23. Del Pg15 with and without BF controller
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706International Journal of Scientific Research Engineering & Technology (IJSRET), ISSN 2278 – 0882
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Abbreviations
Δ Deviations Derivative in terms of Laplacef frequencyω Angular speedTg Governor time ConstantTij Coefficient of i-j tie Lineaij OperatorBi Bias FactorPref The Output of ACEPl Electric Load VariationsR Regulation ParameterApfi ACE Participation FactorsDPM DISCO Participation Matrixcpfi Contract Participation FactorsACE Area Control ErrorPi-jactual Real Tie Line PowerPi-jscheduled Scheduled Tie Line Power FlowPi-j error Tie Line Power ErrorBF Bacterial foragingKp1,2,3 Generator Gain ConstantTp1,2,3 Generator Time ConstantPt Turbine output powerTt Turbine time ConstantPg Governor Output powerTg Governor Time ConstantIII. CONCLUSIONThis Paper encapsulates automatic generation controlof the power system after deregulation includesbilateral contracts. DPM facilitates bilateral contractssimulation. Controller gains are optimized by bothBacterial Foraging and Proportional integral controller.This is study using simulation on a Four area powersystem considering different contracted scenarios. Thedynamic and steady state responses for tie line powerand power generation changes are shown. Thesimulation reveals that the proposed BacterialForaging based integral controller gives betterperformance than Proportional integral controller.APPENDIX-1Base =1000MVAa12 = a13 = a14 = a23 = a24 = a34 = 1Thermal DataTp = 20sTij = 0.086saij = -1Tt = 0.3sR = 2.4 hz/pu . MwKpi = 120 hz/pu. MwTg = 0.08sHydro DataTp = 20sTw = 1s
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