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Inclusion of environmental constraints into siting and sizing
Inclusion of environmental constraints into siting and sizing
Inclusion of environmental constraints into siting and sizing
Inclusion of environmental constraints into siting and sizing
Inclusion of environmental constraints into siting and sizing
Inclusion of environmental constraints into siting and sizing
Inclusion of environmental constraints into siting and sizing
Inclusion of environmental constraints into siting and sizing
Inclusion of environmental constraints into siting and sizing
Inclusion of environmental constraints into siting and sizing
Inclusion of environmental constraints into siting and sizing
Inclusion of environmental constraints into siting and sizing
Inclusion of environmental constraints into siting and sizing
Inclusion of environmental constraints into siting and sizing
Inclusion of environmental constraints into siting and sizing
Inclusion of environmental constraints into siting and sizing
Inclusion of environmental constraints into siting and sizing
Inclusion of environmental constraints into siting and sizing
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Inclusion of environmental constraints into siting and sizing

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  • 1. International Journal of Electrical Engineering and Technology (IJEET), ISSN 0976 –6545(Print), ISSN 0976 – 6553(Online) Volume 4, Issue 3, May - June (2013), © IAEME1INCLUSION OF ENVIRONMENTAL CONSTRAINTS INTO SITINGAND SIZING TECHNIQUES FOR LOCALIZED GAS TURBINESDISTRIBUTED GENERATIONIbrahim Helal1, Mohamed Abdel-Rahman2, MayYoussry31Department of Electrical Engineering, Ain Shams University2Department of Electrical Engineering, Ain Shams University3Egyptian Electricity Utility & Consumer Protection, Regulatory AgencyABSTRACTThe restructuring of electricity markets resulted in an increasing amount of distributedgeneration (DG) connected to the distribution networks to face load growth and demandbottlenecks.The typical approach to meet the increasing demand is to build additional centralpower generating stations or to expand the existing ones. Transmission and distribution T&Dnetworks, in such a case, represent significant cost both fixed and running. In contrary, theDG can provide better service at lower cost in many applications by avoiding the extra cost,besides providing higher reliability level for customers. One of the used technologies for DGis the gas turbine technology. The problem, however, with DG is to reach the optimal sizingand siting of the units. As well as the environmental impact produced by the exhaust gases ofthe DG units. In order to ensure the environmental benefits of the DG units, this paperinvestigates the inclusion of emissions as a constraint of the DG siting and sizing processwith present siting and sizing techniques.Consequently, this paper introduces the emissions environmental constraint based on:(i) the units emission factors, (ii) the power supplied by the network and (iii) the powersupplied by the DG units. The model has been applied to a real case system data.Keywords: Distributed generation (DG), optimal placement, optimal power flow, sizing &siting of DG units, CO2 emissions, and emission factors.INTERNATIONAL JOURNAL OF ELECTRICAL ENGINEERING& TECHNOLOGY (IJEET)ISSN 0976 – 6545(Print)ISSN 0976 – 6553(Online)Volume 4, Issue 3, May - June (2013), pp. 01-18© IAEME: www.iaeme.com/ijeet.aspJournal Impact Factor (2013): 5.5028 (Calculated by GISI)www.jifactor.comIJEET© I A E M E
  • 2. International Journal of Electrical Engineering and Technology (IJEET), ISSN 0976 –6545(Print), ISSN 0976 – 6553(Online) Volume 4, Issue 3, May - June (2013), © IAEME2List of SymbolsDG Distributed generationf(x) The objective functionG(x) The equality constraintsH(x) The inequality constraintsi The bus indexN The total number of system busesC1 The active power component in the unit investment cost (EgyptianPound/MW/hr).C2 The reactive power component in the unit investment cost (EgyptianPound/MVAr/hr).PgimaxThe maximum active that can be generated (MW).QgimaxThe maximum reactive power that can be generated (MVAr).C3 The running cost of generated reactive power (Egyptian Pound/MVAr/hr).Pgi The active DG generated power (MW).Qgi The reactive DG generated power (MVAr).C4 The market price for active power (Egyptian Pound/MWh/hr).C5 The market price for reactive power (Egyptian Pound/MVAr/hr).Ps The system active power (MW).Qs The system active power (MVAr).Ploss The active power losses (MW).Qloss The reactive power losses (MVAr).PD The active power demand (MW).QD The reactive power demand (MVAr).Psmaxthe max distribution substation capacity (MW).∆Vi Maximum permissible voltage drop at bus i.pfi Power Factor of DG unit at bus i.K1 CO2 emission factor of the centralized power stations.K2 Gas turbine CO2 emission factor.Psb The system power for the base case without using any DG units (MW).FE The fuel energy (GJ)FQ Fuel quantity (ton/year).FHV Fuel heating value (GJ/ton).EQ Emission quantity in (ton/year).ER Emission rate in (ton/GJ).EQVCO2 The equivalent CO2 emission quantity (ton/year).GWP Global warming potential factor.EF The emission factor (ton /year).ECO2 CO2 emissions in (ton/GWh).GGE Gross generated energy (GWh/year).1. INTRODUCTIONA typical power system has hierarchical structure composed of generation,transmission and distribution. Under the move towards deregulation, individual entities maybe allowed to generate power on the distribution level, given the attainment of the requiredlicenses from the concerned regulatory body [1]-[3].
  • 3. International Journal of Electrical Engineering and Technology (IJEET), ISSN 0976 –6545(Print), ISSN 0976 – 6553(Online) Volume 4, Issue 3, May - June (2013), © IAEME3The trend of distributed generation started to emerge in the beginning of this century[4]. Internal combustion engines, micro turbines, combustion gas turbines, fuel cells, photovoltaic solar panels and wind turbines are examples of distributed generation technologies[1]-[3]. Renewable resources are gaining popularity. However, still fossil fuel dependenttechnologies are wide spread and in large use. Therefore, a concern may arise is to ensure thatthe spread of fossil fuel generators, including gas turbines technology, does not result inenvironmental deterioration.In order to reach an optimum distribution networks as far as energy losses areconcerned, distribution companies have to perform detailed studies to ensure optimalplanning and operation of their systems, should they decide to use distributed generation. Thechoice of the candidate load buses to install DG units and the determination of theircorresponding capacities is typically a problem that undergoes extensive investigations toensure the optimal network operation, i.e. minimum losses and costs with power quality andreliability improvement.Nevertheless, the earlier methods stopped short from considering the environmentalimpact on the siting and sizing of DG units. In order to fill this gap, this paper proposesconsidering the environmental impact of DG in the form of an emissions constraint. Thepaper presents a formulation methodology to consider the emissions both from the DG unitsand the centralized network. The approach is dependent on the utilization of emission factorsfor both the centralized and decentralized units. The developed methodology has beenapplied to a practical power network of 106 distribution drop points, assuming that all DGunits are of the same type.The paper is structured in five sections including this introductory section. Section IIpresents a DG generic siting and sizing model with technical constraints to obtain the optimalsizing and siting of the DG units. Section III depicts the environmental constraintformulation. Section IV applies the proposed concept to Case study network configurations.The conclusions are summarized in Section V.2. (DG) GENERIC OPTIMIZATION MODEL DESCRIPTIONFig. (1) shows a typical DG connection topology. The connected loads are served byboth the DG and the distribution network. The mode of operation may differ from one case toanother. It may be peak shaving in one case, or base load in another. The customer side mayeven engage in an import and export of energy with the network. For this proposal, it isassumed that the local generation supplies the base load whereas the network covers the restof the demand as well as the system losses.Fig. (1) A typical DG, load and network topology
  • 4. International Journal of Electrical Engineering and Technology (IJEET), ISSN 0976 –6545(Print), ISSN 0976 – 6553(Online) Volume 4, Issue 3, May - June (2013), © IAEME4The mathematical formulation of the optimization, for the siting and sizing of DGunits, problem results in a system of non linear algebraic equations [5], and [6]. The objectivefunction is to minimize both the hourly cost including losses and capital costs of the system.The model considers load flow equations, system constraints. Provided the non-linearity ofthe objective function and the constraints, the optimal solution of the model is achievediteratively, e.g., gradient method. In all cases, a feasible solution must not violate systemconstraints such as capacity limits of active and reactive power sources and environmentalrestrictions. The model solution provides the optimal sizing of the DG units.Nevertheless, many sizing and siting methods have been developed to optimizesystem operation [7], and [9]. The loss reduction technique is used in this work to find thecandidate load buses for DG installation [7]. A complementary technique should be used tofind out the optimal location of the optimal DG size.The problem is a general minimization problem with constraints modeled as inEquation (1).[5], and [6]Minimize f(x)Subject to: g(x) = 0 (1)h(x) ≤ 0Where x is the vector of control and state variables. Control variables are DG active andreactive power outputs. The state variables are voltage and angles of load buses.For this work all DG units are assumed to be gas units and have similar characteristics.Following are the details of the optimization model.2.1 Objective Function FormulationThe objective function presents: (i) the investment cost, (ii) the running cost of theDG units, (iii) the cost of the electrical power supplied by the utility and (iv) the costassociated with network losses. The individual components of the objective function are:2.1.1 DG fixed costThe fixed cost of distributed generation isnf = ∑ (c1Pgimax+c2Qgimax) (Egyptian Pound/hr) (2)i=12.1.2 DG running costThe running cost of the distributed generation isnf = ∑ (ai + biPgi + ciPgi2) + c3Qgi Egyptian Pound/hr) (3)i=1(3) is a quadratic cost function expressing the DG running costs due to active powergeneration where, ai, bi and ci are the generator constants in Egyptian Pound/hr, EgyptianPound/MW/hr and Egyptian Pound/MW2/hr.2.1.3 Cost of system powerThe cost of the utility supplied power isf = c4Ps + c5Qs (Egyptian Pound/hr) (4)
  • 5. International Journal of Electrical Engineering and Technology (IJEET), ISSN 0976 –6545(Print), ISSN 0976 – 6553(Online) Volume 4, Issue 3, May - June (2013), © IAEME52.1.4 Cost of system lossesThe system losses cost isf = c4Ploss + c5Qloss (Egyptian Pound/hr) (5)Where, Ploss and Qloss are calculated from load flow analysis as the algebraic sum of activeand reactive power losses in all system branches [10].Therefore, the final form of the objective function isnf(x) = ∑ (c1Pgimax+c2Qgimax)i=1n+ ∑ (ai + biPgi + ciPgi2)i=1+ c3Qgi + c4Ps + c5Qs+ c4Ploss + c5Qloss (Egyptian Pound/hr) (6)2.2 Equality ConstraintsThe equality constraints g(x) are represented by the power balance constraints, wherethe total active power generation must cover the total power demand and the power losses asinn n∑Pgi + Ps = ∑PDi + Ploss (7)i=1 i=1The same applies for reactive power, where the reactive power supplied by the generatorsshould be in balance with the reactive power consumed or produced throughout the system.Nevertheless, for reactive power flow and voltage stability considerations, this balanceshould not only be globally attained throughout the system but should hold at each bus withinthe networkn n∑Qgi + Qs = ∑QDi + Qloss (8)i=1 i=1The demand data PDi & QDi are given. They can be hourly values. Nevertheless, this requiresreformulating the whole problem as a sum for the whole study period. For the sake ofsimplicity and being on the conservative side, PDi and QDi are considered at the system peakto represent the system most severe operating conditions.2.3 Inequality ConstraintsThe inequality constraints h(x) reflect the limits of DG as well as the limits needed to ensuresystem security. (9) to (13) represent the inequality constrains of the optimization model.The upper and lower bounds of DG generated power (Pg &Qg) arePgimin≤ Pgi ≤ Pgimax(9)Qgimin≤ Qgi ≤ Qgimax(10)The upper limit of substation capacity isPs ≤ Psmax(11)Other technical constraints such as voltage & Power factor limits are also considered in thismodel.Maximum permissible voltage drop is∆Vi ≤ 0.01 p.u (12)
  • 6. International Journal of Electrical Engineering and Technology (IJEET), ISSN 0976 –6545(Print), ISSN 0976 – 6553(Online) Volume 4, Issue 3, May - June (2013), © IAEME6The conservative value of the voltage limit is to compensate for the simplifications anduncertainties in the developed approach and the used parameters.Power factor constraintAccording to the main stream of operation guidelines worldwide, the load power factor islimited between 0.95 leading to 0.90 lagging power factors [11].-0.95 ≤ pfi ≤ 0.9 (13)3. ENVIRONMENTAL CONSTRAINT FORMULATIONAll DG units and centralized power stations produce significant amounts of CO2emissions. Therefore, an environmental constraint is considered in the DG optimizationmodel to ensure that using DG units will not result in the increase of the total systememissions. The environmental constraint isnK1Ps + ∑K2Pgi ≤ K1Psb (14)i=1It is assumed to be a linear inequality constraint based on the emission factors of bothcentralized and DG units. To calculate the emission factors for both centralized powerstations and DG units, both fuel energy and emission quantities must be determined. The Fuelenergy isFE = FQ * FHV (15)In some cases the centralized power stations use different types of fuel. In this casefuel energy is calculated for each fuel type separately according to its heating value.The emission quantity for each fuel type isEQ = ER * FE (16)Appendix (A) summarizes the emission rate for each fuel type.Consequent to emission quantity calculation for each fuel type, all greenhouse gasesemissions are converted to their equivalent CO2 as followsEQVCO2 = GWP * EQ (17)Where, GWP for each greenhouse gas emission is listed in Appendix (B).Upon converting all greenhouse gases emissions to their equivalent CO2 emissions, emissionfactor is easily calculated byEF =ECO2 / GGE (18)Where ECO2 is the total equivalent annual CO2 emissions and GGE is the total annualgenerated energy.4. CASE STUDYThe optimization model described in the preceding sections has been applied to adistribution network in a typical industrial zone. Appendix (C) depicts the utilized sizing andsiting approach. The cost data are given in Appendix (D). Fig. (2) shows the distributionnetwork considered for the case study. The network consists of 106 buses and 116 powerlines of 11 KV.
  • 7. International Journal of Electrical Engineering and Technology (IJEET), ISSN 0976 –6545(Print), ISSN 0976 – 6553(Online) Volume 4, Issue 3, May - June (2013), © IAEME7Bus number (1) represents the transmission substation. It is considered as the slackbus. Buses number (43), (67) and (91) are P-V buses (generator bus) with a controlledvoltage of (1p.u).The generated power at each bus of the P-V buses is assumed to be one forth of thetotal loads. All other buses are considered P-Q buses as the loads are known, with 0.85 powerfactor. The base voltage is 11 KV. The base power is 100 MVA. Analysis is carried out atsystem peak load as it is the worst operational condition. The results are summarized in thefollowing sections.Fig. (2) Case Study Distribution Network4.1 Base Case Solution (without DG)The load flow solution for the base case (without DG) is summarized below:• The delivered power by the utility is equal to 50.6 MW.• System active losses are 5.5 MW.• The system CO2 emission is 58 ton/hr.• The initial cost is 6740Egyptian Pound/hr.
  • 8. International Journal of Electrical Engineering and Technology (IJEET), ISSN 0976 –6545(Print), ISSN 0976 – 6553(Online) Volume 4, Issue 3, May - June (2013), © IAEME8As can be noticed in Table (1) buses (from bus no (50) to bus no (63) & from (67) to (90))exceed the lower limit of voltage by 1% (the permissible level is from 0.99 to 1.01 p.u.).Table (1) Initial Bus VoltageBusNo.|V|BusNo.|V|BusNo.|V|1 1.00 37 1.00 73 0.982 0.99 38 1.00 74 0.983 0.99 39 1.00 75 0.984 0.99 40 1.00 76 0.985 0.99 41 1.00 77 0.986 0.99 42 1.00 78 0.987 0.99 43 1.00 79 0.988 0.99 44 1.00 80 0.989 0.99 45 1.00 81 0.9810 0.99 46 1.01 82 0.9811 0.99 47 1.01 83 0.9812 0.99 48 1.01 84 0.9813 0.99 49 0.99 85 0.9814 0.99 50 0.98 86 0.9815 0.99 51 0.98 87 0.9816 0.99 52 0.98 88 0.9817 0.99 53 0.98 89 0.9818 0.99 54 0.98 90 0.9819 0.99 55 0.98 91 1.0020 0.99 56 0.98 92 1.0121 0.99 57 0.98 93 1.0122 0.99 58 0.98 94 1.0023 0.99 59 0.98 95 1.0024 0.99 60 0.98 96 1.0025 0.99 61 0.98 97 1.0026 0.99 62 0.98 98 1.0127 0.99 63 0.98 99 1.0128 0.99 64 0.99 100 1.0129 0.99 65 0.99 101 1.0130 0.99 66 0.99 102 1.0131 0.99 67 1.00 103 1.0132 0.99 68 0.98 104 1.0133 0.99 69 0.98 105 1.0134 0.99 70 0.98 106 1.0135 0.99 71 0.9836 0.99 72 0.984.2 Optimal sizing & siting without environmental constraintsDG units are ranked according to their impact on the system losses reduction. The DG unit atcertain bus that reduces system losses most effectively has the highest priority. DG units areinstalled one by one at the candidate load buses according to their priorities till the systemlosses are constant or increased. Table (2) shows the ranking of the system load busesaccording to their effect on losses reduction after applying a generation of 10 MW at eachbus.
  • 9. International Journal of Electrical Engineering and Technology (IJEET), ISSN 0976 –6545(Print), ISSN 0976 – 6553(Online) Volume 4, Issue 3, May - June (2013), © IAEME9Table (2) Bus RankingBus No.Ploss(MW)Ranking Bus No.Ploss(MW)Ranking Bus No.Ploss(MW)Ranking1SlackBus---- 28 5.54 63 55 4.92 392 5.39 49 29 5.54 64 56 4.92 383 5.25 46 30 5.54 65 57 4.92 354 5.54 53 31 5.54 66 58 4.92 365 5.54 54 32 5.54 67 59 4.87 256 5.54 55 33 5.54 68 60 4.84 207 5.54 56 34 5.54 69 61 4.87 278 5.54 57 35 5.54 70 62 4.86 249 5.54 58 36 5.54 71 63 4.88 2810 5.54 59 37 5.54 Rejected 64 5.11 4011 5.54 60 38 5.55 Rejected 65 5.17 4212 5.54 61 39 5.55 Rejected 66 5.22 4413 5.54 62 40 5.55 Rejected 67Gen.Bus---14 5.54 Rejected 41 5.56 Rejected 68 4.84 2115 5.54 Rejected 42 5.56 Rejected 69 4.84 1916 5.54 Rejected 43 4.91 30 70 4.87 2617 5.54 Rejected 44 5.15 41 71 4.81 1618 5.54 Rejected 45 5.19 43 72 4.82 1819 5.54 Rejected 46 5.24 45 73 4.85 2220 5.54 Rejected 47Gen.Bus--- 74 4.77 221 5.54 Rejected 48 5.32 47 75 4.77 322 5.54 Rejected 49 4.91 31 76 4.77 423 5.54 Rejected 50 4.89 29 77 4.77 524 5.54 Rejected 51 4.92 37 78 4.77 625 5.54 Rejected 52 4.92 32 79 4.77 126 5.54 Rejected 53 4.92 33 80 4.77 727 5.54 Rejected 54 4.92 34 81 4.77 9DG units are installed one by one at the load buses according to their ranking priorities, whilelosses are calculated at each run as depicted in Table (3). Losses are decreasing due to DGinstallation until bus number (89). At this bus the losses start to increase. Therefore, asindicated in the table, buses no (79, 74, 75, 76, 77, 78, 80, 82, 81, 83, 84, 87, 85, 88, 86 & 71)are the candidate optimal buses to locate the DG.
  • 10. International Journal of Electrical Engineering and Technology (IJEET), ISSN 0976 –6545(Print), ISSN 0976 – 6553(Online) Volume 4, Issue 3, May - June (2013), © IAEME10Table (3) Results of siting DG units at each busDG SitingPloss(MW)Ps(MW)Siting DG at Bus (79) 5.4 49.5Siting DG at Bus (79)&(74) 5.3 48.4Siting DG at Bus (79),(74)&(75) 5.1 47.2Siting DG at Bus (79),(74),(75)&(76) 5 46.1Siting DG at Bus (79),(74),(75),(76)&(77) 4.9 45Siting DG at Bus (79),(74),(75),(76),(77) &(78) 4.8 43.9Siting DG at Bus (79),(74),(75),(76),(77),(78) &(80) 4.7 42.8Siting DG at Bus (79),(74),(75),(76),(77),(78), (80)&(82)4.6 41.7Siting DG at Bus (79),(74),(75),(76),(77),(78) ,(80),(82)&(81)4.5 40.6Siting DG at Bus (79),(74),(75),(76),(77),(78) ,(80),(82),(81)&(83)4.34 39.44Siting DG at Bus (79),(74),(75),(76),(77),(78), (80),(82),(81),(83)&(84)4.3 38.4Siting DG at Bus (79),(74),(75),(76),(77),(78), (80),(82),(81),(83),(84)&(87)4.25 37.4Siting DG at Bus (79),(74),(75),(76),(77),(78), (80),(82),(81),(83),(84),(87)&(85)4.2 36.3Siting DG at Bus (79),(74),(75),(76),(77),(78), (80),(82),(81),(83),(84),(87),(85)&(88)4.1 35.2Siting DG at Bus (79),(74),(75),(76),(77),(78), (80),(82),(81),(83),(84),(87),(85),(88)&(86)4.08 34.18Siting DG at Bus (79),(74),(75),(76),(77),(78), (80),(82),(81),(83),(84),(87),(85),(88),(86) &(71)3.9 33Siting DG at Bus (79),(74),(75),(76),(77),(78), (80),(82),(81),(83),(84),(87),(85),(88),(86) ,(71)&(89)4 32.1Consequent to siting DG units at candidate buses, optimization model is run to obtain theproposed DG capacity at each bus. A standard size of 1MW is selected for each DG unit. Theoptimal solution in this case is to generate the maximum capacity of DG units at all buses.Table (4) shows that the voltages drop for all buses after installing DG units are within thepermissible limits.
  • 11. International Journal of Electrical Engineering and Technology (IJEET), ISSN 0976 –6545(Print), ISSN 0976 – 6553(Online) Volume 4, Issue 3, May - June (2013), © IAEME11Table (4) Bus voltages after installing DGBusNo.|V|BusNo.|V|BusNo.|V|1 1.00 37 1.00 73 0.992 0.99 38 1.00 74 0.993 0.99 39 1.00 75 0.994 0.99 40 1.00 76 0.995 0.99 41 1.00 77 0.996 0.99 42 1.00 78 0.997 0.99 43 1.00 79 0.998 0.99 44 1.00 80 0.999 0.99 45 1.01 81 0.9910 0.99 46 1.01 82 0.9911 0.99 47 1.01 83 0.9912 0.99 48 1.01 84 0.9913 0.99 49 0.99 85 0.9914 1.00 50 0.99 86 0.9915 0.99 51 0.99 87 0.9916 0.99 52 0.99 88 0.9917 0.99 53 0.99 89 0.9918 0.99 54 0.99 90 0.9919 0.99 55 0.99 91 1.0020 0.99 56 0.99 92 1.0121 0.99 57 0.99 93 1.0122 0.99 58 0.99 94 1.0123 0.99 59 0.99 95 1.0124 0.99 60 0.99 96 1.0125 0.99 61 0.99 97 1.0126 0.99 62 0.99 98 1.0127 0.99 63 0.99 99 1.0128 0.99 64 0.99 100 1.0129 0.99 65 0.99 101 1.0130 0.99 66 0.99 102 1.0131 0.99 67 1.00 103 1.0132 0.99 68 0.99 104 1.0133 0.99 69 0.99 105 1.0134 0.99 70 0.99 106 1.0135 0.99 71 0.9936 0.99 72 0.99After installing DG units at the candidate load buses the system supplied power is 33 MW.The system active losses are 3.9 MW. The system losses in this case are reduced by nearly29% compared to the base case. The system hourly cost is 6350 Egyptian Pound/hour. Costreduction due to DG installation is 6%. The CO2 emissions are 59.5 ton/hr which is increasedby 2.7 %.
  • 12. International Journal of Electrical Engineering and Technology (IJEET), ISSN 0976 –6545(Print), ISSN 0976 – 6553(Online) Volume 4, Issue 3, May - June (2013), © IAEME124.3 Optimal sizing and siting with environmental constraintsThe system shown in Fig. (2) is tested while considering the environmentalconstraints. The emission factors for both central power station and DG units are calculatedin Appendix (E). Table (5) summarizes the results of adding DG unit to the candidate loadbuses according to their priorities in Table (2).Table (5) Siting DG units at each bus under environmental constraintDG SitingPloss(MW)Ps(MW)Siting DG at Bus (79) 5.5 50.2Siting DG at Bus (79)&(74) 5.4 49.4Siting DG at Bus (79),(74)&(75) 5.35 49.6Siting DG at Bus (79),(74),(75)&(76) 5.27 49.1Siting DG at Bus (79),(74),(75),(76) &(77) 5.2 47.8Siting DG at Bus (79),(74),(75),(76) ,(77)&(78)5.1 46.4Siting DG at Bus (79),(74),(75),(76),(77),(78)&(80)5.1 46.4These results indicate that system losses become constant after installing DG at bus (80),while the optimal DG capacities are obtained and tabulated in Table (6).Table (6) Results of the DG optimization model for the case study with environmentalconstraints.Bus No. Pg (MW) Qg (MVAR)Generator at bus (79)1 0.484Generator at bus (74) 0 0Generator at bus (75) 1 0.484Generator at bus (76) 0.95 0.48Generator at bus (77) 0 0Generator at bus (78) 0.7 0.349
  • 13. International Journal of Electrical Engineering and Technology (IJEET), ISSN 0976 –6545(Print), ISSN 0976 – 6553(Online) Volume 4, Issue 3, May - June (2013), © IAEME13The results show that system losses are 5.1 MW. Losses reduction is 7.3%. Systemcosts are 6618 Egyptian Pound/hr. The system hourly costs are reduced by 1.8%. System CO2emission is 57.7 ton/hr after installing DG, i.e. no violation for the environmental constraints.The cost reduction may be lower than the case in section C (without environmentalconstraints). This shows that under environmental restrictions DG may not impact systemcost reduction effectively. However, technical losses reduction and voltage profileimprovement are evident. Table (7) shows voltage levels of the system after installing DGunits at the candidate load buses. All voltage tolerances are within the permissible limits of±1%.Table (7) Bus voltages after installing DG under environmental constraintBus No. |V| Bus No. |V| Bus No. |V| Bus No. |V|1 1.00 28 0.99 55 0.99 82 0.992 0.99 29 0.99 56 0.99 83 0.993 0.99 30 0.99 57 0.99 84 0.994 0.99 31 0.99 58 0.99 85 0.985 0.99 32 0.99 59 0.99 86 0.986 0.99 33 0.99 60 0.98 87 0.997 0.99 34 0.99 61 0.99 88 0.998 0.99 35 0.99 62 0.99 89 0.989 0.99 36 0.99 63 0.99 90 0.9810 0.99 37 1.00 64 0.99 91 1.0011 0.99 38 1.00 65 0.99 92 1.0012 0.99 39 1.00 66 0.99 93 1.0113 0.99 40 1.00 67 1.00 94 1.0014 1.00 41 1.00 68 0.99 95 1.0015 0.99 42 1.00 69 0.98 96 1.0016 0.99 43 1.00 70 0.99 97 1.0017 0.99 44 1.00 71 0.99 98 1.0118 0.99 45 1.00 72 0.99 99 1.0119 0.99 46 1.01 73 0.99 100 1.0120 0.99 47 1.01 74 0.99 101 1.0121 0.99 48 1.01 75 0.99 102 1.0122 0.99 49 0.99 76 0.99 103 1.0123 0.99 50 0.99 77 0.99 104 1.0124 0.99 51 0.99 78 0.99 105 1.0125 0.99 52 0.99 79 0.98 106 1.0126 0.99 53 0.99 80 0.9927 0.99 54 0.99 81 0.99
  • 14. International Journal of Electrical Engineering and Technology (IJEET), ISSN 0976 –6545(Print), ISSN 0976 – 6553(Online) Volume 4, Issue 3, May - June (2013), © IAEME145. CONCLUSIONSIn this paper a formulation for the environmental impact of DG is introduced. Theemissions are evaluated based on the use of conversion factors. An additional constraint isadded to the optimization planning problem. The approach is based on the minimization oftotal system cost (capital and operational) subject to particular constraints related to systemand units capacities, operational performance and CO2 emission.The model is applied to a real distribution network composed of 106 distribution droppoints. Optimal sizing and siting of the DG units is obtained by solving the environmentallyconstrained optimization model. The results show that without violating the permissible CO2emission level, DG still can provide lower cost and losses together with complementarypower supply to local loads on the level of distribution networks.Appendix AEmission Factors for electric utility and industrial combustion systems [12]Emission Rates (g/GJ energy input)Utility applications CO2 CO CH4 NOX N2ONatural gas boilers 56100 19 0.1 267 N/AGas turbine,combined cycle56100 32 6.1 187 N/AGas turbine, simple cycle 56100 32 5.9 188 N/AResidual oil boilers 77350 15 0.7 201 N/ADistillate oil boilers 74050 15 0.03 69 N/ACoal, spreader stoker 94600 121 0.7 326 0.8Coal, fluidized bed 94600 N/A 0.6 255 N/ACoal, pulverized 94600 14 0.6 857 0.8Coal, tangentially fired 94600 14 0.6 330 0.8Coal, pulverize, wall fired 94600 14 0.6 461 0.8Wood-fired boilers 26260 147 0.8 112 N/A
  • 15. International Journal of Electrical Engineering and Technology (IJEET), ISSN 0976 –6545(Print), ISSN 0976 – 6553(Online) Volume 4, Issue 3, May - June (2013), © IAEME15Appendix BGlobal Warming Potential Factors [13]Trace Gas GWP Trace Gas GWPCarbonDioxide1 HFC-134 1,000CCl 4 1300 HFC-134a 1300CFC- 11 3400 HFC-143 300CFC-113 4500 HFC-143a 3800CFC-116 >6200 HFC-152a 140CFC-12 7100 HFC-227ea 2900CFC-l 14 7000 HFC-23 9800CFC-l 15 7000 HFC-236fa 6300Chloroform 4 HFC-245ca 560HCFC- 123 90 HFC-32 650HCFC- 124 430 HFC-41 150HCFC-141b 580 HFC-43-lOmee 1,300HCFC-142b 1600 Methane 21HCFC-22 1600 Nitrous Oxide 310HFC- 125 2800Sulphurhexafluoride23900Appendix CDG Sizing & Siting TechniqueMany approaches have been developed to determine optimal sizing and siting of DGunits in electrical distribution networks.The losses-reduction-based technique [7] is used in this paper to determine thecandidate load buses for DG installation. This technique considers primarily considers theDG impact on total system losses reduction. The bus that reduces system losses mosteffectively will have the highest priority for distributed generation installation.Consequent to the choice of the DG candidate buses, the optimization model is used todetermine the distributed generation units output powers. The optimal siting can bedetermined as listed below.
  • 16. International Journal of Electrical Engineering and Technology (IJEET), ISSN 0976 –6545(Print), ISSN 0976 – 6553(Online) Volume 4, Issue 3, May - June (2013), © IAEME16Step 1Perform load flow calculations to obtain the initial conditions of the system, i.e. powersupplied by the system and system losses.Step 2Start with adding a generation of 10 MW at each bus, only one bus at a time, and recalculatesystem losses each time. This capacity is justified as being a typical unit capacity used tocheck the impact of DG units on loss reduction.Step 3Rank system buses according to their effect on system losses reduction with higher rank forthe bus having more impact on loss reduction. The buses that provide losses higher than thebase case (without DG) should be rejected from the ranking list.Step 4Add DG units at the load buses according to their priority obtained in step 3. Recalculatesystem losses after each installation until losses are seemed to be increased or constant.Step 5Once the optimal siting is determined in step 4, the optimization model is solved to obtain theoptimal sizing of DG at each of the optimal locations.Fig. (3) illustrates the main steps to obtain the optimal sizing of each DG unit at each bus.Fig. (3) A flowchart depicting the sizing technique utilized in the proposed approachC a lcu la te syste m lo sse s in th is ca seC h e ck syste mco n stra in tsS u b stitu te lo sse s in to o b je ctivefu nctio nM in im ize th e o b je ctive FnS e le ct th e n e a re st sta n d a rd size o f D G u n its toth e o b ta in e d so lu tio n fo r e a ch b u sF in a l so lu tio n o b ta in e dR u n o p tim iza tio n m o d e l to fin d syste mco stsS to pN oY e sS ta rtS e t in itia l va lu e s fo r P g i, Q gi, P s,Q sfo r th e o b jective fu n ctio nS o lve L o a d flo w e qnu sin g S a m ein itia l co n d itio n s
  • 17. International Journal of Electrical Engineering and Technology (IJEET), ISSN 0976 –6545(Print), ISSN 0976 – 6553(Online) Volume 4, Issue 3, May - June (2013), © IAEME17Appendix DCost DataBased on the case study, electricity price is subsidized such that the average price (csa) is0.022 $/kWh. The reactive power cost is set to be equal zero in this case study. The gasturbine technology is used for DG units due to its low emissions. Investment cost of gasturbine vary from (600–900 $/KW). An average price of 750 $/KW is used. The paybackperiod is assumed as 10 years. DG units operate as base load units, the total fixed DG costs isset to be 8.5 $/MW-hr. Operating and maintenance cost is assumed to be 0.0055 $/kWh. Priceof natural gas is 0.045 $/m3 for the case study. The fuel consumption rate of DG is assumedto be 250 gm/kWh.Appendix EApplying Equation (15) to Equation (18), the central power station emission factor (K1) isequal to 1.14 ton/MWh. DG units are assumed to have fuel consumption rate of 250 gm/kWh,calorific heat value of 38.5 MJ, service hours of 8000 hrs and load factor of 75%, emissionfactor (K2) is 1.35 ton/MWh.REFERENCES[1]Carpinelli, G.; Celli, G.; Pilo, F.; Russo, A. "Distributed Generation Siting and SizingUnder Uncertainty", IEEE Power Tech Proceedings, Vol. 4, 2001.[2]Arijit Bhowmik, Arindam Maitra, S. Mark Halpin, and Joe E. Schatz, "Determination ofAllowable Penetration levels of Distributed Generation Resources Based on Harmonic LimitConsiderations", IEEE Transactions On Power Delivery, Vol. 18, April 2003.[3]Panagis N. Vovos, Aristides E. Kiprakis, A. Robin Wallace and Gareth P. Harrison,"Centralized and Distributed Voltage Control: Impact on Distributed GenerationPenetration", IEEE Transactions On Power Systems, Vol. 22, February 2007.[4]Joos G., Ooi B.T.; McGillis D.; Galiana F.D. and Marceau R.; "The Potential ofDistributed Generation to provide Ancillary Services", IEEE Power Engineering SocietySummer Meeting, Vol. 3, July 2000.[5]Walid El-Khattam, Kankar Bhattacharya, Yasser Hegazy,and M. M. A. Salama, "OptimalInvestment Planning for Distributed Generation in a Competitive Electricity Market". IEEETransactions on power systems, Vol. 19, August 2004.[6]Panagis N. Vovos, Aristides E. Kiprakis, A. Robin Wallace, and Gareth P. Harrison."Centralized and Distributed Voltage Control: Impact on Distributed GenerationPenetration". IEEE Transactions on power systems, Vol. 22, February 2007.[7]T. Griffin, K. Tomsovic, and D. Secrest A. Law. "Placement of Dispersed GenerationsSystems for Reduced Losses". Proceedings of the 33rd Hawaii international Conference onSystem Sciences – 2000.[8]Walid El-Khattam, Y.G Hegazy,and M. M. A. Salama, "An Integrated DistributedGeneration Optimization Model for Distribution System Planning". IEEE Transactions onpower systems, Vol. 20, May 2005.[9]Hasan Hedayati, S. A. Nabaviniaki, and Adel Akbarimajd. "A Method for Placement ofDG Units in Distribution Networks". IEEE Transactions on power delivery, Vol. 23, July2008.
  • 18. International Journal of Electrical Engineering and Technology (IJEET), ISSN 0976 –6545(Print), ISSN 0976 – 6553(Online) Volume 4, Issue 3, May - June (2013), © IAEME18[10]Enrico Carpaneto, Gianfranco Chicco, and Jean Sumaili Akilimali, "Branch CurrentDecomposition Method for Loss Allocation in Radial Distribution Systems With DistributedGeneration", IEEE Transactions On Power Systems, Vol. 21, August 2006.[11]Shangyou Hao. "A Reactive Power Management Proposal for Transmission Operators".IEEE IEEE Transactions On Power Systems, Vol. 18, November 2003.[12]Intergovernmental panel on climate change (IPCC) guidelines for national greenhousegas inventories. (www.ipcc-nggip.iges.or.jp)[13]United Nations Environment Programme (UNEP) guidelines for calculating greenhousegas emissions for buisness and non commercial organizations.(www.unep.org/publications/ebooks)[14] Dr.T.Ananthapadmanabha, Maruthi Prasanna.H.A., Veeresha.A.G. and Likith Kumar.M. V, “A New Simplified Approach for Optimum Allocation of a Distributed GenerationUnit in the Distribution Network for Voltage Improvement and Loss Minimization”,International Journal of Electrical Engineering & Technology (IJEET), Volume 4, Issue 2,2013, pp. 165 - 178, ISSN Print : 0976-6545, ISSN Online: 0976-6553.[15] Om Prakash Mahela and Sheesh Ram Ola, “Optimal Placement and Sizing of Ht ShuntCapacitors for Transmission Loss Minimization and Voltage Profile Improvement: The CaseOf Rrvpnl Power Grid”, International Journal of Electrical Engineering & Technology(IJEET), Volume 4, Issue 2, 2013, pp. 261 - 273, ISSN Print : 0976-6545, ISSN Online:0976-6553.[16] S.Neelima and Dr. P.S.Subramanyam, “Effect of Load Levels on Sizing and Location ofCapacitors in Distribution Systems”, International Journal of Electrical Engineering &Technology (IJEET), Volume 3, Issue 3, 2012, pp. 31 - 42, ISSN Print : 0976-6545,ISSN Online: 0976-6553

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