07047330

timadato67, U

al sssesmpbenet.ed meth

ate t

method [29], mixed integer non-linear programming [12],analytical approaches [10, 1316, 2123, 28, 31], geneticalgorithm (GA) [17, 22, 30], articial bee colony [18],particle swarm optimisation (PSO) [19], evolutionaryp[ds

www.ietdl.org

IEdrogramming [20], hybrid GA and Tabu search (GATS)24], hybrid GA and PSO [26] and Pareto Frontierifferential evolution algorithm [27] have been applied toolve the above DG allocation issues. Different DG

HapthT Gener. Transm. Distrib., 2015, Vol. 9, Iss. 3, pp. 209220oi: 10.1049/iet-gtd.2014.0603sensitivity method for sizing and siting of DG optimally tominimise the power losses in the distribution system wasproposed by Kashem et al. [28].Most of the above methodologies considered the DG type,

which is capable of supplying real power only to the network.owever, there are other types of DG which can supply realnd/or reactive power into the network and improve theerformance to still better extent. Further, the majority ofe general analytical approaches for DG siting and sizingobjective problem formulation. Different optimisationtechniques such as index-based approach [7, 25], heuristic

candidate locations for DG. A technique based on loss

were touched by the researchers using single or multiElectrical power systems are observing rapid changes fromlarge centralised generation plants connected to the bulktransmission network into decentralised systems with smallgenerating systems connected directly to the distributionnetworks near demand centre. The later type of generationsystem is known as distributed generation (DG) [1, 2]. DGcan be powered by renewable energy sources (e.g. solar,wind, small hydro, biomass, geothermal etc.) ornon-renewable energy sources (e.g. gas turbine,microturbine, fuel cell, reciprocating engine etc.). Thebenets of DG include reduction of power losses,improvement in the voltage prole, deferred networkexpansion cost, network reliability improvement and so on[36]. Appropriate size and location of DG offers technical,economical and environmental benets to distributionnetworks. For optimal allocation of DG in distributionnetworks, different objectives such as power lossminimisation [728], improvement of voltage prole [7, 11,21, 23, 2528], network investment cost minimisation [5,29, 30], reduction of environmental impact [7] and so on

merits and demerits, the various aspects of DG planning forpower loss minimisation, and different techniques employedin achieving the goal along with their feasibility has beenreported in [32].A methodology for optimal allocation of DG in distribution

networks based on analytical approach (sensitivity analysisbased on equivalent current injection) for loss reduction hasbeen suggested by Gozel and Hocaoglu [10]. Wang andNehir [13] proposed an analytical method based on phasorcurrent injection method to optimally place DG assuminguniformly, increasingly and centrally distributed loadpattern with in radial distribution network to minimisepower loss. These assumptions may cause erroneous results.In [1416], analytical approach based on exact loss formulafor optimally allocating DGs was presented. This isfollowed by the work of Khan and Choudhary [21] whopresented an analytic-based algorithm to site and size DGin distribution network for reducing the power loss andimproving the voltage prole. An approach based on exactloss formula and GA for power loss minimisation ofdistribution feeder was proposed by Shukla et al. [22]. Theloss sensitivity method is used to identify the strategicPublished in IET Generation, Transmission & DistributionReceived on 22nd December 2013Accepted on 15th July 2014doi: 10.1049/iet-gtd.2014.0603

Analytical approach for opdistributed generation in rSevya Naik Gopiya Naik, Dheeraj Kumar KhAlternate Hydro Energy Centre, IIT Roorkee, Roorkee 2476E-mail: [email protected]

Abstract: This study presents an analytical approach for optimdistribution networks to minimise real and reactive power loderived which are based on change in active and reactive comethod rst determines the DG capacity causing maximumlocation for DG placement which corresponds to highest bensingle as well as multiple DG units. Moreover, the proposdetermine the optimal size of DG unit(s). The proposed msystems. The results obtained by this proposed method validto determine the size and site of DG unit(s).

1 IntroductionISSN 1751-8687

al siting and sizing ofial distribution networksd, Mahendra Pal Sharmattarkhand, India

iting and sizing of distributed generation (DG) in radial power. For this purpose, suitable analytical expressions have beenonents of branch currents cause by the DG placement. Thiset at different buses, and then selects the bus as the bestThe proposed method is applicable for sizing and siting ofethod requires only the results of base case load ow tood is tested on 33-bus and 69-bus radial distribution testhe suitability and importance of proposed analytical method

technologies used in distribution system planning with their209& The Institution of Engineering and Technology 2015

are based on exact loss formula and require the determinationof the bus impedance matrix (Zbus) or Jacobian matrix whichare computationally demanding. Therefore, because of thesize, the complexity and the specic characteristics of thedistribution network, the above methods are not suitable.Therefore, the optimal allocation of DG of any type usingsuitable solution technique needs further attention.In this paper, a methodology based on analytical approach

is presented for optimal sizing and siting of DG in distributionsystem so as to minimise real as well as reactive power losses.This paper is the extension of that proposed in [23]. Thedeveloped analytical method is based on change in activeand reactive components of branch currents cause by theDG placement. The proposed method has been tested on33-bus and 69-bus test radial distribution systems and theresults are found to support the suitability and benets ofproper DG allocation in power distribution system fornetwork performance improvement. This paper is organisedas follows: Section 2 discusses the problem formulation ofproposed method, Section 3 presents the solution algorithm

When a DG is placed at a bus (say bus k) as shown in

www.ietdl.orgFig. 2, it injects current IDG into the network and there byalters the currents in all the branches connected betweensub-station (bus 1) to bus k. However, the currents in the

Fig. 1 Typical N-bus radial distribution system

Fig. 2 Typical N-bus radial distribution system with DG placed atbus kand Section 4 presents the results and discussion of theproposed work. Finally, in Section 5, conclusions aresummarised.

2 Problem formulation

In this section, the mathematical formulation of the proposedanalytical approach is presented. The proposed analyticalapproach aims to determine the optimal size and location ofDG in a given radial distribution network so as to minimiseboth real power loss and voltage drop. The proposedapproach begins with the following assumptions:

1. The radial distribution network under consideration isbalanced.2. The power factor of DG is known.

Consider a typical N-bus radial distribution system asshown in Fig. 1. In this gure, Ik is the phasor current inbranch k while ILk is the load phasor current of loadconnected at node k.210& The Institution of Engineering and Technology 2015remaining branches are unaffected by the DG placed at busk. The injected current by DG placed at bus k can bewritten as

IDG = IaDG + jIrDG = IaDG 1+ j tanf( )

(1)

where IaDG and IrDG are the real and reactive components,respectively, of IDG and f is the phase angle of IDG.Now, the modied current in branch i because of DG

placed at bus k can be given as

Inewi = I i DiIDG = Iai DiIaDG( )+ j Iri DiIaDG tanf( )

(2)

where Ii is the phasor current in branch I before DGplacement and Inewi is the modied phasor current in branchi after DG placement. The value of Di is given by thefollowing relation

Di = 1, if branch i is between bus 1 and bus k0, otherwise.{

Extending the above concept for placement of m DGssimultaneously in an N-bus radial distribution network, themodied current through branch I can be given as

Inewi = I i mk=1

DikIkDG = Iai

mk=1

DikIkaDG

( )

+ j Iri mk=1

DikIkaDG tanf

k

( )(3)

where Inewi is the modied phasor current in branch i; IkDGis

the phasor current injected current by kth DG; IkaDGand fk

are the active component and phase angle, respectively, ofIkDG and the value of Dik is given by the following relation

Dik =1, if branch i is between bus 1 and bus at which

kth DG is placed0, otherwise

2.1 Real power loss saving

The total active power loss [33], that is, PL in a typical N-busradial distribution system as shown in Fig. 1, can be given as

PL =N1i=1

I2i Ri =N1i=1

I2ai + I2ri( )

Ri (4)

where Ii is the current through branch i with Iai and Iri beingits real and imaginary components, respectively, and Ri is theresistance of the branch.Now, using (3), the total real power loss after placement of

m DGs is given by

PnewL =N1i=1

Inewi( )2

Ri

=N1i=1

Iaimk=1

DikIkaDG

( )2+ Iri

mk=1

DikIkaDG tanf

k

( )2[ ]Ri

(5)IET Gener. Transm. Distrib., 2015, Vol. 9, Iss. 3, pp. 209220doi: 10.1049/iet-gtd.2014.0603

Using (4) and (5), the normalised loss saving PS associatedwith multiple DG placement can be given as (see (6)).

2.2 Reactive power loss saving

The total reactive power loss, that is, QL in a typical N-busradial distribution system as shown in Fig. 1, can be given as

QL =N1i=1

I2i Xi =N1i=1

I2ai + I2ri( )

Xi (7)

Now, using (3), the total reactive power loss after placementof m DGs is given by

QnewL =N1i=1

Inewi( )2

Xi =N1i=1

Iai mk=1

DikIkaDG

( )2

+ Iri mk=1

DikIkaDG tanf

k

( )2Xi(8)

Using (7) and (8), the normalised reactive power loss savingQS associated with multiple DG placement can be given as(see (9)).

saving, respectively and should meet the following condition

w1 + w2 = 1 (11)

The DG currents for the maximum benet can be achieved bysolving the following equation

f

I1aDG= w1

PSI1aDG

+ w2QSI1aDG

= 0f

I2aDG= w1

PSI2aDG

+ w2QSI2aDG

= 0

..

. ... ..

.

f

ImaDG= w1

PSImaDG

+ w2QSImaDG

= 0

(12)

The partial derivative of f with respect to IpaDG can be given as(see (13)).

Corresponding to (12), there will be m linear algebraicequations each similar to (13). These equations can bearranged in matrix form and expressed as

[ ]

ik IkaDNi=

(11 I(

(P

ikIkaDNi=

(11 I(

(Q

ikIka

www.ietdl.orgPS = 1PnewLPL

= 1N1

i=1 Iai m

k=1 D([

=N1

i=1 2m

k=1 DikIkaDG Iai + Iri tanfk

( )[N

i=

=N1

i=1 2m


( )[

QS = 1QnewLQL

= 1N1

i=1 Iai m

k=1 D([

=N1

i=1 2m


( )[N

i=

=N1

i=1 2m


( )[

f

IpaDG= 2

N1i=1

Dip Iai + Iri tanfp( ) Dipm

k=1D

{2.3 Net benet

Now, using (6) and (9), the net benet associated withmultiple DG placement can be combined as

f = w1PS + w2QS (10)

where w1 and w2 are the constants representing weightsassigned to real power loss saving and reactive power lossIET Gener. Transm. Distrib., 2015, Vol. 9, Iss. 3, pp. 209220doi: 10.1049/iet-gtd.2014.0603A[ ]mm IaDG m1= B[ ]m1 (14)

The (p, q)th elements of matrix A are calculated by thefollowing expression

Apq =N1i=1

DipDiq 1+ tanfp tanfq( )

w1RiPL

+ w2XiQL

( )

(15)

G

)2+ Iri mk=1 DikIkaDG tanfk( )2]Ri11 I

2ai + I2ri

( )Rim

k=1 DikIkaDG

)2 mk=1 DikIkaDG tanfk( )2]Ri2ai + I2ri

)Rim

k=1 DikIkaDG

)2 mk=1 DikIkaDG tanfk( )2]RiL

(6)

G

)2+ Iri mk=1 DikIkaDG tanfk( )2]Xi11 I

2ai + I2ri

( )Xim

k=1 DikIkaDG

)2 mk=1 DikIkaDG tanfk( )2]Xi2ai + I2ri

)Xim

k=1 DikIkaDG

)2 mk=1 DikIkaDG tanfk( )2]XiL

(9)

DG 1+ tanfp tanfk( )}

w1RiPL

+ w2XiQL

( )= 0 (13)211& The Institution of Engineering and Technology 2015

2. Run the base case load ow using backward and forwardsweep method [34] and obtain real power loss (PL), reactivepower loss (QL) and voltage prole of the network.3. Select the number of DGs to be placed (say m) and theirpower factors (DGs may have different power factors). Also,select the suitable values of the weights w1 and w2considering (11).4. Initialise DG counter, k = 1 and bus counter, i = 2.5. Calculate the required capacity of kth DG at bus I using(19)(21) and then compute and store the benet (say fik)associated using (10) along with the capacity of kth DG.6. Check whether i fik, for i = 2 to N and i j) for kth DG.Connect kth DG at bus j with the capacity as calculatedfrom step 5.8. Run the load ow with kth DG located at bus j and obtainreal power loss (PL), total reactive power loss (QL) andvoltage prole of the network.9. Check whether k

4 Results and discussion

The developed algorithm has been implemented underMATLAB environment and applied on two test systems todetermine the optimal sizing and siting of DGs. For eachtest system, different values of w1 and w2 have beenconsidered as (a) w1 = 1 and w2 = 0; (b) w1 = 0.5 and w2 =0.5; and (c) w1 = 0 and w2 = 1. Apart from this, twodifferent values of DG power factors have also beenconsidered as: (a) all DGs are operating at unity power

factor; and (b) all DGs are operating at a power factor equalto the power factor of total load of the system [15].The following test systems have been considered for the

optimal placement and sizing of DGs by the developedalgorithm.

4.1 33-Bus radial distribution system

The single line diagram of a 12.66 kV, 33-bus radialdistribution system is illustrated in Fig. 4. The relevant data

Fig. 4 Single line diagram of 12.66 kV, 33-bus radial distribution system

r ma

www.ietdl.orgFig. 5 Optimal DG size of unity power factor at different buses foTable 1 Results for UPF DG installation in 33-bus test system with w1

Initial system condition

System description Active powerloss, kW

original base case 202.682.48 MVA, UPF DG connected to bus 6 104.082.48 and 0.41 MVA, UPF DG connected to buses 6and 16, respectively

92.48

2.48, 0.41 and 0.65 MVA, UPF DG connected tobuses 6, 16 and 25, respectively

84.16

original base case 202.68


79.51

IET Gener. Transm. Distrib., 2015, Vol. 9, Iss. 3, pp. 209220doi: 10.1049/iet-gtd.2014.0603ximum real power loss saving= 1 and w2 = 0

Result with DG installation

No. of DGplaced

Bus for DGplacement

DG size,MVA

Active losssaving, kW

1 6 2.48 91.801 16 0.41 10.261 25 0.65 7.81

3 6, 16, 25 1.73,0.53, 0.77

116.75

213& The Institution of Engineering and Technology 2015

for this test system are acquired from [35]. This test systemhas the total demand of (3715 + j2300) kVA with the powerfactor of total load as 0.85 lagging.The number of DG to be placed is taken as 3. In order to

determine 3 suitable buses for DG installation at unity

power factor (UPF) in 33-bus test system for benetmaximisation with w1 = 1 and w2 = 0, rst the optimal sizeof a single DG and the corresponding benet aredetermined using (21) and (10), respectively. For this case,Fig. 5 shows the DG size for all the buses in the system

Table 2 Results for LPF DG installation in 33-bus test system with w1 = 1 and w2 = 0

Initial system condition Result with DG installation


No. of DGplaced

Bus for DGplacement

DG size,MVA


original base case 202.68 1 6 3.01 135.193.01 MVA, LPF DG connected to bus 6 61.72 1 32 0.60 14.823.01 and 0.60 MVA, LPF DG connected to buses 6and 32, respectively

46.07 1 25 0.68 8.47

3.01, 0.60 and 0.68 MVA, LPF DG connected tobuses 6, 32 and 25, respectively

37.38

original base case 202.68 3 6, 32, 25 1.85,0.90, 0.85

127.79


26.63

h w1

Table 3 Results for UPF DG installation in 33-bus test system with w1 = 0.5 and w2 = 0.5


System description Activepower loss,

kW

Reactivepower loss,

kVAr

No. of DGplaced

Bus for DGplacement

DG size,MVA


Reactive losssaving, kVAr

original base case 202.68 135.14 1 6 2.44 91.78 55.412.44 MVA, UPF DG connected tobus 6

104.20 74.78 1 15 0.44 10.72 8.67

2.44 and 0.44 MVA, UPF DGconnected to buses 6 and 15,respectively

92.04 65.09 1 25 0.66 7.83 5.68

2.44, 0.44 and 0.66 MVA, UPF DGconnected to buses 6, 15 and 25,respectively

83.71 59.07

original base case 202.68 135.14 3 6, 15, 25 1.66,0.58,0.76

117.11 75.00

1.66, 0.58 and 0.76 MVA, UPF DGconnected to buses 6, 15 and 25,respectively

79.20 55.60

www.ietdl.orgTable 4 Results for LPF DG installation in 33-bus test system wit

Initial system conditionSystem description Activepower loss,

kW

Reactivepower loss,

kVAr

No.pl

original base case 202.68 135.142.97 MVA, LPF DG connected tobus 6

61.83 48.54

2.97 and 0.62 MVA, LPF DGconnected to buses 6 and 31,respectively

45.39 36.33

1.78, 0.62 and 0.69 MVA, LPF DGconnected to buses 6, 31 and 25,respectively

36.64 29.78

original base case 202.68 135.14

1.81, 0.93 and 0.84 MVA, LPF DGconnected to buses 6, 31 and 25,respectively

26.07 22.43

214& The Institution of Engineering and Technology 2015= 0.5 and w2 = 0.5

Result with DG installationof DGaced

Bus for DGplacement

DG size,MVA



1 6 2.97 135.17 82.031 31 0.62 15.58 11.51

1 25 0.69 8.54 6.37

3 6, 31, 25 1.81,0.93,0.84

128.03 83.41

IET Gener. Transm. Distrib., 2015, Vol. 9, Iss. 3, pp. 209220doi: 10.1049/iet-gtd.2014.0603

except the sub-station bus and corresponding benet (active for this case are summarised in Table 2. For this case, theoptimal sizes of DGs are 1.85, 0.90 and 0.85 MVA at buses6, 32 and 25, respectively. This alternative of DG sizesresults in a total real power loss of 26.63 kW or 86.86%real power loss reduction as compared with base case system.Further, optimal locations and sizes of 3 DGs are also

computed for different values of w1 and w2. Tables 3 and 4present the optimal locations and sizes of 3 DGs operated atUPF and LPF, respectively, with w1 = 0.5 and w2 = 0.5. AtUPF operation of DGs, their optimal sizes are 1.66, 0.58and 0.76 MVA at buses 6, 15 and 25, respectively, resultingin (79.20 + j55.60) kVA loss in the network. On the other

Table 5 Results for UPF DG installation in 33-bus test system with w1 = 0 and w2 = 1


System description Reactive powerloss, kVAr

No. of DGplaced

Bus for DGplacement

DG size,MVA


original base case 135.14 1 7 2.00 55.782.00 MVA, UPF DG connected to bus 7 75.46 1 31 0.58 10.322.00 and 0.58 MVA, UPF DG connected tobuses 7 and 31, respectively

63.57 1 25 0.70 6.50


56.72


77.59


53.36

www.ietdl.orgpower loss saving). The active power loss saving obtainedby running load ow is also plotted in this gure for thesake of comparison. The loss saving computed by proposedmethod is close to that computed by running load ow andboth are following similar trends.It is evident from Fig. 5 that the highest active power loss

saving of 91.8 kW can be achieved by placing a 2.48 MVA,UPF DG at bus 6. However, the actual active power losssaving calculated by running load ow is 98.6 kW. This isbecause, in the developed analytical method, the expressionfor active power loss saving has been derived because ofchange in branch currents only caused by DG placement.When branch currents are reduced by DG placement, thevoltage drops in different branches are also reduced whichin turn improves the voltage prole of the system. Thus, anextra saving of 6.8 kW can also be achieved by placing a2.48 MVA, UPF DG at bus 6 because of voltage proleimprovement.After placing a 2.48 MVA, UPF DG at bus 6, the above

procedure is repeated to identify next and subsequentcandidate buses. The results for this case are summarised inTable 1. From this table, it is clear that buses 6, 16 and 25are the suitable location for DG installation at UPF. Now,the optimal sizes of DGs determined simultaneously byusing (18)(20) are 1.73, 0.53 and 0.77 MVA at buses 6, 16and 25, respectively. This alternative of DG sizes results ina total real power loss of 79.51 kW against 202.68 kWpower loss of base case system.This approach is extended to size and site 3 DGs, operating

at load power factor (LPF) in 33-bus test system for benetmaximisation with w1 = 1 and w2 = 0. The obtained resultsTable 6 Results for LPF DG installation in 33-bus test system with w1



original base case 135.141.80 MVA, UPF DG connected to bus 30 48.621.80 and 0.77 MVA, UPF DG connected to buses30 and 14, respectively

24.28


14.70



11.76

IET Gener. Transm. Distrib., 2015, Vol. 9, Iss. 3, pp. 209220doi: 10.1049/iet-gtd.2014.0603hand, 1.81, 0.93 and 0.84 MVA LPF DGs connected atbuses 6, 31 and 25, respectively, result in (26.07 + j22.43)kVA loss in the network.Tables 5 and 6 summarises the results of optimal locations

and sizes of 3 DGs operated at UPF and LPF, respectively,with w1 = 0 and w2 = 1.0. In this case, at UPF operation ofDGs, their optimal sizes are 1.38, 0.71 and 0.77 MVA atbuses 7, 31 and 25, respectively, causing 53.36 kVArreactive power loss. While at LPF operation of DGs, their

Table 7 Comparison of results for 33-bus test system

Particulars Acharyaet al. [14]

Murthy andKumar [36]

Proposedmethod

DG size, MVA 2.49 2.5 3.01 2.48 3.01DG power factor UPF UPF 0.9 lag UPF 0.85 laglocation 6 6 6 6 6loss saving,% 47.33 47.32 66.39 48.65 69.55= 0 and w2 = 1


No. of DGplaced

Bus for DGplacement

DG size,MVA


1 30 1.80 83.551 14 0.77 23.811 24 1.06 9.44

3 30, 14, 24 1.39,0.81, 1.14

82.73


optimal sizes are 1.39, 0.81 and 1.14 MVA at buses 30, 14 and24, respectively, resulting in 11.76 kVAr reactive power loss.Summarising different cases presented in Tables 16, it is

evident that the optimal locations and sizes of DGs varydepending upon the objective considered (values of w1 and w2)

and power factor of DG. For a considered objective, LPFoperation of DGs improves the system performance in abetter way compared with UPF operation.Finally, to validate the proposed method, the results

obtained by it are compared with those obtained by the

Fig. 6 Voltage prole of 33-bus test system for different cases

www.ietdl.orgTable 8 Results for UPF DG installation in 69-bus test system with w1



original base case 225.001.81 MVA, UPF DG connected to bus 50 83.371.81 and 0.51 MVA, UPF DG connected to buses50 and 17, respectively

71.71


70.20



70.29

Fig. 7 Single line diagram of 12.66 kV, 69-bus distribution system

216& The Institution of Engineering and Technology 2015= 1 and w2 = 0


No. of DGplaced

Bus for DGplacement

DG size,MVA


1 50 1.81 133.031 17 0.51 11.011 39 0.72 1.51

3 50, 17, 39 1.72,0.52, 0.72

149.28

IET Gener. Transm. Distrib., 2015, Vol. 9, Iss. 3, pp. 209220doi: 10.1049/iet-gtd.2014.0603

methods reported in the literature for 33-bus test system andpresented in Table 7. The results presented in this table arefor siting and sizing of single DG to minimise the realpower loss only. From this table, it is evident that moreactive power loss saving is possible by the proposed methodcompared with the other methods reported in the literature.

The voltage proles of 33-bus test system for differentcases considered are given in Fig. 6. These voltage prolesare obtained after placing 3 DGs as given in the last row ofTables 16. It is evident from Fig. 6 that the installation ofDG units in 33-bus test system by proposed methodsignicantly improves the voltage prole of the network.




No. of DGplaced

Bus for DGplacement

DG size,MVA


original base case 225.00 1 50 2.22 200.112.22 MVA, LPF DG connected to bus 50 23.88 1 17 0.61 15.602.22 and 0.61 MVA, LPF DG connected to buses 50and 17, respectively

8.19 1 39 0.88 2.27


5.92


153.91


5.66

ith w

No.

Table 10 Results for UPF DG installation in 69-bus test system with w1 = 0.5 and w2 = 0.5


System description Activepower loss,

kW

Reactivepower loss,

kVAr

No. of DGplaced

Bus for DGplacement

DG size,MVA



original base case 225.00 102.17 1 50 1.83 133.01 57.881.83 MVA, UPF DG connected tobus 50

83.29 40.62 1 17 0.52 10.85 4.39


71.76 35.95 1 39 0.72 1.51 3.70

1.83, 0.52 and 0.72 MVA, UPF DGconnected to buses 50, 17 and39, respectively

70.25 32.24

original base case 225.00 102.17 3 50, 17, 39 1.73,0.53,0.72

149.29 67.50


70.24 32.30

www.ietdl.orgTable 11 Results for LPF DG installation in 69-bus test system w


System description Active Reactive

power loss,

kWpower loss,

kVArpl

original base case 202.68 102.172.25 MVA, UPF DG connected tobus 50

23.87 14.67


8.38 8.45


6.11 2.89

original base case 202.68 102.17


5.66 2.79

IET Gener. Transm. Distrib., 2015, Vol. 9, Iss. 3, pp. 209220doi: 10.1049/iet-gtd.2014.06031 = 0.5 and w2 = 0.5


of DG Bus for DG DG size, Active loss Reactive loss

aced placement MVA saving, kW saving, kVAr

1 50 2.25 200.08 87.081 17 0.62 15.38 6.19

1 39 0.88 2.27 5.55

3 50, 17, 39 2.13,0.64,0.88

153.81 69.94


However, the degree of improvement is different dependingupon the objective considered (values of w1 and w2) andpower factor of DG. Among different cases considered, thebest voltage prole is observed when DGs are operated atLPF with w1 = 0 and w2 = 1.0.

4.2 69-Bus radial distribution system

The single line diagram of a 12.66 kV, 69-bus distribution testsystem is shown in Fig. 7. The necessary data for 12.66 kV,

69-bus distribution test system are obtained from [37]. Thistest system has the total demand of (3802.19 + j2694.6)kVA with the power factor of total load as 0.82 lagging.For this test system also, the number of DG to be placed is

taken as 3. To determine 3 suitable buses for DG installationat UPF in 69-bus test system for benet maximisation withw1 = 1 and w2 = 0, similar procedure is employed asdiscussed for 33-bus test system. The results for this caseare summarised in Table 8. The installation of 1.72, 0.52and 0.72 MVA UPF DGs at buses 50, 17 and 39,

Table 12 Results for UPF DG installation in 69-bus test system with w1 = 0 and w2 = 1



No. of DGplaced

Bus for DGplacement

DG size,MVA


original base case 102.17 1 50 1.86 57.891.86 MVA, UPF DG connected to bus 50 40.56 1 17 0.53 4.311.86 and 0.53 MVA, UPF DG connected to buses50 and 17, respectively

35.96 1 39 0.72 3.70


32.26


67.51


32.27




No. of DGplaced

Bus for DGplacement

DG size,MVA


original base case 102.17 1 50 2.28 87.102.28 MVA, UPF DG connected to bus 50 14.63 1 17 0.64 6.072.28 and 0.64 MVA, UPF DG connected to buses50 and 17, respectively

8.53 1 39 0.88 5.55


2.97


69.90

2.14, 0.66 and 0.88 MVA, UPF DG connected to 2.77

www.ietdl.orgbuses 50, 17 and 39, respectivelyFig. 8 Voltage prole of 69-bus test system for different cases

218& The Institution of Engineering and Technology 2015IET Gener. Transm. Distrib., 2015, Vol. 9, Iss. 3, pp. 209220doi: 10.1049/iet-gtd.2014.0603

www.ietdl.orgrespectively, results in a total real power loss of 70.29 kWagainst 225 kW power loss of base case system.To size and site 3 DGs, operating at LPF in 69-bus test

system for benet maximisation with w1 = 1 and w2 = 0, theobtained results are summarised in Table 9. From this table,it is clear that buses 50, 17 and 39 are the suitable locationsfor DG installation at LPF. The optimal sizes of DGs are2.12, 0.62 and 0.88 MVA at buses 50, 17 and 39,respectively, and results in a total real power loss of 5.66 kWor 97.78% real power loss reduction compared with basecase system.Further, optimal locations and sizes of 3 DGs are also

computed for different values of w1 and w2. Tables 10 and11 present the optimal locations and sizes of 3 DGsoperated at UPF and LPF, respectively, with w1 = 0.5 andw2 = 0.5. Tables 12 and 13 summarise the results of optimallocations and sizes of 3 DGs operated at UPF and LPF,respectively, with w1 = 0 and w2 = 1.0.Summarising different cases presented in Tables 812, it is

evident that the optimal locations for DGs are the sameirrespective of the objective considered and power factor ofDG. Also, the optimal sizes of DGs are approximatelysimilar for a given power factor irrespective of the objectiveconsidered. Among different power factor, LPF operation ofDGs improves the system performance in a better way ascompared with UPF operation.A comparison of results obtained by different methods for

single DG allocation to minimise real power loss in 69-bussystems is given in Table 14. From this table, it is evidentthat more active power loss saving by the proposed methodis in good agreement with the other methods reported in theliterature.The voltage proles of 69-bus test system for different

cases considered are given in Fig. 8. These voltage prolesare obtained after placing 3 DGs as given in the last row ofTables 812. It is evident from Fig. 8 that the installation ofDG units in 69-bus test system by proposed methodsignicantly improves the voltage prole of the network.Since it is seen from Tables 812 that the optimal sizes ofDGs are approximately similar despite of the objectiveconsidered and mainly depends on the power factor of DG,the same can be observed in Fig. 8 also. The best voltageprole is observed when DGs are operated at LPF,irrespective of the objective considered.

Table 14 Comparison of results of 69-bus test system

Particulars Acharya et al.[14]

Murthy andKumar [36]

Proposedmethod

DG size, MW 1.81 1.85 2.20 1.81 2.22power factor UPF UPF 0.9

lagUPF 0.82

laglocation 50 50 50 50 50loss saving,% 62.86 63.02 87.59 62.95 89.395 Conclusions

This paper presents an analytical approach-basedmethodology for optimal sizing and siting of DGs in theradial distribution networks. Both real as well as reactivepower loss minimisation are the objectives for DGplacement. Suitable analytical expressions have beenderived to compute the real as well as reactive power losssaving because of change in branch current caused by DG.The developed method is able to optimise the size and

optimal placement of renewable distributed generators, IEEE Trans.

IET Gener. Transm. Distrib., 2015, Vol. 9, Iss. 3, pp. 209220doi: 10.1049/iet-gtd.2014.0603Power Syst., 2013, 28, (2), pp. 68369521 Khan, H., Choudhary, M.A.: Implementation of distributed generation

(IDG) algorithm for performance enhancement of distribution feederunder extreme load growth, Int. J. Electr. Power Energy Syst., 2010,32, (9), pp. 985997

22 Shukla, T.N., Singh, S.P., Srinivas Rao, V., Naik, K.B.: Optimal sizingof distributed generation placed on radial distribution systems, Electr.Power Compon. Syst., 2010, 38, (3), pp. 260274

23 Gopiya Naik, S., Khatod, D.K., Sharma, M.P.: Sizing and siting of DGin distribution networks for real power loss minimization usinglocation of single as well as multiple DGs. The developedmethodology has been tested on 33-bus and 69-bus testdistribution networks with different values of DG powerfactor. Results obtained by this proposed method showbetter loss reduction as well as voltage prole improvementin the given distribution networks. Further, comparison ofresults for loss reduction with other reported methodsshows the effectiveness of the proposed method.

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