Radial Distribution System Reconfiguration in the Presence of Distributed Generators

Transcription

1 4th Internatonal Conference on Coputer, Mechatroncs, Control and Electronc Engneerng (ICCMCEE 205) Radal Dstrbuton Syste Reconfguraton n the Presence of Dstrbuted Generators Xngquan J, a, Q Lu, GuoZheng Han, Zhpeng Lu 2 and Qngxue Lu Shandong Unversty of Scence and Technology, Qngdao 26650, Chna; 2 Dspatchng and Control Center of Hanan Power Grd Corporaton, Hakou , Chna. a xqj@63.co Keywords: dstrbuton syste reconfguraton; dstrbuted generaton; genetc algorth. Abstract. A dstrbuton network reconfguraton odel wth wnd power generators s proposed, and an proved genetc algorth s appled to nze actve power loss. Forward and backward sweep approach s adopted to calculate the power flow. In addton, the strategy of searchng rando spannng trees s used to ensure the radal structure of network n the process of reconfguraton. Sulaton results show that the proposed ethod can reduce the power loss and prove the voltage qualty of dstrbuton syste.. Introducton As an effectve easure, dstrbuton syste reconfguraton (DSR) s often used as a eans to prove the syste securty or reduce the power loss of network. The coon objectve functons of dstrbuton network reconfguraton odel ncludes: actve power loss, voltage level, load balancng, and syste relablty. The DSR proble wth DGs ncorporated has been recently addressed n dfferent perspectves. ased on the nforaton and functonalty of reote controlled equpent, a ethodology for real-te reconfguraton of dstrbuton network consderng DG was developed n []. In [2], DG placeent was consdered whle solve the DSR proble usng senstvty analyss. In [3], a ult-objectve fraework was proposed whch consderng power losses, DG cost, greenhouse gas essons, and voltage stablty. DSR s usually forulated as a coplex cobnatoral, nonlnear constraned optzaton proble whch s dffcult to get the exact soluton. Many knds of algorths are proposed n the past. Due to the advantages of global searchng and nherently parallel, eta-heurstc algorths, such as genetc algorth (GA) [4], tabu search algorth (TSA) [5], and partcle swar optzaton (PSO) [6] have been successfully appled n DSR. The contrbuton of ths paper s to present the sultaneous optal network reconfguraton and power allocaton of dstrbuted wnd turbne usng an proved genetc algorth. 2. DSR Forulaton 2. Objectve functon The objectve s to nze the total network actve loss whch can be descrbed as: N br 2 2 Pl + Ql n Ploss = r () 2 = V Where, P loss s the syste actve power loss; P l and Q l are actve and reactve power at the end ternal of branch respectvely; V s the end ternal voltage of branch ; r s the resstance of branch. 2.2 Constrants Network reconfguraton needs to satsfy the followng constrants: ()Dstrbuton power flow equatons. For each bus, the actve and reactve power balance should be observed whch can be expressed as: 205. The authors - Publshed by Atlants Press 448

2 N bus ( ) P = V V Y cos θ δ + δ (2) j j j j j= N bus ( ) Q = V V Y sn θ δ + δ (3) j j j j j= where, Y j and θ j are the apltude and angle of j entry of the bus adttance atrx; V and δ are the apltude and angle of bus respectvely. (2)Perssble range of bus voltage Vn V Vax (4) where, V n and V ax are the lower and upper lt of bus voltage. (3)ranch power lts P + Q S (5) 2 2 l l ax where S ax s the axu power transtted through branch. (4)Radal and connectve network constrant. Dstrbuton networks ust have radal topologes wth all of nodes are energzed. 3. Load flow wth wnd power generators 3. Model of wnd power generators The bus that connected to a wnd power generator s regarded as P-Q(V) bus, and for splfyng, the actve power s regard as fxed value. The reactve power can be descrbed as: V V V 4PX Q = + (6) X 2 X where, X and X represent the leakage and exctaton reactance of generator respectvely. Shunt capactor s utlzed to copensate for the reactve power that the wnd power generators absorbed. Suppose the power factor of the wnd turbnes rses fro cosφ to cosφ 2, the reactve power that the shunt capactors provdes can be expressed as: Qc = P e (7) 2 2 ( cosφ ) ( cosφ2 ) Then the nuber of the shunt capactors that need to swtch on s: Q c n = (8) QN Unt Where, QN Unt represents the unt capacty of the shunt capactors. 3.2 Power flow calculaton In order to get the power loss, the forward and backward sweep approach s appled to calculate the power flow of the dstrbuton syste wth wnd power generators. Fg. shows the process. 4. Reconfguraton based on genetc algorth 4. Genetc encodng Here the decal codng ethod s appled. The sequence of the branches s correspondng to a chroosoe. The radal structure of network s obtaned based on spnnng tree theory to ensure all the solutons are feasble. 4.2 Genetc decodng A spannng tree could be fored by genetc decodng. The steps to for a spannng tree are as follow: () Put the branches that not take part n genetc codng nto several subsets, whch the connected branches are n the sae subset. For a gven dstrbuton network, the nuber of the branches that not take part n genetc codng s fxed. 449

3 (2) If the nuber of the branches n all the subsets equals the nuber of the te swtches, the procedure ends, otherwse the step (3) wll be carred out. (3) Put a new bus whch corresponded wth a gene of the chroosoe nto the exstng subsets accordng to the followng four stuatons. If no branch of the exstng subsets connects to the new branch, a new subset T k wll be fored: T k ={ }; 2 If there s only one exstng subset T n whch a branch connected to the new branch, then jon to subset T. 3 If new branch connects to two exstng subsets T and T n, T and T n wll erge nto a new subset and the jon branch to the new subset. All the branches of the new subset are connected each other. 4 If there s one exstng subset n whch two branches are connected to the new branch, then the branch wll be neglected. Go to step (2) to process other branches. Fg.2 shows the procedure of the proposed algorth. Fg. backward and forward sweep power flow Fg.2 Flow chart of algorth 5. Sulaton results Fg.3 shows the typcal IEEE-33 test syste. The rated capacty of the wnd turbne s 600 kw. The unt capacty of the shunt capactor s 0kVar. The power factor of the wnd turbne s 0.85 and s requred to rse to 0.95 after swtchng the shunt capactors. 450

4 Fg.3 Scheatc of 33 nodes syste Suppose the wnd power generator s located at node 24. In order to nvestgate power loss and voltage qualty of dstrbuton syste before and after reconfguraton, we change the actve out power of the wnd turbne fro 0 to 300, 350, and 400kW. Table shows the schee of the reconfguraton when the actve powers of the wnd power generator are dfferent. The sybol represents the branch between the node a and the node b. a b Table Reconfguraton results of 33 nodes syste actve power of wnd turbne(kw) openng branches Table 2 shows the power loss and the lowest voltage of dstrbuton syste before and after reconfguraton when the actve power of the wnd power generator s 0, 300, 350, 400kW. Table2 Indces coparson before and after reconfguraton actve power of wnd turbne (kw) lowest voltage (p.u.) rased (%) Power loss(kw) Orgnal Orgnal Optzed Optzed Orgnal Orgnal Optzed Optzed Orgnal Orgnal Optzed Optzed Orgnal Orgnal Optzed Optzed decreased (%) Conclusons Ths paper proposed an approach to the dstrbuton syste reconfguraton n the presence of dstrbuted generators. Sulaton results show that the proposed ethod can reduce the power loss and prove the voltage qualty of dstrbuton syste. On the condtons that the output of the wnd power generators s less than the power load of the located node, the power loss becoes saller and the voltage qualty of dstrbuton syste becoes better when the actve power of the wnd turbne ncreases. Acknowledgent Ths work s supported by Shandong Scence and Technology Developent Project of Chna (202G ) and Natural Scence Foundaton of Shandong Provnce, Chna (ZR20FM008). 45

5 References [] D. P. ernardon, A. P. C. Mello, L. L. Pftscher et al., Real-te reconfguraton of dstrbuton network wth dstrbuted generaton, Electrc Power Systes Research, 07 (204) [2] R. S. Rao, K. Ravndra, K. Satsh et al., Power loss nzaton n dstrbuton syste usng network reconfguraton n the presence of dstrbuted generaton, IEEE Transactons on Power Systes, 28 (203) [3] M. Sedghzadeh, M. Esal, and M. Esael, Applcaton of the hybrd g ang-g Crunch algorth to optal reconfguraton and dstrbuted generaton power allocaton n dstrbuton systes, Energy, 76 (204) [4] A. M. Tahboub, V. R. Pand, and H. H. Zeneldn, Dstrbuton Syste Reconfguraton for Annual Energy Loss Reducton Consderng Varable Dstrbuted Generaton Profles, IEEE Transactons on Power Delvery, 4 (205) [5] Abdelazz AY, Mohaed FM, Mekhaer SF, adr MAL. Dstrbuton syste reconfguraton usng a odfed Tabu Search algorth. Electrc Power Systes Research,8 (200) [6] A.Y. Abdelazz, F.M. Mohaed, S.F. Mekhaer, M.A.L. adr, Dstrbuton systes reconfguraton usng a odfed partcle swar optzaton algorth, Internatonal Journal of Electrc Power Systes Research, (2009)