An improved Probability Assessment Model of Electric Vehicle Chargers influencing on Distribution Transformer

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1 Intenational Confeence on Enegy and Envionmental Potection (ICEEP 016) An impoved Pobability Assessment Model of Electic Veicle Cages influencing on Distibution Tansfome Fen Qin1,a, Liang Sen1,b, Wei u1,c, Suangtong Cen1,d, Fan e,e and usuang Li,f 1 uang Powe Supply Company of State Gid Zejiang angzou Electic Powe Company, angzou , Cina; State Key Laboatoy of Powe Tansmission Equipment & System Secuity and New Tecnology, Congqing nivesity, Congqing , Cina a @qq.com, b @qq.com, c97376@qq.com, d4190@qq.com, e @qq.com Keywods: distibution tansfome; electic veicle cages; amonic cuent; loss-of-life Abstact. In tis pape, te caging cuent amonics of EV ae analyzed based on te amonically coupled admittance matix of tee-pase ectification cage. Te amonic cuent calculation fomula of single and multiple EV cages in te gid is deived, and subsequent a pobability metod to assess te top oil tempeatue, otspot tempeatue, elative aging ate and loss-of-life of distibution tansfome affected by te caging cuent amonics of EV cages is poposed using te amonic loss facto to quantify te impact of amonic cuent on tansfome and combining te pobabilistic simulation metod of caging load fo multiple types of EV. Intoduction Electic veicle (EV),as te most potential new enegy veicle wic is envionmental potection and enegy saving, as become te main diection of te ca's development of all counties. Wit te speading of EV and constuction of EV caging station, te scale of EV caging will ave significant influence on te safety and economic opeation of powe gid, including decease of te quality of powe supply, incease of netwo loss, lowe equipment utilization ate and so on[1].te impact caused by EV cages caging EV will Incease te pessues of Powe geneation equipments, tansmission equipments and distibution equipments[-4],and it mainly influences te distibution equipments, suc as tansfome, cable and switc equipment. Specifically, In te long un, te access of EV cages will speed up te aging of distibution tansfome. And fom a sot-tem pespective, caging load in pea wic leads to te action of tansfome oveload potection, will cause powe outage fo some electic powe uses[3]. Teefoe, we need to elaboate analysis te influence of EV cages on te distibution tansfome. Ten it can povide guidance fo selection of tansfome in EV caging stations. At ome and aboad, Fo study about te influence of EV cages on distibution tansfome, no one as analyzed te diffeences in diffeent caging metods (conventional, quic caging and battey canges), and tey also doesn't taing into account te amonic cuent geneated in te powe gid wen te EV cages cage EV. nde te same load level, wen te distibution tansfomes supply powe to te nonlinea load, EV cages, as a typical amonic souce[,6], geneating amonic cuent wic will fute ise te ot spot tempeatue of distibution tansfomes winding. Based on te coupled amonic admittance matix wic epesents te elation between cuent amonic and voltage amonic outputted by EV cages, Tis pape puts fowad te cuent amonic algoitm of EV cages connected to powe gid. Maing use of amonic loss facto to quantify life lost of tansfomes wic is caused by te cuent amonic of EV cages, and combining wit caging load pobability simulation, tis pape puts fowad an impoved pobability assessment metod of EV cages influencing on distibution tansfome. Accoding te analysis on a caging station, te coectness of te poposed sceme is validated Te autos - Publised by Atlantis Pess 01

2 Te Tempeatue of Distibution Tansfome and It s Life Loss nde Te amonic Poduced by EV Cages Te caging cuent amonic of EV cages and its influence on te distibution tansfome need to be detemined wen te caging load is nown. As fo oil-immesed self-cooling tansfome, it can be nown, accoding to IEEE C standad, tat te ise of te tansfome top oil tempeatue to ambient tempeatue TO is ougly popotional to te0.8 powe of total loss of tansfome P TL. Based on te total loss P TL of tansfome on ated opeating condition, and unde caging load, te tansfome top oil tempeatue is: P TL TOa = TO a TOR a PTLR TOR P P LL LLR P P NL NL 0.8 a Wee TOR is te ise of te tansfome top oil tempeatue to ambient tempeatue unde ated loss, Toa is te top oil tempeatue, a is te ambient tempeatue, P LL is te load loss of tansfome unde caging load, and P LLR is te load loss of tansfome unde its ated opeating conditions, P NL is te no-load loss. R is te expeience coefficient, and fo oil-immesed self-cooling tansfome =0.8. Tansfome loss includes coppe loss, eddy cuent loss, stay loss and so on. In ode to quantify te effects of te cuent amonic poduced by EV cages, adoptting loss facto [7] to detemine te atio of loss of winding eddy cuent and stay, unde amonic te load loss can be acquied as: (1) P = I R F P F P LL dc L EC L OSL I Rdc FL PEC F LPOSL 1 Te two amonic loss factos can be expessed as follows: () F 1 1 L I 1 1 I I I, F 1 1 L I I I 1 1 I 0.8 Consideing tat te amonic cuent ave influence on eddy cuent loss significantly, Stay loss can be ignoed fo facilitating computations [8]. And ten te ise of winding ot-spot tempeatue g to te top oil tempeatue is popotional to te0.8 powe of tansfome load loss P TL, winding ot-spot tempeatue can be get as follows: P LL g TOa gr TOa PLLR 1 F L P gr 1 PECR ECR TOa Wee is te ot-spot tempeatue, gr is te ise of winding ot-spot tempeatue to te top oil tempeatue unde ated cuent, P LLR and P ECR ae load loss and eddy cuent loss of winding espectively unde ating state. Because of te uneven distibution of tempeatue of tansfome, te patial degadation of tansfome is te most seious wen it is unning on te igest tempeatue. Fo te tansfome wit non-temal modification o temal modification felt pape. Relative aging ate V, wic is based on ot-spot tempeatue of winding, as a value of 1 wen te ot spot tempeatue is 98 o 110. Ten te elative aging ate of distibution tansfome is as follows, (3) (4) 98 6, non temal modification V = e, temal modification () 0

3 In te time inteval [t1, t], te life lost L of tansfome is, (6) L V t = N n n n1 Wee n is te coesponding seial numbe fo [t1, t] wic as been divided into multiple time inteval, N is te total numbe of time intevals, and V n is te elative aging ate of nt time inteval, t n is te lengt of nt time inteval. Analysis of amonic Poduced by EV Cages And Evaluation of Life Loss of Distibution Tansfome As a typical amonic load, te equivalent cuent of amonic analysis of EV cages is as sown in figue 1 []. sing coupled amonic admittance matix can accuately mae eac amonic voltage and eac cuent amonic elate to eac ote. Based on tee-pase uncontolled ectifie, Liteatue [16] deives coupled admittance matix of amonic of EV cages, and ten it convets te nonlinea caging cuent of time domain into linea of fequency domain, I (7) C Tat is, I C1 1,1 1, 1,7 1, K 10 I C,1,,7, K I C7 7,1 7, 7,7 7, K 77 I C K K,1,,7, K 1,1 1, 1,7 1, K 10,1,,7, K 7,1 7, 7,7 7, K 7 7 K K,1,,7, K Wee I C is te Caging cuent amonic vecto, and * ae te voltage amonic and its conjugate vecto, + and - is te coupled admittance matix of amonic, and ae te t amonic voltage RMS and pase, is te igest cuent amonic fequency, and K is te igest voltage amonic fequency. Te coupling elationsip between output cuent amonic of EV cages and teminal voltage elate to eac ote toug te + and -. And te elements of admittance matix elate to te paametes R f L f C and R in te amonic analysis equivalent cicuit, as sown figue 1a. Accoding to liteatue [9], Diffeent caging powe sould only cange te DC equivalent esistance R of EV cage. (8) Rf Lf ua ica D1 D3 D ub uc icb icc C R D4 D6 D (a) te equivalent cuent of amonic analysis of EV cage ZS ZT I IC IL S EV cage PC local load PL (b) system diagam of EV cage in distibution gid Fig. 1 Scematic diagam fo amonic cuent calculation of EV cage in distibution gid 03

4 Consideing tat te coupled admittance matix - is fa less tan + on te amplitude, and fundamental voltage of powe gid is muc geate tan eac voltage amonic, te elements at te fist column of - in (8) ae etained, and ote elements of - can be ignoed. As sown in figue 1b, impedance load model is used to epesent te conventional local load in te low voltage side of distibution tansfome. Afte EV caging load and local load all ave been connected to distibution tansfome, te cuent in low voltage side of distibution tansfome is as follows: I1 L I 0 L 0 0 I L7 7 7 I L K K 1,1 1,1 1, 1,7 1, K 10,1,1,,7, K 7,1 7,1 7, 7,7 7, K 7 7 K K,1,1,,7, K I I ( ) L C L C LC Wee I L is te amonic vectos of local load, C and L ae te amonic admittance matix of EV cage and local load espectively. eac amonic of local load is uncoupling, so L is a diagonal matix wic is consist of L =1/R L -j1/(l L ), wee R L L L and ae te esistance, inductance, and gid ated angula fequency of local load. Fom figue 1b, voltage balance equation of eac amonic can be get as, (9) S ( ZS + ZT )( IL IC ) S Z I (10) Fo a distibution netwo wic connects m sets of EV cages, If node 1 of te distibution netwo is te main souce node and node to m+1 connect wit m sets of EV cages, te cuent moving to te it amonic souce is, i i i i I ( L C) (11) Tat is, I L C I 0 L C 0 m1 m1 m1 m1 I 0 0 L C LC Fundamental cuent and eac amonic cuent of powe gid ae poduced by main souce and m sets of EV cages, wile main souce only injects fundamental cuent into powe gid wen its voltage only contains fundamental component. Maing use of node impedance matix between eac amonic souce, te nodal voltage equation of m sets of EV cages access point can be get as follows, (1) 1 3 ( m1) Z Z Z Z I Z Z Z 0 I IS m1 ( m1)1 ( m1) ( m1)3 ( m1)( m1) m1 Z Z Z Z I Z I S Fo single and multi-macine system, jointing (9) and (10), (1) and (13) espectively, te voltage vecto of cage and local load can be get as, 1 ( E+ ZLC ) S (14) Wee E is te unit matix of KK ode. Substituting (14) into (1), eac amonic cuent of te 04 (13)

5 low voltage side of distibution tansfome unde diffeent EV caging powe can be get. Te size of EV caging powe will cange te DC esistance of equivalent cicuit in figue 1a, influence te admittance matix LC of cage load and ote local load and te eac amonic cuent I of load connected wit distibution tansfome. Te amonic cuent geneated by EV caging will lead te top oil tempeatue and ot-spot tempeatue of distibution tansfome to cange wit te size of it's load, and ten decide te life loss of tansfome toug te elative temal aging ate. Teefoe, combining simulation of EV caging load, amonic cuent analysis of EV cage wit life loss calculation of distibution tansfome, te life evaluation pocess of tansfome can be get. Conclusions Tis pape analyses te caging cuent amonics of EV based on te amonically coupled admittance matix of tee-pase ectification cage. Te amonic cuent calculation fomula of single and multiple EV cages in te gid is deived, and subsequent a pobability metod to assess te top oil tempeatue, otspot tempeatue, elative aging ate and loss-of-life of distibution tansfome affected by te caging cuent amonics of EV cages is poposed using te amonic loss facto to quantify te impact of amonic cuent on tansfome and combining te pobabilistic simulation metod of caging load fo multiple types of EV. Refeences [1] Zao Junua, Wen Fusuan, ang Aimin, et al. Impacts of electic veicles on powe systems as well as te associated dispatcing and contol poblem[j]. Automation of Electic Powe Systems, 011, 3(14): -10, 9 [] Ge Wenjie, uang Mei, Zang Weige. Economic opeation analysis of te electic veicle caging station[j]. Tansactions of Cina Electotecnical Society, 013, 8(): 1-1 [3] Sexaue J M, McBee K D, Bloc K A. Applications of pobability model to analyze te effects of electic veicle cages on distibution tansfomes[j]. IEEE Tansactions on Powe Systems, 013, 8(): [4] Cen Liangliang, Zang ao, Ni Feng, et al. Pesent situation and development tend fo constuction of electic veicle enegy supply infastuctue[j]. Automation of Electic Powe Systems, 011, 3(14): [] Zang Qian, an Weijian, u Jiui, et al. Simulation model of electic veicle caging station and te amonic analysis on powe gid[j]. Tansactions of Cina Electotecnical Society, 01, 7(): [6] Zao Wei, Meng Jinling, Cen Ruimin, et al. Accuate measuement and taceability metod of electical enegy fo caging and discaging devices of electic veicles[j]. Automation of Electic Powe Systems, 013, 37(11): [7] ildiim D, Fucs E F. Measued tansfome deating and compaison wit amonic loss facto (FL) appoac[j]. IEEE Tansactions on Powe Delivey, 000, 1(1): [8] IEEE Std C IEEE Recommended Pactice fo Establising Liquid-Filled and Dy-Type and Distibution Tansfome Capability Wen Supplying Nonsinusoidal Load Cuents[S]. New o: Te Institute of Electical and Electonics Enginees, 008 [9] Zou N, Wang J, Wang Q, et al. Capacity calculation of sunt active powe filtes fo electic veicle caging stations based on amonic paamete estimation and analytical modeling[j]. Enegies, 014, 7(014):