JOl KNALOFSC H NC K&IKCIINOLv/v i ^ I "^li ( y 13 itij I \ C ONTROL OF HI DIRKC IIONAL CONVERTER IN BATTERY ENERGY S T 0 R A ( ; E S \ S lEM (BESS) FOR PEAK POWER SHAVING DILU KlllLN B( )Bn,N DOI IlAl[.]
JOl KNALOFSC H.NC K & I K C I I N O L v / v i ^ I "^li ( y 13 - itij I \ C ONTROL OF HI-DIRKC IIONAL CONVERTER IN BATTERY ENERGY S T R A ( ; E S \ S lEM (BESS) FOR PEAK POWER SHAVING DILU KlllLN B(.)Bn,N DOI IlAl 11U(')NG I KON( I IL I JCl fRlT NANG LUONG DUNG AC(.)UY (BfSS) BU (•(")N(i SUAf DlNll N}iO Due Minh Thainguyen ('niveisilv Nguyen Van Lien Hanoi Ihiiversitv ofScience and 'I'echnology ABSTRACT The issue that the isolated flexible electric grid face is shod time peak power (active and reactive) demand for starting of induction motor, in this shod time the generation can not ramp up for keeping up with the demand and then the starting up can be failled This paper presents a scaled down Battery Energy Storage System (BESS) for peak load shaving applications The design includes a bidirectional converter capable of intedacing a battery bank with the AC power gird In order to match dynamic response of the BESS and to take simplicity for implementation algorithms based on microprocessor or digital signal processing systems (DSP), the authors propose a convetional PID controller for the BESS The experiment shows good results IOM TAT l^ang dien cue bd linh hoat phdi ddi mat vdi thwc ti Id thwdng xuyen cd nhu ciu phu tai cdng suit dinh (tdc dung vd phdn khdng) ngdn han di khdi ddng cdc ddng ca khdng ddng bd, khodng thai gian rit ngdn mdy phdt khdng kip huy ddng cdng suit, kit qud Id cdc ddng ca khdng khoi ddng dwgc Ndi dung bai bdo danh cho viec thiit ki he thing Iwu trir dien acquy (BESS) img dung di san phu tdi dinh Thiit bi bao gdm mdt bd biin ddi hai hwdng cd khd nang lien kit ddn acquy vdi Iwdi dien xoay chiiu Di ddp wng ddng hoc cua BESS du nhanh vd dan gian, bat bdo da sif dung thuat diiu khiin dwa tren vi xir ly hodc he thing xw ly tin hieu sd (DSP), cdc tdc gid sw dung bo diiu khiin PID thdng dung Viec tiin hdnh thwc nghiem da cho cdc kit qud khd tdt va qua dd cd thi diic rut kinh nghiem cho thiit ki he thing Nomencleature As motors start, a large amount of power (about 5-7 times of norminal power) must be required in some seconds However, characteristics of active power control of small hvdro-elcctric generators have long delay-time, so the\ could not response in time (Fig 2) That time makes a chance for BESS to generate supplementary power to help the motors start successfullv and stabili/c the grid PLL-Phase Look Loop PCC-Point of common ccnipling L INTRODUCTION In Flexible AC Transmission Systems (FACTS), the Batterv Lncrgv Storage Svsiems (BESS) arc used as compensators connected parallelly with loads at a PCC in thc grid Specifications of BI-^SS have been researched to stabilize voltage of the grid (compensation o\' reactive power), to shave daily load trend (receiving and generating active power al different time-interval at a da> ) etc In the case of small hydro-electric canal-type power station, BESSs play an important role when they integrate a function of peak power compesation for starting motors C»nal(L, q.) Fig I Small hydro-power station 16 JOUHNAL OF SCIENCE & TECHNOLOGY * No 79B - 2010 50 P = N 40 I i^30 ~^'.i-'.i and: (7) — u,.i '/ ^20^ Time (s) Fig Unstable frequency motor begins to start '' '/ At PCC, (Fig 3), we have equations for balancing power when induclicvi (8) Pr = P, + P, Qr=Lf+Q, In order to control BESS, one can use grid voltage-oriented approach (VOC) with PID convential controllers or direct povver control approach with hvstercsis of 2- or 3position controllers [2 4] Both of these approaches have advantages and disadvantages as well However VOC approach with PID controllers is more appropriate due to it does not require stricly in identification of svstem s parameters If the source is isolated and soft, BESS will create power buffer between the load and the source to ensure stabilization and to improve economics of the system in loadvarv ing mode, especially in the worst case, when induction motor begins to start The model in our study has been described in Fig PCC IT IN IL MATHEMATICAL BACKGROUND AND DESIGN OF A CONTROLLER Load Source —(Q) I Motor 2.1 Instantaneous power control Battery; In the rectangular coordinate (dq), that rotates synchronously with space voltage vector at PCC, components id iq Ud Uq will be slowvarying quantities According to the concept of space vector, vve can get: u = u^+ju^ l= 'j+J'a thenp — Re(u.i ) ; q = Im(w./ ) -(Uj-ij+Uc,f,) 'I 'I' ^ ^ dqN vail \CF^ BESS Fig Block diagramn of soft power network integrated with BESS Set values for power BESS can be calculated as follows: (4) \^P,=Pr-P, (S) That leads the similar expressions for calculating instant power P= ~ (9) Due to the voltages at PCC are equal, then (9) can be m ^clB^ref -{u^.i,-Uj.l) c/H_rcJ ~~ ^cIT ^cIN v-v (10) where ijN and i,jN are given constants depended on limited power barie of the source If the axises d,q are oriented exactly on the grid-voltage space we will have 2.2 Designing of current regulator "c/=N=^«-; ^ = From [3, 4] one can have mathematical model on coordinate system dq as follows: 117 l O l U N A L Ol S( IEN( K & TECHNOLOGY * No 79B - 2010 ',v,/ = /^' \ L-f- \ dt (11) dl ^., f,/,, voltage inputs of converter Thc purpo.sc o\' current controllers is to control the actual currents tracking to thc set value and to eliminate coupling effections between components d.q and disturbance from grid-voltage ii\.i That helps to design current controllers with decoupling structure as described in Fie ik.i - I.I K f R+Lp Pig Simplified structure of current loops lo avoid possible svstem saturations the control action was kept below Dynamics of current loop will be improved when poles of plant are eliminated by controller Then zeros of the loop will be set as time-constant of current controller, linallv the parameters of current controllers can be calculated as below Us., A' - coL •- coL - R_ L Us K (13) P Fig Current Controllers Block diagram for controlling BESS coiinet.n.u wiil, sni.i!! isolated hydro-electric grid in this case can be designed in Fig [3] In order lo calculate parair.ctcrs of current controllers, vve assume the coupling effect be eliminated (due to the compensation of decoupling) The current loops have a simpler structure as depicted in Fig PCC, \ •t- ' t'le i ' " ' " I 'Sd OqA, / I U PCC 'B« 'so 'flc 0\ Ru - aq- J Ri ' Bd ' \ ' l—n UB^^^—T-^ "«^! L — — SVM otro Cdc •'H- battery Fig Block diagram of the system 118 Load JOURNAL OK SCIENCE & TECHNOLOGY * No 79B - 2010 - ^ Isolate Circuit BAUMULLER P.Bbc I- * ^; CT / IF neial R Ch PS 24VDC Fig ~ Experimented system of BESS III EXPERIMENTAL in order to receive characteristics that are similar to isolate soft grid 3.1 Experimental model of BESS Parameters for the controllers can be calculated as follows: BESS will provide 70% power for starting motors, the lelf power will be taken by the supplier From the structure and objective of experiment, the experimental model has been build up at The Key Automation laboratory, Hanoi University of Technology (Fig 7) 3.2 Experimental results Main equipments include: Some basic experimental results have been shown in Figs 8-12 Dsl 104 Card in PC Computer Power converter BUS623 cr::?;-:: Batteries of 12V/7Ah for DC voltage source of 630V 8O00 • 6O00 K 4O0O Induction motor of 2.2 kW 2O00 Induction motor of 3kW iiTfviSSgssssi i Sensors: Measuring load current transformer with 150A/5A ^lOi XI 10O0O Experimental Load: Transformers of 220V/6V measuring voltage fe, BESS ratio %—I 3S » I 40 f''" —'V j"»"i'»ii I—«—t—t—I—I—> 42 44 46 I 4.3 t(s) for Fig Active power of load and BESS by current r7;0\ ,-|n|x| 15000• As motors start with heavy load, the starting time will be long Then in order to check performances of BESS, we choose the starting mode with no load The motor under the experiment is squirrent cage induction motor of 2.2 kW 380/220V 50 Hz Supplier has been created from 3-phase source and combinated with equipment for limiting power 10000 - f Q- 5000 0- - \l_ k-^-r-^- ttMtW 3.6 3.8 4.0 4.2 4.4 4.6 4.8 t( s) Fig Active Power from the soft grid 119 .lOl UNAI, OK ,S( IKN( I, & I Kf -.|n| IIN()L0(;Y * No 7'U{ 21)10 x| ^nJiU ,1 II II ',1IIII1 "1 'fiTiri ,,.» , m i ' :• '- : •: 11 ' • ; •} f ,-; l-'ig 10 Reactive powers of load and BFSS /••/,L; / / AC-ciii i''iii\ of h)ii(l (Iiul P,ESS IV C O N T L l S I O N S |-^xperimcnl.'il lL•>llll^ compensation ul ptak in |-)II\VL-I ini|-ilcnicnting m var_ving4oad mode play impui-iani lolc lor developing of bULI ' > - - « small isolated solt 'i\-\i\ such a> wind generator small hydro-eU'Lii IC NUIIIOH M'lar cell park etc With the battciA bank ^A 4410 \ ' \ thc BESS 550 can supply povsci- with high rate (dP dl = 70 kW/s) In the com inu iinic wlicii Bl:SSsuscthe 500 •' ••—'—'—'—'—•—'-'-^»^—'—'—'—'—'—>—I 3.8 4 4.2 4.4 lis) energy storages liv supcr-ca|\iciotors instead of batteries, then Bi SS will be more attractive Fig 12 DC-voltage on batterv Lhhiill, r\ REFERKNC KS Xiao-PingZhang, Christian Rehtanz Bikash Pal flexible AC Tr.iMsiMi.Moii Svstems: Modelling and Control lSBN-10 3-540-30606-4 Springer Berlin llerdelberg \CN^ ^ n k :o^K^ Bui Quoc Khanh, Nguyen Van Lien; Base of electric machines drive; Publishing House, Ha Noi, 2006 Ngof^ucMinh, NguyenVanLien Dynamic iniprovement of B l S s nMug deadbe.ii iv pe controller in local power networks (II'EE Viet Nam Section, International I oi um on Siratciiic fechnologies (IFOST) 2009, 21-23 October 2009 in IloChiMinh Cilv Vietnam ) Antti 'farkiainen, et al; Current controled line convcr using direct loniue coniiol method Euro Trans Electric Power 2004 Science cV fechnology Author s address: Ngo Due M i n h - lei.: (+84) 982.286.428 email: ngoiniiilulue238 :uven Citv 120 ... Due M i n h - lei.: (+84) 982.286.428 email: ngoiniiilulue238 :uven Citv 120