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Ts. Phm Quang ngTrung tm NCTK Cng ngh cao, HBK H ni

u t v s dng mt cch hiu qu cc h thng iu khin hin i s gp phn khng nhvo vic nng cao hiu qu sn xut, gim chi ph sn xut v nng cao kh nng cnh tranh ca

sn phm trn th trng. Bi vit ny lm r bn cht v cp ti vn ng dng ca cc hSCADA v DCS.

Cc ng dng iu khin trong thc t Trong mt h thng sn xut cng nghip hay dn dng cc ng dng iu khin c th cphn chia thnh ba loi sau:- iu khin logic tun t (sequence logic control)- iu khin iu chnh (regulatory control)- Gim st vn hnh v thu thp s liu (SCADA)Ty theo tnh cht ca qu trnh cc yu cu v cc ng dng ny c th khc nhau. C qu trnhgm ch yu l ng dng iu khin logic nh trong cc phn xng lp rp nhng cng c qutrnh gm ch yu l cc ng dng iu khin iu chnh nh trong cc nh my ha cht ni

qu trnh sn xut l lin tc. Ring yu cu v gim st - vn hnh l tn ti trong hu ht nukhng mun ni l tt c cc h thng, t nht l cho ti thi im hin nay. Cc h thng iu khin c xy dng trong thc t phi p ng yu cu ca qu trnh snxut hay thit b s dng n. C th l n phi p ng yu cu ca v c ba loi ng dng iukhin nu trn. C hai cch thc hin iu ny nh sau:- Cch th nht l thc hin mi ng dng ny bng mt h thng ring bit. Theo ng dngiu khin logic s c thc hin bng cc PLC, ng dng iu khin iu chnh s c thchin bi cc controller v ng dng SCADA s c thc hin bi mt h SCADA ring bit.

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hin vic nhn d liu t cc RTU, hin th cc d liu ny v nhn cc lnh vn hnh t ngivn hnh ri chuyn ti RTU. Ngoi chc nng c bn ny, trm ch trung tm hin i cn thchin mt s chc nng khc lin quan ti qun l, bo tr v ti u ha qu trnh nh thit lptruyn thng, lin kt truyn thng, chun on, ti u ha hot ng ca h thng, Trm ch trung tm cn c gi l thit b u cui trung tm (Master Terminal Unit, vit tt l

MTU) nhng tn gi trm ch trung tm l ph hp hn vi cc h SCADA hin i. Trongcc h SCADA hin i trm ch trung tm thng bao gm mt hoc nhiu my trm, my chc ni mng vi nhau v phi hp vi nhau thc hin cc chc nng, nhim v ca trmch trung tm.- Mng truyn thng

Mng truyn thng s dng kt ni v trao i d liugia cc RTU v MTU. Mng truyn thng cng cs dng kt ni cc phn t trong MTU. Trong mth SCADA c th s dng mt hoc nhiu loi mngtruyn thng khc nhau ty theo tnh cht v c im

ca mi ng dng SCADA.- Ngi vn hnhTrong mt ng dng SCADA bao gi cng c ngi vnhnh do vy vic thit k v xy dng mt h SCADAngoi cc yu t v chuyn mn cng cn phi lu tivn ny. Trong cc yu t lin quan ti ngi vn

hnh th yu t vn ha bn a l quan trng nht. iu ny dn ti kt qu l cng mt ngdng SCADA nhng thit k cho ngi vn hnh ng khc vi ngi vn hnh Chu u.Ngoi ra ngi thit k cn phi quan tm ti nhng vn v m thut cng nghip v tm lhc cng nghip.c im v ng dng ca iu khin phn tn Vic xy dng cc h thng iu khin v gim st ph thuc vo c im v tnh cht ca itng iu khin. Thc t cc qu trnh sn xut thng i hi cng lc phi tin hnh iukhin nhiu i lng. Nu cc i lng ny l c lp vi nhau hay ma trn c tnh caphng trnh trng thi m t i tng ch bao gm cc thnh phn trn ng cho th ta cth thit lp hthng iu khin vi nhiu mch vng iu khin c lp. V bn cht h thngiu khin nh vy l h thng iu khin phi tp trung (Decentred Control System) cho d ccmch vng iu khin ny c thc hin bi cc b iu khin mt mch vng (single loopcontroller) hay s dng mt hoc vi thit b iu khin ln cho cc mch vng iu khin ny.Thng thng tit kim chi ph lp t v bo tr cc h thng iu khin phi tp trung nhvy s c thc hin bi nhiu b iu khin mt mch vng. Khi cc i lng cn iu khin ca i tng iu khin khng c s c lp vi nhau m cs tc ng xen knh hay ni cch khc, ma trn c tnh ca phng trnh trng thi c ccthnh phn ngoi ng cho khc khng th vic thc hin h thng iu khin theo cch phitp trung nh vy s mang li cht lng iu khin khng tt. khc phc ngi ta a ra ccgii php nh sau:- Sa i qu trnh cng ngh v thit b cng nghVic sa qu trnh cng ngh v thit b cng ngh nhm kh tc ng xen knh gia cc biniu khin hay bin cc thnh phn ngoi ng cho ca ma trn c tnh bng khng hoc gnbng khng. Khi ta c th coi cc tc ng xen knh (by gi cn rt nh) nh l nhiu qu

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trnh v thc hin chin lc iu khin phi tp trung cho h thng iu khin. Vic sa i nythng i hi phi xy dng cc khu cha trung gian trong qu trnh sn xut nn thng gytn km v khng phi lc no cng thc hin c.- S dng gii php iu khin tp trung (Centred Control System) loi b tc ng xen knh ngi ta cng c th xy dng cc thut ton iu khin a bin

hoc thc hin tch knh bng cc mch iu khin vt trc (feedforward). Tuy nhin iuny ch c th thc hin c khi ta s dng mt b iu khin v tp trung ha ton b d liuqu trnh vo trong b iu khin . Cch thc thc hin h thng iu khin nh vy c gil iu khin tp trung.Cch thc thc hin h iu khin tp trung c nhc im l phi tp trung cc gi tr o lngv b iu khin dn ti s tn km trong chi ph lp t, i dy v bo tr. Vic thc hin hthng iu khin bi mt h vi x l duy nht cng mang li nhiu ri ro v gim tin cy hotng ca ton h thng. Hn na khi qu trnh ln, phc tp c th s dn ti khi lng tnhton ln v lm qu ti cc h vi x l ca b iu khin.S pht trin ca cc h thng mng truyn thng cng nghip cho php trin khai lut iukhin a bin v tch knh loi b s tc ng xen knh trn nhiu b iu khin c ni mng

vi nhau. Theo cch thc ny, khi lng tnh ton ln ca iu khin a bin v tch knh cchia s thc hin trn nhiu thit b iu khin. Thng tin cn thit phi trao i gia cc thit biu khin ny c trao i thng qua ccmng truyn thng s kt ni cc thit b iu khinny. Vi cch thc hin nh vy chng ta c th tn dng c cc u im c ca iu khintp trung v iu khin phi tp trung v ngi ta gi h iu khin nh vy l h iu khin phntn (Distributed Control System DCS). Nh vy c th ni iu khin phn tn l mt cngngh hay cch thc thc hin h thng iu khin trong cng nghip. H thng iu khin phntn l nhm thc hin cc ng dng iu khin iu chnh v iu khin logic. Cc h thng iukhin phn tn thng phm thng c cu trc ging vi h SCADA l do h thng iu khintch hp c thc hin chc nng SCADA. Trong h thng iu khin phn tn thng phmng dng iu khin logic v iu khin iu chnh c th thit lp theo phng thc iu khinphn tn cn SCADA ch l mt chc nng ca h thng.Vic s dng sn phm h thng iu khin phn tn ca mt nh sn xut no mi ch liu kin thun li ngi k s c th thit lp h thng iu khin phn tn. H thng iukhin c xy dng trn thc t c tr thnh h thng iu khin phn tn thc s hay khngph thuc vo i tng iu khin ca n c cn phi thit lp lut iu khin a bin v/hoctch knh hay khng v ngi k s thit k c thit lp h thng iu khin theo cch thc phntn hay khng.

Them

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