Backup power supply system analysis

POWER ENGINEERING AND ELECTRICAL ENGINEERING VOLUME: 13 |NUMBER: 2 |2015 |JUNE Backup Powe Supply Sys em Analysis Bohusla LAKOTA1, Zdisla EXNAR2, Mi osla MATEJCEK1, Mikulas SOSTRONEK1 1Depa men o Elec onics, A med Fo ces Academy o gen. M. R. S e anik, Demano a 393, 031 01 Lip o sky Mikulas, Slo akia 2Ins i u e o Au el S odola, Facul y o Elec ical Enginee ing, Uni e si y o Zilina, S ee o kp . J. Nalepka 1390, 031 01 Lip o sky Mikulas, Slo akia bohusla .lak[email p o ec ed]k, [email p o ec ed], mi osla[email p o ec ed], [email p o ec ed] DOI: 10.15598/aeee. 13i2.1337 Abs ac . All elec ical o elec omechanical sys ems need elec ic ol age o unc ion. This ol age is ob ained om a dis ibu ion ne wo k o au onomous powe supply. Reliable ope a ion o sys ems/de ices is hen la gely dependen on he eliabili y o deli e ing powe supply ol age. The aim o his a icle is o poin ou o some aspec s o inc eased eliabili y possibili ies o hose sys ems. Keywo ds Backup powe supply sys ems, inc easing elia- bili y, sys em eliabili y. 1. In oduc ion Wi h designing and ope a ion o miscellaneous de ices and sys ems, one can mee he equi emen o li e- ime o pe iod o se ice ha exp esses an ope a ional eliabili y. Mos o he de ices a e composed o subsys- ems de ined by hei eliabili y cha ac e is ics. E e y elec onic o elec omechanical de ice equi es elec ic powe . This powe is supplied by an in e nal powe supply ha is a pa o gi en de ice o by an ex e nal powe sou ce, o example dis ibu ion ne wo k o an au onomous powe gene a o , espec i ely. Ope a ion o he de ice will be dependen mos ly on he elia- bili y o powe supply, because i his ails, hen he o e all sys em ails, oo. To inc ease he eliabili y o impo an sys ems (sa elli e communica ion sys ems, medical ins umen s, weapon sys ems, e c.), i is i al o back up he powe sys em. 2. Reliabili y Cha ac e is ics A endan phenomenons a ising du ing he ope a ion o de ices a e hei ailu es. Occu ence o ailu es a e usually unde in luence o a andom p ocess. This p o- cess o ising ailu es is usually caused by inne o ex- e nal easons ha a e no possible o p edic . Relia- bili y analysis and compu a ions a e based on ope a- ion da a collec ion and so ing o he esul o a ious unc ional es s. Gene ally, he sys em eliabili y is de ined as a sys em a ibu e ha is based on he ca- pabili y o ul ill decla ed unc ions in desi ed ime, in gi en en i onmen and wi h speci ied ope a ional con- di ions. The mos impo an nume ical cha ac e is ics desc ibing he sys em eliabili y a e: • ailu e p obabili y Q( ), •no- ailu e ope a ion p obabili y R( ), • ailu e a e λ( ), • ailu e-p obabili y densi y ( ), •mean ime be ween ailu es (MTBF) M( ). The ailu e p obabili y Q( )in ce ain ime in e al ∈(0; n) o con inuous andom a iable is gi en by Q( ) = Q(0; n) = Z n 0 ( )d , (1) whe e ( ) is a ailu e-p obabili y densi y. The no- ailu e ope a ion p obabili y R( )is a com- plemen a y p obabili y desc ibing ha in gi en ime in e al he sys em will be unc ional. I is gi en by R( )=1−Q( ) = Z∞ n ( )d . (2) c 2015 ADVANCES IN ELECTRICAL AND ELECTRONIC ENGINEERING 115 POWER ENGINEERING AND ELECTRICAL ENGINEERING VOLUME: 13 |NUMBER: 2 |2015 |JUNE The ailu e a e is one o he mos impo an sys em p ope y. Fo con inuous andom a iable i is gi en by λ( ) = ( ) R( )= ( ) 1−Q( ).(3) I exp esses he ailu e p obabili y in an elemen a y ime pe iod wi h he assump ion ha un il he ope - a ion ime he sys em ailu e was no de ec ed. The mean ime be ween ailu es (MTBF) Mis he p e- dic ed elapsed ime be ween inhe en ailu es o a sys- em. MTBF can be calcula ed as he a i hme ic mean ime be ween ailu es o a sys em. The MTBF can be de ined in e ms o he expec ed alue o he ailu e- p obabili y unc ion ( )[9]. M=Z∞ 0 ( )d =Z∞ 0 R( )d . (4) 2.1. Basic Reliabili y Models Basic eliabili y models in e p e he pa s o a sys em by block diag am. P ope ies o indi idual pa s a e p esen ed by s a is ical indexes o hei eal eliabili y alues. 1) Se ial eliabili y model Figu e 1 con ains nelemen s (subsys ems) a anged in se ial. Fig. 1: Se ial eliabili y model. I ep esen s an example in which an inhe en ailu e o he a bi a y elemen leads o ailu e o he o e all sys em. The no- ailu e ope a ion p obabili y o ha sys em is R( ) = 1( ) 2( )... n( ) = n Y i=1 i( ),(5) whe e 1( )is no- ailu e ope a ion p obabili y o he i s elemen , 2( )is no- ailu e ope a ion p obabili y o he second elemen and n( )is no- ailu e ope a ion p obabili y o he n h elemen . Pa allel eliabili y model (Fig. 2) con ains mele- men s a anged in pa allel. I one o he elemen s b akes down hen second (backup) elemen s a s o ope a e. The ailu e p obabili y o his model is Fig. 2: Pa allel eliabili y model. Q( ) = q1( )q2( )...qm( ) = m Y j=1 qj( ),(6) whe e q1( )is a ailu e p obabili y o he i s elemen , q2( )is a ailu e p obabili y o he second elemen and qn( )is a ailu e p obabili y o he n h elemen . 2) Se ies-pa allel eliabili y model Figu e 3 is an example o eal sys ems composed o n se ial connec ed elemen s and melemen s connec ed in pa allel. Fig. 3: Se ies-pa allel eliabili y model. No- ailu e ope a ion p obabili y o ha scheme is gi en by R( ) = 1 −Q( ) = 1 −Qm j=1 qj( ) = = 1 −Qm j=1 [1 − j( )] . (7) 3. Me hods o Inc easing o Sys em Reliabili y The inc ease o sys em eliabili y is ealized by: • he selec ion o sui able elemen s o subsys ems, • he selec ion o p ope ope a ing mode and ope - a ing condi ions, • he ealiza ion o pe iodic se ice ope a ions, • he subsys em backup, •e c. c 2015 ADVANCES IN ELECTRICAL AND ELECTRONIC ENGINEERING 116 POWER ENGINEERING AND ELECTRICAL ENGINEERING VOLUME: 13 |NUMBER: 2 |2015 |JUNE R( )=1−Qbck ( ) = 1 − m+1 Y i=1 Qi( ) = 1 − m+1 Y i=1 [1 −R1( )] ,(8) R( )=1−Qm+1 1( )=1−[1 −R1( )]m+1 ,(9) Qm( ) = (λ1 )m m!,(10) R( ) = RON ( )RGN ( )RS( ) = n Y i=1 si    1− 2 Y j=1 [1 − ONj ( )]  (1− 3 Y k=1 [1 − GNk ( )]),(11) RSUB ( ) = RON ( )RGN ( )RS( ) = n Y i=1 si "1−(λ1 )k k!e−λ1 #1−(λ1 )m m!e−λ1 .(12) The sys em backup can be con inuous, which means ha he backed-up elemen is connec ed o seconda y elemen all o e i s ope a ion. The second possibili y o backup is o connec he seconda y elemen only i he backed-up elemen has a ailu e. This case is called subs i u ion backup (subs i u ion edundancy). I he backed-up and seconda y elemen s ha e he same no- ailu e ope a ion p obabili y R( ) hen I in subs i u ion backup he ailu e p obabili y is unde he in luence o Poisson law, hen o he occu - ence o m ailu es in gi en ime in e al he ailu e p obabili y is Powe supply sys em o i al communica ion, con- ol, de ense o medical sys ems is one o he exam- ples in which he sys em ailu e should be minimized. These sys ems a e usually c ea ed by wo powe supply sys ems wi h •On-boa d supply sys em – i p o ides he DC ol - age. I is ealized in sys em s andby (o u n-o ) by elec ochemical seconda y cells (accumula o s), •AC powe supply sys em – i p o ides AC ol age om an elec ic gene a o . Fig. 4: Example o subs i u e powe supply backup. As we can see on he Fig. 4, an ac i a ion o main AC gene a o (1) is ealized by on-boa d powe supply ne - wo k (2). A ailu e o he on-boa d powe supply leads o a mal unc ion o he main gene a o oo, because i will no be s a ed up. I he e is a equi emen o inc ease sys em eliabil- i y, powe supply backup o he on-boa d powe supply and he main AC gene a o , espec i ely, mus be e- alized. I an accumula o s (3) ail (discha ge, capaci y loss, ageing p ocess, damage, e c.) hen he main AC gene a o (1) will no o be ac i a ed. The accumula- o s backup can be ealized by comp essed ai (4) in ai ank (5) ha can ac i a e he main gene a o (1), oo. I he main gene a o s a s, i c ea es he AC supply ol age ha is necessa y o ac i a ing o e - all on-boa d de ices and ha can cha ge accumula o s (3) o e cha ging ci cui s (6). The main gene a o is backed-up wice, by an in e nal backup gene a o (7) ac ua ed by a d i ing gea (8) and an ex e nal powe supply (9) (mobile AC gene a o , indus ial supply ne - wo k, e c.). Wi h he main gene a o (1) ailu e, he swi ching on backed-up powe supply is ealized man- ually (o au oma ically) o e ol age commu a ion ci - cui s (10). The ex e nal powe supply (9) connec ion is ealized only manually. The no- ailu e ope a ion p obabili y R( ) o backed- up powe supply wi h con inuous backup ( o example pa ially loaded) is hen possible o e alua e by modi- ying Eq. (9). In Eq. (11), R( )is no- ailu e ope a ion p obabil- i y o o e all sys em, RON ( )is no- ailu e ope a ion p obabili y o on-boa d powe supply ne wo k, RGN ( ) is no- ailu e ope a ion o AC powe supply ne wo k, RS( )is o e all no- ailu e ope a ion p obabili y o sys- em 1 up o n, si( )is no- ailu e ope a ion p obabili y o i h sys em, ONj ( )is no- ailu e ope a ion p obabil- i y o j h on-boa d powe supply sys em and GNk( )is a no- ailu e p obabili y o k h powe supply gene a o . c 2015 ADVANCES IN ELECTRICAL AND ELECTRONIC ENGINEERING 117 POWER ENGINEERING AND ELECTRICAL ENGINEERING VOLUME: 13 |NUMBER: 2 |2015 |JUNE The no- ailu e ope a ion p obabili y o he backed- up powe supply wi h he subs i u e edundancy (sub- s i u e backup) when powe supply backup is inac i e can be e alua ed by using Eq. (8) and Eq. (10). In Eq. (12), Rsub( )is no- ailu e ope a ion p obabil- i y o he o e all sys em wi h subs i u e powe supply backup, kis mul iple o on-boa d supply backup; mis mul iple o AC powe supply backup. As one can see he o e all eliabili y o sys em is gi en by a p oduc o p obabili ies RON ( ),RGN ( )and RS( ). Inc easing o he sys em eliabili y is ealized by backup o main powe supply because i i ails he o e all sys em ails, oo. 4. Conclusion The aim o his a icle is o show he meaning o he powe supply eliabili y and abili y o inc ease i . Al- hough he desc ibed model is ocused on mili a y ap- plica ion, i is sui able also o non-mili a y applica- ions whe e he powe supply ailu e can lead o a mal- unc ion o o e all sys em. As an example one can show communica ion sys ems, medical sys ems, a ious spe- cial indus ial sys ems, e c. Howe e in speci ic cases he c i e ia o ime eco - e y o p ima y (o backup) powe supplies a e much mo e igid. Some c i e ia on elec ical dis ibu ion in medical ooms a e de ined in Slo ak Technical S an- da d STN 33 2000-7-710:2013-08 (o CSN 33 2000-7- 710 in Czech Republic) whe e he ime eco e y is in gene al 120 s and in special eme gency powe supply backup i is only 15 s (o 0.5 s) [6]. Re e ences [1] GRAMATOVA, A. and K. JELEMENSKA. Tes - ing, diagnos ic and e i ica ion o digi al sys- ems. 1s . ed. B a isla a: STU B a isla a, 2012. ISBN 978-80-227-3797-5. [2] JANOUSEK, I., J. KOZAK and O. TARABA. Technical diagnos ics. 1s . ed. P aha: SNTL P aha, 1988. ISBN 04-236-88. [3] BIGOS, P. and E. FALTINOVA. Technical Sys- em Reliabili y. Kosice: Technical Uni e si y in Kosice, 2011. ISBN 978-80-553-0802-9. [4] STN IEC 60050-191. In e na ional Elec o echni- cal Vocabula y. Chap e 191: Dependabili y and quali y o se ice. B a isla a: Slo ak O ice o S anda ds, Me ology And Tes ing, 1993. [5] USHAKOV, J. Handbook o Reliabili y in Radio- elec onics and Au oma ized Technique. P ague: SNTL P ague, 1989. ISBN 80-03-00034-3 [6] STN 33 2000-7-710:2013-8. Low- ol age elec ical ins alla ions. Pa 7-710: Requi emen s o spe- cial ins alla ions o loca ions. Medical loca ions. B a isla a: Slo ak O ice o S anda ds, Me ology And Tes ing, 2013. [7] O’CONNOR, P. D. and A. KLEYNER. P ac ical Reliabili y Enginee ing. 5 h ed. Ox o d: Wiley- Blackwell, 2012. ISBN 978-0-470-97981-5 [8] ZAHRAN, M., S. TAWFIK and G. DYAKOV. L.E.O. Sa elli e Powe Subsys em Reliabili y Analysis. Jou nal o Powe Elec onics. 2006, ol. 6, no. 2, pp.104–113. ISSN 15982092. [9] JONES, J., In eg a ed logis ics suppo handbook. 3 d ed. New Yo k: Sole Logis ics P ess/McG aw- Hill, 2006. ISBN 978-007-1471-688. Abou Au ho s Bohusla LAKOTA was bo n in 1951 in Pies any (Slo ak Republic). He ecei ed his M.Sc. om A ia ion and Ai De ense Facul y, Mili a y Academy, B no in 1974. He ob ained his Ph.D. deg ee in 1998 and Assoc. p o . deg ee in 2003, bo h a Mili a y Academy in Lip o sky Mikulas. He wo ks as an associa e p o esso a he Depa men o Elec onics, A med Fo ces Academy in Lip o sky Mikulas. His esea ch a ea mainly includes con ol sys ems wi h he in en ion o ada and guided weapon sys ems. Zdisla EXNAR was bo n in 1948 in Ha licku B od (Czech Republic). He ecei ed his M.Sc. om Elec ical Enginee ing a Mili a y Academy, B no in 1978. He ob ained his Ph.D. deg ee in 1985, in Kie , (Uk aine) He wo ks as an associa e p o esso a he Uni e si y o Zilina – Facul y o Elec ical Enginee ing - Ins i u e o Au el S odola in Lip o sky Mikulas. His a eas o in e es a e au oma ic con ol sys ems and da abase sys ems. Mi osla MATEJCEK was bo n in 1979 in Lip o sky Mikulas (Slo ak Republic). He ecei ed his M.Sc. deg ee in 2002, a Depa men o Ai De ense, Mili a y Academy in Lip o sky Mikulas. He wo ks as an assis an lec u e a Depa men o Elec onics, A med Fo ces Academy in Lip o sky Mikulas. His esea ch a ea mainly includes guided weapon sys ems and con ol sys ems. Mikulas SOSTRONEK was bo n in 1972 in c 2015 ADVANCES IN ELECTRICAL AND ELECTRONIC ENGINEERING 118 POWER ENGINEERING AND ELECTRICAL ENGINEERING VOLUME: 13 |NUMBER: 2 |2015 |JUNE Bojnice (Slo ak Republic). He ecei ed his M.Sc. de- g ee in 1996 a Ai De ense Facul y, Mili a y Academy in Lip o sky Mikulas and Ph.D. deg ee in 2001 a Depa men o Elec onics, Mili a y Academy in Lip o sky Mikulas. He wo ks as a senio assis an a Depa men o Elec onics, A med Fo ces Academy in Lip o sky Mikulas. His esea ch a ea mainly includes con ol sys ems and mic owa e enginee ing. c 2015 ADVANCES IN ELECTRICAL AND ELECTRONIC ENGINEERING 119