Iec tr 60919 3 2016

I EC TR 6091 9-3 ® Ed i ti on 201 6-03 CON SOLI DATED VERSI ON colour in sid e Perform an ce of h i g h -vol tag e d i rect cu rren t (H VDC) system s wi th l i n ecom m u tated verters – I EC 6091 9-3: 2009-1 0+AM D : 201 6-03 CSV(en ) Part 3: Dyn am i c d i ti on s Copyright International Electrotechnical Commission TH I S P U B L I C ATI O N I S C O P YRI G H T P RO TE C T E D C o p yri g h t © I E C , G e n e va , S w i tze rl a n d Al l or ri g h t s by re s e rv e d an y e i th e r m ean s, I EC c o p y ri g h t yo u r I EC 3, or or l o ca l IEC C e n t l ru e de CH -1 1 I E C's h a ve U n l ess o t h e rwi s e e l e c t ro n i c or m em ber an N a ti o n a l e n q u i ry m em ber s p e c i fi e d , m e ch a n i ca l , abou t N a ti o n a l no p a rt i n cl u d i n g C o m m i tte e o b ta i n i n g C o m m i tte e th e p u b l i ca ti o n c o u n t ry a d d i ti o n a l fo r O ffi c e in o f th i s p h o to co p yi n g fu rt h e r ri g h t s an d o f th e to th i s Te l : +41 22 91 02 1 F a x: +41 22 91 03 00 G e n e va i n fo @ i e c c h 20 be re p ro d u c e d re q u e s t e r wi t h o u t If p u b l i ca ti o n , yo u h a ve pl ease or u ti l i z e d p e rm i s s i o n an y co n ta c t in in q u e s ti o n s th e an y fo rm wri t i n g fro m abou t a d d re s s IEC bel ow or i n fo rm a t i o n V a re m b é S wi t z e rl a n d may m i c ro fi l m , ww w i e c c h Ab ou t th e I E C Th e I n t e rn a t i o n a l I n t e rn a t i o n a l E l e c t ro t e c h n i c a l S t a n d a rd s fo r al l Com m i ssi on e l e c t ri c a l , (I E C) e l e c t ro n i c and is th e re l a t e d l ead i n g g l obal o rg a n i z a t i o n th a t p re p a re s an d pu bl i sh es te ch n o l o g i e s Ab o u t I E C p u b l i c a ti o n s Th e te c h n i ca l l a te s t e d i ti o n , co n te n t a of IEC c o rri g e n d a p u b l i ca ti o n s or an is ke p t amend ment u n d er might co n s ta n t h a ve been I E C C atal og u e - webs tore i ec ch /catal og u e Th e s ta n d - a l o n e b i b l i o g p h i ca l Te ch n i ca l a p p l i ca ti o n i n fo rm a ti o n on S p e ci fi ca ti o n s , d o cu m e n ts Ava i l a b l e fo r fo r I EC PC, M ac th e I n te rn a ti o n a l An d ro i d e n ti re S ta n d a rd s , Re p o rts OS , an d o th e r Ta b l e ts an d i Pad a d va n ce d va ri e ty of s e a rch en abl es cri te ri a co m m i tte e , … ) an d th e Th e wo rl d ' s e l e ctri ca l wi th d wn It to ( re fe re n ce al so g i ve s fi n d I EC i n fo rm a ti o n on Pl ease m a ke s u re th a t yo u h a ve th e E n g l i sh an d l an g u ag es on l i n e co n ta i n i n g F re n ch , Al s o wi th kn o wn as d i cti o n a ry 20 000 e q u i va l e n t th e of te rm s e l e ctro n i c an d te rm s I n te rn a ti o n a l an d d e fi n i ti o n s in in a d d i ti o n a l E l e ctro te ch n i ca l on l i n e I E C G l os s ary - s td i ec ch /g l os s ary p u b l i ca ti o n s n u m b e r, I E C l ead i n g te rm s Vo ca b u l a ry ( I E V) I E C pu bl i cati on s s earch - www i ec ch /s earch pu b Th e by E l ectroped i a - www el ectroped i a org co n s u l ti n g Te ch n i ca l re v i e w pu bl i sh ed te xt, by a te ch n i ca l p ro j e cts , re p l a ce d 65 000 F re n ch I EC e l e ctro te ch n i ca l e xtra cte d p u b l i ca ti o n s co l l e cte d p u b l i ca ti o n s fro m fro m i ssu ed e a rl i e r te rm i n o l o g y th e Te rm s s i n ce 2002 p u b l i ca ti o n s e n tri e s an d S om e of in E n g l i sh D e fi n i ti o n s I EC e n tri e s TC 37, an d cl a u s e h a ve 77, of been 86 an d C I S P R I E C J u s t P u bl i s h ed - webs tore i ec ch /j u s u bl i s h ed S ta y up d e ta i l s al so to al l o n ce d a te n ew a on al l n ew p u b l i ca ti o n s m o n th by em l I EC p u b l i ca ti o n s re l e a s e d J u st Ava i l a b l e Pu bl i sh ed on l i n e an d I E C C u s to m er S ervi ce C en tre - web s tore i ec ch /cs c If yo u n eed wi s h fu rth e r C e n tre : Copyright International Electrotechnical Commission to g i ve us a s s i s ta n ce , cs c@ i e c ch yo u r fe e d b a ck pl ease co n ta ct on th e th i s p u b l i ca ti o n or C u s to m e r S e rvi ce I E C TR 60 91 -3 ® Ed i ti on 201 6-03 C ON S OLI D ATE D VE RS I ON colour in sid e Perform an ce of h i g h -vol tag e d i rect cu rren t (H VD C ) s ystem s wi th l i n ecom m u tated verters – Part 3: D yn am i c d i ti on s I N TERN ATI ON AL ELECTROTECH N I CAL COM M I SSI ON I CS 29 200; 29 40 99 I SBN 978-2 -832 2-3241 -5 Warn i n g ! M ake s u re th at you obtai n ed th i s pu bl i cati on from an au th ori zed d i s tri bu tor ® Reg i stered trad em ark of th e I n tern ati on al El ectrotech n i cal Com m i ssi on Copyright International Electrotechnical Commission Copyright International Electrotechnical Commission I EC TR 6091 9-3 ® Ed i ti on 201 6-03 REDLI N E VERSI ON colour in sid e Perform an ce of h i g h -vol tag e d i rect cu rren t (H VDC) system s wi th l i n ecom m u tated verters – I EC TR 6091 9-3: 2009-1 0+AM D : 201 6-03 CSV(en ) Part 3: Dyn am i c d i ti on s Copyright International Electrotechnical Commission – – I E C TR 9 - : 0 + AM D : C S V  I EC 201 C O N TE N TS F O RE WO RD S co p e N o rm a ti ve re fe re n ce s O u tl i n e o f H VD C d yn a m i c p e rfo rm a n ce s p e ci fi ca ti o n s D yn a m i c p e rfo rm a n ce s p e ci fi ca ti o n G e n e l co m m e n ts AC s ys te m p o we r fl o w a n d fre q u e n cy co n tro l G e n e l P o we r fl o w co n tro l S te a d y- s ta te p o we r co n tro l re q u i re m e n ts 2 S te p ch a n g e p o we r re q u i re m e n t F re q u e n cy co n tro l AC d yn a m i c vo l ta g e co n tro l a n d i n te cti o n wi th re a cti ve p o we r s o u rce s G e n e l Vo l ta g e a n d re a cti ve p o we r ch a cte ri s ti cs o f a n H VD C s u b s ta ti o n a n d o th e r re a cti ve p o we r s o u rce s G e n e l 2 C o n ve rte r a s a cti ve /re a cti ve p o we r s o u rce Vo l ta g e ch a cte ri s ti cs o f a c n e two rks d e p e n d i n g o n th e p o we r l o a d i n g a t th e b u s b a r o f th e H VD C s u b s ta ti o n Vo l ta g e ch a cte ri s ti cs o f a c fi l te rs , ca p a ci to r b a n ks a n d s h u n t re a cto rs fo r p o we r co m p e n s a ti o n a t th e H VD C s u b s ta ti o n 5 Vo l ta g e ch a cte ri s ti cs o f s ta ti c va r co m p e n s a to r ( S VC ) Vo l ta g e ch a cte ri s ti cs o f s yn ch ro n o u s co m p e n s a to r ( S C ) Vo l ta g e ch a cte ri s ti cs o f s ta ti c s yn ch ro n o u s co m p e n s a to r ( S T ATC O M ) Vo l ta g e d e vi a ti o n s o n th e b u s b a r o f a n H VD C s u b s ta ti o n Vo l ta g e a n d re a cti ve p o we r i n te cti o n o f th e s u b s ta ti o n a n d o th e r re a cti ve p o we r s o u rce s H VD C co n ve rte rs , s wi tch a b l e a c fi l te rs , ca p a ci to r b a n ks a n d s h u n t re a cto rs H VD C co n ve rte rs , s wi tch a b l e re a cti ve p o we r s o u rce s , S VC H VD C co n ve rte rs , s wi tch a b l e re a cti ve p o we r s o u rce s a n d s yn ch ro n o u s co m p e n s a to rs 4 H VD C co n ve rte rs , s wi tch a b l e re a cti ve p o we r s o u rce s , S T ATC O M 2 AC s ys te m tra n s i e n t a n d s te a d y- s ta te s ta b i l i ty G e n e l C h a cte ri s ti cs o f a cti ve a n d re a cti ve p o we r m o d u l a ti o n 6 G e n e l 2 L a rg e s i g n a l m o d u l a ti o n S m a l l s i g n a l m o d u l a ti o n Re a cti ve p o we r m o d u l a ti o n C l a s s i fi ca ti o n o f n e two rk s i tu a ti o n s 6 AC n e two rk i n p a l l e l wi th th e H VD C l i n k 6 I m p ro ve m e n t o f th e s ta b i l i ty wi th i n o n e o f th e co n n e cte d a c n e two rks 6 D e te rm i n a ti o n o f th e d a m p i n g co n tro l ch a cte ri s ti cs Copyright International Electrotechnical Commission I E C TR 9 - : 0 + AM D : C S V  – – I EC 201 6 I m p l e m e n ta ti o n o f th e d a m p i n g co n tro l l e r a n d te l e co m m u n i ca ti o n re q u i re m e n ts D yn a m i cs o f th e H VD C s ys te m a t h i g h e r fre q u e n ci e s G e n e l Typ e s o f i n s ta b i l i ty L o o p i n s ta b i l i ty ( h a rm o n i c i n s ta b i l i ty) 2 C u rre n t l o o p i n s ta b i l i ty C o re s a tu ti o n i n s ta b i l i ty H a rm o n i c i n te cti o n s I n fo rm a ti o n re q u i re d fo r d e s i g n p u rp o s e s 3 M e a n s a va i l a b l e fo r p re ve n ti n g i n s ta b i l i ti e s D a m p i n g o f l o w o rd e r h a rm o n i cs b y co n tro l a cti o n D e m o n s tra ti o n o f s a ti s fa cto ry p e rfo rm a n ce a t h i g h e r fre q u e n ci e s S u b s yn ch ro n o u s o s ci l l a ti o n s G e n e l C ri te ri a fo r s u b s yn ch ro n o u s to rs i o n a l i n te cti o n wi th a n H VD C s ys te m S cre e n i n g cri te ri a fo r i d e n ti fyi n g g e n e to r u n i ts s u s ce p ti b l e to to rs i o n a l i n te cti o n s P e rfo rm a n ce co n s i d e ti o n s fo r u ti l i z i n g s u b s yn ch ro n o u s d a m p i n g co n tro l s co n tro l l e rs ( S S D C s ) P e rfo rm a n ce te s ti n g 8 Tu rb i n e g e n e to r p ro te cti o n P o we r p l a n t i n te cti o n 9 G e n e l 9 S p e ci fi c i n te cti o n s 9 G e n e l 9 2 F re q u e n cy va ri a ti o n e ffe cts 9 F re q u e n cy co n tro l s i n te cti o n s O ve rvo l ta g e e ffe cts H a rm o n i cs S u b s yn ch ro n o u s a n d s h a ft i m p a ct e ffe cts Re s o n a n ce O ve rvo l ta g e s 9 S tre s s e s i n a c s wi tch i n g e q u i p m e n t U n d e r- fre q u e n cy 1 S ta rti n g p ro ce d u re fo r a n H VD C co n ve rte r S p e ci a l co n s i d e ti o n s fo r a n u cl e a r p l a n t B i b l i o g p h y F i g u re – E l e m e n ts fo r re a cti ve p o we r co m p e n s a ti o n a t a n H VD C s u b s ta ti o n F i g u re – P/Q d i a g m o f a co n ve rte r F i g u re – Re a cti ve p o we r re q u i re m e n ts o f a we a k a c s ys te m d e p e n d i n g o n th e a cti ve p o we r l o a d i n g fo r va ri o u s co n s ta n t vo l ta g e ch a cte ri s ti cs a t th e a c b u s o f a n H VD C s u b s ta ti o n F i g u re – Re p re s e n ta ti o n o f th e a c n e two rk F i g u re – E xa m p l e o f vo l ta g e – cu rre n t ch a cte ri s ti c s h o wi n g p o s s i b l e cu rre n t m o d u l a ti o n n g e i n th e a b s e n ce o f te l e co m m u n i ca ti o n b e twe e n re cti fi e r a n d i n ve rte r F i g u re – Re a cti ve p o we r m o d u l a ti o n i n a n H VD C tra n s m i s s i o n o p e ti n g a t m i n i m u m e xti n cti o n a n g l e Copyright International Electrotechnical Commission γm i n 27 –4– I EC TR 6091 9-3: 2009+AM D1 : 201 CSV  I EC 201 Fi g u re – Reacti ve power mod u l ation in an H VDC tran smission operati n g at exti ncti on an g le γ > γ mi n 28 Fi g u re – Stabi l i ty i mprovemen t of an a c l i n k or n etwork 29 Fi g u re – Prin ciple arran gemen ts of a d ampi ng trol l er 29 Copyright International Electrotechnical Commission I E C TR 9 - : 0 + AM D : C S V – –  I EC 201 I N TE RN ATI O N AL E L E C TRO TE C H N I C AL C O M M I S S I O N P E RF O RM AN C E O F H I G H -VO L TAG E D I RE C T C U RRE N T ( H VD C ) S YS TE M S WI TH L I N E -C O M M U TATE D C O N VE RTE RS – P a rt : D yn a m i c c o n d i ti o n s F O RE WO RD 1) T h e I n t e rn a ti o n a l E l e c t ro te c h n i c a l C o m m i s s i o n ( I E C ) i s a wo rl d wi d e o rg a n i z a t i o n fo r s ta n d a rd i z a ti o n c o m p ri s i n g all n a ti o n a l e l e c tro te ch n i c a l c o m m i tte e s (I EC N a ti o n a l C o m m i tte e s ) Th e o b j e ct of IEC is to p ro m o t e i n t e rn a ti o n a l c o - o p e ti o n o n a l l q u e s ti o n s c o n c e rn i n g s ta n d a rd i z a ti o n i n t h e e l e c tri c a l a n d e l e c tro n i c fi e l d s To th i s end and Te ch n i ca l in a d d i ti o n Re p o rt s , to o th e r a c ti v i ti e s , P u b l i cl y Av a i l a b l e IEC pu bl i sh es S p e c i fi c a ti o n s I n te rn a ti o n a l ( P AS ) an d S ta n d a rd s , G u i d es Tech n i ca l ( h e re a fte r S p e c i fi c a ti o n s , re fe rre d to as “I EC P u b l i c a ti o n ( s ) ” ) T h e i r p re p a ti o n i s e n tru s te d t o te c h n i c a l c o m m i tte e s ; a n y I E C N a ti o n a l C o m m i t te e i n t e re s t e d in th e s u b j e ct d eal t wi th may p a rti c i p a te in th i s p re p a to ry wo rk I n t e rn a ti o n a l , g o v e rn m e n t a l and n on - g o v e rn m e n t a l o rg a n i z a t i o n s l i a i s i n g wi th t h e I E C a l s o p a rti c i p a t e i n t h i s p re p a ti o n I E C c o l l a b o te s c l o s e l y wi t h th e I n te rn a t i o n a l O rg a n i z a ti o n fo r S ta n d a rd i z a ti o n (I S O) in a cc o rd a n c e wi t h c o n d i ti o n s d e te rm i n e d by a g re e m e n t b e twe e n th e t wo o rg a n i z a ti o n s 2) T h e fo rm a l d e c i s i o n s o r a g re e m e n ts o f I E C o n te c h n i c a l m a tt e rs e xp re s s , a s n e a rl y a s p o s s i b l e , a n i n te rn a t i o n a l co n s e n s u s of opi ni on on th e re l e v a n t s u b j e c ts s i n ce e a ch te ch n i ca l c o m m i t te e has re p re s e n ta ti o n fro m all i n te re s te d I E C N a ti o n a l C o m m i tt e e s 3) I E C P u b l i c a ti o n s h a v e th e fo rm C o m m i tt e e s i n t h a t s e n s e P u b l i c a ti o n s is a c c u t e , o f re c o m m e n d a ti o n s fo r i n te rn a ti o n a l u se an d a re a cc e p te d b y I E C N a ti o n a l W h i l e a l l re a s o n a b l e e ffo rts a re m a d e to e n s u re t h a t th e te c h n i c a l c o n te n t o f I E C I EC ca n n o t be held re s p o n s i b l e fo r th e wa y in wh i c h th e y a re u sed or fo r any m i s i n te rp re t a ti o n b y a n y e n d u s e r 4) In o rd e r t o p ro m o t e tra n s p a re n tl y to i n te rn a ti o n a l th e m a xi m u m u n i fo rm i ty, e xt e n t I EC possi bl e in N a ti o n a l th ei r C o m m i tte e s n a ti o n a l and u n d e rta k e re g i o n a l to appl y IEC p u b l i c a ti o n s P u b l i c a ti o n s An y d i v e rg e n c e b e t we e n a n y I E C P u b l i c a t i o n a n d th e c o rre s p o n d i n g n a t i o n a l o r re g i o n a l p u b l i c a t i o n s h a l l b e c l e a rl y i n d i c a t e d i n th e l a t te r 5) I E C i ts e l f d o e s n o t p ro v i d e a n y a tt e s ta t i o n o f c o n fo rm i ty a s s e s s m e n t s e rv i c e s a n d , i n s o m e a re a s , I n d e p e n d e n t c e rt i fi c a ti o n b o d i e s p ro v i d e c o n fo rm i ty a c c e s s to I E C m a rks o f c o n fo rm i ty I E C i s n o t re s p o n s i b l e fo r a n y s e rv i c e s c a rri e d o u t b y i n d e p e n d e n t c e rti fi c a ti o n b o d i e s 6) Al l u s e rs s h o u l d e n s u re th a t th e y h a v e th e l a te s t e d i ti o n o f th i s p u b l i c a ti o n 7) N o l i a b i l i ty s h a l l a tta c h to I E C o r i ts d i re c to rs , e m p l o ye e s , s e rv a n ts o r a g e n t s i n c l u d i n g i n d i v i d u a l e xp e rts a n d m e m b e rs o f i ts t e c h n i c a l c o m m i tte e s a n d I E C N a ti o n a l C o m m i t te e s fo r a n y p e rs o n a l i n j u ry, p ro p e rty d a m a g e o r o th e r d a m a g e e xp e n s e s of any a ri s i n g ou t n a t u re wh a ts o e v e r, wh e t h e r d i re c t of p u b l i c a ti o n , use th e o f, or o r i n d i re c t, re l i a n c e u pon , o r fo r c o s t s th i s IEC ( i n cl u d i n g P u b l i ca ti o n or l eg al fe e s ) and any o th e r IEC P u b l i c a ti o n s 8) At te n ti o n i s d wn to th e N o rm a t i v e re fe re n c e s c i te d i n th i s p u b l i c a ti o n U s e o f th e re fe re n c e d p u b l i c a ti o n s i s 9) At te n t i o n i s d wn to t h e p o s s i b i l i ty th a t s o m e o f t h e e l e m e n ts o f t h i s I E C P u b l i c a ti o n m a y b e th e s u b j e c t o f i n d i s p e n s a b l e fo r t h e c o rre c t a p p l i c a ti o n o f th i s p u b l i c a ti o n p a te n t ri g h ts I E C s h a l l n o t b e h e l d re s p o n s i b l e fo r i d e n ti fyi n g a n y o r a l l s u c h p a te n t ri g h ts D I S C L AI M E R Th i s C o n s o l i d a te d ve rs i o n i s n o t a n o ffi c i a l I E C S ta n d a rd a n d h a s b e e n p re p a re d fo r u s e r c o n ve n i e n c e O n l y th e c u rre n t ve rs i o n s o f th e s ta n d a rd a n d i ts a m e n d m e n t( s ) a re to b e c o n s i d e re d th e o ffi c i a l d o c u m e n ts Th i s C o n s o l i d a te d ve rs i o n o f I E C TR 9 -3 b e a rs th e e d i ti o n n u m b e r I t c o n s i s ts of th e s e co n d am en d m en t e d i ti o n ( 0 -1 ) ( -0 ) [ d o c u m e n ts [d o cu m e n ts 2 F /1 /D TR 2 F /3 /D TR an d an d 2 F /1 /RVC ] 2 F /3 A/RVC ] Th e an d i ts te ch n i ca l c o n te n t i s i d e n ti ca l to th e b a s e e d i ti o n a n d i ts a m e n d m e n t I n th i s Re d l i n e ve rs i o n , a ve rti ca l l i n e i n th e m a rg i n s h o ws wh e re th e te c h n i c a l c o n te n t i s m o d i fi e d b y a m e n d m e n t Ad d i ti o n s a re i n g re e n te xt, d e l e ti o n s a re i n s tri ke th ro u g h re d te xt A p u b l i c a ti o n Copyright International Electrotechnical Commission s e p a te Fi n al ve rs i o n w i th al l ch an g es a cc e p te d is a va i l a b l e in th i s – – I E C TR 9 - : 0 + AM D : C S V  I EC 201 Th e m a i n ta s k o f I E C te ch n i ca l co m m i tte e s i s to p re p a re I n te rn a ti o n a l S ta n d a rd s H o we ve r, a te ch n i ca l co m m i tte e m a y p ro p o s e th e p u b l i ca ti o n o f a te ch n i ca l re p o rt wh e n i t h a s co l l e cte d d a ta o f a d i ffe re n t ki n d fro m th a t wh i ch i s n o rm a l l y p u b l i s h e d a s a n I n te rn a ti o n a l S ta n d a rd , fo r e xa m p l e " s ta te o f th e a rt" I E C 6091 9-3, wh i ch i s a te ch n i ca l re p o rt, h a s b e e n p re p a re d b y s u b co m m i tte e 2 F : P o we r e l e ctro n i cs fo r e l e ctri ca l tra n s m i s s i o n a n d d i s tri b u ti o n s ys te m s , o f I E C te ch n i ca l co m m i tte e 2 : P o we r e l e ctro n i c s ys te m s a n d e q u i p m e n t Th i s e d i ti o n i n cl u d e s th e fo l l o wi n g s i g n i fi ca n t te ch n i ca l ch a n g e s wi th re s p e ct to th e p re vi o u s e d i ti o n : a) th i s re p o rt co n ce rn s o n l y l i n e - co m m u ta te d co n ve rte rs ; b) s i g n i fi ca n t ch a n g e s h a ve b e e n m a d e to th e co n tro l s ys te m te ch n o l o g y; c) s o m e e n vi ro n m e n ta l co n s tra i n ts , fo r e xa m p l e a u d i b l e n o i s e l i m i ts , h a ve b e e n a d d e d ; d) th e ca p a ci to r co u p l e d co n ve rte rs ( C C C ) a n d co n tro l l e d s e ri e s ca p a ci to r co n ve rte rs ( C S C C ) h a ve b e e n i n cl u d e d Th i s p u b l i ca ti o n h a s b e e n d fte d i n a cco rd a n ce wi th th e I S O /I E C D i re cti ve s , P a rt Performance of high-voltage direct current (HVDC) systems with line-commutated converters , ca n b e fo u n d o n th e I E C A l i s t o f a l l p a rts o f th e I E C 9 s e ri e s , u n d e r th e g e n e l ti tl e : we b s i te Th e co m m i tte e h a s d e ci d e d th a t th e co n te n ts o f th e b a s e p u b l i ca ti o n a n d i ts a m e n d m e n t wi l l re m a i n u n ch a n g e d u n ti l " h ttp : //we b s to re i e c ch " in th e th e s ta b i l i ty d a ta d a te re l a te d to i n d i ca te d th e on s p e ci fi c th e I EC p u b l i ca ti o n we b At s i te th i s u n d er d a te , th e p u b l i ca ti o n wi l l b e • re co n fi rm e d , • wi th d wn , • re p l a ce d b y a re vi s e d e d i ti o n , o r • d ed I M P O RT AN T th at it – Th e co n ta i n s u n d e rs t a n d i n g of 'col ou r c o l o u rs i ts i n s i d e' wh i ch co n te n ts l og o a re U s e rs on th e c o ve r c o n s i d e re d sh ou l d pag e to t h e re fo re of th i s be p ri n t c o l o u r p ri n t e r A b i l i n g u a l ve rs i o n o f th i s p u b l i ca ti o n m a y b e i s s u e d a t a l a te r d a te Copyright International Electrotechnical Commission pu b l i cati on u s e fu l th i s fo r i n d i c a te s th e d ocu m en t c o rre c t using a – 30 – I E C TR 9 - : 0 + AM D : C S V  I EC 201 I n ca s e o f a p a l l e l a c l i n k, H VD C d a m p i n g co n tro l ca n s o m e ti m e s i n cre a s e th e a m o u n t o f p o we r th a t ca n b e tra n s m i tte d vi a th e p a l l e l a c ci rcu i t i n a s ta b l e m a n n e r Th e a m o u n t o f i m p ro ve m e n t d e p e n d s on wh a t typ e o f i n s ta b i l i ty d i cta te s th e p o we r l i m i t In a fi rs t s wi n g i n s ta b i l i ty s i tu a ti o n , i m p ro ve m e n ts ca n o n l y b e e xp e cte d i f th e H VD C l i n k i s l a rg e o r h a s a l a rg e s h o rt- ti m e ca s e s wh e re p e rfo rm e d o ve rl o a d th e ca p a b i l i ty m o d u l a ti o n l o ca l l y in th e I m p ro ve d a m p l i tu d e cu rre n t is d ampi n g re l a ti ve l y co n tro l l i n g s ta ti o n ca n , smal l h as h o we ve r, E ve n mad e it al so smal l be si gn al possi bl e to o b ta i n e d in m o d u l a ti o n i n cre a s e th e a m o u n t o f p o we r i n p a l l e l a c l i n e s i n s o m e ca s e s Th e I m p ro ve m e n t o f t h e s t a b i l i t y w i t h i n a b i l i ty of co n fi g u ti o n th e an d H VD C link to ch a cte ri s ti cs p o s s i b i l i ty to o b ta i n o n e o f th e c o n n e c te d i m p ro ve of th e s ta b i l i ty n e two rk re l e va n t i n p u t s i g n a l s to in th i s re q u i ri n g th e d a m p i n g a c ca s e n e tw o rk s d epen d s a s s i s ta n ce co n tro l l e r In l a rg e l y an d al so on th e on th e s o m e ca s e s , inpu t s i g n a l s m a y h a ve to b e tra n s m i tte d to th e H VD C s u b s ta ti o n fro m o th e r s ta ti o n s i n th e a c n e two rk I n p u t s i g n a l s to th e co n tro l l e r ca n b e fre q u e n cy, vo l ta g e , a c l i n e p o we r, l i n e cu rre n t o r a co m b i n a ti o n o f th e s e Wh e n s p e ci fyi n g d amping co n tro l in a ca s e l i ke th i s , co n s i d e ti o n sh ou l d b e g i ve n to th e a b i l i ty o f th e n e two rk co n n e cte d to th e o th e r H VD C s u b s ta ti o n to a cce p t th e re s u l ti n g p o we r s wi n g s Th e g e n e l co n s i d e ti o n s re g a rd i n g th e tra n s fe r fu n cti o n o f th e co n tro l l e r a s g i ve n i n fo r th e ca s e o f a p a l l e l a c n e two rk a p p l y a l s o i n th i s ca s e 6 D e t e rm i n a t i o n Th e n ee d tra n s i e n t fo r a n d s ta b i l i ty o f th e d a m p i n g c o n t ro l c h a c t e ri s t i c s e ffe cti ve n e s s o f H VD C l i n k d a m p i n g co m p u te r p ro g m wi th th e a b i l i ty co n tro l to i s n o rm a l l y s tu d i e d m od el H VD C l i n ks and u si n g a d i ffe re n t co n tro l l e r ch a cte ri s ti cs S u ch a s tu d y ca n re ve a l p o te n ti a l p ro b l e m s i n th e i n te cti o n a t l o w fre q u e n ci e s b e twe e n th e H VD C l i n k a n d o th e r p o we r s ys te m e l e m e n ts s u ch a s s ta ti c va r o r s yn ch ro n o u s co m p e n s a to rs T h e co n tro l l e r e n vi ro n m e n t i n cl u d e s m a n y e l e m e n ts th a t a re , h o we ve r, m o d e l l e d i n a cc u te l y o r n o t a t a l l Th u s m o d e l s tu d i e s s h o u l d b e a u g m e n te d b y m e a s u re m e n ts a n d te s ts p e rfo rm e d i n th e fi e l d wh e n p o s s i b l e to d o s o I t i s i m p o rta n t to s tre s s th e n e e d fo r a n a ccu te re p re s e n ta ti o n o f th e H VD C l i n k a n d i ts co n tro l s ys te m wh e n p e rfo rm i n g tra n s i e n t s ta b i l i ty s tu d i e s An o ve rs i m p l i fi e d m o d e l m a y g i ve ri s e to m i s l e a d i n g re s u l ts Th e d c l i n k m o d e l i n th e s ta b i l i ty p ro g m m e s h o u l d th e re fo re b e va l i d a te d Th e va l i d a ti o n ca n be ca rri e d ou t p re fe b l y against an H VD C TN A or d i g i ta l s i m u l a to r a n d a fte r co n s tru cti o n , a g a i n s t m e a s u re m e n ts p e rfo rm e d u p o n th e H VD C s ys te m N o te th a t th e m o d e l u s e d s h o u l d g i ve co n s e rva ti ve re s u l ts , e ve n i f i t i s m o d e l l e d a s a s i m p l e one Al s o , i t i s ve ry i m p o rta n t to m o d e l th e P L L ( p h a s e l o cke d l o o p ) fo r H VD C fi ri n g co n tro l a s p re ci s e a s p o s s i b l e H VD C s i m u l a to rs a n d e q u i va l e n t p ro g m s ca n b e u s e d to va l i d a te th e i m p l e m e n te d tra n s fe r fu n cti o n s o f th e d a m p i n g co n tro l l e r Th e re a l - ti m e s i m u l a to r i s ve ry u s e fu l fo r th e s tu d y o f va l i d a ti o n o f co n tro l C l o s e d - l o o p te s t u s i n g a re a l - ti m e s i m u l a to r e n a b l e s a q u a s i - re a l co n d i ti o n Th e re a l - ti m e s i m u l a to r ca n b e o f a n a n a l o g u e typ e l i ke TN A o r d i g i ta l S i n ce i t i s a s i m u l a to r te s t, va ri o u s ki n d o f d i s tu rb a n ce s ca n b e i n i ti a te d a n d h e l p to ve ri fy th e co n tro l s ch e m e Al s o , i t i s re co m m e n d e d to ca rry o u t a rti fi ci a l fa u l t te s ti n g i f i t i s p o s s i b l e , e s p e ci a l l y fo r n e w H VD C s ys te m s I n s p i te o f th e fa ct th a t a d a m p i n g co n tro l l e r i s d e s i g n e d to a ct i n a fre q u e n cy n g e b e l o w a b o u t H z , i t m a y h a ve a d e tri m e n ta l e ffe ct o n a co n tro l l e r fo r d a m p i n g o f s u b s yn ch ro n o u s o s ci l l a ti o n s ( s e e C l a u s e ) Copyright International Electrotechnical Commission I E C TR 9 - : 0 + AM D : C S V – 31 –  I EC 201 Th e s p e ci fi ca ti o n o f th e s ta b i l i ty i m p ro ve m e n t fe a tu re o f a n H VD C l i n k ca n b e d e te rm i n e d i n two co n ce p tu a l l y d i ffe re n t wa ys T h e d i ffe re n ce b e twe e n th e two wa ys l i e s i n wh o d e te rm i n e s th e tra n s fe r fu n cti o n a n d o th e r ch a cte ri s ti cs o f th e d a m p i n g co n tro l l e r, th e u ti l i ty p u rch a s i n g th e l i n k, o r th e s u p p l i e r o f th e H VD C s u b s ta ti o n e q u i p m e n t In th e fo rm e r ca s e , th e co n tro l - re l a te d ch a cte ri s ti cs o f th e co n tro l l e r i n l og i c an d o u u t q u a n ti ti e s a s p e cts of th e s p e ci fi ca ti o n te rm s o f i n p u t q u a n ti ti e s , Th e co n tro l eq u i pm en t ca n sh ou l d s p e ci fy tra n s fe r fu n cti o n ( s ) , th e n be d esi g n ed th e a cce s s o ry to co rre ctl y i m p l e m e n t th e s p e ci fi e d ch a cte ri s ti cs , a n d th e n ve ri fi e d b y te s ts I n th e s e co n d ca s e , th e s i tu a ti o n b e co m e s m o re co m p l e x Th e s u p p l i e r s h o u l d b e p ro vi d e d wi th a fu l l s e t o f n e two rk a n d g e n e to r d a ta to a l l o w h i m to p e rfo rm tra n s i e n t s ta b i l i ty a n d re l a te d s tu d i e s p e rfo rm a n ce fo r an a d e q u a te l y re q u i re m e n ts a re b ro a d co m p l e x; n g e of it may be o p e ti n g co n d i ti o n s d i ffi cu l t to In fo rm u l a te th i s ca s e , th e cl e a r p e rfo rm a n ce cri te ri a a n d n e g o ti a ti o n s m a y b e re q u i re d I f th i s m e th o d i s s e l e cte d , s ta b i l i ty s tu d i e s s h o u l d a l s o b e p e rfo rm e d p ri o r to i s s u i n g th e s p e ci fi ca ti o n i n o rd e r to e s ta b l i s h th e l e ve l o f s ta b i l i ty a n d /o r d a m p i n g th a t ca n b e e xp e cte d to b e a ch i e ve d b y d c l i n k co n tro l a cti o n I n e i th e r ca s e , th e ca p a b i l i ty o f th e s u b s ta ti o n e q u i p m e n t, i n p a rti cu l a r th e va l ve s , s h o u l d b e co n s i d e re d i n th e d e te rm i n a ti o n o f th e g a i n a n d a m p l i tu d e l i m i ta ti o n s o f th e co n tro l l e r E xp l i ci t p ro vi s i o n s sh ou l d be mad e fo r e n g i n e e ri n g re vi e w of co n tro l l e r p e rfo rm a n ce d u ri n g co m m i s s i o n i n g te s ts a n d p e ri o d i ca l l y th e re a fte r I m p l e m e n ta ti o n o f th e d a m p i n g c o n t ro l l e r a n d t e l e c o m m u n i c a t i o n re q u i re m e n t s Th e d a m p i n g co n tro l l e r ca n e a s i l y b e i n te g te d i n to th e H VD C co n tro l e q u i p m e n t I t i s u s u a l l y a l l o ca te d to th e H VD C s u b s ta ti o n co n tro l l e ve l ( s e e C l a u s e o f I E C 9 - ) I n th e c a s e o f l a rg e s i g n a l m o d u l a ti o n , co n s i d e ti o n s h o u l d b e g i ve n to th e ca p a ci ty o f th e te l e co m m u n i ca ti o n l i n k b e twe e n th e two H VD C s u b s ta ti o n s , wh i ch s h o u l d b e a b l e to tra n s m i t th e m o d u l a ti o n s i g n a l s a n d i n m a n y ca s e s a l s o i n p u t s i g n a l s ( e g fre q u e n cy) to th e co n tro l l e r wi th o u t ca u s i n g to o l a rg e p h a s e d i s p l a ce m e n ts Wh e re th e m o d u l a ti o n co n tro l re q u i re s te l e co m m u n i ca ti o n , th e re l i a b i l i ty o f th e co m m u n i ca ti o n l i n k i s o f p ri m a ry i m p o rta n ce Th e te l e co m m u n i ca ti o n s ys te m s h o u l d b e d e s i g n e d i n s u ch a wa y th a t “ o u t o f p h a s e m o d u l a ti o n ” ca n n o t re s u l t fro m co m m u n i ca ti o n fa i l u re s , i e i f th e re i s an i n te rru p ti o n in th e te l e co m m u n i ca ti o n ch a n n e l , th e s ys te m sh ou l d be d esi g n ed so th a t m o d u l a ti o n i s re s u m e d co rre ctl y wh e n th e ch a n n e l re s u m e s o p e ti o n D y n a m i c s o f t h e H VD C s y s t e m a t h i g h e r fre q u e n c i e s 7.1 Th i s G e n e l cl a u s e a d d re s s e s th e d yn a m i c p e rfo rm a n ce fu n d a m e n ta l fre q u e n cy a n d b o th an d i n te g e r p e rfo rm a n ce is a b o ve n o n - i n te g e r d epen d en t H VD C m u l ti p l e s on th e of an co n ve rte rs of fu n d a m e n ta l i m p e d a n ce of H VD C s ys te m g e n e te th e an d fre q u e n cy, a c and in th e re a ct to an d d c th u s n g e of h al f o s ci l l a ti o n s th e s ys te m s at co n ve rte r In som e ci rcu m s ta n ce s , i n s ta b i l i ty ca n o ccu r, s o th a t th e co n ve rte r p e rfo rm a n ce i s u n a cce p ta b l e F o r p re s e n t p u rp o s e s , th e d i s ti n cti o n b e twe e n s ta b i l i ty a n d i n s ta b i l i ty i s th a t i n a s ta b l e s ys te m , e ffe ct ( e g n o n - ch a cte ri s ti c h a rm o n i cs ) i s p ro p o rti o n a l to ca u s e ( e g u n b a l a n ce i n a n a c s ys te m ) , wh e re a s i n s ta b i l i ty u sually i n vo l ve s th e g e n e ti o n of o s ci l l a ti o n s at n o n - i n te g e r m u l ti p l e s o f fu n d a m e n ta l fre q u e n cy a n d ca n “ g ro w fro m n o th i n g ” e ve n i n a p e rfe ctl y b a l a n ce d s ys te m A d e ta i l e d d e s cri p ti o n o f th e s e s u b j e cts i s co ve re d i n re fe re n ce s l i s te d i n th e b i b l i o g p h y a n d i n p a rti cu l a r i n C I G RE TF - /I E E E , P a rt [1 ] Th i s te ch n i ca l re p o rt wi l l th e re fo re onl y p ro vi d e b ri e f d e s cri p ti o n s , bu t it wi l l o u tl i n e re l e va n t re q u i re d i n fo rm a ti o n a n d p a rti cu l a r a s p e cts o f th e s p e ci fi ca ti o n o f H VD C s ch e m e s Copyright International Electrotechnical Commission th e – 32 – 7.2 T yp e s o f i n s ta b i l i t y 7.2.1 L o o p i n s ta b i l i ty ( h a rm o n i c i n s ta b i l i ty) IEC TR 6091 9-3:2009+AMD1 :201 CSV  IEC 201 This instability was found on some early HVDC schemes, and was often referred to as harmonic instability It can occur at both integer and non-integer multiples of the fundamental frequency and it involves the main power circuit and control circuit (including measurements) loop It is strongly related to the control and measuring system parameters Instability can occur, even if the a.c system is perfectly balanced and without distortion, if unsuitable control characteristics are used and can be seen on both the a.c and the d.c side It often starts from a near integer multiple of fundamental frequency, nearly always close to the main circuit resonance It may then lock into the nearest harmonic frequency as the instability amplitude grows Instability rarely occurs with present day “equidistant firing” type of control 7.2.2 C u rre n t l o o p i n s ta b i l i t y The speed of the response of an HVDC system is limited primarily by the capacitances and inductances of the a.c and d.c systems The response of the converter itself is generally considerably faster than that of an a.c system or machine However, excessive forcing of the response by the use of high gains in the current control loop can lead to instability of the HVDC system, particularly if the response of the d.c system with its measuring and control devices is comparable to the response time of the a.c system The need to provide a system which is stable overall may, in some cases, mean that the HVDC control response has to be slowed down 2.3 C o re s a tu ti o n i n s ta b i l i ty This instability involves partial saturation of the converter transformers A fundamental frequency component in the d.c current causes second harmonic and d.c in the valve winding current If the d.c component reaches a level comparable to say 50 % of the transformer magnetizing current, the partial saturation of the transformer may result in significant levels of additional harmonics (including second harmonic) in the magnetizing current The various second harmonic current contributions enhance the second harmonic in the a.c voltage, and under some circumstances a full instability can result A high impedance resonance near to the second harmonic on the a.c side, and/or a lowimpedance resonance near to fundamental frequency on the d.c side makes the instability more likely In some cases, it is practicable to design the main circuit parameters (e.g d.c reactor or a.c filters) such that these resonances are avoided In some cases however, the line impedance is so dominating that resonance at fundamental or harmonic frequencies cannot be avoided by selection of realistic parameters for HVDC substation equipment In cases where such resonances cannot be avoided, the instability can be ”cured” either by modifying the control constants or by the provision of special feedback loops in the controls However, in such cases special care should be taken to control transients, e.g overvoltages, particularly if the resonance is lightly damped 7.2.4 H a rm o n i c i n te c ti o n s Harmonics in the a.c voltage will result in the generation of harmonics in the direct voltage at the two sideband frequencies, and thus in the flow of current on the d.c side at these frequencies Similarly, harmonics in the direct current will result in the generation of harmonic a.c currents in the transformer valve windings and a.c systems at the two sideband frequencies, and thus in the creation of harmonic voltage distortion on the a.c side at these frequencies Under resonance conditions this may result in unacceptable harmonic distortion on either the a.c side or the d.c side, or both Unlike the instabilities described in 7.2.1 to 7.2.2, this phenomenon occurs only if there is an internal driving source in either the a.c or the d.c system One example of this phenomenon Copyright International Electrotechnical Commission I E C TR 9 - : 0 + AM D : C S V  – 33 – I EC 201 i s th e s u p e ri m p o s i ti o n o f a fu n d a m e n ta l fre q u e n cy co m p o n e n t o n th e d i re ct cu rre n t, a s m a y o ccu r i f a n o ve rh e a d d c l i n e ru n s p a l l e l to a n a c l i n e o ve r a s i g n i fi ca n t d i s ta n ce Th e m o s t s e ve re ca s e i s th a t a c l i n e a n d d c l i n e a re o n th e s a m e to we r T h e fu n d a m e n ta l fre q u e n cy co m p o n e n t wi l l th e n ca u s e d i re ct cu rre n t an d s e co n d h a rm o n i c in th e co n ve rte r va l ve wi n d i n g s I t i s n o t fe a s i b l e to re d u ce th e s e co n d re s u l ta n t h a rm o n i c co m p o n e n t i n j e cte d i n to th e a c s ys te m at th e same ti m e Th u s , it may be n e ce s s a ry to ta ke a cti o n s s u ch as tra n s p o s i n g th e a c l i n e o r b y a p p l yi n g h a rm o n i c fi l te ri n g o n e i th e r th e d c o r th e a c s i d e o f th e co n ve rte r O th e r d ri vi n g fre q u e n cy, s o u rce s or a re u n b a l a n ce s i m p e d a n ce u n b a l a n ce ) in th e or a c s ys te m i n e q u a l i ty of ( n e g a ti ve l e a ka g e s e q u e n ce re a cta n ce s fu n d a m e n ta l of co n ve rte r tra n s fo rm e rs ; a l l o f th e s e ca u s e s e co n d h a rm o n i c o n th e d c s i d e , wh i ch re a cts b a ck o n th e a c sid e On e si d eban d o f th e l a tte r i s a t th i rd h a rm o n i c, and ca n s o m e ti m e s re q u i re th e a d d i ti o n o f th i rd h a rm o n i c fi l te rs to p re ve n t e xce s s i ve a c vo l ta g e d i s to rti o n B e ca u s e th e ci rcu l a ti o n b e twe e n m e ch a n i s m of h a rm o n i cs th e m U n l ess fo r th e g e n e ti o n on th e d c sid e d c line or th e o f n o n - ch a cte ri s ti c h a rm o n i cs of th e ca b l e co n ve rte rs , an d th e d c th e re fi l te rs may h a ve d epen d s be a an u pon i n te cti o n ve ry l ow sh u n t i m p e d a n ce co m p a re d to th e i m p e d a n ce o f th e o th e r co n ve rte r, th e two co n ve rte rs a re co u p l e d at th e s e ca rri e d fre q u e n ci e s Th e re fo re , th e tre a tm e n t o f n o n - ch a cte ri s ti c o u t i n d e p e n d e n tl y fo r th e two H VD C s u b s ta ti o n s , h a rm o n i cs s i n ce th e co u p l i n g ca n n o t b e twe e n be th e m m e a n s th a t e a ch co n tri b u te s to th e n o n - ch a cte ri s ti c h a rm o n i c b e h a vi o u r o f th e o th e r Th e re i s e ve n th e p o s s i b i l i ty th a t a s ta n d i n g wa ve m a y b e s e t u p o n th e d c l i n e , m a g n i fyi n g th e e ffe ct at b o th H VD C s u b s ta ti o n s Onl y an a n a l ys i s in wh i ch th e ci rcu i t p a m e te rs a re d e l i b e te l y d i s to rte d to e xp o s e th i s p o s s i b i l i ty i s l i ke l y to b e u s e fu l I n fo rm a t i o n re q u i re d fo r d e s i g n p u rp o s e s I n o rd e r to e n s u re th a t th e H VD C s ys te m g i ve s s a ti s fa cto ry d yn a m i c p e rfo rm a n ce a t h i g h e r fre q u e n ci e s , th e cl o s e i n te cti o n s b e twe e n th e d i ffe re n t p a rts o f th e o ve l l s ys te m s h o u l d b e ta ke n i n to a cco u n t i n th e d e s i g n Th e o ve l l s ys te m i n cl u d e s th e a c s ys te m s a t b o th H VD C s u b s ta ti o n s , co n ve rte r th e tra n s m i s s i o n co n tro l s p e ci fi ca ti o n s ys te m s ta g e to It l i n es is d e fi n e / ca b l e s , u n l i ke l y s p e ci fi c th a t th e H VD C m e a n i n g fu l re q u i re m e n ts fo r s u b s ta ti o n s tu d i e s th e ca n H VD C main be ci rcu i t, and p e rfo rm e d s u b s ta ti o n at th e th e co m p o n e n ts Th e re fo re , th e s p e ci fi ca ti o n s h o u l d b e fu n cti o n a l , re q u i ri n g th a t th e m a n u fa ctu re r d e s i g n s th e H VD C s u b s ta ti o n s o th a t s a ti s fa cto ry p e rfo rm a n ce i s a ch i e ve d a t h i g h e r fre q u e n ci e s fo r a l l p cti ca l co m b i n a ti o n s o f s ys te m co n d i ti o n s A d i s cl o s u re o f th e p ro ce d u re s b y wh i ch m a n u fa c tu re r i n te n d s to d e m o n s tra te s a ti s fa cto ry d yn a m i c h a rm o n i c p e rfo rm a n ce th e at h ig her fre q u e n ci e s ca n b e re q u e s te d Th e co n d i ti o n s e xte rn a l to th e H VD C s u b s ta ti o n wh i ch n e e d to b e ta ke n i n to a cco u n t wh e n d e s i g n i n g s a ti s fa cto ry d yn a m i c p e rfo rm a n ce o f th e H VD C s ys te m a t h i g h e r fre q u e n ci e s a re a s fo l l o ws : – th e i m p e d a n ce a n d p h a s e a n g l e o f th e a c s ys te m a n d th e kn o wn d c s ys te m a s s e e n fro m e a ch co n ve rte r B o th we a k and s tro n g a c s ys te m re p re s e n ta ti o n s sh ou l d be p ro vi d e d , a n d i f p o s s i b l e , n e two rk co n fi g u ti o n s wi th p ro b a b l e o u ta g e co n ti n g e n ci e s ; – re s o n a n ce s o n th e a c o r d c s i d e , i n p a rti cu l a r wh e th e r co m p l e m e n ta ry re s o n a n ce s ca n e xi s t ( e g , ƒ re s , a c = ƒ re s , d c ƒ re s , d c – – ± ƒ , wh e re ƒ i s th e fu n d a m e n ta l fre q u e n cy a n d ƒ re s , a c a n d a re a c a n d d c s i d e re s o n a n t fre q u e n ci e s re s p e cti ve l y) ; u n b a l a n ce s i n th e a c s ys te m i m p e d a n ce o r vo l ta g e ; th e p re s e n ce o f o th e r h a rm o n i c s o u rce s wi th co rre s p o n d i n g s o u rce i m p e d a n ce s a n d n o n l i n ear l oad s e l e ctri ca l l y cl o s e to th e H VD C s u b s ta ti o n a c a n d /o r d c te rm i n a l s Th e p re s e n ce o f a fu n d a m e n ta l fre q u e n cy s o u rce o n th e d c s i d e i s a s p e ci a l ca s e o f th i s ; – possi bl e a c l i n es co u p l i n g to th e d c line at fu n d a m e n ta l fre q u e n cy Th i s re q u i re s g e o m e tri ca l co n fi g u ti o n o f a c a n d d c l i n e s wh e n ru n n i n g i n p a l l e l , a c l i n e m a xi m u m cu rre n t a n d vo l ta g e , p o i n ts o f tra n s p o s i ti o n , e tc ; Copyright International Electrotechnical Commission – 34 – – i m pe d a n ce ve rs u s fre q u e n c y I E C T R 9 - : 0 + AM D : C S V © I EC 201 c h a c te ri s ti cs , i n cl u d i n g va ri a ti o n of sh u n t ca p a ci to r n u m b e rs ; – poss i b i l i ty of i sl a n d i n g , re m a i n i n g wi th n e a rb y g e n e to rs , i s o l a te d fro m re s t o f th e a c n e two rk T h e a b o ve i n fo rm a ti o n s h o u l d b e i n c l u d e d i n th e s p e c i fi ca ti o n o r a l te rn a ti ve l y, s u ffi c i e n t d a ta d e s c ri b i n g th e a c and d c s ys te m to enabl e th i s i n fo rm a ti o n to be d e vi s e d shou ld be p ro v i d e d I t ca n b e s e e n th a t th e a b o ve - l i s te d i n fo rm a ti o n l a rg e l y co rre s p o n d s to th a t re q u i re d also fo r sh ou l d th e s te a d y- s ta te be n o te d th a t i n d esi g n som e of th e H VD C a p p l i ca ti o n s , s u b s ta ti o n (see th e fu n d a m e n ta l I EC 60 91 9-1 ) fre q u e n c y ƒ ca n H o we ve r, it va ry o ve r a l a rg e n g e ( e g fo r a n i s o l a te d g e n e ti n g s ta ti o n ) , a n d th a t th i s m a y e x p o s e re s o n a n ce s n o t n o rm a l l y e n c o u n te re d M os t M e a n s a v a i l a b l e fo r p re v e n t i n g i n s ta b i l i ti e s at i n s ta b i l i t i e s h i g h e r fre q u e n c i e s can be a vo i d e d o r c o rre cte d b y a l te ti o n s to th e co n tro l s ys te m T h i s m a y s i m p l y i n vo l ve th e s e l e c ti o n o f a p p ro p ri a te tu n i n g I n o th e r c a s e s , i t m a y b e n e c e s s a ry to i n tro d u c e a d d i ti o n a l fe e d b a c k l o o p s , e g fro m th e a c o r d c vo l ta g e o r th e a c va l ve wi n d i n g c u rre n ts o r th e d c c u rre n t T h e s o l u ti o n a d o p te d m a y d i ffe r b e twe e n m a n u fa ctu re rs a n d i n d e e d fro m s ch e m e to s ch e m e C o n tro l te c h n i q u e s a re a l wa ys i n ve s ti g a te d fi rs t, b e ca u s e th e y n o rm a l l y o ffe r a re l a ti ve l y ch e a p s o l u ti o n to i n s ta b i l i t y p ro b l e m s H o we ve r, th e re wi l l b e o cc a s i o n s i n wh i c h th e co n tro l s ys te m a cti n g a l o n e i s i n s u ffi c i e n t to a cc o m p l i s h a l l o f th e d e s i re d a cti vi ty O n c e th i s s ta g e h a s b e e n re a ch e d , e i th e r a co n tro l ta rg e t h a s to b e c o m p ro m i s e d , o r o th e r m e a n s fo u n d B ro a d b a n d d a m p e d fi l te rs ca n s i g n i fi c a n tl y i m p ro ve th e p e rfo rm a n ce o f th e o ve l l s ys te m b y re m o vi n g s h a rp re s o n a n ce s H o we ve r, th e h a rm o n i c s u p p re s s i o n a t i n d i vi d u a l fre q u e n c i e s i s m u ch l o we r p e r kVAr fo r a d a m p e d fi l te r th a n fo r a tu n e d fi l te r T h e re fo re , th i s m e th o d of p re ve n ti n g i n s ta b i l i t y ca n b e ve ry co s tl y, p a rti c u l a rl y i f th e i n s ta b i l i t y o ccu rs a t a re l a ti ve l y l o w fre q u e n c y H o we ve r, in th e case of s i g n i fi c a n t e xte rn a l h a rm o n i c s o u rce s , su ch as an u n tra n s p o s e d a c l i n e b e i n g ru n i n p a l l e l to a n o ve rh e a d d c l i n e o ve r a g re a t d i s ta n c e , i t m a y n o t b e p o s s i b l e to o b ta i n s a ti s fa cto ry p e rfo rm a n ce wi th o u t th e a p p l i ca ti o n o f e xp e n s i ve fu n d a m e n ta l fre q u e n c y b l o cki n g fi l te rs o n th e d c s i d e o r s e c o n d h a rm o n i c s h u n t fi l te rs o n th e a c s i d e Dam pi n g M o d e rn o f l o w o rd e r h a rm o n i c s b y c o n t ro l ( e q u i d i s ta n t fi ri n g ) c o n tro l s ys te m s a re a cti on able to a cti ve l y d am p l ow o rd e r n on - ch a c te ri s ti c h a rm o n i cs , ( e g fro m th e a c n e two rk) T h i s i s a c h i e ve d b y s u i ta b l e m o d u l a ti o n o f th e delay an g le ( α) Th i s ca n be b e n e fi c i a l u n d er sp eci a l ci rc u m s ta n ce s , s u ch as th e a p p l i ca ti o n o f H VD C to we a k a c n e two rks a n d /o r to a c n e two rks wh o s e p h a s e co n d u c to rs a re n o t tra n s p o s e d , o r e ve n d u ri n g re co ve ry fro m a c n e two rk fa u l ts wh e n th e wa ve fo rm i s te m p o ri l y d i s to rte d re s tra i n i n g i n fl u e n c e Al th o u g h on th e it is l ow o fte n possi b l e u n c h a c te ri s ti c a va i l a b l e to a cc o m m o d a te a l l s u c h a cti vi t y T h u s , to a d j u s t th e h a rm o n i cs , c o n tro l on l y a s ys te m si n g le to e x e rt a va ri a b l e ( α) is th e s a m e te ch n i q u e m a y b e i n c a p a b l e o f re s tra i n i n g s i m u l ta n e o u s l y th e s e c o n d h a rm o n i c o n th e d c n e two rk a n d th e th i rd h a rm o n i c o n th e a c n e two rk D e m o n s t t i o n o f s a t i s fa c t o ry p e rfo rm a n c e a t h i g h e r fre q u e n c i e s T d i ti o n a l l y, H VD C s i m u l a to rs h a ve b e e n u s e d to d e m o n s tra te d u ri n g th e d e s i g n s ta g e th a t a n H VD C s c h e m e i s fre e fro m u n d e s i b l e i n s ta b i l i ti e s S i m u l a to rs a re a co n ve n i e n t to o l fo r s u ch a n a l ys i s , en abl i n g a m u l ti p l i c i t y of s ys te m co n d i ti o n s an d c o n fi g u ti o n s to be i n ve s ti g a te d re l a ti ve l y p i d l y T h e i n ve s ti g a ti o n s a re g e n e l l y c a rri e d o u t a s s te p re s p o n s e s tu d i e s , wi th p i d d a m p i n g o f th e re s p o n s e s h o wi n g g o o d re s i s ta n ce to i n s ta b i l i t y H o we ve r, th e a cc u c y o f s u c h i n ve s ti g a ti o n s i s s u b j e ct to s i m u l a to r co m p o n e n t l i m i ta ti o n s F o r e xa m p l e , m a n y o f th e n o rm a l h a rm o n i cs to b e o b s e rve d a re s o s m a l l th a t th e y te n d to b e b u ri e d by s p u ri o u s Copyright International Electrotechnical Commission h a rm o n i cs cau s e d by m od el co m p o n e n t u n b a l a n ces M od el c o n v e rte r I E C TR 9 - : 0 + AM D : C S V – 35 –  I EC 201 tra n s fo rm e rs h a ve re a ch e d a high d e g re e o f p e rfe cti o n in s i m u l a ti n g re a l tra n s fo rm e r B - H ch a cte ri s ti cs , b u t m o s t m o d e l s a re n o t a d e q u a te to ch e ck fo r co re s a tu ti o n i n s ta b i l i ty C o m p u te r s i m u l a ti o n h as b e co m e a vi a b l e a l te rn a ti ve to th e H VD C TN A s i m u l a to r fo r d e m o n s tra ti o n o f a b s e n ce o f i n s ta b i l i ty A co m p u te r s i m u l a ti o n i s l i ke l y to b e m o re co n ve n i e n t th a n on e u n d e rta ke n by means of th e H VD C TN A s i m u l a to r, an d th e a n a l ys i s ca n be p o te n ti a l l y m o re a ccu te , s i n ce th e a ctu a l s ys te m a n d co m p o n e n t l o s s e s ca n b e re p re s e n te d U n l e s s th e co m p u te r s i m u l a to r o p e te s i n re a l ti m e i t wi l l n o t b e p cti ca l to u s e th e a ctu a l a n d co m p l e te co n tro l h a rd wa re I t i s i m p o rta n t th a t th e s i m u l a ti o n i s va l i d a te d b y co m p a ri s o n o f re s u l ts wi th a ctu a l m e a s u re m e n ts p e rfo rm e d o n a re a l s ys te m U s e fu l n e s s o f th e re a l - ti m e s i m u l a to r s h o u l d b e m e n ti o n e d h e re A cl o s e d - l o o p te s t ca n b e p e rfo rm e d b e fo re i m p l e m e n ta ti o n o f th e co n tro l l e r, u s i n g re a l - ti m e s i m u l a to r Va ri e ty o f te s t ca s e s ca n b e d e m o n s tra te d S i n ce th e co n ve rte r i n te cts wi th i ts h a rm o n i c e n vi ro n m e n t ( h a rm o n i c i m p e d a n ce s o n th e a c and d c si d es as we l l as h a rm o n i c i n j e cti o n fro m o th e r s o u rce s ) , it is i m p o rta n t to d e m o n s tra te th a t th e co n ve rte r d o e s n o t m a g n i fy l o w o rd e r n o n - ch a cte ri s ti c h a rm o n i cs to a n u n a cce p ta b l e e xte n t a n d th a t l a rg e a m p l i tu d e s o f s u ch h a rm o n i cs wi l l n o t ca u s e i n s ta b i l i ty S tu d i e s ca n b e u n d e rta ke n b y m o d e l l i n g th e co n ve rte r a n d i ts co n tro l s i n a s ys te m wi th l o w o rd e r h a rm o n i c co m p l e m e n ta ry re s o n a n ce s b e twe e n th e a s s o ci a te d a c a n d d c n e two rks B y a p p ro p ri a te te s ts , i t i s o fte n p o s s i b l e to s h o w th a t th e b e h a vi o u r o f th e co n ve rte r a n d i ts co n tro l s a re n o t u n d u l y d i s tu rb e d b y h a rm o n i cs , e ve n wh e n th e h a rm o n i cs e xh i b i t s u b s ta n ti a l a m p l i tu d e D u ri n g co m m i s s i o n i n g i t s h o u l d b e a rra n g e d ( i f a p p l i ca b l e ) fo r th e a c s ys te m a n d /o r th e d c s ys te m to b e i n wo rs t re s o n a n ce wi th th e co n ve rte r s ta ti o n , a n d th e a d e q u a cy o f th e i n s ta b i l i ty co u n te r m e a s u re s sh ou l d be d e m o n s tra te d by m e a s u ri n g th e s ys te m re s p o n s e to s te p ch a n g e s a n d /o r s m a l l s i g n a l m o d u l a ti o n a t th e a p p ro p ri a te fre q u e n ci e s o f th e cu rre n t o rd e r S u b s y n c h ro n o u s o s c i l l a t i o n s 8.1 G e n e l O n l y tu rb i n e - g e n e to r u n i ts l o ca te d n e a r a re cti fi e r s u b s ta ti o n a n d h a vi n g we a k co n n e cti o n to th e a c n e two rk a re vu l n e b l e to s u b s yn ch ro n o u s o s ci l l a ti o n s C o m m o n l y, to rs i o n a l n a tu l fre q u e n ci e s l o we s t lie to rs i o n a l in th e n g e fre q u e n cy of may be Hz as to 40 l ow H z as F o r l a rg e H z, wi th n u cl e a r tu rb i n e - g e n e to rs , o th e r to rs i o n a l mod es at th e h i g h er fre q u e n ci e s To rs i o n a l vi b ti o n s i n a tu rb i n e - g e n e to r ro to r m a y b e s ti m u l a te d b y m a n y co m m o n e l e ctri ca l d i s tu rb a n ce s in th e tra n s m i s s i o n s ys te m F u rth e rm o re , u n d er ce rta i n co n d i ti o n s , to rs i o n a l vi b ti o n s m a y b e a m p l i fi e d , o r re i n fo rce d , b y a n e a r re s o n a n t i n te cti o n b e twe e n th e tu rb i n e g e n e to r ro to r a n d a s e ri e s co m p e n s a te d tra n s m i s s i o n l i n e , o r b y i n te cti o n wi th a n H VD C co n tro l s ys te m S i n ce tu rb i n e - g e n e to r to rs i o n a l m o d e s h a ve ve ry l i ttl e i n h e re n t d a m p i n g , s h a ft o s ci l l a ti o n s p e rs i s t fo r a co n s i d e b l e ti m e a fte r th e y a re s ti m u l a te d Re p e a te d s ti m u l a ti o n o f e xce s s i ve m a g n i tu d e ca n l e a d to l o s s o f s h a ft l i fe , a n d i n th e e xtre m e , fa ti g u e fa i l u re I n a n H VD C s ys te m , th e co n s ta n t p o we r a n d co n s ta n t cu rre n t re g u l a ti o n m o d e s m a y h a ve a d e s ta b i l i z i n g i n fl u e n ce o n ro to r to rs i o n a l s Wi th i n th e typ i ca l b a n d wi d th o f a n H VD C cu rre n t co n tro l re g u l a to r, two o r th re e s u b s yn ch ro n o u s to rs i o n a l m o d e s o f o s ci l l a ti o n m a y b e p re s e n t To cl e a rl y i d e n ti fy th e d i ffe re n ce b e twe e n S S R a n d s u b s yn ch ro n o u s to rs i o n a l i n te cti o n , th e l a tte r i s ca l l e d a n S S TI , wh i ch i s a n i n te cti o n b e twe e n H VD C co n tro l a n d tu rb i n e - g e n e to r Copyright International Electrotechnical Commission – 36 – I E C TR 9 - : 0 + AM D : C S V  I EC 201 S u b s yn ch ro n o u s re s o n a n ce ( S S R) i n vo l vi n g s e ri e s co m p e n s a te d a c tra n s m i s s i o n l i n e s h a s som e fu n d a m e n ta l a s s o ci a te d wi th fre q u e n ci e s d i ffe re n ce s s e ri e s wh i l e wi th th e co m p e n s a ti o n to rs i o n a l H VD C a ffe cts i n te cti o n wi th to rs i o n a l p ri m a ri l y H VD C i n s ta b i l i ty th e ph en om en on h i g h er p ri m a ri l y a ffe cts n g e th e of SSR to rs i o n a l l o we r fre q u e n cy to rs i o n a l m o d e s S S R a s s o ci a te d wi th s e ri e s co m p e n s a ti o n ca n b e m u ch m o re s e ve re th a n H VD C re l a te d to rs i o n a l i n te cti o n i n th e m a g n i tu d e o f to rs i o n a l d e s ta b i l i za ti o n 8.2 C ri t e ri a fo r s u b s yn c h ro n o u s t o rs i o n a l N e g a ti ve d am pi n g to tu rb i n e - g e n e to r i n t e c t i o n w i t h to rs i o n a l mod es o b j e cti ve o f co n tro l l i n g cu rre n t i n a n H VD C s ys te m of a n H VD C s ys t e m o s ci l l a ti o n is i n h e re n t to th e S o m e d e g re e o f n e g a ti ve d a m p i n g wi l l e xi s t wi th i n th e b a n d wi d th ( B W) o f th e cu rre n t co n tro l re g u l a ti o n l o o p O n l y tu rb i n e - g e n e to r u n i ts l o ca te d n e a r a re cti fi e r s u b s ta ti o n a n d h a vi n g a we a k co n n e c ti o n to th e a c n e two rk e xp e ri e n ce m u ch a re vu l n e b l e d e s ta b i l i z a ti o n to to rs i o n a l s i n ce i n te cti o n s i n ve rte rs U n i ts n ear an re a ct d i ffe re n tl y to i n ve rte r d o ph ase angle n ot va ri a ti o n s th a n d o re cti fi e rs Tu rb i n e - g e n e to r ro to r m o ti o n ca u s e s va ri a ti o n s i n b o th m a g n i tu d e a n d p h a s e a n g l e o f th e a c vo l ta g e s u p p l yi n g th e co n ve rte r T h e e ffe ct o n co n ve rte r a n g l e o f d e l a y, a n d th e cl o s e d l o o p co n tro l re a cti o n to th e a p p a re n t fi ri n g a n g l e s h i ft re s u l t i n ch a n g e s i n d i re ct vo l ta g e a n d cu rre n t, th e re b y, d c p o we r tra n s fe r T h e u l ti m a te e ffe ct o f ch a n g e i n H VD C p o we r i s ch a n g e i n g e n e to r e l e ctri ca l to rq u e I f th e g e n e to r a ccu m u l a te d p h a s e l a g s b e twe e n th e ch a n g e i n th e g e n e to r s h a ft s p e e d , a n d th e re s u l ti n g ch a n g e i n e l e ctri ca l to rq u e o n th e g e n e to r ro to r e xce e d s ° , th e to rs i o n a l o s ci l l a ti o n m a y b e co m e u n s ta b l e A co n s ta n t p o we r l o a d p re s e n ts a n e g a ti ve ch a cte ri s ti c to a n y d e vi a ti o n o f g e n e to r s h a ft speed Wi th th e i n ve rte r co n tro l l i n g g e n e to r ro to r s p e e d cu rre n t, i n cre a s e s , th e s o wi l l d c a c vo l ta g e vo l ta g e wi l l fo l l o w I f th e th e re cti fi e r re cti fi e r i s i n an Wh e n al ph a th e co n tro l m o d e , d c vo l ta g e wi l l a l s o i n cre a s e a n d l e a d to a p o we r i n cre a s e Th u s p o s i ti ve d a m p i n g re s u l ts wi th i n th e cu rre n t co n tro l BW an d a p p ro a ch e s th e i n h e re n t p o s i ti ve d ampin g ch a cte ri s ti cs a s s o ci a te d wi th n o co n tro l a cti o n Tu rb i n e g e n e to r u n i ts n e a r th e i n ve rte r o f a n H VD C s ys te m wi l l a l wa ys h a ve a p a l l e l a c i n te rco n n e cti o n to th e l o a d a n d h e n ce e xp e ri e n ce l e s s i n fl u e n ce o n th e H VD C co n tro l th a n m i g h t a u n i t n e a r a re cti fi e r Al s o , wh e n s h a ft s p e e d i n cre a s e s o n a u n i t n e a r th e i n ve rte r, th e vo l ta g e m a g n i tu d e at th e i n ve rte r i n cre a s e s , wh i ch ca u s e s a d e cre a s e in d c cu rre n t m a g n i tu d e ( i e l e a d i n g to a n o p p o s i te d a m p i n g e ffe ct co m p a re d to th e re cti fi e r) A s te a d y- s ta te fi ri n g an gl e of o p e ti o n of th e co n ve rte r h as s i g n i fi ca n t i m p a ct on th e i n te cti o n Th i s a ri s e s fro m th e i n h e re n t n o n - l i n e a ri ty co s i n e re l a ti o n s h i p b e twe e n fi ri n g a n g l e a n d d c vo l ta g e G a i n l i n e a ri z a ti o n fo r th e cu rre n t re g u l a to r fi ri n g a n g l e wi l l re d u ce b u t n o t e l i m i n a te th e i n te cti o n O p e ti o n at l a rg e an g les of d elay ca n s i g n i fi ca n tl y re d u ce to rs i o n a l s ta b i l i ty Th e re fo re , co n s i d e ti o n s h o u l d b e g i ve n i n th e H VD C s ys te m s p e ci fi ca ti o n s wh e n o p e ti o n i s p l a n n e d a t re d u ce d vo l ta g e fo r vo l ta g e co n tro l p u rp o s e s , o r b e ca u s e o f re d u ce d i n s u l a ti o n s tre n g th o f th e tra n s m i s s i o n s ys te m T o rs i o n a l i n te cti o n d oes n ot o ccu r o n h yd ro g e n e to r u n i ts , on l y on th e rm a l g e n e to r u n i ts F o r ve ry l o w a n d m e d i u m s p e e d ( l o w h e a d ) u n i ts , th e ve ry l a rg e h yd ro g e n e to r i n e rti a wi th re s p e ct to tu rb i n e i n e rti a re d u ce s i n te cti o n wi th th e e l e ctri ca l s ys te m a n d p cti ca l l y e l i m i n a te s th e p o s s i b i l i ty o f to rs i o n a l i n te cti o n p ro b l e m s b o th wi th th e s e ri e s co m p e n s a te d a c tra n s m i s s i o n an d H VD C For a p p l i ca ti o n s u ti l i z i n g high speed i n e rti a ti o o f h yd ro g e n e to r a n d tu rb i n e s m a y n o t b e l a rg e , to rs i o n a l p ro b l e m i n te cti o n ca n Copyright International Electrotechnical Commission o ccu r in Th e th e s p e ci fi ca ti o n g i ve n sh ou l d co n fi g u ti o n s re q u i re An cl a ri fi ca ti o n e xa m p l e (h i g h h ead ) u n i ts , th e i n cre a s i n g th e p o s s i b i l i ty o f of th e on wh e th e r s i m p l i fi e d an S S TI m e th o d fo r I E C TR 9 - : 0 + AM D : C S V  – 37 – I EC 201 s cre e n i n g p o s s i b i l i ti e s fo r S S TI o ccu rri n g is p re s e n te d in In th e ca s e wh e re S S TI is p o s s i b l e , m o re d e ta i l e d s ys te m s tu d i e s a re re q u i re d C o n tro l s a p p l i e d to th e d c s ys te m to a u g m e n t d a m p i n g o f p o we r s wi n g o s ci l l a ti o n s , typ i ca l l y i n th e fre q u e n cy n g e o f , H z to , H z , ca n i n te ct wi th to rs i o n a l m o d e s a n d s o m e ti m e s re s u l t i n a s i g n i fi ca n t d e s ta b i l i z i n g i n fl u e n ce o n n e a rb y tu rb i n e g e n e to r u n i ts T h i s i n fl u e n ce s h o u l d b e co n s i d e re d i n th e s p e ci fi ca ti o n o f a n y H VD C s ys te m wh e n e ve r d a m p i n g co n tro l s and s u b s yn ch ro n o u s re s o n a n ce co n s i d e ti o n s e xi s t S i n ce b o th co n tro l s a re n e ce s s a ry i n s o m e i n s ta l l a ti o n s , i t i s i m p e ti ve th a t th e y co e xi s t i n a co m p l i m e n ta ry m a n n e r On s e ri e s co m p e n s a te d l i nes th a t a re to rs i o n a l l y s ta b l e , th e a d d i ti o n of an H VD C s ys te m s h o u l d h a ve n e g l i g i b l e e ffe ct o n th e to rs i o n a l s ta b i l i ty Th e a d d i ti o n o f th e H VD C s ys te m a d d s a small p o s i ti ve d ampin g to th e to rs i o n a l m od es, e s p e ci a l l y i f a s u b s yn ch ro n o u s d am pi n g co n tro l l e r i s i m p l e m e n te d H o we ve r, s p e ci fi ca ti o n s s h o u l d re q u i re th a t e a ch s u ch s ys te m b e i n ve s ti g a te d to e n s u re th a t th e re i s n o S S TI p ro b l e m On s ys te m s co n ta i n th e in wh i ch th e i n fo rm a ti o n p o te n ti a l on to rs i o n a l fo r to rs i o n a l fre q u e n ci e s i n s ta b i l i ty and e xi s ts , d ampi n g th e s p e ci fi ca ti o n o f vi b ti o n an d sh ou l d m e ch a n i ca l m o d e s h a p e s fo r a l l th e g e n e to r u n i ts o f i n te re s t I f n o t a va i l a b l e , S S TI fre q u e n ci e s ca n b e o b ta i n e d b y a re l a ti ve l y s i m p l e fi e l d te s t P e rti n e n t tra n s m i s s i o n n e two rk d a ta s h o u l d a l s o b e su ppl i ed 8.3 S c re e n i n g c ri t e ri a fo r i d e n t i fyi n g g e n e t o r u n i t s s u s c e p t i b l e t o t o rs i o n a l i n t e c t i o n s S p e ci fi ca ti o n s fo r a n y n e w H VD C s ys te m i n wh i ch th e re i s a p o te n ti a l fo r to rs i o n a l i n te c ti o n wi th tu rb i n e - g e n e to rs sh ou l d co n ta i n p ro vi s i o n s fo r s cre e n i n g s tu d i e s to d e te rm i n e if in- d e p th s u b s yn ch ro n o u s re s o n a n ce s tu d i e s a n d p o s s i b l e s u b s yn ch ro n o u s d a m p i n g co n tro l l e rs ( S S D C ) a re re q u i re d O n H VD C s ys te m s wh e re s u b s yn ch ro n o u s re s o n a n ce m a y p o te n ti a l l y b e a p ro b l e m , b u t n o S S D C co n tro l i s re q u i re d i n i ti a l l y, th e s p e ci fi ca ti o n s h o u l d re q u i re a p p ro p ri a te H VD C co n tro l i n p u t p ro vi s i o n s fo r a d d i ti o n o f a fu tu re s u b s yn ch ro n o u s d a m p i n g co n tro l l e r An a p p ro xi m a te s tre n g th h as re l a ti o n s h i p been b e twe e n d e ve l o p e d Th i s th e m a g n i tu d e re l a ti o n s h i p , of u sed th e as a i n te cti o n q u a n ti ta ti ve and a c s ys te m s cre e n i n g to o l to i d e n ti fy u n i ts a n d s ys te m co n ti n g e n ci e s wh i ch re q u i re d e ta i l e d s tu d y, i s a s fo l l o ws : UIFi = PdN  − SCi  Si  SCtot  wh e re i UIF P SC i s th e u n i t i n te cti o n fa cto r o f -th g e n e ti n g u n i t; i i s th e M W ti n g o f th e H VD C s ys te m ; dN is i th e s h o rt- ci rcu i t ( e xcl u d i n g SC ca p a b i l i ty at H VD C co m m u ta ti n g bu s e xcl u d i n g unit a c fi l te rs ) ; i s th e s h o rt- ci rcu i t ca p a b i l i ty a t H VD C co m m u ta ti n g b u s i n cl u d i n g to t i-th i-th u n i t ( e xcl u d i n g a c fi l te rs ) Re s u l ts o f e xte n s i ve s tu d i e s s u g g e s t th a t a n i n te cti o n fa cto r l e s s th a n a p p ro xi m a te l y , wi l l n o t h a ve s i g n i fi ca n t i n te cti o n a n d ca n b e n e g l e cte d fro m fu rth e r s tu d i e s If th e UIF b e co m e l a rg e r th a n 0, , fu rth e r s tu d i e s a re n eed ed S u ch s tu d i e s i n cl u d e e i g e n va l u e a n a l ys i s , fre q u e n cy re s p o n s e a n a l ys i s a n d p o we r s ys te m s i m u l a ti o n u s i n g E M T P typ e s o ftwa re , Copyright International Electrotechnical Commission an d re a l - ti m e s i m u l a to r In e a ch s tu d y, p re ci s e mod el l i n g s o f H VD C fi ri n g – 38 – I E C TR 9 - : 0 + AM D : C S V  I EC 201 co n tro l b l o ck ( e g AC R a n d P L L ) , a n d tu rb i n e - g e n e to r m a s s s ys te m i n cl u d i n g m e ch a n i ca l d a m p i n g a re e s s e n ti a l 8.4 P e rfo rm a n ce c o n s i d e ti o n s fo r u ti l i z i n g s u b s yn c h ro n o u s d a m p i n g c o n tro l l e rs (SSDCs) S u b s yn ch ro n o u s dampin g co n tro l l e rs a ct to m o d u l a te th e H VD C fi ri n g co n tro l in s u ch a m a n n e r a s to e n s u re p o s i ti ve d a m p i n g o f to rs i o n a l o s ci l l a ti o n s o n a l l n e a rb y g e n e to r u n i ts fo r a l l p cti ca l s ys te m o p e ti n g co n d i ti o n s Typ i ca l s i g n a l s u ti l i ze d fro m th e a c s ys te m i n th e S S D C d e s i g n i n cl u d e th e re cti fi e r a c b u s fre q u e n cy, g e n e to r s h a ft an g u l ar ve l o ci ty or a s yn th e s i z e d si g n al fro m b o th co n ve rte r vo l ta g e s a n d cu rre n ts Th e d yn a m i c n g e o f th e S S D C s h o u l d b e wi d e e n o u g h to p ro vi d e a t l e a s t s o m e p o s i ti ve d am pi n g to a to rs i o n a l o s ci l l a ti o n a fte r it h as been s ti m u l a te d to th e m a xi m u m amou n t p o s s i b l e b y a s ys te m d i s tu rb a n ce T h e s p e ci fi ca ti o n s s h o u l d i n cl u d e re l i a b i l i ty re q u i re m e n ts fo r th e S S D C a t l e a s t e q u a l to th e re m a i n d e r o f th e co n tro l s , a n d th e fu n cti o n s h o u l d b e fa i l - s a fe Th e S S D C s h o u l d n o t b e co n s i d e re d a s a p ro te cti ve d e vi ce , o n l y a d a m p i n g co n tro l l e r Th e S S D C s h o u l d n o t d e g d e a n y o th e r a s p e cts o f co n ve rte r p e rfo rm a n ce ( i e h a rm o n i cs , fa u l t re s p o n s e , e tc ) S tu d i e s s h o u l d co n s i d e r th e i m p a ct o f S S D C a n d s e ri e s ca p a ci to r co m p e n s a ti o n co n n e cte d i n th e a s s o ci a te d a c s ys te m P e rfo rm a n c e te s ti n g Dampin g p e rfo rm a n ce o f th e S S D C s h o u l d b e ve ri fi e d b y co n d u cti n g a s e ri e s o f co n tro l l e r fi e l d te s ts i n vo l vi n g th e H VD C s ys te m a n d th e a ffe cte d tu rb i n e g e n e to r u n i ts M e a s u re m e n ts o f th e to rs i o n a l vi b ti o n s s h o u l d b e m a d e a t th e g e n e to r u n i ts G a i n m a rg i n o f th e S S D C s h o u l d b e ch e cke d b y m e a s u re m e n t ( i e m e a s u re th e o p e n l o o p tra n s fe r fu n cti o n s th ro u g h th e S S D C a n d th e s ys te m to wh i ch i t i s co n n e cte d ) 8.6 Tu rb i n e g e n e to r p ro te cti o n Based on a co m b i n a ti o n i m p l e m e n ta ti o n wi th fu l l of d e ta i l e d re d u n d a n cy, s ys te m a n a l ys i s , d esi g n of th e th e e xp e ri e n ce fro m o p e ti o n co n tro l s ys te m and o f H VD C s ys te m s wi th i n s ta l l e d S S D C s h a s s h o wn th a t i t i s n o t n e ce s s a ry to i n cl u d e to rti o n a l p ro te cti ve re l a ys To rs i o n a l o s ci l l a ti o n s th a t m a y b e d a m a g i n g to a m a ch i n e ca n n o t b e re l i a b l y a n d d e te cte d a t th e co n ve rte r s ta ti o n B a s e d o n th e m e a s u re m e n ts , a S S TI s e cu re l y s u p e rvi s i o n ca n b e i n cl u d e d i n th e co n tro l s ys te m , wi th th e a b i l i ty to tri p th e H VD C o n b o th l e ve l a n d d e ri va ti ve cri te ri a H o we ve r, a n y tu rb i n e - g e n e to r th a t ca n p o te n ti a l l y i n te ct wi th a n H VD C co n ve rte r s ys te m m a y b e p ro te cte d wi th a to rs i o n a l p ro te cti ve re l a y Copyright International Electrotechnical Commission I E C TR 9 - : 0 + AM D : C S V – 39 –  I EC 201 P o we r p l a n t i n t e c t i o n 9.1 G e n e l Th e cl o s e r a p o we r p l a n t i s co n n e cte d e l e ctri ca l l y to a d c l i n k, th e m o re i t wi l l b e a ffe cte d b y th a t l i n k A g e n e ti n g s ta ti o n m a y fe e d m u ch o r a l l o f i ts p o we r i n to th e re cti fi e r o f a d c tra n s m i s s i o n s ys te m , o r s h a re i ts s u p p l y to a l o a d wi th p o we r b e i n g d e l i ve re d fro m a n i n ve rte r s ta ti o n I f th e l o a d i n g o n th e d c l i n k co m e s d i re ctl y fro m th e g e n e to r o f a p o we r p l a n t, th e re i s b o u n d to b e s i g n i fi ca n t i n te cti o n Th i s s h o u l d b e a d d re s s e d i n th e d e s i g n o f th e d c l i n k a n d a s s o ci a te d a c p o we r s ys te m , i n cl u d i n g th e s p e ci fi ca ti o n o f th e tu rb i n e a n d g e n e to r Wh e re th e p o we r i n te cti o n s g e n e te d d i s cu s s e d in by th i s th e p o we r cl a u s e a re plan t s ti l l al so fe e d s p re s e n t, bu t an a c o th e r l oad or a s p e cts s ys te m , re l a te d th e to th e i n fl u e n ce o f th e a c /d c s ys te m o p e ti o n o n th i s l o a d o r s ys te m s h o u l d a l s o b e co n s i d e re d 9.2 S p e c i fi c i n t e c t i o n s 9.2.1 G e n e l E l e ctri c p o we r i s u s u a l l y g e n e te d fro m a p o we r p l a n t wh i ch d e ri ve s i ts e n e rg y fro m e i th e r h yd ro , th e rm a l o r n u cl e a r s o u rce s I n te cti o n b e twe e n a d c l i n k cl o s e l y a s s o ci a te d wi th a n y o f th e va ri o u s ki n d s o f p o we r p l a n t wi l l l e a d to co m m o n co n ce rn s i d e n ti fi e d i n th i s cl a u s e I n ca s e s wh e re i n te cti o n s m a y a ffe ct a p a rti cu l a r ki n d o f p o we r p l a n t i n a d i ffe re n t o r m o re s e n s i ti ve m a n n e r, s p e ci fi c re fe re n ce i s m a d e a cco rd i n g l y I t s h o u l d b e a p p re ci a te d th a t a c tra n s m i s s i o n s ys te m s , a s a n a l te rn a ti ve to d c tra n s m i s s i o n , i n te ct wi th d oes not g e n e to rs mean , wi th h o we ve r, si m i l ar an d th a t d c link eq u al co n ce rn s a s p re s e n te d i n te cti o n s wi th a p o we r in th i s cl a u s e plan t sh ou l d Th i s not be co n s i d e re d i n p re p a ri n g a s p e ci fi ca ti o n fo r a d c l i n k 9.2.2 F re q u e n c y va ri a t i o n G e n e to rs sh ou l d d e te rm i n e d e ffe c t s o p e te wi th i n a s p e ci fi c fre q u e n cy n g e , th e l i m i ts of wh i ch a re a c p o we r s ys te m P o we r l o s s i n th e d c tra n s m i s s i o n s ys te m b e ca u s e o f co m m u ta ti o n fa i l u re , fa u l ts o r va l ve g ro u p b y wh e th e r i t i s s yn ch ro n o u s o r a s yn ch ro n o u s to th e m a i n b l o cki n g wi l l re s u l t in fre q u e n cy e xcu rs i o n s in th e p o we r p l a n t E xtre m e fre q u e n cy o ve rs h o o t wi l l o ccu r wh e n th e d c l i n k co m p l e te l y b l o cks a n d th e re i s n o a l te rn a te p a th fo r th e p o we r fro m th e g e n e ti o n to re a ch th e l o a d , re s u l ti n g i n fu l l l o a d re j e cti o n fo r th e p o we r p l a n t A m o re s e ve re s tre s s o n g e n e to rs i s i m p o s e d wh e n th e y a re i s l a n d e d wi th a d c i n ve rte r a n d s e p a te d fro m th e l o a d E l e ctri c p o we r re ve rs a l a t th e g e n e to r, d u e to p o we r fe d to i t fro m th e i n ve rte r th a t i s n o t p ro te cte d b y a d c l i n k p o we r o rd e r re d u cti o n , co u l d l e a d to ro to r d am ag e S tu d i e s s h o u l d b e u n d e rta ke n to e xa m i n e i n d e ta i l th e co n s e q u e n ce s o f d c l i n k o u ta g e s T h e p o we r s ys te m sh ou l d be plan ned s o th a t fu l l d c l i n k l oad re j e cti o n i f i t o ccu rs , d oes n ot i m p a ct o n th e p o we r p l a n t b e yo n d i ts d e s i g n l i m i ts Th e typ e o f p o we r p l a n t, wh e th e r h yd ro , th e rm a l o r n u cl e a r, wi l l d i cta te wh a t a d d i ti o n a l tra n s m i s s i o n fa ci l i ti e s a n d p ro te cti o n s ys te m s wi l l b e e s s e n ti a l to l e s s e n th e i m p a ct o f a d c l i n k fu l l l o a d re j e cti o n o n i t N u cl e a r p l a n ts m a y re q u i re th e m o s t s tri n g e n t l i m i ts o n tra n s m i s s i o n d e s i g n fo r p ro te cti o n a g a i n s t fu l l d c l o a d re j e cti o n b e ca u s e o f th e l e n g th y d e l a y i n re s u m i n g fu l l p o we r p ro d u cti o n An H VD C s ys te m wh i ch tra n s m i ts a m a j o r p a rt o f th e p o we r o f a n u cl e a r p l a n t to th e l o a d s h o u l d b e d e s i g n e d wi th h i g h re l i a b i l i ty F o r p o l e o u ta g e s , o ve rl o a d ca p a b i l i ty o n th e re m a i n i n g p o l e ( s ) s h o u l d b e co n s i d e re d to a vo i d g e n e to r p l a n t s h u td o wn o r fa ci l i ta te a n o rd e rl y p o we r re d u cti o n i n th e p l a n t 9.2.3 F re q u e n c y c o n t ro l s i n t e c t i o n s Ve ry l o w fre q u e n cy i n s ta b i l i ty ( b e l o w , H z ) ca n d e ve l o p a s a n i n te cti o n b e twe e n m a ch i n e s p e e d co n tro l b y tu rb i n e g o ve rn o rs a n d th e d c tra n s m i s s i o n s ys te m i f n o p a rti cu l a r m e a s u re s a re ta ke n to Copyright International Electrotechnical Commission co o rd i n a te th e m S tu d i e s and te s ts to o p ti m i z e g o ve rn o r s e tti n g s ca n be – 40 – I EC TR 6091 9-3: 2009+AM D1 : 201 CSV  I EC 201 u nd ertaken H VDC l i nk trol s can also be d eveloped to tri bu te to th e d ampin g at these i n stabi l i ti es by th e ad d iti on of special trol l oops respond in g to measu red in cremen tal freq u en cy of th e a c systems Fu rther in formati on i s avai lable i n Clau se 9.2.4 O ve rvo l t a g e e ffe c t s DC li nk l oad rej ecti on overvol tag es wil l affect a power pl an t wh en th e load rej ecti on is al so tran sferred to i ts gen erator Overvol tag es can d amag e th e g en erators an d oth er eq u ipmen t if fi l ters an d sh u n t capacitor ban ks remain on after l oad rej ection Overvol tag es on the au xi l i ary servi ce motor and exci tati on system h ave to be speci al l y born e in d Th ere is a possi bi l i ty of sel f-exci tation of the gen erator on l oad rej ecti on u n l ess su i table cross trippi n g i s i n corporated i n to th e system d esi gn Combi n i ng verter bl ockin g trols wi th tri ppi ng of fi l ters an d sh u n t capaci tor ban ks may be req u i red Wh en circu it-breakers are req u i red to cl ear a c fi l ter an d sh u n t capaci tor banks u n d er d i ti ons of l oad rejecti on overvol tag es and sel f-exci tati on , breaker ratin g sh ou ld be sized to accommod ate th e stresses i mposed as d i scu ssed in of I EC 6091 9-2: 2008/AM D1 : 201 Th e sensi ti vi ty and speed of protection for swi tch i ng fi lter and capaci tor ban ks u nd er d i ti ons of sel f-exci tati on sh ou l d be ad eq u ate to protect mach in e an d stati on eq u i pmen t ag ain st the overvol tag es an d also d i scrimi nate between a temporary and permanen t d c l i n k l oad rej ection Th i s is becau se removal of fi l ters an d capaci tors throu g h a temporary d c l in k sh u td own may l eave th e system wi th i n ad eq u ate reacti ve power su pport to fu l l y recover its pre-d istu rban ce power l evel I n su ch cases, the swi tch in g back i n of fi l ters an d capaci tors sh ou l d be carefu l l y coord in ated wi th eq u ipmen t capabi l iti es an d d c li n k recovery seq u ences, particu larl y wh en the d u rati on of th e temporary ou tage is to be mi ni mi zed Th e combin ation of a g enerator stati on and an H VDC su bstati on may exh ibi t l ow d ampin g on th e a c si d e i n cases wh ere l ocal a c l oad i s small or non -exi sten t U n d er su ch ci rcu mstan ces, resonan ces, overvol tag es and tran si en t recovery vol tages for circu i t-breakers may req u i re speci al attenti on 9.2.5 H a rm o n i c s Ch aracteristic an d n on -ch aracteristi c h armon ic cu rren ts g en erated from a verter station n ot ad eq u atel y fi l tered and d amped may fl ow i n to th e gen erator U n d esi rabl e mech an i cal vi brati on s may resu l t i n h yd ro and th ermal u n i ts, as wel l as d evel op in tern al h eati ng , parti cu l arl y on th e rotor I n both i nstan ces, d amag e can be cau sed An tici pated or permi tted h armon i c l oad i n g in to g enerators at or cl ose to d c l in ks shou l d be d etermi ned an d u sed as i npu t to g en erator speci fi cati ons an d a c fil ter d esi gn Fu rth er d i scu ssion is fou n d in Cl au se of I EC 6091 9-1 I n the case of a steam tu rbi n e g en erator, special atten ti on sh ou l d be g i ven to th e magn i tu d e of the fi fth an d seven th h armon i cs Th is i s of special concern becau se the i n teraction of th e mag n etic field prod u ces a pu lsati ng torq u e at th e si xth h armon ic on the rotor I f coin cid en t wi th a su persyn ch ronou s mech ani cal reson an t freq u ency i n vol vi ng torsion al osci ll ation s of th e rotor el emen ts and flexin g of th e tu rbi n e bu ckets, fati g u e i n th e tu rbi ne sh afts an d bu ckets may resu l t 9.2.6 S u b s yn c h ro n o u s a n d s h a ft i m p a c t e ffe c t s Su bsyn chron ou s effects can be d ang erou sl y i mposed u pon th e g enerator, sh aft an d tu rbi ne as d i scu ssed i n Clau se Su bh armon ic cu rren ts g enerated by certai n types of d i esel g en erators can i n teract wi th d c l i nks I f su ch a probabi l i ty exists, system tests sh ou l d be u nd ertaken to d etermi ne th e su bsysch ron ou s presen t i n th e system, an d su ch in formati on provid ed in th e speci ficati on so th at d ampin g can be d esig n ed i n to the trols of the d c l in k A related probl em is th e i mpact on a sh aft of a g en erator of th e step ch an g e i n torq u e wh ich can resu l t from a d c li n k load rejecti on or even from a commu tation fai lu re Even i f th e resu l ti n g mech an i cal oscil lations between masses on th e tu rbi ne an d g en erator sh aft are d amped , some loss of sh aft l i fe may occu r Th erm al an d n u cl ear pl an t may be most sen si ti ve Copyright International Electrotechnical Commission I E C TR 9 - : 0 + AM D : C S V – 41 –  I EC 201 to th i s co n ce rn Th e p o te n ti a l fo r co m m u ta ti o n fa i l u re s co n tri b u ti n g to l o s s o f s h a ft l i fe s h o u l d b e m i n i m i z e d i f th i s i s i d e n ti fi e d a s b e i n g a p o s s i b l e p ro b l e m S h a ft i m p a ct e ffe cts a re also ca u s e d wh e n d c l i n k re s ta rt s e q u e n ce s a re a d o p te d u n s u cce s s fu l re s ta rt ca n i m p o s e a d d i ti ve s tre s s e s to th e s h a ft o f a tu rb i n e g e n e to r e ffe ct s h o u l d b e s tu d i e d and a n ti ci p a te d in th e s p e ci fi ca ti o n o f th e d c E a ch Th i s l i n k i n s o fa r a s th e re s ta rt s tra te g y i s co n ce rn e d 2.7 Re s o n a n ce Th e co n fi g u ti o n o f th e a c s ys te m i n te rco n n e cti n g th e p o we r s ta ti o n a n d co n ve rte r, u s u a l l y i n vo l vi n g s h o rt l i n e s , g re a t co n ce n tra ti o n o f re a cti ve p o we r e q u i p m e n t, e tc h a s a p o te n ti a l ri s k o f p ro n o u n ce d re s o n a n ce co n d i ti o n s a n d a ve ry l o w d e g re e o f d a m p i n g 2.8 O ve rvo l ta g e s As a re s u l t o f th e re s o n a n ce co n d i ti o n s i n d i ca te d i n a b o ve , a s we l l a s th e l o w d e g re e o f d am pi n g , te m p o ry co n s i d e re d Am o n g o ve rvo l ta g e s o th e r th a n th o s e th e s e o ve rvo l ta g e s th a t ca n ca u s e d by b e m e n ti o n e d l oad a re a c re j e cti o n sh al l fa u l t cl e a ri n g be o ve r- vo l ta g e s a n d o ve rvo l ta g e s re s u l ti n g fro m tra n s fo rm e r e n e rg i z a ti o n 9.2.9 S tre s s e s i n a c s wi tch i n g e q u i p m e n t I n a d d i ti o n to th e p ro b l e m s d i s cu s s e d i n a b o ve , th e a c s ys te m co n fi g u ti o n wi th s h o rt l i n e s m e n ti o n e d i n m a y i m p o s e tra n s i e n t re co ve ry vo l ta g e ( TRV) re q u i re m e n ts a b o ve th e s ta n d a rd va l u e s fo r th e ci rcu i t- b re a ke r to b e u s e d i n th i s a p p l i ca ti o n 2.1 U n d e r-fre q u e n c y U n d e r- fre q u e n cy co n d i ti o n s a s a re s u l t o f a m a j o r d i s tu rb a n ce , s u ch a s th e l o s s o f g e n e ti o n u n i ts , s h o u l d a l s o b e co n s i d e re d 9.2.1 S ta rti n g p ro ce d u re fo r a n H VD C co n ve rte r C o n s i d e ti o n sh ou l d b e g i ve n to fre q u e n cy re g u l a ti o n o f th e s e n d i n g en d s ys te m an d th e g e n e to r re a cti ve p o we r ca p a b i l i ty re q u i re m e n ts d u ri n g th e s ta rt- u p p ro ce d u re o f a co n ve rte r u n i t 9.3 S p e c i a l co n s i d e ti o n s fo r a n u cl e a r p l a n t Th o s e ch a cte ri s ti cs re l a te d to p ro te cti ve re l a ys wh i ch ca n ca u s e a n u cl e a r re a cto r s cra m s h o u l d b e m o d e l l e d i n d e ta i l i n s i m u l a ti o n s tu d i e s I f a s te a m b yp a s s ca p a ci ty i s a s m u ch a s a re a cto r ca p a ci ty, a d i s tu rb a n ce i n a d c s ys te m o r re ce i vi n g e n d a c s ys te m m a y n o t ca u s e a re a cto r s cra m Wh e n s tu d yi n g m e ch a n i ca l s u b s yn ch ro n o u s re s o n a n ce re s o n a n ce fre q u e n cy o f a ph en om en a, l o we r th a n th a t o f o th e r typ e s o f s te a m tu rb i n e - g e n e to rs Copyright International Electrotechnical Commission it tu rb i n e - g e n e to r o f a sh ou l d be n o te d th a t n u cl e a r p o we r u n i t i s th e u su al l y – 42 – I E C TR 9 - : 0 + AM D : C S V  I EC 201 B i b l i o g p h y [1 ] “G u i d e fo r P l a n n i n g D C L i n ks Te rm i n a ti n g a t A C S ys te m L o ca ti o n s H a vi n g Low S h o rt C i rcu i t C a p a ci ty” C I G RE d o cu m e n t TF - /I E E E , P a rts I a n d I I [2 ] AN D E RS S O N G., S VE N S S O N S , LI SS G., D i g i ta l “ an d An a l o g S i m u l a ti o n of I n te g te d A C a n d D C P o we r S ys te m s ” C I G RE p a p e r - , [3 ] G RU N D C E , P O L L ARD E.M., P AT E L H., N I LSSON S L , RE E VE J., “ P o we r M o d u l a ti o n C o n tro l s fo r H VD C S ys te m s ” C I G RE p a p e r - , [4 ] “ Te n ta ti ve C l a s s i fi ca ti o n and T e rm i n o l o g i e s Re l a ti n g to S ta b i l i ty P ro b l e m s o f P o we r S ys te m s ” E l e ctra , N o , J a n , p p - [5 ] “ A C H a rm o n i c Re fe re n ce to F i l te rs and Re a cti ve C o m p e n s a ti o n N o n - ch a cte ri s ti c H a rm o n i cs ” C I G RE fo r H VD C p u b l i ca ti o n no wi th 65 P a rti cu l a r June 990 C o m p l e m e n t to th e E l e ctra p a p e r o f i s s u e ( 9 ) [6 ] KAU F E RL E J , S AD E K K , KO E L S C H , A C “ S ys te m Re p re s e n ta ti o n Re l e va n t to A C F i l te ri n g a n d O ve rvo l ta g e s fo r H VD C Ap p l i ca ti o n ” C I G RE p a p e r - , [7 ] S AL G AD O E , LI M A A C G , P I L O T TO L A S , S Z E C H TM AN M., C U ARI N I A P , RO I TM AN M , “ T e ch n i ca l a n d E co n o m i c As p e cts o f th e U s e o f H VD C C o n ve rte rs a s Re a cti ve P o we r C o n tro l l e rs ” C I G RE p a p e r - , [8 ] G AVRI L O VI C A , “ I n te cti o n B e twe e n A C a n d D C S ys te m s ” C I G RE p a p e r - , 986 [9 ] L AM B AI E T , H O L M B E RG J AAS KE L AI N E N D., J ON SSON U., AU RAN N E E., H AG M AN E , K , “ F e n n o - S ca n H VD C L i n k a s a P a rt o f I n te rco n n e cte d A C /D C S ys te m ” C I G RE p a p e r - , 8 [1 ] T AAM M., E RI KS S O N P RAC A K , A S , “ I ta i p u P O RAN G AB A H VD C F D , Tra n s m i s s i o n DE S ys te m TO L E D O P ri n ci p a l F , M E N ZI E S As p e cts D., o f A C /D C I n te cti o n ” C I G RE p a p e r - , 8 [1 ] YAN G YU , QI U WE I , Z H AO XI AO - B I N , DEN G JING, WAN G XI - TI AN , " E va l u a ti o n of ±5 0 kV S u b s yn ch ro n o u s O s ci l l a ti o n o f Xi l u o d u Ri g h t S ta ti o n – G u a n g d o n g D o u b l e l i n e D C Tra n s m i s s i o n P ro j e ct” , I E E E I n te rn a ti o n a l C o n fe re n ce o n P o we r S ys te m Te ch n o l o g y ( P O WE RC O N ) , 2 _ Copyright International Electrotechnical Commission Copyright International Electrotechnical Commission INTERNATIONAL ELECTROTECHNICAL COMMISSION 3, rue de Varembé PO Box 31 CH-1 21 Geneva 20 Switzerland Tel: + 41 22 91 02 1 Fax: + 41 22 91 03 00 info@iec.ch www.iec.ch Copyright International Electrotechnical Commission