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发表于 2009-11-16 11:53:02
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本帖最后由 yizhangsjtu 于 2009-11-16 12:00 编辑
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回复 1# bcpan118
, T3 s4 M, u: Y) v( E/ B6 aSorry I cannot write Chinese in this computer. But I would like to comment on the question you raised, as this topic might confuse many people.
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The question itself on UHVDC is kind of new, but the property of voltage stability of HVDC won't have any change if it is UHV. Choosing such topic seems attract eyeball but in fact causes extra confuse for students. Atucally HVDC AC has more special problem. While in UHVDC, the hard things are main on insulation and equipment. There is no speical on anything about voltage stability.; X% c, o8 D6 u7 }# [
: K3 M: A1 L$ `. wLet me be clear here. 8 @% E" I4 ^: d1 n; A
+ N3 P: L. r; [7 g6 C2 w: M( [( I1. The voltage stabilty (often means steady state ability) of HVDC system should be understood in 2 different aspects. - a7 o. i- K+ K. S/ W- U
(1) One is the power stability. The HVDC has no angle stabilty problem. The so call stability problem of HVDC is a control stability, in which the maximum available power (MAP) transfer is started.1 Q, {/ W: _. p/ j3 i/ S/ D# G
/ J- W# h' m& M4 s6 u2 _9 |. g(2) The other is seen from AC side. DC is a nonlinear load from AC side, which has its special impact on PV curve of AC side.( C( ^. Z4 ?* E! h
4 _5 d& _: N7 `7 t$ B( Y* R% ~Those two problems are different, and they have different Pmax and Qmax. Reach either of them will lead to instability.5 q' Y$ |! d6 M- j5 v, H
# S8 V U+ x5 y/ ?* T2. Transient voltage stability
: `1 u2 M3 I# m0 c# d" nThere is concern from AC side of convert bus transient voltage. Those concerns include over voltage of DC, AC fault, DC block, and AC/DC voltage recovery during and after fault. Different reactive support methods are studied based on EMT type simulation. The reason to use EMT type simulation is the mechanism of the problem is not clear, so there is no good simplified model available for use. Therefore, choosing detail model is a MUST for the current situation.
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2 ]% k. |5 ]7 [As far as I know, there is no transient voltage stability thing in DC side.
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I would like to comment here that the most important thing here is understanding the problem rather than choosing a software and run. As you may understand, the DC is kind of special thing so it is not very accurate modeled in most of the software. That is why people like to choose PSCAD, since its model is detail so the users don't need many knowledge before use it. For those simple model program, as good as TSAT or VSAT, you should understand DC first then you can wisely use it get the result you expect. It is very easy to go into "garbage in and garbage out" here. Very careful prepare work is desired before you start to analyse the DC stability problem.4 e4 X* E. }7 U. i. m. Z" r5 Q
3 O' m) y# G9 i# d) qThe hard thing is the DC is not well taught in any text book. As someone mentioned before, Taylor's book has charpter on this issue. This charpter is all correct and well written. However, it has same issue as above. The readers need good back ground to understand it. It is too brief and contains too much things.& C! _; ]# B, p1 n- \/ o
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Spent 45 minutes, Hope 版主 加精华, heheh... |
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