Christoph Haederli - Les thèses en ligne de l'INP - Institut National ...
Christoph Haederli - Les thèses en ligne de l'INP - Institut National ...
Christoph Haederli - Les thèses en ligne de l'INP - Institut National ...
You also want an ePaper? Increase the reach of your titles
YUMPU automatically turns print PDFs into web optimized ePapers that Google loves.
ML Converter Topologies 35<br />
TABLE 16, MAXIMUM NUMBER OF PARALLEL CURRENT PATHS AND PARALLEL CURRENT PATH RATIO<br />
MLDC MC SMC<br />
Note 1<br />
ANPC 1<br />
SCx+FCx<br />
ANPC 2<br />
FCx+SCx<br />
ANPC 3<br />
FCx+FCx<br />
FSx+FCx FC2 *<br />
x<br />
M 2 LC<br />
Max.<br />
number<br />
of paths<br />
2*N<br />
(dio<strong>de</strong>s)<br />
2 3 4 4 4 2*N N 4<br />
Max.<br />
divi<strong>de</strong>d<br />
by Min.<br />
number<br />
of paths<br />
N 1 1 (full)<br />
1.5<br />
(NPC<br />
output)<br />
2 2 2 N N/2 1 (full)<br />
2 (shared)<br />
output<br />
cell)<br />
Note 1: including the ANPC variations in Figure 31 (c) – (e) and Figure 32<br />
The MC provi<strong>de</strong>s the most favorable configuration regarding parallel paths and resulting loss<br />
distribution. MC converter and casca<strong>de</strong>d H-bridge converter have inher<strong>en</strong>tly balanced losses in all<br />
<strong>de</strong>vices; all others have differing curr<strong>en</strong>t distribution at low and high modulation <strong>de</strong>pth. Also active<br />
schemes cannot fully balance the resulting losses. The SMC and its variations also provi<strong>de</strong> a low<br />
number of maximum parallel paths and allows for <strong>de</strong>signs with a constant number of paths. All<br />
ANPC variations have a higher maximum path number and always inclu<strong>de</strong> sections with differ<strong>en</strong>t<br />
path numbers. However, the maximum number of paths is constant and does not scale with N as<br />
for some other topologies. In addition, the strategies proposed above provi<strong>de</strong> reasonable switch<br />
usage by proper balancing of the losses. The M 2 LC provi<strong>de</strong>s a constant number of parallel paths in<br />
all sections; on the other hand, the total number of switches is high.<br />
3.7.2.1 Total semiconductor losses<br />
Overall semiconductor losses are very similar in all of the pres<strong>en</strong>ted topologies for a giv<strong>en</strong><br />
average <strong>de</strong>vice switching frequ<strong>en</strong>cy. This can be stated without <strong>de</strong>tailed calculation based on the<br />
following two assumptions:<br />
1. The curr<strong>en</strong>t path is always through N switching <strong>de</strong>vices (as there are N sections, see Figure<br />
23), either active switch or dio<strong>de</strong>, in<strong>de</strong>p<strong>en</strong>d<strong>en</strong>tly of topology. The share betwe<strong>en</strong> IGBT<br />
and dio<strong>de</strong> may vary slightly, but will have no significant impact on the overall conduction<br />
losses. All topologies perform very similar in that respect, unless a differ<strong>en</strong>t switch<br />
dim<strong>en</strong>sioning (silicon area) is used.<br />
2. A change of one output level involves a commutation from one IGBT to one dio<strong>de</strong> or<br />
vice versa for all topologies. A giv<strong>en</strong> output voltage waveform <strong>de</strong>fines the number of<br />
commutations for all topologies, resulting in similar overall switching losses for all<br />
topologies.<br />
Nevertheless, the consi<strong>de</strong>red topologies may vary a lot regarding loss distribution (as pres<strong>en</strong>ted<br />
above) and the total switching losses: The <strong>de</strong>sign of differ<strong>en</strong>t topologies may not be optimized for<br />
the same average switching frequ<strong>en</strong>cy. To minimize capacitance, all cells g<strong>en</strong>erating single level<br />
steps should be operated at high frequ<strong>en</strong>cy, whereas cells g<strong>en</strong>erating multiple level steps should be<br />
operated at low frequ<strong>en</strong>cy. This means that topologies with a large number of high frequ<strong>en</strong>cy<br />
switching cells are likely to g<strong>en</strong>erate higher losses. E.g. the ANPC 3 will g<strong>en</strong>erate more losses than