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 ...
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NP Control with Carrier based PWM 117<br />
1<br />
I NP / I out_peak<br />
Standard SMC<br />
SMC A alone<br />
SMC B alone<br />
-0.5 0.5<br />
U CM / U DC<br />
Physical CM limits<br />
Standard and A min.<br />
Standard and A max.<br />
All types min.<br />
All types max.<br />
-1<br />
Figure 78, NP curr<strong>en</strong>t with ext<strong>en</strong><strong>de</strong>d modulation scheme (α = 0.64, ϕ = 1.51, θ = 0.68) in function of<br />
CM voltage<br />
It can be se<strong>en</strong> that the functions for the minimum and maximum NP curr<strong>en</strong>ts are not trivial.<br />
They are piecewise linear functions, but now with up to 3 midpoints per phase, which all g<strong>en</strong>erate<br />
singularities in the resulting function. As there are three phases and each phase can make use of a<br />
differ<strong>en</strong>t modulation scheme, there are a total of 27 individual NP curr<strong>en</strong>t functions per operating<br />
point. All these 27 functions have up to 9 singularities. This is a level of complexity that can easily<br />
be calculated online if required for a giv<strong>en</strong> control scheme (see also 5.1.2 on NP control with real<br />
time NP curr<strong>en</strong>t function).<br />
5.3.3 NP control<br />
The previous paragraph has shown the impact of the differ<strong>en</strong>t modulation schemes on the NP<br />
curr<strong>en</strong>t. Dynamic application of these schemes can be used to control the NP voltage. The<br />
following scheme applies to the SMC, a very similar scheme would be possible for the ANPC type<br />
3 making use of the differing NP curr<strong>en</strong>t function as shown in Figure 72. The proposed scheme<br />
does not make use of CM injection at all. It only makes use of the differ<strong>en</strong>t modulation types to<br />
control the NP.<br />
5: Standard and B<br />
Modulation<br />
type<br />
4: Standard and A<br />
3: Standard only<br />
2: Standard and A<br />
Delta U_NP<br />
1: Standard and B<br />
T1 T2 T3 T4 T5 T6<br />
Figure 79, Hysteresis NP-voltage controller for SMC (thresholds: T1 to T6)<br />
A hysteresis controller for the SMC with six thresholds is proposed. It is acting on a state<br />
machine with 5 states (Figure 79). The modulation type is th<strong>en</strong> <strong>de</strong>termined dynamically according