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Christoph Haederli - Les thèses en ligne de l'INP - Institut National ...

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76 3-L DC Link ML Converter Properties<br />

and maximum NP curr<strong>en</strong>ts can easily be <strong>de</strong>termined by the known NP curr<strong>en</strong>t function in each<br />

operating point as pres<strong>en</strong>ted in the previous paragraph.<br />

TABLE 23, MINIMUM AND MAXIMUM NP CURRENT IN DIFFERENT OPERATION POINTS APPLYING<br />

STANDARD MODULATION SCHEMES, APPLIES TO ALL TYPE OF 3-L DC LINK CONVERTERS<br />

cos(ϕ)=1<br />

cos(ϕ)=0.81<br />

(inductive)<br />

cos(ϕ)=0<br />

(inductive)<br />

I NP-min<br />

m * 2<br />

3<br />

θ<br />

m * 2<br />

3<br />

θ<br />

m * 2<br />

3<br />

θ<br />

I NP-max<br />

m * 2<br />

3<br />

θ<br />

m * 2<br />

3<br />

θ<br />

m * 2<br />

3<br />

θ<br />

App<strong>en</strong>dix 9.5.1 gives an overview of maximum and minimum NP curr<strong>en</strong>ts in differ<strong>en</strong>t<br />

operating points.<br />

4.7.3 Zero average NP curr<strong>en</strong>t areas in function of CM<br />

Zero NP curr<strong>en</strong>t operation is <strong>de</strong>sirable to keep the low frequ<strong>en</strong>cy NP voltage ripple as low as<br />

possible. Limits of the zero average NP curr<strong>en</strong>t can easily be <strong>de</strong>termined from the NP curr<strong>en</strong>t<br />

function. If the NP curr<strong>en</strong>t function crosses the zero line within the allowable operating range of<br />

the CM voltage (e.g. as in Figure 61), zero neutral point curr<strong>en</strong>t operation is possible in the giv<strong>en</strong><br />

operating point with the appropriate CM voltage. If it does not cross the zero line, zero NP curr<strong>en</strong>t<br />

is not possible. Figure 63 shows the zero average NP curr<strong>en</strong>t limits for a variety of load angles.

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