15.05.2015 Views

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 ...

SHOW MORE
SHOW LESS

You also want an ePaper? Increase the reach of your titles

YUMPU automatically turns print PDFs into web optimized ePapers that Google loves.

NP Control with Carrier based PWM 91<br />

For best NP voltage control, the controller always applies the CM with the lowest possible NP<br />

curr<strong>en</strong>t in case of zero NP voltage offset. However, it doesn’t necessarily have to be that way. A<br />

strategy with a non minimum NP curr<strong>en</strong>t ripple can be chos<strong>en</strong> instead, for example to minimize<br />

losses or output curr<strong>en</strong>t distortion. The zero NP-voltage-offset operating point (see also glossary) can be<br />

chos<strong>en</strong> quite flexibly. A NP voltage feedback controller will th<strong>en</strong> acts from this zero NP-voltageoffset<br />

operating point by adding or subtracting a suitable CM value as a function of NP voltage<br />

offset and controller gain.<br />

The zero NP-voltage-offset operating point varies over time and <strong>de</strong>scribes a trajectory<br />

according to the black lines in the graphs of TABLE 30. The three columns <strong>de</strong>scribe differ<strong>en</strong>t<br />

strategies for the <strong>de</strong>finition of the zero NP-voltage-offset operating point trajectory over θ. Note<br />

that the four graphs in a giv<strong>en</strong> column <strong>de</strong>scribe the same function from a differ<strong>en</strong>t viewpoint. This<br />

type of repres<strong>en</strong>tation is used as a standard in all tables of that kind throughout the thesis.<br />

1.00<br />

NP curr<strong>en</strong>t<br />

0.50<br />

0.00<br />

-0.50<br />

NP curr<strong>en</strong>t<br />

Range<br />

Min. U-CM<br />

CSPD PWM<br />

Min. I-NP<br />

-1.00<br />

-1 -0.5 0 0.5 1<br />

s CM<br />

Figure 66, Differ<strong>en</strong>t zero NP-voltage-offset operating points for m = 0.95, ϕ = 0.86, θ = 1.67<br />

TABLE 29, DEFINITION OF REAL TIME NP CURRENT FUNCTION CONTROL SCHEME<br />

1. Determine maximum and minimum NP curr<strong>en</strong>t points of piecewise linear NP curr<strong>en</strong>t<br />

function.<br />

2. Constrain the CM to the range betwe<strong>en</strong> the values g<strong>en</strong>erating maximum and minimum<br />

NP curr<strong>en</strong>t.<br />

3. Determine a suitable zero NP-voltage-offset operating point for the feedback controller<br />

a. Optimization for bearing curr<strong>en</strong>t minimization: Lowest possible CM voltage<br />

(TABLE 30 [a])<br />

b. Optimization for DC link <strong>de</strong>sign: Lowest possible NP curr<strong>en</strong>t (TABLE 30 [b])<br />

c. Optimization for DM waveforms (harmonic standards for AFE, motor losses<br />

in drives): Use of primary modulator of choice (e.g. CSPD PWM, TABLE 30<br />

[c] or 3 rd harmonic injection, offline optimized patterns etc.)<br />

4. Determine the gain for the feedback controller<br />

a. Tra<strong>de</strong> off betwe<strong>en</strong> NP control dynamics and steady state performance<br />

according to the criteria un<strong>de</strong>r point 3 (a – c).

Hooray! Your file is uploaded and ready to be published.

Saved successfully!

Ooh no, something went wrong!