Parameters vacon • 154
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6
MPPT correction parameters
This algorithm changes the DC voltage reference, to compensate temperature variations (usu-
ally slow) and to correct the error in feed-forward curve.
Correction can be up to +/- 150V.
The correction term is determined by ”perturb-and-observe” logic (P&O).
P3.22.2.8 P&O
UPDATE TIME
P3.22.2.9 P&O VOLTAGE STEP
DC voltage reference is periodically (at intervals defined by P3.22.2.8) increased or decreased
by a small value (P3.22.2.9). If the variation brings a higher motor power, next variation will fol-
low the same direction, otherwise it will be reversed.
A short perturb period (P3.22.2.8) makes the regulation faster, assuming that the PI gains are
not too low (power variation has to complete within the period).
The correction term can be monitored (V2.2), to help the tuning of reference feed-forward.
When the panels temperature is close to standard, 25°C, the correction term should result
small (+/- 20 to 30V).
The correction decreases towards negative maximum as temperature increases.
The correction term increases towards positive maximum in case of low temperature.
If something different is observed, feed-forward values should be improved.
P3.22.2.10 P&O
POWER VARIATION
P3.22.2.10 determines the variation in motor power, above which iteration of voltage reference
change continues in the same direction.
Small value leads to a regulation very close to the maximum of the panel curve, with possible
instability. Higher values lead to a more stable point, but with lower efficiency.
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