Vacon 100 INDUSTRIAL - Page 180

vacon • 180 Parameters
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P&O in local max points
A panel with partial irradiation, or somehow defective, could cause a discontinuity on the power/
voltage curve of the array. In this situation the basic P&O logic (perturb and observe) could lead to
a local maximum point, that is not corresponding to maximum available power.
Figure 70.
P3.22.2.11 P&O LOCAL MAX VOLT STEP
To bypass discontinuity on power/voltage curve of array, after having reached a stable point, the
P&O takes a bigger downward step (P3.22.2.11) in voltage. This step allows to overcome the local
maximum and continue to search for the actual MPP.
If the point is the real MPP, the lower voltage reference will cause a drop in DC voltage and some
oscillations, that are recognized and automatically damped by increasing the DC voltage reference.
The function can be disabled by programming P3.22.2.11= 0 V.
P3.22.2.12 P&O
LOCAL MAX TIME
Further attempts to reach a higher MPP after an unsuccessful attempt will follow only after the pro-
grammable masking time (P3.22.2.12).
P3.22.2.13 P&O LOCAL MAX FREQ
The downward step is done only when output frequency is above minimum frequency + P3.22.2.13.
MPPT Oscillation Damping
If the power regulation enters the “current source” branch of the panel current/voltage character-
istic, the typical result is a oscillation in DC voltage and output frequency. The damping logic rec-
Voltage across PV array (V)
Power from PV array (W)
50 100 150 200
2
1.5
1
0.5
0
2.5
250
3
0
x10
4
P
MAX1
P
MAX2
P
MAX3
Local maximum points
Global maximum point