vacon • 155 Parameters
6
P&O in local max points
A panel with partial irradiation, or somehow defective, could cause a discontinuity on the pow-
er/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 58.
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= 0V.
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 programmable 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.
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
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