Pos. Description
A Power from PV array (W)
B Voltage across PV array (V)
C Global maximum point
D Local maximum points
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
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.
MPPT Oscillation Damping
If the power regulation enters the "current source"
branch of the panel current/voltage characteristic, the
typical result is a oscillation in DC voltage and output
frequency. The damping logic recognizes oscillation in
DC voltage and quickly increases the voltage
reference correction term. This brings the panels
back in "voltage source" branch.
P3.22.2.14 Damping sensitivity
P3.22.2.14 parameter determines the amplitude of
oscillation, to be recognized.
If the value is too low, normal variation in voltage level
could be considered oscillation, and the DC voltage
reference incorrectly increased.
P3.22.2.15 Damping time
Oscillation is recognized when the logic sees three
maximum and minimum point during the time defined
by P3.22.2.15.
If the time is too short, the logic could fail with slow
oscillations.
If the time is too long, spaced and unrelated min and
max points could be confused with an oscillation.
P3.22.2.16 Minimum DC voltage
The value depends on the voltage range.
Voltage range
Value Default
230 VAC 230–300 V 230 V
Voltage range Value Default
400/500 VAC
300 (new
xml)/410 (old
xml)–600 V
410 V
525/690 VAC 530–800 V 530 V
The value (+ 5 V) is also used as the minimum limit
for the DC voltage related parameters P3.22.1.1,
P3.22.2.1, P3.22.2.2.
8.2.24 Dual supply parameters
Common settings
P3.24.1.1 AC Voltage
Nominal voltage of AC grid.
V3.24.1.2 Nominal DC Voltage
Monitor of calculated value of nominal DC voltage,
when supply is from AC grid.
P3.24.1.3 Dual supply Mode
• 0 - Always active
• 1 - Closed loop Irradiation
• 2 - Closed loop Sensorless
P3.24.1.4 DC Offset for AC Off
Offset added to M3.24.1.1, as DC voltage threshold
above which AC can be switched Off. If DC value is
above threshold, it means that the PV modules can
sustain the full power, in present motor working
condition.
P3.24.1.5 AC Off at Stop Delay
Delay to switch AC Off at stop, if it happened with AC
On condition.
Mode 0 always active
In mode 0, relay for AC supply is always On when
pump is running. There are two possible conditions,
to switch the relay On.
P3.24.2.1 AC On Condition
At Run: as AC switch relay is Off at power-on, the
drive must start from PV modules supply, after that
the relay is immediately switched On. AC grid backup
will avoid further stops, in case of low power from
modules.
At Start: external Start signal is sufficient condition to
switch the relay On and connect to AC grid. This can
happen also if the drive is powered up with only
backup 24V on control board.
Mode 1 irradiation
In mode 1, relay for AC supply is managed
accordingly to measurement of irradiation from
analogue signal.
There is an absolute minimum threshold for switching
On, and an offset added to this as threshold to switch
Off.
AC relay is switched On also in case of Low Power
alarm at start or Undervoltage fault.
165
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