© EPS Stromversorgung in 2022, this information is subject to change without notice
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30000800_manual_psb_10000_4u_30kw_en_04
3.11.17
MPP tracking function
MPP stands for the maximum power point (see principle view to the
right) on the power curve of solar panels. Solar inverters, when con-
nected to such panels, constantly track this MPP once it has been
found.
The device imitates this behavior in sink mode. It can be used to test
even huge solar panels without having to connect a usually big solar
inverter device which also requires to have a load connected to its AC
output. Furthermore, all MPP tracking related parameters of the load
can be adjusted and it’s thus more flexible than an inverter with its
limited DC input range.
For evaluation and analysis purposes, the device can also record
measured data, i. e. DC input values such as actual voltage, current or
power, to USB stick or provide them for reading via digital interface.
The MPP tracking function offers
four modes
. Unlike with the man-
ual handling of other functions, values for the MPP tracking are only
entered by direct input via the touch screen.
3.11.17.1 Mode MPP1
This mode is also called “Find MPP”. It’s the simplest option to have
the device find the MPP of a connected solar panel. It requires to set
only three parameters. Value U
OC
is necessary, because it helps to
MPP
Po
w
er
Voltage
find the MPP quicker as if the device would start at 0 V or maximum voltage. Actually, it would start at a voltage level slightly
above U
OC
.
I
SC
is used as a upper limit for the current, so the device would not try to draw more current than the panel is specified for.
Following parameters can be configured for tracking mode
MPP1
:
Value
Range
Description
U
OC
(open circuit voltage)
0...
U
Nom
Voltage of the unloaded solar panel, taken from the panel specs
I
SC
(short-circuit current)
0...
I
Nom
Short-circuit current, taken from the panel specs
Tracking interval (Δt)
5...60000
ms
Time between two tracking attempts when finding the MPP
Application and result:
After the three parameters have been set, the function can be start-
ed. As soon as the MPP has been found, the function will stop and
switch off the DC input. The acquired MPP values of voltage (U
MPP
),
current (I
MPP
) and power (P
MPP
) would then be shown in the display.
The time of a function run depends on the parameter Δt. Even with
the minimum setting of 5 ms one run usually takes already a few
seconds.
3.11.17.2 Mode MPP2
This mode tracks the MPP, so it’s closest to the operation of a real
solar inverter. Once the MPP is found, the function won’t stop, but
try to track the MPP permanently. Due to the nature of solar panels
this can only be done below the level of the MPP. As soon as this
point is reached, the voltage starts to sink further and so does the
actual power. The additional parameter
Delta P
defines how much
the power may fall before the direction is reversed and the voltage
starts to rise again until the load reaches the MPP. The result are
zigzag shaped curves of both, voltage and current.
Typical curves are shown in the picture to the right. For the exam-
ple the
Delta P
was set to a quite small value, so the power curve
looks almost linear. With a small
Delta P
the load would always
track close to the MPP.
