User Manual

Page 68
PSI 9000 3U Series
www.elektroautomatik.de
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EA Elektro-Automatik GmbH
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Fax: +49 2162 / 16230
3.8.13 PV table function (photovoltaics)
3.8.13.1 Preface
This function uses the standard XY generator to make the power supply simulate
solar panels or solar cells with certain characteristics. The device calculates
an IU table from four typical values.
While the function is running, the user can adjust a parameter “Irradiance”
between 0% (darkness) and 100% (bright light) in 1% steps to simulate differ-
ent light situations.
The most important characteristics of a solar cell are:
• the short-circuit current (I
SC
), which is proportional to the irradiance
• the open circuit voltage (U
OC
), which almost reaches its maximum value
even in low light situations
• the maximum power point (MPP), at which the solar panel can provide the
maximum output power
The voltage of the MPP (here: U
MPP
) lies typically 20% below U
OC
, the current
of the MPP (here: I
MPP
) lies typically 5% below I
SC
.Incasetherearenodenite
values for the simulated solar cell available, Impp and Umpp can be set to this
rule of thumb.
The device limits the I
MPP
value to I
SC
as upper limit, the same applies for U
MPP
and U
OC
.
3.8.13.2 Safety notices
Due to high capacities on the DC outputs of the power supplies of this series, not every
available solar inverter can be operated without problems. Check the technical speci-
cations of the solar inverter and probably contact the manufacturer for an evaluation. In
case option HS is installed in the device (see „1.10.5. Options“), the result of operating
critical inverters can be optimised.
3.8.13.3 Usage
InthePVtablefunction,whichisbasedupontheXYgeneratorwithIUcharacteristics,theMPPisdenedbythe
two adjustable parameters Umpp and Impp (also see diagram below). These parameters are usually stated in data
sheets of solar panels and have to be entered here.
The following parameters can be set for the PV table function:
Value Range Description
Uoc Umpp...Nominal device voltage Open circuit voltage at no load
Isc Impp...Nominal device current Short-circuit current at max. load and low voltage
Umpp 0 V...Uoc DC output voltage at the MPP
Impp 0 A...Isc DC output current at the MPP
Schematic diagram: Application and result:
U
I
Isc
Uoc
MPP
Impp
Umpp
Adjust all four parameters on screen to the desired values. Whether the
calculated IU and P curves, which result from those values, make sense or
notcanbeveriedwithatool(Exceltableorsmallsoftware),whichiseither
included with the device on CD or can be obtained upon request. The tool
visualises the curves as calculated from the adjusted values.
While the simulation is running, the user can see from the actual values
(voltage, current, power) of the DC output, where the operating point of the
power supply resp. of the simulated solar panel is. The adjustable value Ir-
radiance (0%...100% in 1% steps, see screenshot below) helps to simulate
different light situations from darkness (no power output) to the minimal
amount of light that is required to make the panel provide full power.