Page 76
EPS Stromversorgung GmbH
Alter Postweg 101 • 86159 Augsburg
Germany
Fon: +49 821 / 570451-0
Fax: +49 821 / 570451-25
www.eps-germany.de
PSI 9000 2U Series
3.10.13 PV table function (photovoltaics)
3.10.13.1 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 definite
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
.
3.10.13.2 Safety notices
Due to high capacities on the DC outputs of the power supplies of this series, not every avail-
able solar inverter can be operated without problems. Check the technical specifications of
the solar inverter and probably contact the manufacturer for an evaluation. In case option HS
is installed in the device (see
), the result of operating critical inverters can be
optimised.
3.10.13.3 Usage
In the PV table function, which is based upon the XY generator with IU characteristics, the MPP is defined 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
Is
c
Uoc
MPP
Im
pp
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 verified with a tool like Excel by generating a diagram.
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.
