SMA SUNNY DESIGN 3 - Manual (Page 33)

SMA Solar Technology AG 7 Glossary
User Manual SD3-SDW-BA-en-20 33
Maximum DC Current
The inverter can only process input currents below a certain upper limit. However, this upper limit is not relevant when
designing and operating a PV system, since the inverter completely controls its DC input.
Maximum DC Power
The maximum DC power is the maximum power the inverter can process. This limiting value strongly depends on the input
voltage and the ambient conditions.
Maximum DC Voltage
The inverter is designed for operation below a maximum DC voltage. If the limiting value for the DC voltage is exceeded,
parts of the inverter may be damaged. Therefore, when designing a PV system, the maximum DC voltage is particularly
important when it comes to feed-in interruptions at low PV cell temperatures.
Maximum Power Point (MPP)
The operating point (current/voltage characteristic curve) of a PV array where the maximum power can be drawn.
The actual MPP changes constantly depending, for example, on the level of solar irradiation and the temperature.
Maximum PV Array Current
When operating a PV system, the maximum PV array current is generated if the PV modules are operated at the maximum
power point (MPP) and the cell temperature of the PV modules is very high. If necessary, the inverter limits the PV array
current to the maximum DC current. In this case, the inverter cannot set the MPP. This will only rarely lead to reduced
yields, though, since the peak power of the PV array is already limited due to the inverter being undersized.
Maximum PV Short-Circuit Current
See maximum short-circuit current.
Maximum PV Voltage
The maximum PV voltage occurs if the PV cells are very cold and the PV array is in no-load operation. A common design
point for maximum PV voltage is therefore the open-circuit voltage at a PV cell temperature of ‒10°C.
Maximum Short-Circuit Current
It can make sense in certain situations to short-circuit the PV array to protect the PV modules or the inverter. SMA inverters
with Optiprotect offer this option. However, the PV array can only be short-circuited if the short-circuit current resulting
from the short-circuit does not exceed a certain maximum value. The PV system must therefore be designed in such a
manner that the short-circuit current of the connected PV array does not exceed the maximum short-circuit current of the
inverter inputs.
Minimum DC Voltage
The minimum DC voltage must exceed a minimum value in order for the inverter to feed into the utility grid. Depending
on the inverter working principle, the minimum DC voltage is either preset or varies with the current grid voltage. When
designing a PV system, the minimum DC voltage for operation at high PV cell temperatures and for the time at which the
inverters start feed-in in the morning must be observed.
Minimum PV Voltage
When operating a PV system, the minimum PV voltage only occurs if the cell temperature of the PV modules is high and
the PV modules are operated at their maximum power point (MPP). Therefore, the MPP voltage at a cell temperature of
+70°C is a common design point for minimum PV voltage.