6 Electrical Connection
User Manual
28
and the impedances between the negative terminal of the PV string and
Earth are larger than 1Mohm.
6.3.1 PV Inputs Configuration
The inverter has two PV input areas DC1 input and DC2 input, each with its
MPP tracker.
The two PV inputs can be configured in independent mode or parallel mode.
There is a risk of inverter damage! The following requirements should be
met; otherwise they will lead to loss of any and all warranty rights.
Make sure that the maximum short circuit current of each DC input is less
than inverter allowable limit.
Make sure that the maximum open voltage of each string is less than
1000V. Voltage over 1000V can damage the inverter.
PV Configuration Mode- Independent Mode
For independent mode, the two PV inputs work independently, each with its
own MPPT. Therefore the two PV inputs can be different with each other,
including different PV module types, different numbers of connected in PV
string, different tilt angles or orientation angle of PV modules.
As shown in the following diagram, the inverter should choose independent
mode due to different orientation angle between the two PV inputs.
To make sure maximum DC power can be utilized, PV strings
connected to individual input area should have a homogenous
structure, including the same type, the same number, identical tilt and
identical orientation.
Prior to connecting the inverter to PV inputs, the following electrical
specifications must be met simultaneously:
Total DC Power Limit
Open-circuit Voltage
Limit for Each Input
Short-circuit Current
Limit for Each Input
40500W
1000V
40A
Considering the negative voltage temperature coefficient of PV module, more
attention should be paid to the open-circuit voltage of PV strings when
designing at the lowest ambient temperature.
TakeYL250P-29bPV cells for example.
Item
Parameter
PV cell type
YL250P-29b
Power
250W
Open-circuit voltage (STC)
37.6V
Short-circuit current (STC)
8.92A
Open-circuit voltage temperature coefficient
(
β
)
-0.32%/°C
No. of PV cells in a PV string
23
Under the STC condition, where ambient temperature is 25°C, the open-circuit
voltage of PV cells is 37.6V
×
23=864.8V<1000V.
Supposed that the lowest temperature is -25°C, the open-circuit voltage of PV
cells is 23×37.6V×[1+β×(min. ambient temperature- STC temperature)] =
23×37.6V×[1+(-0.32%/°C) ×(-25°C-25°C)]=990V<1000V (meet the operation
