SMA SUNNY DESIGN 3 - Manual (Page 36)

7 Glossary SMA Solar Technology AG
36 SD3-SDW-BA-en-20 User Manual
STC (Standard Test Conditions)
In order to compare the power of different PV modules, standard test conditions (STC) are used:
• Global radiation 1,000 W/m²
• Temperature 25°C
• AM 1.5 (AM= Air Mass, a relative measurement for the path that light covers through the earth's atmosphere to the
ground. The air mass at the equator is AM=1 and approximately 1.5 in Europe)
String
A group of electrical series-connected PV modules. Normally, a PV system is made up of multiple strings.
String Inverter
Decentralized inverter concept where the PV array is divided up into individual strings. The individual strings are
connected to the utility grid through their own string inverters. This greatly simplifies installation and reduces the yield
losses which can be caused by variations in production or variations in shading on the PV modules.
Subproject
In Sunny Design, a subproject is part of a planned PV system project and consists of up to three PV arrays and the
associated inverters.
Typical PV Voltage
The typical PV voltage is the MPP voltage of a PV module whose cell temperature corresponds to the NOCT: Normal
Operation Cell Temperature = cell temperature at irradiation of 800 W/m², ambient temperature of 20°C and a wind
speed of 1.0 m/s. The NOCT is also often shown on the datasheet of the PV modules.
Unbalanced Load
The unbalanced load is the maximum power difference that may occur between any two line conductors of a PV system
feeding into the multi-phase utility grid. In the planning phase of a PV system, this value refers to the distribution of nominal
AC power from single-phase feed-in inverters to the three line conductors of the utility grid at the feed-in point.