2. Function Description
2.1. Definition of Operation Modes
The inverter has four modes:
Standby mode:
In standby mode, the inverter is ready to switch into connecting mode. As decision variable the
input voltage of the PV generator is used. If the input voltage exceeds a preset nominal value,
the inverter shifts from “standby” to “connecting”, or continues into the operation mode “OFF” if
the PV voltage drops.
Connecting mode:
After performing the system tests, which check whether all connection conditions are met, the
inverter goes from standby mode to connecting mode. During the specified cut-in time, the in-
verter continues testing the system values and connects the inverter to the grid if the system tests
are okay. The minimum cut-in time is specified by the supplier and authorities and can vary from
region to region.
Grid mode:
In this mode, the inverter is connected to the grid and supplies power to the grid. The inverter is
only uncoupled from the grid in case of abnormal grid conditions or when PV power is not available.
PV configuration mode
Having completed the connecting mode the PV module wiring is automatically tested to detect
whether any of the DC inputs are wired in parallel string configuration. If so, the DC modules are
automatically run in parallel string configuration mode (Master/Slave).
Derating temperature
If the display shows (DRT. TEMP), the inverter is derating due to high temperatures.
Derating grid
If the display shows (DRT GRID), the inverter is derating due to high voltage on the grid.
Off:
If there is no PV power available, the inverter waits ten minutes (specified value) before it disen-
gages. In this mode, the power supply to all processors is switched off to conserve energy. This
is the normal night mode.
2.1.1. Grid Surveillance
In order to safeguard the people working on AC power lines and the inverter, the inverter shuts
down in the event of abnormal grid conditions or failures. The inverter continuously monitors grid
voltage and frequency by means of an internal control circuit. Subsequently, the inverter will re-
connect as soon as the grid is within limits.
2.1.2. PV Configuration
Upon connecting to grid an automatic test of the PV module wiring is performed by the inverter.
This test is made in order to determine the wiring configuration of the modules. It is established
whether the modules are connected in individual string configuration or in parallel string config-
uration and the inverter is automatically configured accordingly.
2. Function Description
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