Siemens SINAMICS S120 System Manual page 30

Function modules
5.1 Overview
● Function module for grid droop control
The "Grid droop control" function module enables an island grid to be created. The
inverter for feeding into the grid has the task of controlling the frequency and the voltage
in the grid, and assumes an "grid former function". The power that is output is defined by
the consumers (loads) and where relevant, other power generating units in the island
grid. The DC voltage present in the DC link must be controlled by other participants, such
as generator-side inverters, or provided by other sources (e.g. from a battery).
The "Grid droop control" function module requires a license that must be (additionally)
ordered.
The transition between the operating modes "Grid control" and "Current control or Vdc
control" is possible at any time while operational. However, it should be noted that when
exiting grid control, the power is controlled down to zero. As a consequence, loads still
available in an island grid must be temporarily supplied from another source
When grid control is exited, at least one other power generating unit in the island grid
must still control frequency and voltage.
The function module includes the following subfunctions:
– Grid droop control for voltage and frequency
– Grid voltage control for the connection point
– Island grid black start to establish an autonomous island grid
– Synchronizing an island grid to another grid
– Provision of short-circuit currents in the case of a grid fault (riding through grid faults)
– Supplementary droop and damping input to avoid load peaks or power oscillations to
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stabilize the grid (emulation of the generator dynamic response)
System Manual, 04/2015, A5E03347436A
Grid infeed