Siemens SINAMICS S120 System Manual page 31

● Function module dynamic grid support
The "Dynamic grid support" function module allows grid faults to be ridden through and
allows grid-supporting reactive currents to be injected; this is specified in many grid codes
in order to clear short-circuits. Contrary to line droop operation for island grids, in this
particular case, the Active Line Module is operated as grid support element with DC link
voltage and grid current control. In this operating mode, the complete power injected into
the DC link is output to the grid.
The "Dynamic grid support" function module requires a license that must be (additionally)
ordered.
The Active Line Module is operated in current and DC link voltage control.
The grid droop control must be deactivated (p5401 = 0).
As a consequence, "Dynamic grid support" is typically used for feeding power grids.
However, this operating mode can also make sense in island grids, e.g. for PV inverters,
which are operated with DC link voltage controlled to optimize the yield. Other power
generating units in this island grid must ensure adequate frequency and grid voltage
control.
In addition to dynamic support, the function module also provides a range of
comprehensive functions for grid monitoring regarding frequency and voltage amplitudes.
The monitoring limits can be parameterized with either a fixed value or with a
characteristic, as a function of time.
Further, using the anti-islanding function, the unintended and undesirable creation of an
island grid can also be detected. This function is normally used when generating power in
a power grid. Isolating a partial grid without adequate frequency and grid voltage control
causes the Active Line Module to be shut down (which is connected to this partial grid).
The function module includes the following subfunctions:
– Dynamic grid support with reactive current (symmetrical and non symmetrical grid
– Provision of short-circuit currents in the case of a grid fault (riding through grid faults)
– Active anti-islanding detection with active frequency shift algorithm
– Extended voltage and frequency check for automatic restart after a grid fault
– Freely-definable curves with support points (voltage-time monitoring and frequency-
Grid infeed
System Manual, 04/2015, A5E03347436A
support can be set)
to comply with grid codes
time monitoring) to monitor voltage and frequency during a grid fault corresponding to
local grid codes).
Function modules
5.1 Overview
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