Siemens SINAMICS S120 System Manual page 51

Conversely, a reactive current results in a voltage change at inverter outputs u12, u23. The
characteristic is selected so that the line voltage change is counteracted, therefore helping to
stabilize the grid voltage (inverter acts as grid support element).
Application
The "Dynamic grid support" function module must be activated to use this functionality
(p5500 to p5529).
The overall function comprises two subfunctions that are coupled with one another: On one
hand, reactive current injection corresponding to the characteristic defined with p5505 and
p5506, which can be configured to address the requirements of the local power utility
company. The other subfunction involves the settings for fast current limiting when riding
through low and possibly non-symmetrical line dips (FRT).
By specifying the signal sources for line current (p5503) and line voltage (p5504), the grid
support function can be configured for various connection points of the power generation
system. It is especially important to note that a connection point can be selected at the grid
side of a connection transformer.
We recommend that configuration bit p5500.3 = 1 is set (default setting). Otherwise,
generally current symmetry cannot be attained – especially during an unsymmetrical grid
fault. During a grid fault, if active and reactive power injection are not required (Z mode) then
the system can also operate in the mode p5500.3 = 0 without negative sequence system
controller. This can be advantageous for difficult grid conditions (e.g. for grids with low
system fault levels).
Generally, for grid voltage dips, it is not possible to transfer the available active power to the
grid. As a consequence, the DC link voltage increases. Depending on the general conditions
of the application, this increase can result in a fault trip due to DC link overvoltage if no
countermeasures are taken on the power generating side. To prevent this and to reduce V
when the V
current component. Correspondingly, when a V
motoring active current can be injected in order to prevent a pending shutdown due to an
undervoltage condition.
Note
By dynamically limiting the grid currents (for example, see p3524, p3528, p3529, p5520)
depending on the operating state of the grid support (r5502, r5522), the system can be
adapted to address the specific requirements of individual grid codes.
Grid infeed
System Manual, 04/2015, A5E03347436A
6.1 Additional closed-loop controls for current-controlled operation
threshold p5508[0] is reached, the active current has priority over the reactive
dc
Detailed descriptions of the function modules
threshold is fallen below (see p5508[1]), a
dc
,
dc
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