Current Limiting For Dynamic Grid Support - Siemens SINAMICS S120 System Manual

Commissioning
7.10 Commissioning supplementary controls
7.10.4

Current limiting for dynamic grid support

Depending on the grid codes of the power utility company, special requirements apply to
power generating systems regarding the current characteristic during a grid fault. Generally,
a certain participation in the short-circuit current is specified, i.e. impressing a defined
reactive current during a grid fault. When grid support is active (p5501 = 1), the reactive
current setpoint has priority over the active current, contrary to normal operation. As a
consequence, when necessary the active power of the Active Line Module is reduced in
order to supply reactive power to the grid according to p5506.
The settings of the following parameters are valid when the "Dynamic grid support" function
is activated (p5501 = 1):
● p5509[5]: Additionally effective apparent current limit.
● p5509[7]: Additionally effective reactive current limit when the tolerance range for voltage
dissymmetry is exceeded (r5502.2 = 1).
With the setting p5509[7] = 0.1 %, for example, the grid-supporting reactive current can
be deactivated according to the characteristic (p5506) for non-symmetrical grid faults.
● p5509[8]: Additionally effective limit for the apparent current of the negative sequence
system when the tolerance range for voltage dissymmetry is exceeded (r5502.2 = 1).
For the setting p5509[8] = 0.1 %, the non-symmetrical support current is prevented, which
is actually necessary for non-symmetrical grid faults. Most grid codes specify this.
● p5509[10]: Additionally effective active current limit when the tolerance range for the grid
voltage is exceeded (r5502.1 = 1).
This means that the active power of the power generating system can be reduced when
the grid voltage manifests a deviation.
● p5520: Additionally effective dynamic apparent current limit when the tolerance range for
the grid voltage is exceeded (r5502.1 = 1).
This allows application-specific apparent current characteristics to be implemented during
grid faults.
● p5500.6 = 1: Additionally effective internal apparent current limit when the tolerance
range for the grid voltage is exceeded (r5502.1 = 1). The value corresponds to the
smoothed apparent current before the grid fault.
Corresponding to individual grid codes, this means that the total current can be kept
constant before and during a grid fault.
● p5500.8 = 1: During a grid short-circuit (r5502.4 = 1, r5522.3 = 1) the active current
setpoint is internally set to zero.
Corresponding to the directives of individual grid codes, a fault ride through (FRT) can be
executed with pure reactive power output (Q mode).
● p5500.9 = 1: During a grid short-circuit (r5502.4 = 1, r5522.3 = 1) the active current
setpoint and the reactive current setpoint are internally set to zero.
Corresponding to the directives of individual grid codes, a fault ride through (FRT) can be
executed without power output (Z mode).
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System Manual, 04/2015, A5E03347436A
Grid infeed