Siemens SINAMICS S120 System Manual page 78

Commissioning
7.4 Commissioning example for an infeed with voltage and frequency control for an island grid.
Parameter Value
p5436
1)
p5451 e.g. 1
p5478[0, 1] e.g.:
chassis format devices:
p5478[0] = 90 %
p5478[1] = 123 %
booksize format devices:
p5478[0] = 90 %
p5478[1] = 90 %
Grid transformer
p5480 e.g. 1 (normal operation)
p5481[0] e.g. 2 s
78
Comment
DC component controller P gain
Especially if an island grid contains transformers or line motors, it is absolutely
necessary that this control is activated to prevent DC components in the AC cur-
rent. The controller parameters are preset based on the rated Active Line Module
data (assumption: the transformer rating approximately corresponds to the Active
Line Module power rating).
However, depending on the particular system, adaptations may be required in
order to achieve stable operation of the grid droop control. To achieve this, the
identification p5480 = 11 of the transformer magnetizing inductance p5492 can be
used if data sheet values are not available. In operation, it is possible that the
controller gain p5436 must be adapted. To achieve this, evaluate the characteris-
tic of the current DC components r5448[2, 3].
Note
Parameter p5436 is not effective while the transformer is being magnetized. To
avoid saturation effects in the transformer during magnetization (especially for
high modulation depth r0074), we recommend that the DC component control is
activated using p3650.
BI: Current hysteresis controller operating mode
This parameter is used to define as to whether the Active Line Module in the
island grid is presently the most powerful generating unit (= 0) – or not (= 1). In
this case, the rated power of the power generating unit is not decisive, but the
short-circuit power (for example, a nominally smaller diesel generator can supply
higher short-circuit currents). The operating mode information is used in the Ac-
tive Line Module to facilitate fast and stable resynchronization after a grid short-
circuit with the support from possibly other power generating units.
Grid droop control current limits
The current limits for current controlled operation (e.g. p3530ff) are not effective
in grid droop operation, but only the apparent current limiting according to p5478.
In so doing, a distinction is made between normal operation (island grid voltage >
p5459[2]) and grid short-circuit. For example, a lower current limit in normal oper-
ation makes sense so that larger motors in an island grid can be started (heavy-
duty starting). When the current limit is reached, the output voltage decreases so
much that the current limit is permanently maintained (and the motor continues to
accelerate with reduced voltage). The current limit [0] is also applicable for short-
circuit situations (i.e. grid voltage < p5459[2], if a power source with a higher
rating for the short-second current is available in the island grid (p5451 = 1). The
resulting current limits in amps are indicated in r5479.
Transformer magnetization mode
Activating the transformer magnetization
Notice:
When magnetization is deactivated, with the DC link precharged, the circuit
breaker is controlled independent of the operating state of a transformer that may
be available.
This can result in overloading grid or plant components or even damage if a
transformer is present.
We recommend that an external, independent synchronizing monitoring function
is used.
Also see the following chapter about transformer magnetization.
Transformer magnetization times: Voltage ramp-up time
Ramp-up time to magnetize the transformer
System Manual, 04/2015, A5E03347436A
Grid infeed