Siemens SINAMICS S120 System Manual page 77

7.4 Commissioning example for an infeed with voltage and frequency control for an island grid.
Parameter Value
p5416[0] e.g. 0
1)
p5417 e.g. 4 %
1)
p5419 e.g. 150 ms
p5425[0, 1] e.g. r5488[1, 2]
p5426 e.g. 50 %
p5427 e.g. 500 ms
5430[1] e.g. 105 %
p5432[0, 1] e.g.:
p5432[0] = 50 V
p5432[1] = -50 V
Grid infeed
System Manual, 04/2015, A5E03347436A
Comment
Line droop control voltage droop supplementary setpoint
In island grids with several power generating units, the no-load voltage is dynami-
cally adapted to the instantaneous load and power generating conditions using a
higher level island grid control.
Grid droop control voltage droop gradient
A suitable value is obtained from the corresponding gradient values of the other
power generating units in the island grid as well as from the required load distri-
bution.
In the example, the following procedure provides a practical value to be set:
Measure the gradient of the diesel generator characteristic, and set p5417 to the
same value.
Line droop control voltage droop smoothing time
Other power generating units in the island grid must also manifest a voltage
droop, however they respond to load changes with a specific "inertia". In order to
avoid load peaks in individual power generating units for load steps in an island
grid, at least power generating units with similar power ratings must manifest a
comparable dynamic response. This dynamic response for reactive power
changes is set using p5419.
CI: Line droop control voltage control signal source
Selecting the signal source for the voltage control defines at which point the volt-
age error should be compensated (or at which point, the voltage droop should be
active).
With the example setting, the terminal voltage of the Active Line Module is cor-
rected/tracked so that at the selected measurement point (here: VSM2 voltage at
the circuit breaker) the setpoint voltage is set according to the droop.
Line droop control voltage control P gain
Voltage droop p5415ff supplies the setpoint for the output voltage of the power
generating unit. Initially, this voltage is realized at the terminals of the grid invert-
er. Under load, especially the voltage drops across the inductances (commutating
reactor, transformer) result in the corresponding voltage deviations at the connec-
tion point (e.g. at the circuit breaker). The voltage control is used to compensate
these voltage errors.
Line droop control voltage control integration time
The voltage control is intended to correct steady-state voltage errors, compara-
tively slowly. As a consequence, the integration time constant should be selected
to be somewhat higher than the smoothing times of the voltage and frequency
droop.
Modulation depth controller setting – setting the maximum modulation depth.
Limits the modulation depth to avoid harmonics in the output voltage.
Modulation depth controller output voltage limiting
The pulse-frequency harmonic component of the Active Line Module output volt-
age depends on the modulation depth (ratio between the AC voltage and DC
voltage) and is optimal when r0074 = 94 %.
This means that with the modulation depth controller, the setpoint for the DC link
voltage can be adapted to the actual AC island grid voltage. When doing this, in
the particular application, it must be noted whether, in all operating states, the
component is suitable for the Vdc control (in this case: inverter on the generator
side) for a corresponding change of the DC link voltage (voltage reserve of the
generator control, Vdc_max limiting, etc.).
Commissioning
77