Siemens sinamics dcp Operating Instructions Manual page 238

Operation
8.9 Closed-loop control
The switchover from loading (100% power) to regeneration (100% power) and vice versa, is
possible within a parameterizable time window (see p55065).
The parameters for limiting the modulation depth (P55305 and p55306) allow limiting of the
working range of the SINAMICS°DCP.
Examples:
● Modulation depth limited to 0% .. +200 %: only positive current possible
● Modulation depth limited to -200% .. 0 %: only negative current possible
● Modulation depth limited to -100% .. +100 %: only stepping down possible
PV array flying restart
The function "PV array flying restart" can be activated with p55110 = 1 or 2.
p55110 = 0: no PV array connected
p55110 = 1: PV array on side 1 connected
p55110 = 2: PV array on side 2 connected
This function is required for SINAMICS DCP applications in photovoltaic installations. With it,
a PV array with a no-load voltage of 800 V to 1000 V can be drawn into the continuous
running duty range of the SINAMICS DCP (up to 800 V and/or 900 V, see technical data).
If p55110 = 1 or 2, this function is automatically executed after each ON command (if the PV
voltage is above 800 V and/or 900 V). The function monitors whether the PV voltage can be
drawn into the continuous running duty range within 30 s. If it cannot, F60500 is output.
5 minutes must elapse after this fault message before the ON command can be issued
again. This means that if the "flying restart" attempt fails, you must wait 5 minutes before
making another attempt. During this 5-minute period, the SINAMICS DCP remains in
operating status r50000 = 8.2 (Switching On Inhibited).
During operation, the other side of the DCP is also continuously monitored for overvoltage. If
the voltage set in p55182 and/or p55187 is exceeded, switch-off is initiated immediately with
fault message F60500.
Control of the current ripple
With DC/DC converters with pulse width modulation, the current always contains a certain
amount of ripple. The size of this current ripple can differ markedly depending on the ratio of
the voltage on side 1 with the voltage on side 2. The largest current ripple occurs at a
voltage ratio of 1:2. The smallest current ripple occurs at a voltage ratio of 1:1. However, a
small current ripple at certain operating points is not advantageous.
So the switching frequency of the pulse width modulator can be reduced for individual
operating points so that the current ripple at all operating points is equal to the ripple when
the voltage ratio is 1:2. This has the advantage that the switching losses of the
semiconductors are reduced and the efficiency of the devices is increased.
The switching frequency can be set in parameter p55322.
Value = 0 ... fixed switching frequency (20 kHz for a 30 kW device or 15 kHz for a 120 kW
device)
Value = 1 ... variable switching frequency (controlled to constant current ripple)
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Operating Instructions, 05/2016, A5E34382853K
SINAMICS DCP