Siemens SINAMICS DCM Operating Instructions Manual page 427

The following diagram shows the topology of a 6-pulse series connection, where additional
converters are connected in parallel to each of the two 6-pulse converters connected in
series.
Figure 10-58 6-pulse series connection (2)
Operating modes
There are 2 operating modes:
● Operation with the same firing pulses (p51799 = 0 or p51799 = 31):
● Operation with sequence control (p51799 = 32):
Note
● The phase sequence at the master and the slave must be the same.
SINAMICS DCM Control Module
Operating Instructions, 06.2010, C98130-A7067-A1-02-7619
Both partial converters are fired at precisely the same point. The master calculates the
firing point and this is transferred to the slave via the parallel interface. Synchronization to
the line supply is exclusively performed by the master. The slave must be connected to
the line supply with the same phase sequence as the master.
Both partial converters synchronize to the line supply and generate their own firing points.
The firing angle for the master and the firing angle for the slave are calculated by the
master and the firing angle and the torque direction for the slave are transferred to the
slave via the parallel interface. The firing angle for the master and slave are generated so
that the reactive power load of the line supply is as low as possible. This is then the case
if one of the two partial converters is at a control limit and the other carries-out the closed-
loop control. This type of closed-loop control is only possible for continuous current
operation. Operation with the same firing points is automatically selected in the
discontinuous (pulsating) current range.
Descriptions of functions
10.23 Connecting units in parallel and in series
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