Operation
7.11 Closed-loop control
SINAMICS DCP
326 Operating Instructions, 09/2019, A5E34382853K
7.11 Closed-loop control
7.11.1 General information
The SINAMICS DCP basically uses two control modes:
● Current control
● Voltage control
Current control
In a typical current control application, the SINAMICS DCP is connected on side 1 and on
side 2 to a voltage source (for example, DC link of a frequency converter, battery, solar
panel, etc.).
The current control establishes the required current flow between both sides of the device.
This means that energy is transferred from one voltage level to the other voltage level.
In current-controlled operation, SINAMICS DCP receives the setpoint via parameter p55050
(current setpoint signal source), see function diagram 6805 in List Manual SINAMICS DCP.
This setpoint can be interpreted differently by the device, see Chapter "Setpoint specification
for current control (Page 328)".
Internally, SINAMICS DCP comprises several DC-DC converters connected in parallel
(power units), and exclusively controls the current in the energy storage reactors of these
power units.
As a consequence, the specified setpoint is always converted over to the current in the
energy storage reactors, and only this current is measured in the device.
The sum of the currents in the energy storage reactors of the individual power units is called
"Reactor current".
The magnitude of the voltage level on both sides of the SINAMICS DCP can be any arbitrary
value within the limits specified in the technical data of the DCP.
However, it is crucial that the maximum voltage is not exceeded; further, the current and
power limiting (Chapter "Current limitation and power limitation (Page 336)") and the derating
(Chapter "Derating (Page 357)") must be carefully taken into consideration.
In addition, there is a restriction that when current flows from a lower to a higher voltage level
("stepping up/boosting"), a voltage ratio of 8 must not be exceeded.
For example, a voltage of 100 V can be stepped up as a maximum to a voltage of 800 V.
For a higher step-up factor, the modulation depth (see parameter r55250, r55251) is
automatically limited.
As a consequence, the current is also limited and the current actual value can no longer
follow the setpoint.
However, neither a fault nor alarm is initiated.
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