Closed-Loop Control - Siemens sinamics dcp Operating Instructions Manual

Operation

8.9 Closed-loop control

8.9 Closed-loop control
General information
The SINAMICS DCP basically uses two control modes:
Current control
A current setpoint is defined for the DCP (by a higher-level controller). (see FP6805,
parameter p55050).
The DCP on side 1 and on side 2 are each connected to a voltage source (for example, DC
link of a frequency converter, battery, solar panel, etc.). The current control establishes the
required current flow. This means that energy is transported from one voltage level to
another voltage level. Basically, any voltage level is possible. However, the maximum
voltage stated in the technical data must not be exceeded. Additionally, a current flow from a
lower to a higher voltage ("step up") must not exceed a voltage ratio of 1:8. For example, a
current flow from a 100 V voltage source to a 800 V voltage source can be generated. If the
voltage ratio is increased, the modulation depth (see parameter r55250) is automatically
limited. As a result, the current is reduced. The current actual value can no longer follow the
setpoint. However, no fault or warning message is output.
Voltage control
A voltage setpoint is defined for the DCP (by a higher-level controller). (see FP6818,
parameter p54100).
The DCP is connected on one side to a voltage source (for example, battery). The other side
is connected to a capacitive energy store (for example, DC link of a frequency converter).
The voltage of this energy store is controlled to the specified setpoint. The closed-loop
control is implemented as a cascade control. This means that the voltage control specifies a
current setpoint for the lower-level current current control. The statements above apply to the
current control.
Setpoint specification for current current control
See function diagram 6805 in the SINAMICS DCP List Manual.
The SINAMICS DCP requires a setpoint that can be specified via fieldbus.
This setpoint can be the:
● current setpoint (current on side 1 or current on side 2)
● Power setpoint
The setpoint must be specified as a signed relative value (percentage of the rated current or
rated power):
● positive setpoint means current flow from side 1 to side 2
● negative setpoint means current flow from side 2 to side 1
The setpoint is used to limit the steepness via a settable ramp.
(p55055, factory setting: 0 ... 100% in 50 ms).
Setpoints whose values are below a parameterizable threshold (p55056) are considered to
be zero.
232
Operating Instructions, 05/2016, A5E34382853K
SINAMICS DCP