Siemens sinamics dcp Operating Instructions Manual page 237

The voltage controller is implemented as a PI controller. It has a derivative/lag element in the
actual value channel, with which the control quality can be improved.
A current limit during voltage control can be defined via two BICO inputs.
Switchover from voltage control to current control and vice versa can also be performed via a
BICO input.
Automatic DC link buffering:
This function is used to supply the DC link of a frequency converter, which is usually fed from
the three-phase network via an infeed unit, from a battery if the power fails and, in this way,
to maintain uninterrupted operation of a connected motor.
For this, a deadband must be defined (p54124). As long as the voltage actual value is in the
"voltage setpoint +/- deadband" range, the voltage controller of the DCP is disabled. The DC
link voltage is controlled by the infeed unit. As long as the voltage actual value is in the
"voltage setpoint +/- deadband" range, the voltage controller of the DCP is disabled. It
controls the voltage back to the setpoint and remains enabled until the set minimum time
(P54146) has expired. A higher level control can also enable the voltage controller via a
BICO input.
If p54124 = 0 %, the voltage controller is always enabled.
If p54124 = 100 %, the voltage controller can be enabled or disabled via BICO (p54145).
For values in between, the voltage controller can always be enabled via BICO (p54145), but
it can only be disabled if the voltage is within the tolerance range.
Main current control
See function diagram 6820 in the SINAMICS DCP List Manual.
The main current control ensures fast closed-loop control.
It comprises two components:
● Precontrol
● Main current controller
The precontrol is used to relieve the integral component of the actual main current controller.
The main current controller is designed as an adaptively working PI controller.
The gain and integral time controller parameters can be parameterized.
Differential current controller
See function diagram 6825 in the SINAMICS DCP List Manual.
The differential current controller ensures that the current is evenly distributed between the
two (30 kW device) or three (120 kW device) bridges that make up the power unit.
Pulse-width modulation
See function diagram 6830 in the SINAMICS DCP List Manual.
The pulse-width modulation generates the control signals for the semiconductor switch of the
power unit. It also controls the switchover of the current direction.
SINAMICS DCP
Operating Instructions, 05/2016, A5E34382853K
Operation
8.9 Closed-loop control
237