Siemens SINAMICS S120 Function Manual page 176

Vector V/f control (r0108.2 = 0)
5.4 Vdc control
● Undervoltage in the DC link
Properties
● Vdc control
● Vdc_min control (kinetic buffering)
● Vdc_max control
Description of Vdc_min control
Figure 5-7
176
Reduce the regenerative torque to maintain the DC link voltage within permissible
limits.
– Typical cause
Failure of the supply voltage or supply for the DC link.
– Remedy
Specify a regenerative torque for the rotating drive to compensate the existing losses,
thereby stabilizing the voltage in the DC link (kinetic buffering).
– This comprises Vdc_max control and Vdc_min control (kinetic buffering), which are
independent of each other.
– Joint PI controllers. The dynamic factor is used to set Vdc_min and Vdc_max control
to a smoother or harder setting independently of each other.
– With this function, the kinetic energy of the motor is used for buffering the DC link
voltage in the event of a momentary power failure, thereby delaying the drive.
– This function can be used to control momentary regenerative load without shutdown
with "overvoltage in the DC link".
– Vdc_max control is only recommended with a supply without active closed-loop control
for the DC link and without feedback.
Switching Vdc_min control on/off (kinetic buffering)
Function Manual, (FH1), 07/2007 Edition, 6SL3097-2AB00-0BP4
Drive Functions