Chapter 3 - Device Overview
UNITROL 1020 User Manual 3BHS335648 E82 51
3.4.2.8 Start sequence with dead bus synchronization
With regard to support dead bus synchronisation and line charging in combination,
UNITROL 1020 provides a special start sequence.
In case digital input Sync Dead Bus Enable is active, Excitation On and Line Charging
are enabled, the soft start ramp (Internal Excitation ON status) is started after the
generator breaker is closed. Generating the close command of the generator breaker is
only applied if SYNC is enabled.
3.4.3 On-line Operation Functions
3.4.3.1 Voltage Droop Compensation (VDC)
For island operation only
UNITROL 1020 offers a special feature called Voltage Droop Compensation or VDC. This
feature equally shares the amount of reactive power between generators connected in
parallel to the same bus by using the RS485 bus for communication between AVRs.
During VDC mode all AVRs operate in Auto mode with a voltage droop control. Each
AVR sends the value of its own amount of reactive power over the RS-485 bus, while the
other AVRs take this information to calculate a common average MVAR setpoint and
compensate the effect of the voltage droop. The setpoints are calculated to maintain the
voltage level on the busbar at 100% (not adjustable).
The AVRs that are considered to calculate the common average MVAR can be selected:
A) All units which are connected to the busbar, only dependent on the GCB status
B) All units working in VDC mode
In order to get a smooth transition between any mode and VDC mode the load sharing is
activated over a ramp time. The ramp time defines the time after switching on VDC mode
until VAR on all machines is equalized.
Machine voltage
Reactive current
100
[%]
Var SPmax
Var SPmin
Important:
The Compensation Droop Kq shall be set at -5% (negative value) if VDC mode is used.
The voltage is kept at 100% Um inside the VAR SP min/max. If VAR is outside this range
the voltage will be adjusted according to the set droop (Kq).
VDC Mode will keep the bus voltage at 100% within the Var Setpoint min and max limits.
To Next Page
Loading...
