Woodward DSLC, Installation And Operation Manual, Page: 82 / 114

DSLC Digital Synchronizer and Load Control Manual 02007
76 Woodward
Chapter 6.
VAR/Power Factor Control Description
Introduction
The VAR/PF control is operational in full-function DSLC™ models only.
When a small generator is paralleled with a utility, the synchronizer voltage
matching function adjusts the generator voltage to match that of the utility.
Voltage variations that may occur in the utility system after paralleling can cause
large changes in reactive current in the generator. The VAR/Power Factor
Control provides closed loop control of either VARs or power factor when
operating in parallel with another power system when that system can accept the
reactive load.
Voltage adjustment, however, can only affect reactive power when another
system is available to accept the reactive load. So the VAR/Power Factor control
functions are automatically switched to Power Factor sharing when single unit or
isochronous load sharing modes of operation are selected (Base Load contact to
terminal 50 is open).
The VAR/PF control mode of operation is selected by setting the VAR/PF Control
Mode set point on Menu 4. When either VAR or PF control mode is selected, the
control function is set to Auto by closing both the Voltage Raise and Voltage
Lower contacts. The VAR/PF control is disabled when both switch contacts are
open. Manual operation of voltage level is provided by closing the Voltage Raise
or Voltage Lower contacts individually.
The voltage bias output is reset to 0% when automatic VAR/PF control is
selected and the CB Aux input is opened.
NOTE
If cross-current compensation is installed on the voltage regulator, it must
be removed prior to using the VAR/PF mode of control, or instabilities may
result. The droop CTs must remain connected to their voltage regulator.
VAR Control
The VAR control adjusts generator voltage to maintain a constant reactive power
(kVAR) load on the generator throughout the KW operating range. This assures
sufficient excitation of the generator field under all load conditions. A set point is
provided to set the desired VARs. The VAR control function may be enabled with
VAR/PF Control mode selection set point.
Power Factor Control
The power factor control adjusts generator voltage to maintain a constant power
angle throughout the KW operating range. A set point is provided to set the
desired power factor reference. The power factor control function may be
enabled with the VAR/PF Control mode selection set point.