Kohler 20EKOZD

211Section 12 Paralleling System InformationTP-6953 7/19
kVAR Control
The reactive power controller measures and controls
reactive power (kVAR). Some modes allow direct control
of the kVAR to a target that is independent of the real
power supplied by the generator or generator system.
The VAR Control mode parameter allows selection
between the kVAR and Power Factor control modes.
VAR control is always used when in load sharing mode.
These modes are listed below.
D kVAR sharing
While the controller is operating as part of a standby
power system or a p rime power system that is not in
parallel with another source, the primary (and default)
reactive power control mode is kVAR sharing. In this
mode, each generator tries to control output reactive
power to the percentage of the bus capacity (the ratio
between the total reactive load on the bus and the
total reactive power capacity of all online generators).
Generators that a re making too much reactive power
will adjust their voltage bias down, while generators
that are not making enough power will adjust their
voltage bias up. The result is that there is no net
change in the bus voltage.
If the bus voltage does drift away from nominal (due to
soft loading, soft unloading, or reactive droop) there is
a voltage trim feature in the controller that constantly
drives the voltage toward the nominal voltage to
correct for such errors. Trims must be enabled to
allow the voltage trim to adjust the voltage bias to
maintain constant output voltage. Trim should only be
disabled on an islanded (not connected to the utility
grid) system if the system is having trouble sharing
load, and then only as a troubleshooting step.
Voltage Trim is unnecessary in synchronism with the
utility grid.
Note: Voltage and Frequency Trim a re enabled
and disabled with a common parameter
(Enable Trims). To disable one individually,
the P, I, and D gains must be set to 0.
D Baseload
Reactive Power Baseload mode operates similarly to
kVAR sharing mode except that the target reactive
power level is a stored controller p arameter instead of
an average bus load. Baseload mode is intended for
use when in parallel with a distant or uncontrolled
source (such as the utility grid).
Reactive Power Baseload is enabled when Real
Power Baseload is enabled (if the VAR control mode
is set to VAR control). Baseload mode is not
responsive to changes in the reactive load
requirement on the paralleling bus, so placing a
generator in baseload mode on an islanded system
may very well cause the other generators in the
system to experience an apparent loss of field
condition if the reactive load decreases. Baseload
modecanbeusedasatestingmodeunder
supervision, but should not be used long-term in an
islanded application.
Voltage Trim is not active in Baseload mode.
The Reactive Power Controller uses the Reactive
Power Baseload g ains for operation in Reactive
Power Baseload mode.
D System Control
System Control mode controls the reactive power
level of all generators on a paralleling bus to a target
level that is determined by the voltage bias input. The
bias input only needs to be supplied to a single
generator on the communication bus in order to
control all the generators on that bus. The generator
that is receiving the signal does not have to be
running or paralleled to the other generators, but it
does need to have the system control mode and
external bias enabled. If the signal is sent to multiple
generators in the system, only one of them will control
the bus (the others will be ignored). The preference
order of the generator controllers is based on the
controller serial number.
System Control mode provides an interface that
allows the generators to be controlled by an external
controller for soft-unloading/loading and peak
shaving against a distant or uncontrolled source
(such as the utility grid). The power output increases
with increasing voltage bias, as described in the
following:
Voltage Bias < 0.5V = 50% of rated reactive power
Voltage Bias = 0.5V = 0% of rated reactive power
Voltage Bias = 2.5V = 50% of rated reactive power
Voltage Bias = 4.5V = 100% of rated reactive power
Voltage Bias > 4.5V = 50% of rated reactive power
Voltage Trim is not active in System Control mode.
The Reactive Power Controller uses the System
Reactive Load Control gains for operation in System
Control mode.