Kohler 23EKOZD

210 Section 12 Paralleling System Information TP-6953 7/19
Baseload
Real Power Baseload mode operates similarly to kW
sharing mode except that the target power level is a
stored controller parameter 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).
Real Power Baseload mode is not responsive to
changes in the load r equirement on the p aralleling bus,
so placing a generator in Baseload mode on an islanded
system may very well cause the other generators in the
system to experience a reverse power condition if the
load decreases. Baseload mode can be used as a
testing mode under supervision, but should not be used
long-term in an islanded a pplication.
Frequency Trim is not active in Baseload mode.
The Real Power Controller uses the Real Power
Baseload gains for operation in Baseload mode.
System Control
System Control mode controls the power level of all
generators on a paralleling bus to a target level that is
determined by the speed 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 p rovides 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 speed bias,
as described in the following table:
Speed Bias < 0.5V = 50% of rated power
Speed Bias = 0.5V = 0% of rated power
Speed Bias = 2.5V = 50% of rated power
Speed Bias = 4.5V = 100% of rated power
Speed Bias > 4.5V = 50% of rated power
Frequency Trim is not active in System Control mode.
The Real Power Controller uses the System Real Load
Control gains for operation in System Control mode.
Soft Load/Unload
The Real Power Control references a ramping target
(according to the Real Power Ramp Rate) from 0 kW to
the mode-related target for the Real Power Control
when soft-loading. The target ramps from the target to 0
according to the same ramp rate in soft-unload mode.
A generator will soft-load any time that it synchronizes to
a live paralleling bus. Soft-unloading is triggered by the
removal of the load enable signal to the controller or by
Generator Management. In both cases, the breaker will
be signaled to trip when the real power drops below the
disconnect level.
12.4.7 Reactive Power Control
The reactive power output of a generator is related to the
magnetization energy in the alternator. When a
generator is operating as a single unit, there is no good
way to control the magnetization energy in the alternator
without changing the output voltage of the generator. In
a parallel system, there is more than one source than
can supply reactive power to the load—hence the
reactive power can be shared between the sources,
allowing it to be controlled.
Because the output of the generators is tied together,
the voltage amplitude of the generators will remain
essentially identical, regardless of the magnetization
energy that a single alternator provides (providing that
the load requires enough magnetization energy that the
single alternator isn’t overpowering the other alternators
on the bus and forcing them to increase output voltage
and that it doesn’t require more than the other
alternators can handle).
If the voltage bias is increased, the voltage regulator will
try to increase the field current to the alternator rotor to
cause the magnetic energy in the alternator to increase,
increasing the voltage output of the alternator. If the
alternator voltage output is unable to change, the field
current will steadily increase as long as the target
voltage remains higher than the actual voltage. This
allows the Power Control logic to increase the reactive
load on a paralleled generator.
If the voltage bias is decreased, the voltage regulator will
try to decrease the field current to the alternator to
decrease the magnetization energy in the alternator and
to cause the output voltage to decrease. If the alternator
voltage output is unable to change, the field current will
steadily decrease as long as the target voltage remains
lower than the actual voltage. This allows the Power
Control logic to decrease the reactive load on a
paralleled generator.