Woodward 2301D, Инструкция по установке и эксплуатации, Страница: 98 / 130

2301D/2301D-EC Digital Control Manual 26247
90 Woodward
Base Load on an Isolated Bus
Base Load is a method of setting a base or fixed load on a machine operating in
parallel with an isolated bus. This is accomplished by using an isochronous load
control and providing a reference at which to control the load. The governor will
force the generator output to increase or decrease until the output of the load
sensor is equal to the reference setting. At this point, the system is in balance.
This method can only be used where other generator sets are producing enough
power to meet the changes in load demand. This operating mode is ideal for
either soft loading additional units into an isochronous system, or for derating or
unloading a machine.
Base Load
Base Load for a system paralleled to an infinite bus or utility is the same as base
load in an isolated system. The advantage of base loading over droop is that
when separating from a utility, there is no frequency change. Simply removing
the bias signal on breaking from the utility returns the system to isochronous.
Actuator Droop
Droop is dependent on load (this is the measured kW) or on the actuator
position. As already mentioned, droop based on the measured load in kW by the
PT’s and CT’s (terminals 1 to 9) of the 2301D is used.
With actuator droop the speed reference is decreased when the actuator output
increases. In Menu G**Speed Setting** the minimum and maximum actuator
position settings are adjusted. The droop function is active from this minimum
position (actuator at rated speed, no load) to the maximum actuator position
(actuator at rated speed, full load).
The droop is a percentage of the rated speed. When droop is set at 0 there is no
actuator droop. For example:
Rated speed is set for 900 rpm.
Droop is set for 3%.
Speed reference is at maximum actuator position = 900 - 27 = 873 rpm.
Loadpulse / Load Rejection
Loadpulse
The loadpulse logic has been tested in August 2002 on a DG-set. Activating the
loadpulse logic did not result in significant improvement of load-acceptance.
There was improvement on the load-rejection tests.
The loadpulse logic measures how fast the engine load changes in time. When a
large increase in engine load is detected, then the speed reference output is
increased momentarily to compensate for a drop in speed.
Load rejection
If a large decrease in engine load is detected, the speed reference or actuator
output is decreased momentarily to compensate for a large speed overshoot.
With this logic an overshoot can be reduced or an overspeed can be prevented
when an engine is at 100 % load and is unloaded instantly.