Woodward 2301E, Инструкция по установке и эксплуатации, Страница: 53 / 182

Manual 26641 2301E Digital Control
Woodward 43
Isochronous Load Sharing on an Isolated Bus
Isochronous load sharing operates all generator sets in a system in the
isochronous mode. Load sharing is accomplished by adding a load sensor to
each electric isochronous governor. The load sensors are interconnected by the
load sharing lines. Any imbalance in load between units will cause a change to
the regulating circuit in each governor. While each unit continues to run at
isochronous speed, these changes force each machine to supply a proportional
share of power to meet the total load demand on the system (see Figure 3-8).
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 de-rating 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
PTs and CTs (terminals 1 to 9) of the 2301E 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.
Load Pulse / Load Rejection
Load Pulse
The load pulse logic measures how fast the generator load changes with respect
to time. When a large increase in generator load is detected, from the measured
PT and CT input, then the speed reference output is increased momentarily to
compensate for a drop in speed.