Woodward 2301D, Инструкция по установке и эксплуатации, Страница: 87 / 130

Manual 26247 2301D/2301D-EC Digital Control
Woodward 79
Constant dynamics refers to dynamics parameters that will remain constant as
entered and do not vary with engine speed. Dynamics may be configured to vary
with load by using the 5-Gain mapped dynamics. Constant dynamics are useful
for fuel systems and processes that tend to be equally stable throughout the
prime movers speed and load range. Variable dynamics vary gain by the ratio of
actual engine speed to rated speed. The 5 point Gain mapped dynamics is a two-
dimensional curve with five breakpoints that vary gain as a function of fuel
demand or kW. The 5 point Gain mapped dynamics compensate for non-linear
fuel systems and are useful for engines or processes whose dynamics change in
a non-linear manner with load.
The control can automatically switch between two gain settings, based on engine
speed error, to provide improved transient load performance. Speed error is the
difference between the speed reference and engine speed. The control
automatically increases gain by an adjustable ratio when a speed error
exceeding an adjustable window occurs (See Figure 3-2). During steady-state
constant-load operation, the control uses the base gain setting. This base gain is
adjusted by the user to a value which prevents the control from responding to
minor speed fluctuations inherent with reciprocating engines. This feature
essentially eliminates harmful jiggle of the actuator and fuel system linkage.
When the speed error exceeds an adjustable window width (e.g., during a load
transient), the control automatically increases gain by an adjustable ratio. This
increased gain produces a faster fuel response and quickly restores engine
speed at the speed reference. The base gain is restored once the control senses
a return to steady-state operation. This feature is available for all gain choices.
Furthermore, this feature is active when paralleled to a utility grid. Although
actual engine speed does not change, the speed reference is changed when
corrective bias signals are applied by load sharing or droop during load
transients. Large corrective bias signals will produce a large speed error to
automatically increase gain.
The control also provides a second complete set of dynamic adjustments which
are selected when the CB Aux discrete input is activated. Two sets of dynamics
are useful where engine operating conditions change, such as in electrical power
generation systems where the unit operation changes when in parallel with a
bus.
Minimum Fuel Function
The Minimum Fuel Function brings the fuel demand to zero. This occurs when
the Close to Run discrete input goes FALSE. It also occurs if the speed sensor
input has failed when the Close MPU Fail Overrd B input is FALSE. The Close to
Run command is the preferred means for a normal shutdown of the engine.
The Close to Run discrete input is not intended for use as the sole
means of shutdown in any emergency stop sequence. To prevent
possible serious injury and engine damage from an overspeeding
engine, do NOT use the Close to Run discrete input as the sole
means of shutdown in any emergency stop sequence.