The DEIF controller is the secondary regulator. It does not regulate the engine's fuel directly. Rather, it modifies the set point
for the governor, for example, based on the power management requirements. The DEIF controller can use proportional or
PID control.
The primary regulator and the system can be different for each application, and unknown to the DEIF controller. In addition,
the tuning of the primary regulator may affect the tuning of the secondary regulator. It is therefore not possible to pre-tune the
DEIF controller. For example, for a slow governor and/or slow system, the secondary regulator (the DEIF controller) must not
change the set point too fast. However, for a more responsive governor and system, the DEIF controller can change the set
point more aggressively. For every system, the control response can be optimised for an acceptably fast control response,
without the control response causing instability.
Relay control
For relay outputs, only proportional (P) control is available. However, there are a number of other relay output parameters
that may need to be adjusted.
In the governor/AVR, it may be necessary to adjust the resolution of the control range.
For the relay output, you can adjust the Period time and the Minimum ON time.
For each of a number of control scenarios, you can adjust the controller gain and deadband.
Analogue control
For analogue outputs (this includes PWM outputs), proportional-integral-derivative (PID) control is available. For each of a
number of control scenarios, you can adjust the PID parameters.
6.1.3 Optimum regulation
Optimum regulation ensures that the controller response is stable, without the response being too long. After a sudden
change, as the controller brings the operating value back to the set point. Up to a total of three corrections (overshoot or
undershoot) are okay. An overshoot is when the correction is higher than the set point, and an undershoot is when the
correction is lower than the set point. If too many overshoots and/or undershoots are present, decrease the gain (Kp), then
check the controller response to the change.
The example below shows a situation where the frequency was lowered due to a change in the system (1). The first
correction overshoots the frequency set point (2). The second correction undershoots the frequency set point (3). During the
third correction the frequency settles inside the stable range around the set point. In this example the controller only required
a total of two corrections to become stable.
Figure 6.2
Example of an optimum frequency response to a load increase, with one overshoot and one undershoot
50.0
time
Frequency
[Hz]
49.0
51.0
Change
1
2
3
Set point
PPU 300 Commissioning guidelines 4189341106 UK
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