Basler Electric DGC-2020 - Manual (Page 584)

the combined controller-process stability. However, differentiation of a signal amplifies noise in
the signal, and thus, this term in the controller may be sensitive to noise in the error term, and can
cause a process to become unstable if the noise and the derivative gain are sufficiently large.
Larger K
d
decreases overshoot, but slows down transient response and may lead to instability. In
general K
d
is not recommended in the DGC controllers unless testing shows that it benefits
system performance.
Table C-1 shows the effects of increasing parameters.
Table C-1. Effects of Increasing Parameters
Parameter Rise Time Overshoot Setting Time Steady State Error
K
p
Decrease Increase Small Change Decrease
K
i
Decrease Increase Increase Eliminate
K
d
Small Change Decrease Decrease None
Tuning Procedures
Prior to performing any controller tuning, it is strongly recommended that Generator Protection, in
particular Reverse Power protection and Loss of Excitation protection, should be configured to protect the
machine in case any reverse power or reverse var situations occur during the tuning process.
Voltage Controller Tuning Procedure
The voltage controller is tuned prior to the speed controller. Set all K
p
, K
i
, and K
d
gains in the voltage
controller, speed controller, kW load controller and var/PF controller to 0. Set the K
g
values to 0.1.
The voltage controller is active during synchronization when the DGC-2020 is trying to close the
generator breaker, and also when the generator breaker is closed and the generator is not paralleled to
utility power and the voltage trim function is enabled. In order to tune the voltage controller, the unit is
operated with the generator breaker closed and voltage trim enabled. We can then change the rated
voltage of the machine to change the voltage controller set point and observe the response. Set the
Voltage Trim function and the var/PF controller to enabled, and verify in logic that when the generator
breaker is closed, the Parallel to mains logic element is not true. When the engine is running and the
generator breaker is closed, the voltage controller should be operating to accomplish voltage trim, driving
the system voltage to the level set by the Rated Voltage setting in the system ratings.
K
p
- Proportional Gain
Each time K
p
is set, we will modify the rated voltage setting in the Rated Data and observe how the
generator output voltage responds to the change.
Set an initial value of 1 for K
p
. Start the generator and close the generator breaker to the dead bus.
Verify that the generator’s output approaches the Rated Voltage in a stable manner. Since K
i
is zero at
this point, there may be a difference between the generator’s output and the Rated Voltage set point.
The important thing is that the generator’s output behaves in a stable manner. If it is not stable, lower the
value of K
p
and repeat.
Now modify the Rated Voltage setting to a level that is 3% to 5% higher than the initial setting. Verify that
the generator’s output approaches the new value in a stable manner. Set the Rated Voltage Setting back
to its original value and observe the generator’s output. Next, modify the Rated Voltage setting to a level
that is 3% to 5% lower than the initial setting observe the generator output voltage. Finally, set the Rated
Voltage back to its initial value, and observe the generator output voltage to verify it operates in a stable
manner.
Repeat this procedure, raising K
p
until the system begins to operate in an unstable manner, and then
lower it back to the highest value where stable operation was achieved. Note that if the generator output
is not coming very close to the set point value, it is often an indication that the value of K
p
is too low.
If it is not possible to obtain stable voltage operation, it may be necessary to reduce the control gains in
the voltage regulator which has its analog bias input driven by the LSM-2020.
C-2 DGC-2020 Tuning PID Settings 9400200990 Rev X