Basler Electric DGC-2020 - Manual (Page 585)

K
i
- Integral Gain
Set the initial value of K
i
to be a tenth of the value set for K
p
. Start the generator and close the generator
breaker to the dead bus.
Next, 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. If stable operation is not achievable, it may be necessary to lower the value for K
i
. Repeat this
procedure, raising K
i
until the system is unstable, and then lower it to the highest value that achieved
stable operation.
K
d
- Derivative Gain
If the performance with K
p
and K
i
alone is satisfactory, it is recommended K
d
be left at a value of zero. K
d
can amplify noise in a system so it should be used with great care. Otherwise K
d
, the derivative controller
gain, can be used in conjunction with T
d
, the noise filter constant, to reduce overshoot obtained with PI
control. Setting K
d
and T
d
is an iterative process.
Tuning of K
d
can be achieved through the following steps. Set an initial value of K
d
that is 1/10 th the value
of K
p
or 1/10 th the value of K
i
, whichever is smaller. Start the generator and close the generator breaker to
the dead bus.
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 with higher values of K
d
until the system begins to be unstable, then enter half this value
as the K
d
gain.
If high frequency noise seems to be entering the system, T
d
is the constant of the low pass filter which
filters the controller input to reduce the effects of such interference when derivative control is employed.
T
d
ranges from 0 to 1 with an increment of 0.001. T
d
=0 is no filtering, T
d
=1 is heaviest filtering. If T
d
adjustment is necessary, set T
d
to 0.001 and see if the noise induced behavior is reduced. Raise T
d
until
desired reduction of noise behavior is achieved. Once T
d
has been set, tune K
d
again. If noise again
appears to be a problem, adjust T
d
until desired behavior is achieved, then retune K
d
.
Speed Controller Tuning Procedure
The speed controller is tuned prior to the kW load controller. Set Load Control to enabled, and speed trim
to enabled. Set all K
p
, K
i
, and K
d
gains in both speed controller and kW load controller to 0. Set the K
g
values to 0.1.
K
p
- Proportional Gain
Set an initial value of 1 for K
p
. Start the generator and close the breaker to the dead bus.
Each time K
p
is set, execute step responses in the following manner to observe the machine’s response
to the change in the Speed Trim set point.
Next, modify the Speed Trim set point to a level that is one or two hertz higher than the initial setting.
Verify that the generator’s output frequency approaches the new value in a stable manner. Set the Speed
Trim set point back to its original value and observe the generator’s output frequency. Next, modify the
Speed Trim set point to a level that is one or two hertz lower than the initial setting observe the generator
output frequency. Finally, set the Speed Trim set point back to its initial value, and observe the generator
frequency to verify it operates in a stable manner.
Since K
i
is zero at this point, there may be some difference between the generator’s output and the speed
it is trying to reach. The important thing is that the generator’s output behaves in a stable manner. If the
system is unstable, lower K
p
and repeat.
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 is attained. 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 speed operation, it may be necessary to reduce the control gains in the
governor which has its analog bias input driven by the LSM-2020.
9400200990 Rev X DGC-2020 Tuning PID Settings C-3