Basler Electric DGC-2020 - Manual (Page 590)

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. In both machines start with small values of K
d
that are
1/10 th K
p
or 1/10 th K
i
, whichever is smaller.
Tuning of K
d
can be achieved through the following steps. Set load control K
d
in both machines, parallel
them together, and check for stability. Then, drop the second generator and check that both units are still
stable. Raise K
d
in both machines until the system is unstable, and then lower it to half the value where
instability is first attained. Test at various levels of kW load if a means of varying kW load is available.
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
.
Generic Gains for Multiple Machine Types
The following method is suggested for determining generic gains for multiple machine types.
1) Decide what levels of reverse power and reverse var (loss of excitation) protection are needed.
2) Once the criteria of step 1 have been established, tune a unit so that one machine can be
paralleled to another unit at no load and not cause any trips.
3) Parallel two machines onto a load, and verify that acceptable load sharing occurs.
4) Add and drop loads with machines paralleled to verify acceptable load sharing occurs, and no
trips occur.
5) Once the settings are deemed “good”, save them as initial settings for a given machine
configuration for all future jobs. The settings shouldn’t need changed unless there is tripping or
load sharing characteristics need to be changed.
6) Test the units paralleled under no load and verify that no trips occur.
7) Parallel two machines onto a load, and verify that acceptable load sharing occurs.
8) Add and drop loads with machines paralleled to verify acceptable load sharing occurs and no
trips occur.
9) If the settings for a particular machine type need to be modified, keep those settings to be used
as initial settings for all future machines of that type.
10) Test every machine with steps 6, 7, and 8.
It is not expected that one set of numbers works for all machines, but it is probable to have 6 to 12 sets of
settings that cover a wide range of machine sizes and engine manufacturers. However, once a set of
gains has been determined for a particular machine type, the same gains should work in all identical
machines.
C-8 DGC-2020 Tuning PID Settings 9400200990 Rev X