Basler Electric DGC-2020 - Manual (Page 587)

Raise K
p
and repeat the test until unstable operation occurs. Then lower K
p
to the highest value where
stable operation was attained.
If it is not possible to obtain stable var controller operation, it may be necessary to reduce the control
gains in the voltage regulator which has its bias input driven by the LSM-2020.
K
i
- Integral Gain
Set the initial value of K
i
to be a tenth of the value set for K
p
.
Each time K
i
is set, synchronize the generator to the utility so that var control becomes active. Check that
operation appears stable. Change the var setpoint in 10% steps and check for stable operation. If the
system is not stable, lower K
i
and repeat the test.
Repeat this procedure, raising K
i
until the system is unstable, and then lower it to the highest value for
which stable operation is achieved.
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. Start with small values of K
d
such as 1/10 th the value of
K
p
or 1/10 th the value of K
i
, whichever is smaller.
Tuning of K
d
can be achieved through the following steps. Set an initial value of K
d
, then synchronize the
generator to the utility so that var control becomes active, and check for stability. Change the var setpoint
in 10% steps and check for stable operation. Raise K
d
, repeating the tests until the system is unstable,
and then lower it to half the value where instability is first attained.
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 .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
.
var/PF Controller Tuning Procedure Using Multiple Machines in Island Parallel operation
In Island Parallel operation the var/PF controller regulates the kvar output of the machine to a level
determined from inter-genset communications to accomplish kvar sharing with the other machines in the
system. When properly tuned, the var/PF controller regulates the kvar output of the machine to a level
equal to the average system kvar load, on a percentage of capacity basis. Thus, each machine will share
kvar equally on a percentage of capacity basis.
The procedure below is written for the case where you have two machines that need to be tuned. Thus,
any time a PID gain change is made, the change should be replicated in both machines before any
testing for stability.
If a machine is available that is already tuned, but another one needs tuned against it, the following
procedure still applies, except that PID values in the machine that have already been tuned should not be
changed.
K
p
- Proportional Gain
On both machines set the K
p
, K
i
, and K
d
gains in var/PF controller to 0. Set the K
g
value to 0.1. Set an
initial value of 1 for K
p
.
Close the breaker of the first machine onto a load. Parallel the second generator and check for stable
kvar sharing between the two machines. Then, open the generator breaker on the second generator and
check that both units are still stable. Since K
i
is zero at this point, there may be some error in the kvar
sharing. The important thing is to verify stable sharing is achieved. Repeat for various levels of kvar load if
a means of varying kvar load is available.
Raise K
p
in both machines and repeat the test until unstable operation occurs. Lower K
p
to the highest
value yielding stable operation. If one machine becomes unstable before the other as gains are raised, it
may be necessary to do any further gain increases in only one machine. If the machines are not similar,
you may end up with different gains in each machine. If it is not possible to obtain stable kvar sharing, it
may be necessary to reduce the control gains in the AVR which has its analog bias input driven by the
LSM-2020.
9400200990 Rev X DGC-2020 Tuning PID Settings C-5