Basler Electric DGC-2020 - Manual (Page 589)

Repeat this procedure, raising K
i
until the system is unstable, and then lower it to the highest value
yielding 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 P
i
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 kW control becomes active, and check for stability. Change the base load
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 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
.
kW Load Controller Tuning Procedure Using Multiple Machines in Island Parallel
Operation
In Island Parallel operation the kW Load Controller regulates the kW output of the machine to a level
determined from the analog load share line or inter-genset communications to accomplish kW sharing
with the other machines in the system. When properly tuned, the kW controller regulates the kW output of
the machine to a level equal to the average system kW load, on a percentage of capacity basis. Thus,
each machine will share kW equally on a percentage of capacity basis.
The procedure below is written for the case where two machines 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 you need to tune another one against it, the following
procedure still applies, except that PID values in the machine that has already been tuned should not be
changed.
K
p
- Proportional Gain
Disable the Speed Trim function in all machines when tuning the kW load controller gains.
On both machines set the K
p
, K
i
, and K
d
gains in kW load 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
load 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 error in the load sharing.
The important thing is to verify stable load sharing is achieved.
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 kW operation, it
may be necessary to reduce the control gains in the governor which has its analog bias input driven by
the LSM-2020. Test at various levels of kW load if a means of varying kW load is available.
K
i
- Integral Gain
Set the initial value of K
i
to be a tenth of the value set for K
p
in both machines.
Each time K
i
is set in both machines, parallel the machines and check for stable load sharing then open
the generator breaker on the second generator and check that both units are still stable. If the system is
not stable, lower K
i
and repeat the test. Test at various levels of kW load if a means of varying kW load is
available. Repeat this procedure, raising K
i
in both machines until the system is unstable, and then lower
it to the highest value yielding stable operation.
9400200990 Rev X DGC-2020 Tuning PID Settings C-7