Winco DGC-2020 - Manual (Page 332)

C-2 DGC-2020 Tuning PID Settings 9400200990 Rev K
TUNING PROCEDURES
Voltage Controller Tuning Procedure
The voltage controller is tuned prior to the speed controller. Set all gains in voltage controller, speed
controller, and KW load controller to 0. Start the generator and close the breaker onto some load.
The voltage controller is only active during synchronization when the DGC-2020 is trying to close the
generator breaker. In order to tune it, a variable AC voltage source must be connected across the bus
input of the DGC-2020. The generator must be started, then a breaker close sequence initiated by
applying a breaker close pulse to a discrete contact input to cause the synchronizer to become active. In
addition the Breaker Close Wait Time parameter and the Sync Fail Activation Delay should be set to a
large value such as 120 seconds or more. This will allow the voltage controller to run for a long enough
time to get meaningful response information.
If the synchronizer times out during the tuning process resulting in a synchronizer fail pre-alarm or a
breaker close failure occurs while tuning, press the Reset button on the front of the DGC-2020 to clear
the associated pre-alarm, then issue a breaker open pulse to a discrete contact input. The synchronizer is
now reset, so a pulse can be applied to the breaker close discrete contact input to restart the
synchronizer. Tuning can resume at this point.
KP - Proportional Gain
Set an initial value of 1 for KP.
Each time KP is set, disturb the system by changing the voltage on the bus input of the DGC-2020 so that
the DGC-2020 will try to follow it. Verify that the generator’s output approaches the new value in a stable
manner. Since KI is zero at this point, there may be some small difference between the generator’s output
and the bus it is trying to follow. The important thing is that the generator’s output behaves in a stable
manner. If it is not stable, lower the value of KP and repeat.
Repeat this procedure, raising KP until the system is unstable, and then lower it to half the value where
instability is first attained.
If it is not possible to obtain stable voltage operation, it may be necessary to reduce the control gains in
the voltage regulator that has its analog bias input driven by the LSM-2020.
KI - Integral Gain
Set the initial value of KI to be a tenth of the value set for KP.
After setting a value for KI, disturb the system by changing the voltage on the bus input of the DGC-2020
so that the DGC-2020 will try to follow it. Verify that the DGC-2020 controls the voltage to go to the new
value in a stable manner. It is not stable, lower the value of KI and repeat.
Repeat this procedure, raising KI until the system is unstable, and then lower it to half the value where
instability is first attained.
KD - Derivative Gain
If the performance with KP and KI alone is satisfactory, you may stop here. Otherwise, KD, the derivative
controller gain, can be used in conjunction with TD, the noise filter constant, to reduce overshoot obtained
with the PI control. Setting KD and TD is an iterative process. Start with small values of KD such as 0.1 or
half the KI value, whichever is less.
TD is the constant of the low pass filter which filters the controller input if high frequency interference
presents a problem when derivative control is employed. TD ranges from 0 to 1. TD=0 is no filtering.
TD=1 is heaviest filtering.
Tuning of KD can be achieved through the following steps. First set TD=0 to eliminate filtering. Raise
speed KD and check for stability. Each time KD is raised, disturb the system by changing the voltage on
the bus input of the DGC-2020 so that the DGC-2020 will try to follow it. Verify that the DGC-2020
controls the voltage to go to the new value in a stable manner. Raise KD until the system is unstable, and
then lower it to half the value where instability if first attained.
If high frequency noise seems to be entering the system, set TD to 0.001 and see if the noise induced
behavior is reduced. Raise TD until desired reduction of noise behavior is achieved. Once KD has been
set, tune KD again. TD ranges from 0 to 1 with an increment of 0.001. TD=0 is no filtering, TD=1 is
heaviest filtering. If noise again appears to be a problem, adjust TD until desired behavior is achieved,
and then retune KD.