In order to reduce oscillations of WEB-AHU COLD loop, on September 4th, we modified the WEB-AHU PID Controller parameters, in detail:

9:11 UTC removed derivative term (from 90 sec to 0 sec)

11:45 UTC increased proportional band from 3 to 4

14:25 UTC increased derivative time fro 0 to 90 sec.

Fig.1 summarizes consequences of our actions.

In details, the removal of derivative term stops the oscillation (period 120sec). The residual oscillation in the correction signal, follows the chiller temperature (Fig2).

The reintroductiion of derivative term causes a further reduction of the temperature error signal (Fig1).

PID parameters:

Integration time: 360 sec

Derivative time 90 sec

Proportional band 4°