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Re: [TRNSYS-users] PID controller parameters setting - Cooling coils Type508

Newer versions of Type 508 have internal controls in the model to maintain outlet temperatures, humidity, etc.  The changes were made to make it much easier to control the outlet conditions without having to use difficult control sequences.  The latest version of the TESS HVAC library contains this updated model as well as later version of the previous HVAV library (I believe).  I do know there has been a recent fix that I found when the air flow rate >> water flow rate.

Jeff 

Jeff 

Sent from my iPhone

On Mar 29, 2022, at 8:21 AM, Clement Nevers via TRNSYS-users <trnsys-users@lists.onebuilding.org> wrote:

 
Hi everyone,

I have encountered some problems when the PID controller(type23) was used for controling the outlet air temperature of cooling coil (type508).

The fluid flow rate of cooling coil is conected with a outlet of flow diverter (type11). Thus, the fluid flow rate of cooling coil is determined by the control signal of the flow diverter. I build this mechanism in order to model a cooling cooling with a bypass in fluid side (3-ways valve flow controlling).

Then, the PID controller is used for keeping the outlet air temperature (Controlled variable) of cooling coil at a setpoint, the control signal is basically the fluid proportion of the flow diverter. 

But no matter how to adjust the parameters of PID, the outlet air temperature oscillation cannot be eliminated.

So, I have the following questions :

How to determine the parameters of PID controller, such as Gain constant, Integral time and Derivative time, to avoid  Controlled variable oscillation ? 

Is there a better way to accurately model this system? 

Thanks in advance,

Regards

NEVERS Clément
Research Assistant - LMDC, Toulouse
 


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