Controller tuning problem in HYSYS-help please

[naprirfan]

Hi my name is napz
i have a problem in using HYSYS. i'm dealing with PID controller and i can't get the oscillation graph.
the kc value for oscillation graph is between converges and diverges graph. the problem is when i set the appropriate kc, HYSYS is running for a few minutes seems like getting start to oscillate, but then there's always an error. the error message is equation failed to converge
does anybody knows why?
thx a lot

 

[Samiran]

Dear Napz,

What do you mean by oscillation graph ? Are you trying to say that you want to see the effect of PID parameters on your process control system. Have you entered any integral time value ? If not please do so. And also use a small change to start your control.

Samiran

 

[naprirfan]

Thanx for the reply, Mr Samiran.

i want to tune my controller in ZN online methode, and get the best value for PID constant. the procedure is :
1. set the extreme value of integral time(eg :ti = 100,000)
2. set the small value of proportional time (eg : 0.5) if the graph is converges, it means we've set too little value, and if the graph is diverges, means we've set too big value. the oscillation graph is needed to get to the next tuning procedure, to find the best PID value..
but i can't get it,,, ( - do you have any idea?

best regards,
napz