Process tunning with PID ISA GE 90-30

Hi Experts?
I am very greatful to this site who helps me on each steps but now i am stuck to tune up the PID setting of the gas turbine fuel.
I hope many experts are there who helps me out. I attached an image while PID Enable.

First of all i mark two lines on the image. I can not understand that is it a PV minimum (00000)or maximum (11522)?

At that time SP increase or decrease by the user the following logic execute. For example user press the push button a 1 is add in the previous setpoint and then this setpoint is converted into frequency. Suppose 62% is equal to 7144 of the 11522 Hz.

Now PV is directly address by the %AI (Frequency).

But the problem is that there is always a error show within 1 second so the speed sometime goes too 61% or some time goes to 63% if the setpoint is 62%.

I want to use percentage instead of %AI and as well as SP is also in percentage. But when i do it the engine is contineously rampup and shutdown.

I also change the 11522 (which i mark) to 100 when using percentage with same gains.

CV is not manipulated when using %age at SP and PV it shows always 20000(Lower clamp) and 0%.

How can i minimize the speed variation?
Is KP increase or decrease? Is KI increase or decrease?

My scan time while engine is running is 15ms. I set the sample time to 10 ms is it correct?

i want that when both error is zero then speed not changed untill user increase or decrease the setpoint.

whenever user increase the setpoint suppose 62% to 65% the PV goes to 66% then back to 63% and after that it stays on 65% but after sometime 64 to 65 flactuation noted.
I check the noise but there is nothing found.
I hope guys you will help me.
Thanking you i will remain
Regards

Friends;
Please help me?
Regards

The two values you flagged are the minimum and maximum display values for the SP and PV. They are set by the values you write to the upper display limit and lower display limit parameters of the PID function block (Base Ref +26 and Base Ref +27).

If your scan time is 15 mS and you have set the sample period to 10 mS, the PID equation is evaluated every scan. You can make it evaluate less frequently by increasing the sample period, but you can never make it evaluate more frequently than once per scan and never more frequently than once every 10 mS even if the PLC scan is less than 10 mS.

As presently set up, your deadband is effectively zero. I assume you actually want a +/- 2 count deadband. If that is the case you need to use -2 in the Deadband - register. When the difference between the SP and the PV falls between Deadband - and Deadband + values, the PID equation is not evaluated.

Thanks steve. I understand a little bit.
How can i apply a dead time in this configration?
Means i want the PV takes some time to starts change when CV change?
Minimum slew time describe that a CV not more move than as you calculated.For example
32000*1sec/5 sec=6400 counts per solution.
But i want delay in PV to start change?
How can?

What about when i use the SP and PV in percentage instead of Hertz? Is not possible in this configration?
Regards

You have no control over how the process reacts to a change in CV. When the PID function changes the CV, that value is sent to the analog output module and the process reacts to it. The PV is the signal the process returns to the PLC. The slew rate will only apply a limit to the rate of change of the CV.

If you change the SP and PV to units of percantage instead of hertz, you will probably need to adjust the gains to compensate. The error is multiplied by the P gain to get the proportional component of the CV. If the error expressed in percentage is larger then the error expressed in Hertz, the proportional contribution to the CV will be a larger value.