azecraze
Member
Before I go on with anything else, I would first of all like to thank all who helped me thru a very difficult time I was having a few months ago while setting up a mini hydro power plant. This is in relation to analog input to a ML1200 PLC.
Special thanks to Tom, Ron & Mtn_Bkng_Dave.
Here is the post in question.
Ok now to recap on that:
I have a turbine running at 50Hz no load and as I increase the water supply to the turbine, the load is proportionally increased via a Watlow load controller to an element bank load dump. With no PID control, this causes a steady state oscillation of 6 Secs. (The water increases the speed, so the load is increased, so the turbine slows down, so the load is dumped etc etc etc).
I have set up the PID in the PLC using the method described in the ML1200/ML1500 manual and that smooths it out just fine. In fact I am very pleased with the way it has smoothed it out. This then means that as I add actual a SMALL user load to the turbine the load is nicely transferred from the load dump to the actual user. Great Great Great.
The problem is that there is a very poor response to a LARGE load change.
eg 20% of the CV
Invariably, the PID does not think that it should be dumping load to compensate for the increased load and the turbine underspeeds, and that is the end......
So I try tweaking I and D and this causes violent response.
Any ideas as to the correct procedure to correct this would be great.
Special thanks to Tom, Ron & Mtn_Bkng_Dave.
Here is the post in question.
Ok now to recap on that:
I have a turbine running at 50Hz no load and as I increase the water supply to the turbine, the load is proportionally increased via a Watlow load controller to an element bank load dump. With no PID control, this causes a steady state oscillation of 6 Secs. (The water increases the speed, so the load is increased, so the turbine slows down, so the load is dumped etc etc etc).
I have set up the PID in the PLC using the method described in the ML1200/ML1500 manual and that smooths it out just fine. In fact I am very pleased with the way it has smoothed it out. This then means that as I add actual a SMALL user load to the turbine the load is nicely transferred from the load dump to the actual user. Great Great Great.
The problem is that there is a very poor response to a LARGE load change.
eg 20% of the CV
Invariably, the PID does not think that it should be dumping load to compensate for the increased load and the turbine underspeeds, and that is the end......
So I try tweaking I and D and this causes violent response.
Any ideas as to the correct procedure to correct this would be great.