Speed pid control of turbine

[kolma 0]

Dear all,

For quite some time I would like to make pid speed control of water turbine for synchronization purpose. But with on off valve of needle. So open or close. With analog value on proportional valve is working, but running to get pulses from pid regulator, not successful. If someone could help me with an example I would be really grateful. I'm using S7-300 PC.

Thanks, Kolma

[Bryll 31]

Start to create your PID circuit as you should do with an analog proportional valve.

The you create a circuit with a time base that works like a PWM.

I made a similar function for my heating system in the house.

The heating system is circulating water for the floor heating, and each section is controlled by a wax valve.

These are very slow when they open and close.

My PWM period is 1 minute, and the maximum PID output is 600.

The shortest pulse or pause (Duty cycle) is then 100mS.

I'm using transistor outputs connected to solid state relays to control my valves.

So if my PID has an output signal of 367 will the valve have power for 36,7 seconds, and will be out of power for 23,3 seconds.

 

You can chop up the PID value into pulses by creating a counter that (for example) overflows at the value of 600.

The PWM period is then 60,0 seconds if you increment the counter every 0,1 seconds.

Compare the PID output (in this case 0-600) with the counter created above.

If the counter value is smaller or equal to the PID output, then hold your output high.

If the counter value is greater than the PID output, then hold your output low.

 

Before creating anything, check how fast your output can be controlled.

A relay output is a bit slower than a transistor output.