Cascading PID Loops Siemens TIA V12

[dabanani]

I am wondering if its a good idea to cascade pid loops. For example If I want to control two variables Current and Voltage. If i can feed output of the Voltage PId in to the Current Pid to create a cascaded control loop.

Thanks any help will be highly appreciated.

 

[Peter Nachtwey]

I am wondering if its a good idea to cascade pid loops.

It depends on the application.

For example If I want to control two variables Current and Voltage. If i can feed output of the Voltage PId in to the Current Pid to create a cascaded control loop.

You can't control two variables at the same time. You can control one and limit the other. You can work out a cost function and minimize that.

Thanks any help will be highly appreciated.

You need to state EXACTLY what you are trying to do.

 

[dabanani]

I am trying to control output of a rectifier either by current or voltage. And i want to be able to switch this control at any time. So i can start my process by controlling the voltage and at any time i can switch to control by current.

I have both current and voltage feedback, and controlled variable = rectifier firing angle.

 

[KalleOlsen]

Hi!
What kind of application is it? Furnace/heating/melting/dryer/...

For some applications it could be better to control I*I or P.

Kalle

 

[dabanani]

Its going to be for heating for a school project. And all i am required to do is provide either constant current or voltage at any given time. So i am thinking of feeding output of the voltage pid into current pid so that i can control the output either by changing set point on current or voltage.
Please let me know if this is possible or if its a good idea. Or what is the best way to go about this