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cascade PI, whith simulation betwen simulink and Psim!

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hello, I am trying to tune 2 PI in cascade that are in simulink, but as I do the autotune this error appears.
"The plant model in the PID loop linearizes to zero, and therefore cannot be used in PID controller design. This problem occurs when one or more blocks in the PID loop have zero gain or the feedback loop is not physically closed. Click "Continue" to launch the PID Tuner and obtain a new plant model in the "Obtain plant model" dialog. Click "Cancel" to abort PID design and return to the block dialog. For more information, see the Simulink Control Design documentation. "
my questions are:
1-is it because of the co simulation whit PSIM? And how can I solve this 2- can anybody explain to me a way to tune it manually

Answers (1)

Arkadiy Turevskiy
Arkadiy Turevskiy on 23 Jul 2014
Yes, most likely the root cause is cosimulation with another tool. PID Tuner linearizes the model and uses the resulting linear model to compute PID gains. If the block used to call 3rd party software does not linearize, you will end up with the error you see.
To get around this, you can try to figure out what your plant transfer function is using other methods. One is frequency response estimation, which puts a sinestream through the model and uses the data to compute the frequency response. See this example showing the workflow.
If you have 14a, another option is to inject a step signal to the plant, record the output, and compute a transfer function using system identification. This workflow is shown here .
Hope this helps.

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