PID fpga synchronous generator

[carlo93]

Good evening,

I’m trying to realize a control for a synchronous generator in stand-alone mode. The problem is in the calculation of the rms of the voltages values at terminals of generator (rate 230 V phase to neutral) . I acquire the data from a NI 9225 module but when I calculate the rms, the values obtained moves in a range too wide.

For example, if I measure 8 volts with a normal multimiter, in the labview program this values moves between 7 and 9.

I’m using a NI chassis 9076 and two modules 9225 and 9076 for input and output and working with FPGA.

May you help me?

Thanks

Best regards

[Blokk]

I cannot access LabVIEW now, but i think you should give more details. Like your exact wiring diagram, and ranges. That ai module can read voltages up to +-10 volts. You mentioned 230V level in your text. Can you describe further?

[carlo93]

Thank you for the answer.

In the photo there is the scheme.

It is a real generator (1kw rated power). NI 9225 has 300 Vrms as maximum input. I mentioned the example about 8 volts but i have the same problem with other voltage,if I want to measure 101 volts (phase to neutral voltage) in the labview program i see an rms value moving between 98 and 103 (not a constant value).

The 9225 has three inputs and I connected the three phase to each positive and the grounds of the module to the common neutral,so I'm measuring the phase to neutral voltage and the rated value is 230V.

If you need more information,let me know

Thank you very much

[LeahE]

I wonder whether the phases on your real generator are not completely balanced, or that there is some sort of fluctuation. What sort of excitation does the generator have?

I see that your 'DC and RMS Measurements' express vi in altaprova.vi is set to 1000 samples at 50kS/s to give a measurement time of 20ms (i.e. 50Hz), perhaps you need to take more samples to get the same value as on your multimeter.

Could you look at NI MAX test panels for your input modules to check what it is receiving?

[carlo93]

Thank you all for the answers, I solved that first problem....there was something wrong in the pin connections; anyway,now another issue with PID: 

I gonna attaching a short video (it is in youtube because is too big the file)  with the answer of my PID to an input; the answer is totally strange and I don't understand why.

can someone help me?

https://youtu.be/WiA0ht2sP0I

[carlo93]

Good evening, 

I’m trying to realize a control for a synchronous generator in stand-alone mode.

Using a NI chassis 9076 and two modules 9225 and 9076 for input and output and working with FPGA.

In the photo there is the scheme.

It is a real generator (1kw rated power). NI 9225 has 300 Vrms as maximum input.

The 9225 has three inputs and I connected the three phase to each positive and the grounds of the module to the common neutral,so I'm measuring the phase to neutral voltage and the rated value is 230V.

 If you need more information,let me know

Issue with PID: 

I gonna attaching a short video (it is in youtube because is too big the file)  with the answer of my PID to an input; the answer is totally strange and I don't understand why.

can someone help me?

Thank you

https://youtu.be/WiA0ht2sP0I

[GerdW]

Hi Carlo,

no need to post in two places: keep discussion in just one thread!

[carlo93]

Hi, I'm sorry but the topic now is totally different, is there a way to change the main title of the post?

Best regards

[GerdW]

Hi Carlo,

the answer is totally strange and I don't understand why.

Which part of this video is strange to you? What don't you understand?

in the first minute the pv only reaches a minimum value when the sp==0. This might be a result of bad output limits or limits of your controlled system…

[carlo93]

Thanks for your answer,

It's strange because I didn't expect that 'stair' waveform when i move (second 15-16 of the video) the SP from zero to 20. I don't understand if it is a problem in the loop timer ( I thought this just now) or if the problem is another one.

What you mentioned about the constant value when there is a SP=0 is normal, it's not that my issue.