Why all the plots from my program originate from (0,0).

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Lei 2012-9-10

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I am building a state-space feedback controller for a single phase bipolar inverter by using MATLAB Simulink.

I want to extact the angle of the output voltage as part of the control strategy. However, I found out all the voltage plots originate from (0,0). In such a case, how to tell the phase difference and which voltage is the reference?

I attempted to use code "Angle(V)" and FFT function block. It either give me 0 degree or 180 degrees.

I have also tried to use "phasor solver", however, my IGBT switches are not compatible with this mode.

Anybody has experience of extracting phase anlge of a voltage in MATLAB Simulink? I really appreciate any suggestions and it is urgent.

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Lei 2012-9-20

Thanks for replying. I am not too sure if Simulink automatically find the reference. I also managed to do exactly the same controller in PSCAD and I didnot specifically define a reference.

If I have to define a reference, does anyone know how to define a reference?

Thanks guys again

Daniel Shub 2012-9-24

Lei, please do not add meaningless bumps. Further, if you insist on bumps, don't add them as answers since this reduces the likelihood of people looking at the question (since it is already answered).

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Answer 1

Babak 2012-9-18

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The reason that usually simulink generated plots (out of scope) start from (0,0) is that the initial conditions of the Simulink blocks are set to zero.

In my opinion you should check the initial conditions of the source blocks you migt have.

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Lei 2012-9-20

How should I check the initial condition?

Babak 2012-9-20

first find out what source blocks you are using in your Simulink model (like step, clock, time, input, ramp,... ) then double click on those blocks that are placed in your simulink model file. For each block a GUI opens up. The GUI includes information on how to set up the parameters corresponding to those blocks. source blocks usually have a parameter to be set up which is their initial condition

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