Simulink vector space alpha beta transformation

Join the discussion
Registration is free. Start your own thread to ask a follow-up.
2 replies · 3K views · last reply
Cdz
Messages
20
Reaction score
1
<< Thread moved to the HH forums from the technical engineering forums, so no HH Template is shown >>[/color]

The model:
Simulink block diagram: a yellow block labelled reference generation has outputs mag and angle; mag goes to a Terminator block, and angle goes to a Gain block labelled 180/pi, which feeds a Scope.

Simulink block diagram titled reference generation subsystem: three cosine voltage blocks (Varef, Vbref, Vcref) feed a bus into alpha and beta transformation blocks, then a Cartesian to Polar block with mag and angle outputs.

The goal:
1. Create a three phase voltage
2. Do a alpha-beta transformation
3. Do a Cartesian to Polar transformation
4 Check the output angle
The expected result:
Since the space vector rotates counter-clock wise the angle should from 0 to 180o and drop to -180o(instantly!) and rise again and repeat.
But the actual result is:
Sawtooth plot of angle in degrees against time, rising from about -160 to 180 and dropping back, with some peaks short of 180 and troughs short of -180 marked in red.

As you can see it does not reach 180 or -180 sometimes..I need your help.
 
Attachments
  • Plot of a sawtooth-like angle signal against time, with yellow traces ramping between about -180 and 180 on the y-axis; some peaks are circled in red and annotated as not reaching 180 and not reaching -180.
    result.PNG
    28.6 KB · Views: 642
  • Simulink block diagram titled reference generation subsystem: three cosine voltage sources (Varef, Vbref, Vcref) feed a bus into alpha and beta transformation blocks, then a Cartesian to Polar block with mag and angle outputs.
    reference generation subsystem.png
    51.6 KB · Views: 881
Last edited by a moderator:
Physics news on Phys.org
I changed three phase voltage generation part to a Three Phase Sine Generator and the angle output is as I expected.
So the problem lies in three phase voltage generation.
But i can not figure out how that is wrong. Help!
 
Problem solved. The problem is that the scope is running with too low a sample rate. I changed the sample rate from 0.01(default) to 0.00002 and the result is good.