AC-DC-AC Circuit Design

[dharrington86]

Hi all,

I am currently a studying Electrical Engineering and for my final year project I am studying the way in which an electrical tram works (light rail system). These systems distribute electricity in DC and convert it to AC on the tram to feed the motors.
For this project i will need to build a circuit using a software package (PSpice, Yenka or something similar), i will also be building a physical model once i have a working version figured out using a software package. My degree so far has been largely based on electric Power systems rather than electronics. i was wondering if anybody could advise me on a three phase converter system that i could build to change an three phase AC input to DC and then back to AC again. I have been trying it with IGBT's and diodes but with little luck. Any help would be greatly appreciated.

Thanks in advance
Derek

 

[Tahmid]

For AC to DC rectification, use a 3-phase rectification configuration:

For DC to AC conversion, use a 3-phase bridge configuration:

So, here's what you'll need for AC to DC to AC:

Hope this helps.
Tahmid.

 

[dharrington86]

Hi Tahmid,

Thank you for your help, your pictures are very helpful. Would you know what would be the best way to fire the IGBT's either in a software package or in a real model?

Thanks again
Derek

 

[Tahmid]

To fire the IGBTs, you will need to generate 3 signals that are 120 degrees out of phase. I have used dsPIC33 previously for this purpose.

There are many application notes available on induction motor control where the 3 phase sinusoidal pulse width modulation is explained quite well.

http://ww1.microchip.com/downloads/en/DeviceDoc/93004A.pdf
http://ww1.microchip.com/downloads/en/appnotes/00955a.pdf
http://ww1.microchip.com/downloads/en/appnotes/00843a.pdf
http://ww1.microchip.com/downloads/en/AppNotes/00889b.pdf
http://www.atmel.com/Images/doc7546.pdf
http://www.atmel.com/Images/doc7545.pdf

Hope this helps.
Tahmid.