Hello saifi,
Since this thread is from 2009 it is now closed, I would recommend generating a new one to try getting assistance from other users. In the meantime in order to assist you, I would like to mention that there are some examples on Multisim that might help you as reference to start your application. You might be able to search for it, by going to the example finder (Menu bar > help > Find Examples and search for ControlledThreePhaseRectifier.ms14. Have you tried looking into those?
There might be some other examples that you might want to take a look at.
Thank you very much. Have a very nice day.
Regards,
Luis