Some other user have been trying to accomplish this. I think you could take a look at this thread https://communities.intel.com/thread/61067. CMata_Intel suggested that by using the lines below you can put the Edison into and out of standby mode.
echo -n "mem" > /sys/power/state
echo -n "freeze" > /sys/power/state
But some other users have reported that this works just once, so they have to reboot the board to make it work again. However, not so long ago someone post a link to a patch that makes the sleep mode more reliable than before. I would suggest you to try with that.