Automatic Transfer Switch Project with Microcontroller

Hey guys,

For a school project we are building an automatic transfer switch system that will switch between Hydro power and another alternate AC source, in our case a windmill.

Basically what we want to accomplish is we want to feed power from hydro and if our windmill is supplying enough power for our load, for now lets keep it simple at about 200-400W or so, the automatic transfer switch will sense that the windmill is outputting sufficient power and switch over and if the power output drops below sufficient levels, it will switch back to hydro.

I was thinking of rectifying the 2 sources to DC and have them monitered by comparator OP Amps that will send a signal to a microcontroller (we decided we would try and use a PIC16F877) and then have it switch on a relay. After that we could have batteries in parallel to supplement power if theres a slight loss and make the transition smoother. It will then go into an inverter that will give us the 200-400W and AC Voltage again.

My electronics skills are slightly intermediate but nothing really advanced. So any help or suggestions to this design would be appreciated to improve this design or other ways of approaching it.

Thanks alot.

Please explain how do you sense that the windmill is outputting sufficient power?

I would have the windmill going into a comparator Op Amp that will send a +5V signal or -5V signal out depending on the voltage coming in. So my basic understanding of how it works is that;

If Windmill >= 120VAC then the Op Amp will send out +5V
If windmill <120VAC or so then the op amp will send out -5V

After that I was thinking of using that voltage sent out by the op amp into the microcontroller and have it control a relay.

in my way i will
use thrystor as power controller
first i will sense the power delivered through both sources
then controlling the firing angle of thrystor to regulate power delivered from the both sources

You do not need a microcontroller to realize your job!

Use your comparator output to drive a transistor switch, the switch control a dual pole dual thru relay for Automatic Transfer Switch