i want to make a inverter in which at 180v mains apto 230vac , inverter and charger both should on. at 230vac, only charger on, and below 180vac, only inverter on.
Pl. suggest any method or topology to developed the same.

 

What you are looking for is an uninterruptible power supply - http://en.wikipedia.org/wiki/Uninterruptible_power_supply

These things are quite expensive, especially if your load is large.