Here are two Sine wave Inverter circuit applications that can be made into an UPS or Uninterrupted Power Supply. These are used in Home, Office and Shops. It provides emergency power when Mains power goes down or browns out.
800VA Pure Sine Wave Inverter - High Performance Isolated Power
This application note describes the design principles and the circuit operation of the 800VA pure Sine Wave Inverter.
800VA Pure Sine Wave Inverter's Reference Design, slaa602 - TI.com
The pure Sine Wave inverter has various applications because of its key advantages such as operation with very low harmonic distortion and clean power like utility-supplied electricity, reduction in audible and electrical noise in Fans, fluorescent lights and so on, faster, quieter and cooler running of Inductive loads like microwaves and motors.
Power inverter is a device that converts electrical power from DC form to AC form using electronic circuits. It is typical application is to convert battery voltage into conventional household AC voltage allowing you to use electronic devices when an AC power is not available. There are basically three kinds of Inverter out of which, the first set of inverters made, which are now obsolete, produced a Square Wave signal at the output.
Texas Instruments, Application Report SLAA602 , June 2013