Here I have explained about a couple of simple circuit configurations which will convert any low power inverter to a massive high power inverter circuit. You'll find a plenty of small and medium sized inverter.
[pdf] The circuit of a simple 100 watt inverter discussed in this article can be considered as the most efficient, reliable, easy to build and powerful inverter design. It will convert any 12V to 220V effectivel.
[pdf] The high-frequency inverter first uses high-frequency DC/DC conversion technology to invert low-voltage direct current into high-frequency and low-voltage alternating current; then, after being boosted by a high-frequency transformer, it is rectified by a high-frequency rectifier filter circuit to usually above 300V High-voltage DC power; finally, 220V power frequency AC power is obtained through the power frequency inverter circuit for the load.
[pdf] 
