I am working on Multilevel Inverter and successfully achieved modified sine wave with 7 level, that is much better according to my requirement. But the problem is output AC voltages is too low which is 10-12 VAC. Every thing works fine. Output frequency is 50Hz and required modified sine wave are achieved. How can I increase this low AC voltages to 180-220 VAC with 0.25 watt? In Input side I connect 3 individual batteries with 12 Volt DC 1 Amp. Here is the circuit Diagram of my 7-level H-bridge inverter.