I found a PDF of a pure sine wave inverter that is 250 Watts. The PDF can be found here. I like the fairly simple design of that inverter. I found the file pretty interesting and I understood it fairly well. What modifications would need to be made if I wanted to increase it up to 1000 Watts. I can understand that is a big increase from the original 250 Watts. I also found this one on the website from a college close to where I live. The inverter PDF can be found here. That one is only about 100 Watts though. The second one doesn't give the full schematic like the first PDF that I linked, only bits and pieces.