50 watt audio amplifier, 50 hz sine wave generator, and a 30 or so volt power transformer that can be wired for either 120 or 240... use the transformer backwards with the secondary driven by the amplifier, and the primary will be your 230V output.... back in the 1970s, Sony had an application note on using one of their amplifiers as a variable frequency line voltage source...Maybe 20-30 watts at maximum.