Very high current very low voltage application
Power supplies from arc welding devices are quite capable of what you describe. You may also try a soldering gun (the kind with a transformer inside) replacing the tip with your stuff.

Just be aware that you need really really thick wires for 100A. The problem will be worse with high frequency AC because of the skin effect.

As far as the regulation is concerned you should be able to use a simple PID regulator with a thyristor output for the soldering gun. The arc welding supplies may be more difficult depending on their internal construction.