Solution for shoreline to 50Hz 100V

Most appliances won't notice a frequency difference if you can step up the voltage to closer to 120 VAC. Anything with a motor, like your AC will not run right on the 50Hz. It will run 20% slower and the lower voltage will probably burn it up. It will also try to draw more current which can blow circuit breakers.
Some electronic items may operate just fine but it would be a gamble to try without reading their specs.
I'm not sure what this will do to your converter/inverter/battery charger. Most have over and under voltage protection.