Use a servo-motor stabilizer. It works fine with Ac. It has a lower cap of 150V and upper cap of 320V. No matter what volts you'll get in this range, your Ac will get stable volts. It has a motor which physically rotates to stable the volts. It is widely use with electric equipments. Do your own search as well for servo-motor stabilizers. Also don't buy a local one. Try to get a branded one which comes with check warranty i guess but works fine.