In case your voltage levels are unstable (ie: power stays on, but the actual voltage amount may differ quite a bit from your 220V normal), then I believe that's the sort of situation in which an AVR is useful. For big power models, dynamic uninterruptible power provides (DUPS) are sometimes https://cesaryjqwc.blogsmine.com/34255617/ups-uninterruptible-power-supply-can-be-fun-for-anyone