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Power companies use ‘tap changers’ on long medium voltage lines to keep the day/night voltage within range. These are auto-transformers that adjust themselves, used in groups of three on medium voltage (13.8kv) lines. Capacitor banks are used to correct power factor. Similar to supplying DC in old cities, up to 1999 a power plant was supplying 25 cycle AC to mines and factories in SW Missouri and NE Okla, legacy from installations ~1910. I think Pennsylvania has railroads still operating on 25 cycle AC. There was a lot of 25 in early days, including Niagra falls.
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