If thyristors, IGBTs, MOSFETS existed in 1890s, I bet Edison would have won the war of currents.
Generating plants would still use turbo alternators that produce AC power, but rectified to high voltage DC, for impedance free transmission of power — similar to in your car. I expect they would output around 400 Hz power prior to rectification, for maximum efficiency. You’d boost the voltage up for high voltage transmission, buck it when it got to household for safety.
Household electric motors would be driven by transistors producing high frequency (400 Hz or above) 3-phase alternating current, for maximum efficiency. Other DC-based electronics would use buck converters to further reduce voltage down to safe, usable levels. Every outlet and switch though would have to have heavier contacts due to the lack of zero point to withstand arching or use a MOSFET/IGBT to break connections rather then a mechanical switch.
Such a system would be more efficient, and use a lot less copper for transformer windings, but arching would be concern when contacts or wires broke. Might be more of a fire risk, and certainly a much greater shock risk, as you can’t let go of a high voltage DC wire easily due to lack of a zero point.
Such systems sort of exist in the world today — High Voltage Direct Current power transmission. But all existing HVDC systems are inverted back to AC power when connecting back to local substation — nobody uses DC down to the household level. But as more renewables come online, more people are switching power supplies and inverter-driven AC motors, this is a technology whose future might eventually come to the entire power grid.
