Abstract: Control of grid voltage in a power grid. A power transformer converts alternating current (AC) electrical power at a higher voltage on the primary leads to AC electrical power at a lower grid voltage on the secondary leads. An auxiliary AC/AC power converter converts input AC electrical power at the input conductors to output AC electrical power at the output conductors, The auxiliary AC/AC power converter converts substantially less electrical power than the AC electrical power converted by the power transformer. The secondary leads of the power transformer are series-connected to the output conductors of the auxiliary AC/AC power converter. Input conductors of the auxiliary AC/AC power converter are parallel-connected to either (i) the primary leads of the power transformer, or (ii) the secondary leads of the power transformer. The output alternating voltage of the auxiliary AC/AC power converter adds to the output alternating voltage of the power transformer to control the grid voltage in the power grid.