A power conversion system comprises: a source of multiphase high frequency alternating current (AC) electrical input power; a high frequency controlled magnetics transformer for each phase of the multiphase high frequency AC input power, with each transformer having a primary winding coupled to its respective phase of the multiphase high frequency AC input power, at least one secondary winding that produces high frequency AC output power and at least one control winding responsive to a direct current (DC) control signal that changes the high frequency output power in proportion to the amplitude of the DC control signal; a power converter that receives the multiphase high frequency AC output power from each high frequency transformer secondary and converts it to system output power without the high frequency AC content; and a system controller responsive to the system output power that produces a DC control signal for each control winding that changes in amplitude in response to changes in a measured parameter of the system output power.