An electrical DC generation system is disclosed. According to one aspect, a system for electrical DC generation system includes an electrical machine, having a positive output terminal and a negative output terminal, a plurality of stator windings, a plurality of passive rectifiers connected to the plurality of stator windings, the plurality of passive rectifiers being connected in series to form an intermediate bus having a positive terminal and a negative terminal. The system also includes a DC-DC converter circuit having input terminals connected to the positive and negative terminals of the intermediate bus and having output terminals electrically isolated from the input terminals and connected in series with the intermediate bus. The DC-DC converter output voltage is adjusted to regulate torque of the electrical machine by adjusting stator current of the electrical machine.