A rotary controlled system includes first and second alternators electrically connected to one another via a DC voltage bus. The alternators may optionally be further mechanically connected to one another via corresponding rotationally coupled components (such as rotationally coupled stators). A first field oriented controller is electrically connected with the first alternator and configured to cause the first alternator to provide a constant DC voltage to the voltage bus. A second field oriented controller is electrically connected with the second alternator and configured to receive electrical power from the voltage bus and cause the second alternator to provide servo angular position control of the rotationally coupled components. The system may be employed in a downhole rotary steerable tool to provide servo angular position control of a roll stabilized housing.