A method and system for controlling power transfer includes the operations of receiving a power transfer value indicating a power level to be transferred either to or from an energy storage sub-system and receiving an input comprising a rotational speed of a rotating mass in the energy storage sub-system. The operations further include calculating a torque value corresponding to the power transfer value based on the rotational speed of the rotating mass and determining whether the torque value exceeds a maximum allowed torque. The operations further include defining an adjusted torque value as the maximum allowed torque value if the torque value exceeds the maximum allowed torque value or defining the adjusted torque value as the torque value if the torque value does not exceed the maximum allowed torque value, and providing the torque value to a direct torque controller for controlling the torque of the rotating mass.