Energy Management of a Power Unit without Throttle Actuator to Supply a Grid

Supplying a grid in island operation and reacting to dynamic energy demands requires reliable control of the output voltage of the power plant. Forth sake of efficiency power units with internal combustion engines (ICE) operates with variable speed while supplying the grid through a back-to-back converter. The problem of such operation mode is the necessary acceleration to achieve a higher output power. This leads to a drop in output power and possibly grid voltage when changing the operating point. This paper presents the control structure of an ICE, whose power is controlled without a throttle actuator to reduce gas exchange losses, directly coupled to an electric generator, connected to a back to back converter. One inverter is used to control the grid voltage and a second one to control the electric machine. The inverters share the DC-link capacitor, giving the ability to supply or store energy from both systems. The capacitor bank can be designed to overcome the power drop when the power demand is increased. The DC-link voltage is controlled without additional power electronic components. The proposed control scheme is explained in this paper and validated with experiments.