General Interface for Power Management of Micro-Grids Using Nonlinear Cooperative Droop Control

This paper presents a comprehensive and general nonlinear control/power management strategy for both converter- and synchronous-machine-based units in microgrids. The proposed controller offers the following advantages as compared to previously reported controllers: 1) It can fulfill requirements of both islanded and grid connected microgrids without a need for reconfiguration; 2) the controller-manager adopts cascaded angle, frequency and power control loops, which give enhanced power sharing accuracy and nominal-frequency operation at steady-state conditions (i.e., permanent frequency drop is eliminated); 3) the controller provides an emulated performance of synchronous machines with controllable damping and synchronization power components, which provide additional degrees of freedom to improve the dynamic performance of the system and easy integration in systems with multiple converters synchronous machines; 4) the controller is equipped with a nonlinear supplementary controller to mitigate large power angle swings associated with large-signal disturbances; 5) the controller can be easily adapted to conventional synchronous machines; and 6) the controller provides seamless operation under out-of-phase reclosing. The proposed controller can realize the concept of plug-and-play of DG units and micrgrids in smart power environment. The effectiveness of the controller to damp power oscillations and ensure system seamless performance in a wide range of operating conditions is validated by simulation results under various microgrid operating scenarios.