Plug-and-Play Nonlinear Droop Construction Scheme to Optimize Islanded Microgrid Operations

The operating cost of islanded microgrids (μGs) can be minimized by performing an optimal power sharing among the distributed generators (DGs). In this study, a plug-and-play optimization scheme (PPOS) for developing nonlinear droop relations is proposed to achieve an optimal power sharing among DGs in islanded μGs. The PPOS constructs optimal nonlinear relations for each DG, which are used as nonlinear droop curves that adjusts the output power of the DGs subsequent to any load variation to minimize the μG operating cost effectively. The construction of nonlinear droop relations in the PPOS is performed individually for each DG by optimizing each one against hypothetical DGs. This approach provides an indirect optimization among different DGs in the μG network and ensures an operating cost minimization irrespective of the μG topology. An islanded μG topology has been developed and simulated in MATLAB/Simulink environment to verify the effectiveness of the proposed method and the performance of the nonlinear droop control. An experimental study has also been conducted on a μG test bed to prove the effectiveness of the nonlinear power sharing and to verify the performance of the nonlinear droop control in the μG operating cost minimization.