Hierarchical Optimal Control of the Resilient Community Microgrid in Islanded Mode

This paper studies a three-level hierarchical control strategy for the resilient community underground microgrid in Potsdam, NY, operated in the islanded mode. Specifically, an AC Optimal Power Flow (ACOPF) problem is solved via rank-relaxed semidefinite programming (SDP) method on the tertiary level to derive an optimal operating point of the microgrid. Two decentralized secondary control methods based on proportional-integral (PI) control are proposed, one is to make PI controllers continually act and the other is to periodically reset the PI outputs to zero. Both methods allow distributed generation (DG) units to closely track the optimal economic dispatch commands by generating frequency correction terms to the primary P - f droop controllers. Simulation studies are carried out with PSCAD/EMTDC, where the proposed methods are compared.