A multistage centralized control scheme for islanded microgrids with PEVs

This paper proposes a multistage centralized control scheme for droop-controlled islanded microgrids (IMGs) with high penetration of plug-in electric vehicles (PEVs). The proposed control scheme optimally coordinates the distributed generation (DG) units' droop characteristics, the shedding of microgrid power demand (during inadequate generation periods), and the PEVs charging/discharging decisions to support the IMG operation for a large time frame. This coordination allows the PEVs to play a pivotal role in the successful and optimized operation of the IMG systems. To this end, a novel multistage droop-based optimal power flow algorithm is proposed in order to: 1) minimize the load shedding; 2) satisfy the PEVs customers' requirements; and 3) minimize the microgrid cost of operation. The proposed algorithm takes into consideration: 1) the special features and operational philosophy of droop-controlled IMG systems; 2) the variability associated with the output power of renewable DG units; and 3) the random behavior of PEV charging. Several case studies have been carried out to show the effectiveness and robustness of the proposed control scheme. The simulation studies show that the proposed control scheme can enhance the operation of IMG systems and facilitate a successful implementation of the IMG concept in the presence of high PEV penetration.