An accurate current sharing method for an Islandeddroop‐controlled dcmicrogrid without communication between remote buses

Abstract

Summary The traditional droop control method in a DC microgrid (DCMG) fails to achieve accurate current sharing among parallel‐connected dispatchable units when the connecting feeders have unequal resistances, or when the units supply local loads apart from loads at the common dc bus. In this paper, a novel modification of the droop control strategy (additional feedback term in the outer control loop) is suggested to overcome the above limitations. The proposed method is robust, noise‐resilient, amenable to the “plug and play model”, and employs local measurements, thereby, dispensing with the need for communication between remote nodes. A small‐signal model of the system with the proposed control strategy is derived for carrying out eigenvalue and participation factor analysis. A sensitivity analysis is also carried out to inspect the impact of variation of system parameters on small‐signal stability. The effect of time delay and noise on system small‐signal stability is also studied. A robust stability analysis is also carried out. The proposed control strategy is easily implementable on digital hardware. Time domain simulations using PSCAD (Power System Computer Aided Design)/EMTDC(Electromagnetic Transients including DC) is carried out to validate and compare the performance of the proposed technique vis‐a‐vis other existing methods. Performance of the proposed method is good even with time delay and noise.