An enhanced power sharing strategy for droop controlled microgrids based on consensus algorithm

For an islanded microgrid, load power should be properly shared among multiple distributed generation (DG) units, not only for the fundamental power but also for the harmonic power. In this paper, the operation of microgrids under imbalanced and nonlinear load conditions is studied, and a dynamic consensus based power controller is proposed for DG units to realize enhanced power sharing performance. Firstly, the fundamental and low order harmonic powers of a DG unit are detected by using second-order generalized integrator (SOGI) modules. Then, the obtained local power information is transmitted to the neighbor DG units to help tuning their virtual impedances at fundamental and selected harmonic frequencies. After this, accurate fundamental and harmonic power sharing performance will be achieved. In the proposed control strategy, DG units only communicate with their neighbor units, thus the "plug and play" function will be reserved. Compared with those centralized control methods, the proposed strategy with distributed consensus protocol can simplify the maintenance and expansion of the system, making the microgrid more flexible. Moreover, as the knowledge of the detailed network is not required, it is convenient to be applied in practice. Simulation results are presented to demonstrate the proposed method.