Economically Optimal and Stability Preserving Hybrid Droop Control for Autonomous Microgrids

Cost-based droop schemes for microgrids (MG) have been developed to achieve cost reduction; meanwhile, microgrid stability depends on the droop control design and its parameters. This paper proposes a hybrid cost-based droop control that achieves both optimal economical operation and stability preserving for autonomous microgrids. The impact of cost-based droop schemes on stability is investigated utilizing a modified cost-based small-signal linearized model. Low-frequency eigenvalues tend to migrate towards instability when the load increases if a cost-based droop scheme is adopted. The proposed hybrid droop control manages to achieve the optimal generation by incorporating the incremental cost in the active power droop while ensuring stable performance by utilizing active and reactive power derivative controllers. The reactive power derivative controller is utilized to suppress the migration of the low-frequency eigenvalues towards instability. The active power derivative controller is utilized to damp the oscillations of the active power-sharing among the distributed generators (DG). The effectiveness of the proposed droop control to ensure an optimal and stable operation is validated on Matlab/Simulink.