Evaluating Power Sharing Performance of Distributed Generators in Microgrids with Hybrid Sources and Mixed Tie-lines

Abstract

Proportional output power sharing amongst distributed sources in an islanded microgrids is necessary to maintain a good voltage profile, avoid tripping of sources and avoid circulating current flows. Typically, researchers consider microgrid networks with overhead lines (OHL) in their studies. This paper examines the power sharing performance among inverter and inertial distributed sources in a system with hybrid/non-uniform tie-line configurations i.e., network sections with both OHL and underground (UG) cable based lines. Furthermore, two strategies to vary the virtual impedance linearly as a function of the DG output currents have been examined for their effectiveness to improve the proportional power sharing. The studies have been performed considering a system with four sources operated with the popularly used L and RL droop controllers through detailed simulations in MATLAB/Simulink. The enhancement of power sharing has been verified for different R/X ratios of the OHL and UG cables used in the system and in a meshed network configuration.