Droop characteristics based damping and inertia emulation of DC link in a hybrid microgrid

Abstract

In this study, a proportionate power sharing among the parallel inverters operating in an islanded microgrid isachieved using droop and virtual inductance control. The same droop coefficients are used to achieve the frequency regulationas well. The frequency changes which are inevitable in droop control are measured and used to emulate the behaviour ofdamping and inertia to the DC link voltage using hybrid energy storage system consisting of battery and supercapacitor units.The proposed DC link voltage regulator restores the DC link voltage quickly by providing power corresponding to the rate ofchange of frequency and frequency deviation. This reduces the impact of voltage variations on the DC-load and keepsmodulation index within the linear range for voltage source inverter. The design aspects of DC link voltage regulator, dampingand inertia constants, selection of battery and supercapacitor units based on rating of the DC link voltage are discussed. Theproposed decentralised droop control and DC link voltage restoration methods are validated through detailed simulation andexperimental studies.