Inertia emulation using HESS in a microgrid environment by droop control

The voltage source inverters operating in islanded microgrid are used as sources of power similar to synchronous generators (SG) in conventional power system. Unlike synchronous generators, these inverters neither have a natural droop (P-f and Q-V) characteristics nor rotational inertia. The electrical time constant is much lesser than mechanical time constant and hence the load changes will show immediate effect on inverter's performance. It necessitates an immediate response to the load demand which is possible by incorporating the sufficient fast acting energy storage devices. This paper emulates the behaviour of inertia and damping power of SG by using hybrid energy storage system that connected to the emulated PV system. The battery, super capacitor, emulated PV and inverter are treated as one unit and total two such units of different ratings are operated in parallel. The DC-link voltage regulation is done by energy storage devices with reduced stress on the battery. Inverters are operated in decentralized droop control to share proportionate power among themselves and the same droop characteristics are used to regulate the operating frequency. The proposed power sharing scheme is validated by simulation studies using MATLAB.