Impact of virtual inertia on increasing the hosting capacity of island diesel-PV ac-grid

A key constraint to the penetration level or hosting capacity (HC) of PV power in ac-island power systems (IPS) is the resulting frequency volatility. Frequency volatility is directly tied to the inertia level in the grid. Since inertia-less PV power displaces synchronous generators (SG), and thereby their available rotational inertia, the inertia level is reduced and the frequency volatility increased. Frequency volatility can be quantified by the Rate of Change of Frequency (RoCoF). The RoCoF is used as a performance index to determine the HC. Virtual inertia compensation (VIR) by chemical battery storage (BESS) can increase the HC of the grid and allow for more PV power to be integrated. The impact of PI-based VIR on increasing the HC in a 17.5 MVA diesel powered IPS is studied. Results indicate that when added PV without VIR displaced SGs the RoCoF limit could not be upheld. When VIR is added the RoCoF is improved and an HC of up to 3 MW PV is obtained. For the suggested RoCoF limit of -1.45 Hz/s and the studied scenarios it is shown that, in percentage of peak load, diesel-based generation could be replaced by 25% PV, providing that 9% of BESS with VIR is added.