A systematic approach to estimate the frequency support from large-scale PV plants in a renewable integrated grid

Abstract

Photovoltaic systems, one of the major renewable energy systems (RESs), are getting integrated into conventional power grids in large-scale, substituting synchronous generators. However, PV systems lack inertia inherently and cannot provide any reserve power. Consequently, large-scale PV integrated grid faces severe frequency instability problems following a synchronous generator tripping event. Although various kinds of external storage systems are utilized to improve frequency response, they pose substantial economic challenges for grid operators. Deloaded PV systems, on the other hand, can assist in enhancing frequency stability without any external supporting mechanisms. In order to maintain frequency stability with minimal expenditure, an accurate estimation of the deloading percentage of PV systems is required. To this end, this paper proposes a novel methodology of estimating appropriate deloading percentages for PV systems in terms of frequency response parameters, using multiple linear regression analysis (MLRA). Simulations are conducted for different PV penetration levels on modified IEEE 39 bus test system. Additionally, a thorough performance comparison of deloaded PV integrated grid with both battery energy storage system (BESS) and synchronous condenser (SC) installed PV integrated grid is conducted. The findings support the feasibility of our method, allowing for accurate estimation and justifying the deployment of grid-connected deloaded PV systems. Deloaded PV systems also outperform other supporting mechanisms in terms of performance. Moreover, they provide insights on how the required deloading percentage decreases with increasing PV penetration. This paper can be used as a guide for grid designers to ensure that PV systems are properly deloaded to maintain frequency stability in large-scale PV integrated grids.