A novel framework for integration analysis of large-scale photovoltaic plants into weak grids

Developing countries can deploy large-scale photovoltaic (PV) plants extensively for supplying their rapidly growing electricity demand as PV plants are becoming more cost competitive. However, weak power grids are predominant in these emerging economies. Prior to integrating new PV plants into weak grids, the impacts of such plants on steady-state voltages of the grid should be studied comprehensively, and accurate energy analysis undertaken as part of the economic assessment of the plants. This study proposes a novel framework that uses distinct generation profiles for integration analysis of large-scale PV plants into weak grids. A probable maximum generation (PMG) profile based on clear-sky radiation is suggested for voltage evaluation while an average generation (AG) profile based on average radiation is used for energy analysis. The case study examined large-scale PV plant integration into one of the regional power systems in Mongolia. Load flow analysis was carried out every hour for a full year on a simplified 15-bus case network for 5, 10, 15 and 20 MW PV plant integration scenarios. Application of the PMG profile provided a more robust evaluation of the PV plants’ impact on the voltage profile of a weak grid and resulted in between 1032 and 16,011 possible voltage violations in the integration scenarios, while the AG profile resulted in 75 to 11,059 violations. Conversely, the AG profile outperformed the PMG profile for energy analysis, and total annual generations of PV plants were 7.4 to 29.7 GWh for the case study. The PMG profile overestimated the total annual PV generations by about 51%. The results show the proposed framework could help to improve the assessment of PV plant integration into weak grids by providing robust voltage and accurate energy estimations.