Maximum Loadability Assessment of Multi-Infeed Renewable Energy Systems Considering Reactive Power Support and Small-Signal Stability Constraints

As the penetration of renewable resources increases, the system strength of multi-infeed renewable energy systems (MIRES) is progressively weakening. Currently, most renewable devices use grid-following converters (GFLs), which has introduced small-signal stability (SS) issues to power systems, especially in weak grids. One way to enhance system strength is rationally allocating the capacity of GFLs based on the maximum loadability of MIRES. There exits some studies which focus on assessing the loadability of MIRES, yet often neglect the SS constraints or the impacts of AC power flow and reactive power support. To address these limitations, this paper proposes a modified system strength evaluation metric, QgSCR0 (reactive power considered critical generalized short-circuit ratio), which incorporates reactive power support and AC power flow. This metric is integrated as a critical constraint into the maximum loadability assessment optimization model. Furthermore, to enhance the feasibility of the optimization problem, QgSCR0 is formulated as an analytical equation dependent on power flow parameters, and the original optimization problem is decomposed into a sequence of sub-optimization problems (SOPs). Finally, the proposed methodology is validated through a two-area system case study.