Stability assessment of inverter-based renewable energy sources integrated to weak grids

The worldwide electricity network is undergoing a crucial transformation, shifting from traditional synchronous generators to inverter-based renewable energy sources (IRESs). This shift is expected to reduce the grid's available fault level (AFL), potentially impacting grid functionality, particularly during the integration of IRESs into weak grids. This paper examines the challenges associated with weak grids, focusing on the steady-state and dynamic stability of IRES when integrated into these systems. In the steady-state analysis, the effects of AFL, injected power volume, and grid characteristics on the steady-state voltage at the point of interconnection were explored. For dynamic stability, eigenvalue and H2 norm analyses are used for evaluation. Sensitivity analysis is conducted to assess the impact of these factors on the stability of IRESs connected to weak grids. A detailed case study using the IEEE 39 bus test power system is included to demonstrate our findings, where the steady-state and dynamic stability of IRES connected to the test system are assessed using the proposed methods. The accuracy of these analyses is confirmed by extensive simulation studies on the OPAL-RT real-time digital simulator platform.