A Unified Analytical Framework Linking V-Q Sensitivity, Inverter PQ Limits, and Grid-Code LVRT Requirements in RES-Dominated Grids

The primary actuator, even in power systems dominated by inverter-interfaced renewable energy sources (IB-RES) for voltage regulation and short-term stability, is reactive power. In such systems, Inverter-based resources provide reactive power support only within explicit apparent-power and current limits, while modern grid codes mandate defined steady-state and faultmode behaviour. This Letter proposes a compact analytical framework bring together local voltage-reactive power sensitivity, inverter PQ capability constraints, and grid-code-mandated low-voltage ride-through (LVRT) reactive current requirements using a two-bus Thevenin representation. The voltage stability margins and proximity to collapse are disclosed by closedform V-Q relations, whereas inverter limits bound achievable voltage support under steady-state and faulted conditions. The framework unifies grid-following and grid-forming inverter behaviour, enabling rapid screening of reactive power adequacy and planning margins coherent with prevailing interconnection standards.