N-1 voltage security is a critical issue for transmission systems.

With changes from synchronous generation to inverter-based resources, i.e. wind and solar, current grid code requirements may need to be updated to assure N-1 voltage security.

Various grid code changes have been considered, putting new requirements on inverter-based resources such as changes in control mode, control point position, and STATCOM operation.

Here, STATCOM operation implies delivery of reactive power from inverter-based resources even at zero active power generation.

In this work, we analyse the impact of control point position and STATCOM operation changes on N-1 post-contingency static voltage security for a 400 bus Nordic synchronous transmission system (i.e. Norway, Sweden, Finland and Eastern Denmark).

Both a historic (2022) and a future (2050) scenario are analysed.

The future case was created by a capacity expansion energy system optimization model with the same grid topology used in this N-1 analysis.

We apply various types of contingencies and evaluate whether post contingency states are statically voltage secure.

We find that the future case has a higher share of voltage insecure contingencies than the historic case for all considered grid codes.

For the future scenario there is a similar reduction in voltage insecure contingencies from a change in voltage control point position (−21%) and a change to STATCOM operation (−18%), with both performing better together (−35%).

Overall, our findings underscore the importance of future-appropriate reactive power grid code requirements for inverter-based resources.