A Long-term Reactive Power Planning Framework for Transmission Grids with High Shares of Variable Renewable Generation

The focus of this paper is how to account for the impacts of high shares of variable renewable energy sources such as wind farms and solar PVs on transmission grid steady-state operation in long-term planning of reactive power resources. The increased variability of nodal voltages due to the volatility of such sources will require adequate reactive support capability at the point of connection to the grid as well as throughout the grid if traditional reactive power supplies, i.e. conventional generation, are not available either because they are not dispatched at moments of high availability of wind and solar or they are already decommissioned. An optimization-based approach is proposed, namely a multi-period, multi-scenario corrective security-constrained optimal power flow, to identify the optimal size and location of reactive power sources for long-term planning in scenarios with increasing penetration of variable renewable sources. The proposed reactive power planning formulation optimizes the reactive power investments, considering different energy scenarios (multi-scenario) in a given planning horizon in discrete time steps (multi-period). The proposed formulation is demonstrated on a modified IEEE 14-bus system.