Transmission-distribution long-term volt-var planning considering reactive power support capability of distributed PV

High penetration of grid-edge, inverter-based photovoltaic (PV) can cause significant voltage fluctuations not only at the distribution but also sub-transmission levels due to PV output intermittency. This paper proposes a reactive power planning tool for systems mitigate violations and caused by high intermittency with minimum investment cost. The considers all existing var assets in both reduce need new equipment. It closely coordinates an optimization-based volt-var operational selecting set scenarios testing final decision. obtains each scenario based on proposed optimal power-flow framework. Because number discrete variables this optimization problem, efficient technique recover feasibility solution relaxed problem is included. After obtaining separated solutions scenarios, two options are provided making decision: i) conservative direct combination ii) machine learning-based selection representative needs most time steps. decision verified using realistic large-scale system 5-min load data. results show performance improvement lower cost additional equipment compared conventional approaches.