Planning of Active Distribution Systems: Assessing the Impact of PV Inverter Volt-VAR Control on Reinforcement Strategies

Abstract The increasing photovoltaic (PV) penetration in distribution systems poses technical and economic challenges for both operation and planning. This paper proposes a short-term planning model formulated as a mixed-integer linear programming (MILP) problem that coordinates line reconductoring, allocation of fixed and switched capacitor banks (CBs), and installation of voltage regulators (VRs). The model incorporates PV inverters with Volt-VAR control (VVC), in accordance with the IEEE 1547-2018 standard, and represents the progressive evolution of load and distributed generation across three operational stages. The framework is validated on two distribution test systems with distinct characteristics: a 135-bus and the IEEE 123-bus feeders. The results show that, although both systems benefit from VVC, the effects on investment decisions are system-dependent. In the 135-bus feeder, the reactive support provided by smart inverters allows VRs to be eliminated once PV multiplying factor exceeds 1.6, while also reducing energy loss costs. In the IEEE 123-bus system, which exhibits a more pronounced voltage drop, the VR is installed regardless of VVC considerations; nonetheless, adopting PV-provided VVC allows deferral of investment in switched CBs, thereby reducing total planning costs. The proposed model, therefore, offers a flexible decision-support tool that adapts its reinforcement recommendations to each network.