A techno-economic assessment of combining smart inverter control and network upgrades for hosting rooftop PVs

The growth in rooftop photovoltaic systems (PVs) installation can lead to violations of technical and regulatory limits in electric power distribution systems, such as overload and overvoltage issues, creating challenges for utilities and regulators. Traditionally, the solution has been to upgrade the network, incurring non-recurring capital expenses. To avoid or delay these expenses, the use of smart inverter controls has been explored, transforming capital expenses into yearly operating expenses (recurring expenses). To inform related decisions, this work proposes a “breakeven” time index (equivalence time) that expresses how long it takes for the recurring expenses to equal the avoided non-recurring expenses. The studies present a utility-scale techno-economic comparative assessment including four control approaches: Volt/Watt, Volt/var, Volt/var with an oversized inverter, and Volt/Watt with Volt/var. The results demonstrate that for the evaluated cases the lowest operating expenses were achieved with Volt/var curves with 10%-oversized inverters.