Volt–var curves for photovoltaic inverters in distribution systems

Photovoltaics (PV) are a technology that is becoming increasingly prevalent in the residential sector. The impacts of this new type of generation are not always desirable from a distribution system standpoint, as large penetration levels can lead to voltage increases, considerable unbalance, and excessive tap operations. Recent standard changes have allowed the inverters that are used to grid connect PV systems, to utilise their reactive power capability for voltage regulation. Although this new capability is desirable, it is important to ensure that it is being applied in the most beneficial way. The work in this study makes use of a three-phase optimal power flow method to find optimal volt-var curves for grid-connected rooftop PV inverters, which can perform autonomous voltage control. A number of scenarios are applied to produce a sufficient range of voltages, and the resulting reactive power settings are utilised to determine the volt-var curve for each PV system on a test feeder. An active control scheme is also presented, and the results are compared with the proposed autonomous scheme for a test 24 h period.