Phase-to-Phase Connection of PV Systems in Brazilian LV Networks: Modelling and Impacts

Abstract

Most commercially available residential PV systems in the world are single-phase 220-240 V systems with rated power up to 8 kWp. In Brazil, LV networks are typically three-phase four-wire. Houses have a single-phase connection (127 V phase-to-neutral) for most loads and a two-phase connection (220 V phase-to-phase) for large loads such as air conditioners or electric showers. Due to the voltage level, single-phase PV systems are being connected phase-to-phase (ungrounded). In this type of connection, the absorption of reactive power, a strategy used to reduce voltages, can have unintended consequences. This paper presents the modelling of this type of connection, laboratory tests, and an impact analysis on a real Brazilian LV network. Results demonstrate that reactive power absorption can actually exacerbate voltage rise and unbalance issues. Consequently, in Brazil and other countries with similar LV networks, it is imperative for PV integration studies to adequately model their phase-phase connection.