LV Harmonic Analysis of Single-Phase Rooftop Solar PV Systems with Non-Linear Loads

Abstract

Grid-connected photovoltaics (PV) systems in low voltage $(\pmb{L}\pmb{V})$ networks are becoming viable due to feed-in-tariffs or net-metering provisions. However, the legacy distribution systems are typically designed for unidirectional power flows from substations to consumers. Therefore, the bidirectional power flows due to grid-connected solar PV systems impact the voltage levels and introduce harmonic distortion in the LV feeder, particularly in weak grids with non-linear loads. The effects of significant non-linear loads on LV power quality are assessed at the point of common coupling (PCC) in this paper. To analyze total harmonic distortion in the current (THDi) at PCC, three examples of (low to high) solar PV penetration are evaluated using practical feeder data in a weak grid setting using the radial IEEE-34 bus system. Results show lower power losses with solar PV systems installed at alternate nodes (50% PV penetration) in the LV network. In addition, the per unit voltages of the overall system gets significantly improved, with none of the buses critically and marginally loaded due to solar generation.