Harmonic emissions in grid connected PV systems: A case study on a large scale rooftop PV site

With rapid increase in installation of rooftop Solar Photovoltaic (PV) systems in low voltage (LV) distribution networks, power quality becomes a key area of interest. Among various poor power quality problems in LV networks, harmonic distortions, which could come from several sources, have become a major concern. The solar PV systems can generate harmonics itself. Besides this, the increasing use of power electronics based nonlinear loads and PV system penetrations in the network inducing harmonics lead to poor power quality resulting in overheating of equipment and malfunction of controls. In this paper, harmonic distortion issues accompanied with solar PV inverter due to variations in solar irradiance has been thoroughly analyzed. Simulations have been performed in IEEE-13 bus distribution system with nonlinear loads to examine the harmonic emissions from conventional PV system for varying solar condition. To verify the simulation results and capture the trends harmonic measurements were made at the University of Queensland 1.2 MW PV site. The paper has also proposed a control algorithm for the harmonic compensation. Simulation results confirm that the proposed controller has effectively eliminated the harmonic issues for varying solar conditions.