A Study on the Effects of Single-Phase Rooftop Solar Photovoltaic Systems on Relay Protection of Distribution Networks

With the increasing penetration level of single-phase rooftop solar photovoltaic (PV) in low-voltage distribution networks, the analysis of harmonic currents generated by PV systems in different states is necessary for power quality and relay protection in low voltage station area. This paper constructs a simulation model for a single-phase grid-connected PV system. It investigates the mechanism of low-order harmonic current generation in single-phase PV systems and proposes analytical expressions for steady-state and transient low-order harmonic currents. Furthermore, steady-state and transient equivalent current source models for single-phase PV systems are developed for simulation research. The simulation results provide significant references for studying power quality and relay protection in low voltage station area.