Harmonic Analysis of LV distribution networks with high PV penetration

This paper presents a harmonic study of different parallel photovoltaic (PV) systems connected to a low voltage distribution network to identify potential resonance between PV inverters and system impedance. LCL filters are commonly employed in PV inverters and recommended by IEEE 929-2000. These filters, however, by interacting with each other as well as with the system, may generate multiple harmonic resonances at the Point of Common Coupling (PCC). The harmonic modelling of the current source and the resonance mechanism is presented and explained through mathematical analysis. The resonance peaks and the voltage harmonic distortion can be efficiently attenuated by adding a passive damping resistor in the filter, the value of which may be obtained from the parametric results. Moreover, the potential of operating the PV as an active power filter is considered, by modelling the harmonic source of the PV under an out-of-phase strategy, to achieve a cancellation effect of the injected harmonic currents at the PCC. The reported simulation results suggest that the multi-resonance adverse effects caused by different PVs may be significantly mitigated and will not cause real problems in low voltage networks.