Potential Harmonic Resonance Impacts of PV Inverter Filters on Distribution Systems

This paper presents a clarification study to identify the potential resonance phenomenon between photovoltaic (PV) inverters and the distribution system. LCL and LC filters are widely applied in PV inverters to mitigate high-order harmonic components generated by PV inverters. There is a possibility that these filters will excite harmonic resonance by interacting with the system impedance. The mechanism of this phenomenon is investigated here by mathematical analysis and measurement. The results indicate that the resonance can be attenuated if the damping resistance, such as damping resistor and residential linear loads, is large enough. Alternatively, three sets of field tests are conducted in the laboratory to verify and clarify the potential harmonic resonance and its factors. Furthermore, a full case of an actual North American distribution system with PV installations is also studied. The results indicate that the harmonic resonance caused by the PV filter is almost attenuated and cannot cause serious problems. At the same time, the filter may have some advantages in mitigating harmonics. Finally, to complete this paper, other sustainable energy resources with voltage-source converters (VSCs) are compared.