Current harmonic emission of string inverters based on cable length on a large grid-connected PV plant

The integration of solar photovoltaic systems into distribution networks has grown significantly, bringing benefits but also power quality challenges, such as harmonic distortion. While harmonic emissions from PV inverters have been widely studied, the impact of cable length on harmonic behaviour in large-scale grid-connected PV plants remains underexplored. This work analyses the harmonic emissions of three photovoltaic string inverters in a 35 MW PV plant with varying cable lengths. Key findings reveal that even harmonics (excluding H2) decrease with longer cables, acting as a low-pass filter, while odd harmonics show no clear trend, suggesting additional influencing factors such as inverter switching characteristics. Notably, H2 exhibits an inverse relationship, increasing with cable length. THD I is inversely related to power levels, with THD I below 2% under stable irradiance. Distinct emission patterns are observed at different power levels, with H5 and H7 showing strong power dependence. These results highlight the importance of cable length and power conditions in mitigating harmonic distortions, addressing a critical research gap and offering insights for renewable energy integration. • H5, H7, H11, and H13 are the main current harmonics emitted by the PV plant. • Even harmonics decrease with cable length, except H2, which increases with distance. • Longer cable lengths reduce phase imbalance in harmonic distortion. • H5 and H7 show strong correlation with inverter output power levels. • High-frequency harmonic correlation decreases as cable length increases.