Performance Analysis of Grid-Connected Solar Inverter Systems in Nigeria Under Varying Irradiance Conditions

This study analyses the performance of grid-connected solar photovoltaic inverter systems under the varying irradiance conditions experienced at three sites across Nigeria's climatic zones, specifically in Sokoto (North West), Ibadan (South West), and Port Harcourt (South South). Performance differences between sites are driven by differences in annual solar irradiance totals, cloud cover patterns, and ambient temperature, all of which affect the energy yield and conversion efficiency of PV inverter systems. Performance data were collected from three existing 5kWp grid-connected residential PV installations of identical equipment specification at each site over 12 months using dataloggers recording irradiance, module temperature, AC output power, and grid voltage at five-minute intervals. Performance ratio, capacity factor, specific energy yield, and inverter efficiency were computed for each site from the logged data. The Sokoto installation achieved the highest performance ratio of 82.3 percent, benefiting from the highest irradiance and lower humidity, though elevated module temperatures during summer months suppressed efficiency. The Port Harcourt installation recorded the lowest performance ratio of 71.4 percent, attributable to higher cloud cover frequency and elevated humidity affecting module soiling rates. Inverter operating efficiency varied between 94.1 and 96.8 percent across the three sites, with the Sokoto site showing marginally lower inverter efficiency due to more frequent high-temperature derating. The study provides empirical benchmarking data to inform realistic energy yield projections for grid-connected PV projects across different Nigerian climatic zones. Keywords: grid-connected PV, performance ratio, solar inverter, irradiance, Nigeria.