For reasons of cost-effectiveness, multiple solar panels are connected serially in photovoltaic plants, which creates a "string." Among these strings, there are inevitable variations in performance due to manufacturing differences, non-uniform string lengths , differences in shading, soiling, misalignment, tracking system (if exists), and more. These lead to string mismatches. Plus, with today’s 1,500V inverters, string variation is getting even more severe.
Even the smallest string mismatch impacts total efficiency, reducing the overall energy yield by 2-10%, sometimes even more.