Maximizing power harvest of a large PV farm

A modular conversion system has many advantages over a centralized system in a grid-connected photovoltaic (PV) application. Panel-level (micro-inverter) and string-level (string-inverter) extraction of maximum power have been demonstrated to be effective for smaller solar power installations. This paper argues that these strategies, if applied judiciously, will achieve higher power harvesting in large solar power installations as well. If one modular converter (called stack module) is used for a specific number of series-parallel connected PV panels, they can be treated as an independent structure. Many of these structures can be connected with their outputs in parallel to increase the power rating of the system. This strategy will alleviate the need of current sharing between stack modules. Thus, it leads to simplified feedback controller design. The impact of partial shading on a 472 kW modular PV system is studied. This case-study demonstrates higher power harvest under partial shading as the number of parallel stack module structure increases. An experimental prototype and its results are provided for a 2.5 kW system with two parallel 300 V to 600 V boost converters.