Partial shading abatement through cell level inverter system topology

Abstract

Partial Shading has a disproportional impact on power production of photovoltaic systems. A microinverter system architecture with a 72- cell Sanyo module is presented as baseline system for comparison. Results are presented on worst case shading scenarios for a micro inverter system. This work presents a two stage system architecture which is robust to module level partial shading. The first stage of this system architecture couples a DC- DC converter for each PV solar cell, allowing for maximum power point tracking at the cell level. The second stage utilized a cascaded multilevel inverter topology for DC-AC power conversion. A local H-bridge couples with each converter stage, allowing for bus voltage management and DC-AC power conversion to utility grid. The two stage system design effectively minimizes power lost due to partial shading. Simulation results are presented to demonstrate and verify system design performance. Under a worst case cell shading scenario, the proposed system allows for a 1.2% decrease in PV power. Comparisons between the micro- inverter baseline and our proposed system design is presented. These results demonstrate a 31.1% increase in power production using the proposed topology.