Fuzzy Logic Based Module-Level Power Electronics for Mitigation of Rapid Cloud Shading in Photovoltaic Systems

A module-level DC optimization device is proposed to increase the efficiency of photovoltaic (PV) strings by minimizing the negative effects of shading caused by intermittent cloud cover while reducing cloud induced fast frequency fluctuations. The decentralized inverter approach combines the benefits of string and microinverter technology. This device can be affixed to pre-existing or new systems and operates in compliance with IEEE 1547 and California rule 21 standards by operating in maximum power point tracking (MPPT) or curtailment mode whenever necessary. The modular level device encapsulates three individual processes: an optimization engine to determine minimum power requirements, a fuzzy logic controller (FLC) to eliminate affects from passing cloud cover, and a voltage regulation stage to monitor and appropriately adjust output voltage of the device. Field data was collected and used for model validation of resiliency to partial shading, reduction of ramp rates during passing cloud coverage, and optimized output voltage of each panel while maintaining a constant DC link voltage of 120 V.