Efficient Digital Control for MPP Tracking and Output Voltage Regulation of Partially Shaded PV Modules in DC Bus and DC Microgrid Systems

Abstract

The integration of photovoltaic (PV) modules into dc microgrids relies on the capabilities of maximum power point (MPP) tracking and output voltage regulation (OVR). Under partial shading or mismatches between PV submodules, accurate global MPP tracking and efficient OVR are challenging processes. For global MPP tracking, the distributed MPP tracking is a potential solution but comes at the expense of increased system complexity. For the OVR, operating the PV module in its current source region would result in rather high power losses in the converter circuit and, thus, in increased heat accumulation. The existence of multiple current source regions in the mismatched PV characteristics complicates the control design. The novel digital controller for module integrated converters developed here supports the effective integration of mismatched and partially shaded PV modules while employing a minimal number of sensors. The proposed double-stage global MPP tracking algorithm realizes fast and accurate MPP tracking with neither periodic scanning nor oscillations around the optimum. For the OVR, the algorithm targets the reduction of the converter power losses through effective allocation of the PV operating point. A prototype of the control is realized as a proof of concept.