Central and Distributed MPPT Systems under Varying Weather Conditions

Ansel Barchowsky, Jeffrey P. Parvin, Gregory F. Reed, Matthew J. Korytowski, and Brandon M. Grainger


MPPT, photovoltiac, solar irradiation, Inverter


Photovoltaic (PV) energy generation is becoming an increasingly prevalent means of producing clean, renewable power. PV is renewable, reliable, and domestically secure. However, these panels show a large decrease in performance under non-ideal weather conditions. When PV panels become covered by clouds or shadows, the current produced by the panel drops drastically. In order to continue to produce as much power as possible from the array, Maximum Power Point Tracking (MPPT) is employed. As the solar irradiation changes, this varies the output voltage accordingly in order to maintain the maximum amount of power output. It is generally applied as a centralized system to the whole array, directly before the inverter which is tied to the grid. However, such a system is not ideally suited to handling the current changes on individual panels when only part of the system is shaded. To improve efficiency on a system in various parts of an array are shaded, distributed MPPT systems are employed. This involves the placement of a MPPT DC-DC buck converter on each individual panel, which are then collectively fed through central inversion. In order to demonstrate the difference in performance between such a system and the more traditional central MPPT system, PSCAD models were developed for each method. A clouding model was then developed to simulate the effect of lower solar irradiance on distributed panels throughout the system. In doing so, the stability, efficiency, and quality of the power conversion in each system was observed in cases of both ideal and non-ideal irradiation.

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