Origin of cross coupling effects in distributed dc–dc converters in photovoltaic applications

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Long strings of photovoltaic modules are vulnerable to shading effects, reducing power output. To overcome this, distributed maximum power point tracking schemes connect individual DC-DC converters to each PV module to enable extracting maximum power from each module. This paper presents small-signal models for two distributed maximum power point tracking configurations - series and parallel - explaining observed operational peculiarities. The models are verified using a system with two maximum power point tracking buck-boost converters.

ORIGIN OF CROSS-COUPLING EFFECTS IN DISTRIBUTED DC–DC
CONVERTERS IN PHOTOVOLTAIC APPLICATIONS
ABSTRACT:
Long strings of photovoltaic (PV) modules are found to be vulnerable to shading effects, causing
significant reduction in the system power output. To overcome this, distributed maximum power pointtracking (DMPPT) schemes have been proposed, in which individual dc-dc converters are connected to each
PV module to enable module-wise maximum power extraction. There are two main concepts to implement
DMMPT systems: series and parallel configuration, describing the connection of the output terminals of the
converters. Both systems are studied intensively, with innovative solutions to encountered operational
challenges and novel control methods. However, a comprehensive dynamic model for neither system has
been presented so far. This paper fills the gap by presenting small-signal models for both configurations,
explaining the observed operational peculiarities. The analytical claims are verified with a practical system
comprising two maximum power point-tracking buck-boost converters.

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