Distributed PV Power Extraction Based on a Modified Interleaved SEPIC for Nonuniform Irradiation Conditions

Nonuniform irradiation of a photovoltaic (PV) source, consisting of series-connected modules with bypass diodes, results in multiple peaks in the power-voltage characteristics. This makes the maximum power point tracking (MPPT) difficult because the conventional MPPT algorithms can only deal with single power peak characteristics. This paper proposes a novel distributed MPPT (DMPPT) scheme based on an interleaved single-ended primary inductor converter (SEPIC) converter configuration for compensating the mismatch in characteristics of series-connected PV modules. The proposed scheme obviates the need for bypass diodes across the modules, resulting in single-peak power-voltage characteristics. The proposed DMPPT circuit is derived from an interleaved SEPIC converter that works on the “return energy” concept. The proposed configuration equalizes the voltages across PV modules of the string, resulting in their operating close to its maximum power point. Discontinuous conduction mode of operation is implemented, obviating the voltage-sensing requirements across modules, eliminating the reverse recovery loss of diodes and the turn-on loss of the main switch. The proposed DMPPT scheme uses a simple circuit with reduced control complexity and needs only a few passive elements and only one switching device, compared with the existing DMPPT schemes. The theoretical claims are validated with simulations and extensive hardware experiments.