Assessment of cross-coupling effects in PV string-integrated-converters with P&O MPPT algorithm under various partial shading patterns
Suneel Raju Pendem, Suresh Mikkili
Abstract
A significant challenge in the progress and development of Building-Integrated-Photovoltaic (B-I-PV) systems is the extraction of maximum power from PV modules. The PV system architecture is an essential feature to extract the maximum power. The conventional PV-central-inverter architecture consists of various connections among the PV modules, which are sensitive to shading effects and produces mismatching power loss under partial shading conditions (PSCs). Hence, photovoltaic-distributed-maximum power point tracking (PV-D-MPPT) architecture has been proposed to extract the maximum power. In PV-D-MPPT architecture, the output terminals of DC-DC converters are connected either in series or parallel configuration. The main limitation of the series configuration in open-loop MPPT control is the cross-coupling effect. Because of cross-coupling effects, the maximum-powerpoint (M-P-P) operation of shaded PV modules is lost under PSCs. The lost in M-P-P operation of shaded PV module also affects the unshaded modules M-P-P operation. Under cross-coupling effects, the DC-DC converters are consuming the power instead of delivering to the load. Despite the research activity, there are hardly any papers presenting a clear, comprehensive and mathematical analysis on the existence of cross-couplings in PV string-integrated-converters (S-I-Cs). This article presents a mathematical analysis and also explains the conditions for the existent of cross-coupling effects. The experimental results also validate with the mathematically analysed results. This article also discusses the modeling of the two-diode model of PV module, design of boost type S-I-C, and the Perturb& Observe (P&O) MPPT algorithm implementation.