In this paper, a comparative analysis has been presented on various topologies of isolated and non-isolated DC-DC converters. Here, the major focus remains on transformer-less (TL) DC-DC converters, based on the conventional basic boost converter. In addition, to attain high voltage gain, a classification of non-isolated converters based on extendable and non-extendable design has been presented. For comparative and theoretical analysis, the parameters chosen are the number of components utilized by each converter topology, high voltage gain offered, voltage stresses on each component involved and the efficiency of the high gain topologies. For the converters under discussion, operation under ideal and non-ideal conditions has also been highlighted. Based on this study, authors present a guide for the reader to identify various high voltage gain topologies for photovoltaic (PV) systems.

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Application of Classical numerical methods (CNM) for Digital maximum power point tracking (DMPPT) confronts g limited range of operation, PV array dependence and accuracy of the initial guess. In addition, the DC-DC converter cannot be treated as a black box for DMPPT, by ignoring the effects of the converter topological design and dynamics. In order to address such issues Hybrid Techniques (HT) have been presented, along with theoretical analysis to determine the optimum performance of DMPPT applications on various DC-DC converter designs. In this paper, the HT is a combination of the modified incremental conductance method (MINC) and modified CNM. An overview of MCNM, which applied to the photovoltaic (PV) application, has also been presented. The HT not only address the issues confronted by the CNM, but also remove the steady state error for the conventional MPPT technique. To measure the effectiveness of the proposed MCNM techniques, Boost, 2-Stage Switch Capacitor Based (2-SSC) Boost, and Optimum Buck Converters (OBC) have been employed. Simulation and experimental results are provided to validate the effectiveness of the proposed techniques.

In the case of grid-tied PV inverters, in general terms, the quality of current remains the determinant of the power quality, as voltage of a PV inverter cannot be controlled. Therefore, the current control strategy carries a prime importance for a grid-tied system. Low levels of harmonic distortion, increased dynamic response, and the DC-link voltage regulation are the fundamentals requirements that must be satisfied by a grid-tied system. Here, the entire output produced by the PV systems largely depends on the current-control technique employed. This paper offers an overview of various current control schemes and presents a novel current control technique for grid-connected cascaded H-bridge PV inverters. This control technique is implemented on a π (Pi) type thriteen level cascaded H-bridge (PiCHB) PV inverter.