Conversores CC-CC de alto ganho interleaved baseados na célula de comutação SC-PFM sem sensor de corrente para sistemas fotovoltaicos

Abstract

In this work, a switching cell with pulse frequency modulation (SC-PFM) integrated with coupled inductors and an input inductor operating in continuous conduction mode (CCM) with low current ripple and providing high static gain is employed. Converters based on SC-PFM have the characteristic of being voltage followers, whose behavior allows the development of a control system or a maximum power point track (MPPT) without the need to use a current sensor, a component that increases complexity and cost. Other important features are soft switching for a wide switching frequency range, the diodes block without reverse recovery losses, it requires few components and the output voltage ripples do not cause an impact on the input current. Based on the SC-PFM, two converters were developed, the first one is an interleaved boost-flyback type (IBFC-PFM), and the second one is an interleaved flyback (IFCPFM), a non-isolated option, and an isolated. The principles of operation, analysis, and mathematical modeling are presented, including the non-idealities inherent to the used semiconductors. Additionally, voltage and current stresses are determined to obtain theoretical losses and efficiency. Prototypes of 450 W and 190 W were built, respectively, which were tested in open loop using a two-channel pulse generator, with a 180-degree phase shift. The waveforms and electrical measures are compared with the computer simulation and with the values obtained by mathematical equations, attesting to the correct functioning and conformity of results, in addition to proving the highlighted qualities. Benefiting from the voltage follower property, both proposed converters, in addition to a third topology, an interleaved boost converter, were used as an interface between photovoltaic systems and a DC bus, tracking the maximum power point with a perturb and observe (P&O) based programming. The MPPT results are presented for variations in incident irradiance and temperature, individually and mutually, as these climatic factors are responsible for different effects on the system functioning. In all cases, the converters present fast transition and stable operation.