Dynamic characteristics of current-fed semi-quadratic buck-boost converter in photovoltaic applications

A buck-boost-type converter is required to interface a photovoltaic (PV) generator to a voltage bus, which has lower or higher voltage than the voltage of the PV generator. Due to the semiquadratic nature of the proposed converter, it can be used in transformerless modular PV energy systems needing wide conversion ratio. Dynamic analysis provides the tool for proper control design and the analysis of interactions imposed by the load and source impedances. PV generator is internally a current source but has highly nonlinear terminal characteristics resembling both current and voltage sources depending on its operating point in respect to the maximum power point (MPP). Accordingly, the MPP tracking converter can be either current-fed (CF) or voltage-fed (VF) converter. The feedback method would finally determine the dynamic properties of the converter in the PV applications. In this paper, the dynamic analysis of the proposed converter in the single-phase grid-connected inverter application is carried out taking into account the dynamic properties of the PV generator.