Transformerless high step up dc-dc cascode converter with maximum power point tracking

Abstract

A MPPT based transformer less high step-up dc-dc cascode converter is proposed in this paper. The cascode converter utilizes two buck-boost converters (lower and upper semi-stage converters); they are integrated with a single active switch. The input voltage of lower semi-stage is from the dc source. The input voltage of upper semi-stage is from the dc source and the output voltage of the lower semi-stage by series. Thus the overall output voltage of the converter is the sum of output voltages of the two semi-stages by cascode. Hence a dc-dc converter with high voltage gain is achieved without extremely high duty ratio. Then the performance of this cascode converter is investigated with the utilization of maximum power point tracking (MPPT). So this paper also deals with mathematical modeling and simulation of a solar photovoltaic module. The PV cell exhibits non-linear voltage-current characteristics or non-linear power curve, so its maximum power point varies with weather conditions such as solar insolation and ambient temperature. It is observed that there is a unique maximum power point for a PV cell at a particular weather condition. This maximum power point can be tracked efficiently based on incremental conductance method. The system includes a dc-dc cascode converter, PV module and a MPPT controller. The complete system is analyzed using MATLAB/Simulink.