solated Bidirectional DC-DO Converters to Integrate PVwith Energy Storage Systems for High Power Density Applications

Abstract

An isolated bidirectional DC-DC converter is a solution to integrate renewable energy-generating units with energy storage systems. This concept can overcome the drawback of intermittency or non-availability of renewable energy sources throughout the day, e.g., solar energy, by supplying the energy to loads through battery storage units. This research is to find a suitable isolated bidirectional dual active bridge (DAB) resonant DC-DC converter for high power density applications and investigate its performance. Therefore, in this work, the literature survey on isolated bidirectional dual active bridge converter topologies, their switching and power control schemes, and analysis methods are presented. Single phase-shift control technique a fixed-frequency control scheme makes the design of isolation transformer, inductive and capacitive filters easy for better filtering. The modeling, steady-state analysis and design of the converter have been presented. The detailed performance analysis of the proposed converter during various intervals of operation for both forward and reverse mode operation is presented. It has been found that the use of a single phase-shift control scheme, leads to continuous conduction mode operation of the converter without loss of duty cycle. This switching scheme successfully maintains constant output voltage with a small change in pulse width for wide variations in input voltage and load conditions. A 135 W, 48V converter has been proposed and its performance has been studied through theoretical calculations, simulations and experiment in the laboratory. The boundary condition of the soft-switching of the converter is studied by establishing an expression for instantaneous switch current and dead time in terms of the parasitic capacitance of the switching device i.e., MOSFET.