Expandable Isolated Bidirectional Three-Port DC-DC Converter With High Voltage Conversion Ratio For PV-Battery Systems

This paper proposes an isolated three-port bidirectional DC-DC converter with low voltage and current stresses on switches. In the proposed converter, there is an storage port that increases the reliability of the converter. Bi-directional operation exists for all three dc ports, and this is a feature needed to charge and discharge the energy storage port. Moreover, the proposed converter has high voltage conversion ratios between the low and high voltage sides and is useful for PV systems. By considering that the voltage transfer function is calculated based on three parameters of a number of switches (or capacitors), the turn ratio of the transformer, and the duty cycle, the proposed converter can be designed in a way that achieves maximum efficiency and the optimized structure. So, the proposed converter has high flexibility. Also, the input-currents-ripple at the high current side is low and equal to the ripple of the triangular continuous current of input inductors. Furthermore, a simple-gate driving is utilized for operating the proposed converter which makes the maximum power point tracking (MPPT) controlling system much simpler. Finally, the simulation results are extracted for 40V/310V/600V voltage and reconfirm the accuracy performance of the proposed converter.