This paper presents a novel bidirectional DC-DC converter with high conversion ratio for the renewable energy systems. The proposed converter uses the coupled-inductor technique to achieve high conversion ratio. Besides, this converter has simple circuit topology and simple control technique. In the discharging mode, the proposed converter likes two stage boost converters and only needs to control one active switch that can achieve high voltage step-up ratio conversion. When the charging mode, it likes two buck converters in cascaded, and the active switches are operated in the same duty cycle that can achieve high voltage step-down ratio conversion. This paper has analyzed the proposed converter operating principles, steady-state circuit characteristics. Eventually, a prototype circuit with conversion voltage 24 V/ 200 V and output power 200 W is implemented to verify the feasibility of the proposed converter. The maximum efficiency is about 94.3 % and 91.6% at discharging and charging mode respectively.