In this paper, a new ultra-high voltage gain quadratic DC-DC converter based on coupled-inductor is introduced for renewable energy applications. In this presented topology, a two-winding coupled-inductor along with voltage multiplier cells are combined with a quadratic boost converter to enhance the voltage gain ratio. The main features of the suggested converter are its ultra-high voltage conversion ratio, low voltage stress across switching devices, continuous input current with low ripple, and common ground between the input source and output sides. Moreover, the current sharing of the high DC source current between the coupled-inductor and another input inductor leads to the reduction of the overall power losses of the magnetic components of this circuit. Furthermore, the voltage maximum stresses on the switches of this converter are mitigated with the help of regenerative passive clamp circuits. The operating principle, the steady-state DC analysis, comparison study along with the efficiency analysis of the introduced topology are presented in detail. Finally, the performance of the proposed converter is justified with the help of a 200 W (25 V-400 V) laboratory sample prototype.