In this study, a sliding mode-based controller is designed for regulating the output voltage of a high step-up DC-DC converter with three coupled inductors called Y-source impedance network. As Y-source converter can provide a very high boost at a lower shoot-through duty cycle of the switch and it has one more degree of freedom to achieve voltage boost. In order to accurately analyse the converter operation, the leakage inductance impact on diodes function in addition to other parasitic elements has been modelled. Hence, four different time intervals corresponding to switch and diode conduction have been considered. Also, an exposition of a variable structure control approach is mentioned. The method employs cascaded slidingmode control (CSMC) to output voltage regulation of the converter. The stability and robustness of the CSMC against the variation of reference voltages and the uncertainties of the load demands have been explained. Simulation and experimental results confirm the capability and effectiveness of the proposed control method.