This paper concerns the control design of Hybrid Power System(HPS). Dynamic equations describing the coupling of buck converters are derived and a robust fuzzy sliding mode dynamic controller is designed. The aim is to show that the proposed control leads to good results in terms of robustness and stability according to the fluctuations of renewable sources and the load variations, without the use of cascade structure commonly used in literatures. The proposed control method is stable, good behavior to external disturbances, and does not request to know the system parameters exactly. Simulation results show good dynamic performances in term of response time of the DC bus voltage and robustness according to the load and the input voltage variations.