This paper presents a modular approach to model and control multi-source systems or networks. This method derives from an energy-based modeling approach called functional modeling in which predictive functional control algorithms have been implemented. A concept of cost function is introduced and associated to each source. The design of the control has several objectives: remain as generic as possible, satisfy the needs from the consumers and distribute flows in order to minimize the cost functions. This methodology is applied to a use case consisting in the management of an isolated production unit composed of a wind power plant and a backup battery. The system is modeled and controlled in order to ensure the active power balance between consumers needs and sources supplies.