Flatness based control of a fuel cell-supercapacitor multi source/multi load hybrid system

This paper presents the flatness based control of a multi-source/multi-load electrical hybrid system (EHS) composed of a fuel cell and a supercapacitor-bank (SCB) as the main and auxiliary source, respectively. The main and auxiliary sources are connected to a DC link which has a floating voltage. This DC-power source supplies three independent 5V, 12V and 24V loads which are connected to the DC link through different buck converters. A flatness based method is used in this paper to control the hybrid system. For this purpose, the electrostatic energy stored on the DC link and also output capacitors are considered as the flat outputs of the system. Then, different reference trajectories are planned on these outputs and they are forced to track their references. The dynamics of fuel cell is limited by controlling the DC link voltage variation which is carried out by putting a filter on the reference of DC link trajectory. The proposed method does not contain commutation algorithm whereas the different operating modes exist. The implementation results are presented to validate operation of the proposed method in the multi source/multi load hybrid system.