Flatness control of batteries/supercapacitors hybrid sources for electric traction

Multi-source systems are the attractive solutions in transport applications like electric vehicles. These systems are often made of the assembly of clean energy sources such as fuel cells (FC), batteries (BAT), supercapacitors (SC) and photovoltaic systems. In this paper, a multi-sources system using lithium-ion batteries considered as the main source (energy source) and SCs considered as the auxiliary source (power source), are in charge of the vehicle traction. The objective is to control the DC bus voltage by absorbing the excess or supplying the lack of power during the transient, satisfying the vehicle power requirement, and by recharge the supercapacitors. A new nonlinear control strategy based on the differential flatness approach is applied to the BAT/SC hybrid source. The advantage of this strategy is that the state and control variables are downright estimated by the flat outputs trajectories without the need to integrate any differential equation.