Nonlinear controllers for fuel cell, photovoltaic cell and battery based hybrid energy management system

Due to limitations of conventional energy sources like petrol, diesel, hydro, nuclear etc., hybridization of green energy sources like photovoltaic cell, wind, fuel cell etc. has become a challenging task. In this research photovoltaic (PV) and fuel cells (FC) have been considered as primary sources of energy while battery as a storage unit for a Hybrid Energy Storage System (HESS). Extraction of maximum power from PV panel and output voltage regulation is another challenge due to its nonlinear characteristics. In this paper, single stage multi input multi output (MIMO) buck converter has been considered and four controllers: Fuzzy Logic Based (FLB) robust, nonlinear Backstepping (BS), Integral Backstepping (IBS) and Synergetic controllers have been proposed to track the output voltage, to control the battery charging and to extract maximum power from the PV cell. Asymptotic stability of the proposed controllers has been proved using Lyapunov theory. The performance of nonlinear controllers has been checked under input power and load variations on the converter having only one inductor and two input sources. They have been compared with each other and conventional PID controller under different operating conditions by simulations in MATLAB/Simulink. The results have also been validated by an experimental setup on a lab prototype.