Energy harvesting from the fuel cell hybrid power source based on extremum seeking control schemes

Abstract

Abstract Energy harvesting is known as the conversion process of ambient energy into usable electrical energy, including the available and free energy of the renewable and green energy sources. This chapter analyzes the possibility to use the Extremum Seeking Control schemes for harvesting the hydrogen energy via a Fuel Cell Hybrid Power Source. The new Extremum Seeking Control schemes proposed here are based on a band-pass filter with the frequencies’ band larger than that of the series combination of high-pass and low-pass filters used in the classical Extremum Seeking Control scheme. The mathematical modeling of the Extremum Seeking Control scheme that is applied to nonlinear dynamic plant shows the close relations between the search speed, the derivatives of the unknown input-to-output map, and the cut-off frequencies of the band-pass filter. The simulation results are compared with the results of classical Extremum Seeking Control schemes. The ratio of these search speeds is used as the performance indicator, besides the tracking accuracy evaluated for each control scheme. A Maximum Power Point tracking technique is proposed for the Fuel Cell stack based on a modified Extremum Seeking Control that slightly improves the performance. A higher value of the searching speed is obtained for the same tracking accuracy. The search speed will increase proportionally with the product of both control parameters (the closed loop gain and the dither gain), so it is practically limited for safe reasons. An advanced Extremum Seeking Control scheme is proposed here to further reduce the power ripple and obtain the imposed performance related to the search speed and tracking accuracy. Finally, the dynamical operation of the Fuel Cell stack under constant and variable load is shown.