Supercapacitor based energy storage for the use of recuperated energy on metros

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Dr. Farkas Csaba
Department of Electric Power Engineering

With the help of regenerative braking, railway vehicles are able to convert the kinetic energy of braking into electric energy and send it back to the overhead line or the third rail. In case of the metro network of Budapest, feeding back energy to the grid is not feasible because of the diode rectifiers. If at the moment of braking there is an accelerating vehicle nearby, it can absorb the recovered energy, but with moderate losses it is only possible within a few hundred meters. The remaining electric energy is dissipated to the braking resistors. With the use of energy storage systems it is possible to store this, and use it during the next acceleration and by this energy can be saved. At the beginning of my thesis I summarize the different energy storing methods, especially the supercapacitor, which has ideal properties for application in public transportation. Based on a speed profile simulation of the M4 metro I calculated the accelerating and braking energies between each stop. Then I simulated the power and energy conditions along the M4 metro line using measurement data. Later I analyzed two different control strategies assuming an onboard supercapacitor. Finally I compared and evaluated the results.


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