This doctoral thesis is devoted to the study on supercapacitors based braking energy storage system parameters in order to increase the efficiency and profitability of such systems. Doctoral thesis introductory part shows the topicality of this theme and gives a brief historical insight in energy storage systems applications in railway systems. This part also contains the analysis of various research results on supercapacitors usage in energy storage systems. Information about various commercialized technologies that can be used to recover braking energy is collected in the first chapter. In this section a novel technical approach of measuring individual cell voltages of series connected supercapacitors is proposed. In the second chapter of this work Matlab/Simulink model that allows detailed simulation of public electric transport system is showed. This chapter also contains the description of a method that allows obtaining a simplified equivalent electrical model of transport system feeding lines. A new method for estimation of potential profit from energy storage system implementation is proposed in the third chapter. Proposed method also determines the optimal number of supercapacitors that must be used to meet specific energy and power parameters of energy storage system. Method is used to determine optimal power and energy parameters for one stationary and one mobile energy storage system. The fourth chapter is devoted to the study on energy storage system control parameters effect on recoverable energy amount. Optimal control parameters for one stationary and one mobile energy storage system are found.