Abstract
Purpose. Development of a method for determining the main functional parameters of on-board supercapacitor recuperative energy storage based on the asymptotic theory of extreme statistics by Gumbel, taking into account stochastic nature of changes in recuperated voltage and current. Methodology. To achieve this purpose, methods, devices and computer systems for temporary registration of recuperated voltages and currents on operating electric locomotives, methods of the theory of random processes and methods of probabilistic and statistical processing of registrograms of voltages and currents were used. Findings. A computational and experimental method for estimating recuperative energy has been proposed and practically applied. A probabilistic method has been developed for determining the energy and electric capacity of on-board supercapacitor recuperative energy storage units. Numerical probabilistic and statistical calculations of the energy and electric capacity of on-board storage for the VL8 and VL11M6 electric locomotives during their operation in the sections of Prydniprovska railway have been carried out. It was found that the energy and electric capacity of on-board storage devices are distributed according to an exponential law with a clear prevalence of their minimum values and in compliance with direct proportionality between them. Originality. For the first time, an autonomous phase of recuperative braking mode of an electric rolling stock has been developed, which makes it possible to significantly reduce the mass and dimension of a supercapacitor storage. The asymptotic theory of extreme statistics by Gumbel was adapted to the method for calculating energy and electric capacity of an on-board storage device, which made it possible to take into account the influence of stochastic nature of changes in the recuperated voltage and current. The probabilistic influence regularities of the change nature in the recuperation energy on the capacity of on-board storage in the phase of recuperative braking have been established. Further development was obtained by a computational-experimental method for assessing the recuperative energy, based on monitoring and using the time dependences of voltage and current obtained in real modes of recuperative braking. For the first time in electric traction systems, it was proposed to carry out the transition from the recuperative braking mode to the recuperative regeneration mode. Practical value. The developed method and technique based on it make it possible to evaluate functional parameters of on-board storage device of all types of electric rolling stock, considering stochastic nature of recuperated voltages and currents. Numerical-graphic dependences of the energy intensity and capacity of the on-board storage are recommended for predicting and evaluating these parameters for various modes of recuperative braking. Since the task of designing an on-board storage unit (in terms of mass and dimensions) is ambiguous, therefore, in each specific case of the type of electric locomotive and recuperation modes, it must be solved individually, taking into account the probability of the corresponding capacitance values.
Highlights
The main disadvantages of the existing system of regenerative braking of electric rolling stock (ERS) of direct current, preventing its efficient implementation, are caused by the necessary connection, that is, non-autonomy of recuperating ERS with the traction power supply system [5, 14]
The energy capacity is taken to be equal to the recuperation energy Wр and is determined by the above experimentalcalculation method based on the voltage Uр and current Iр obtained under real conditions of the recuperative braking mode
The capacity was assessed for three cases: according to the average values of Wр,Uр for the recuperative braking (RB) phase, according to formula (2) as the most probable value of the statistical values, according to the statistics of the maximum values by Gumbel according to formulas (11), (12)
Summary
The main disadvantages of the existing system of regenerative braking of electric rolling stock (ERS) of direct current, preventing its efficient implementation, are caused by the necessary connection, that is, non-autonomy of recuperating ERS with the traction power supply system [5, 14]. Currently, the issue of increasing the reliability, stability and electric power efficiency of recuperative braking (RB) is acute. In our opinion, this problem can be solved by transition from the systems and modes of RB to the regenerative braking systems [5]. In the definitions of the concept of regeneration, there is no condition for the return of regenerated electricity to the supply network This necessitates the need for a regeneration energy storage at the ERS itself – an onboard storage unit operating in a buffer mode. The on-board buffer energy storage unit (SU) means device, whose primary function is the operational use of electrical braking energy by accumulation, short-term storage and its subsequent implementation in the traction mode
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