Determination of optimal characteristics of braking energy recovery system in vehicles operating in urban conditions
Vyacheslav Rakov
Abstract
The results of the research presented in this article characterize the influence of various factors on the current processes of the kinetic energy recovery system (KERS) for recovering kinetic energy of vehicles with electromechanical or electric drive (hybrid and electric cars) under braking. The article presents the basic limits of variations in accelerations and initial speeds during braking in urban traffic using WLTC (Worldwide harmonized Light-duty vehicles Test Cycles) as an example. Relationships affecting braking recovery are identified, which makes it possible to determine the power of the braking forces acting on a vehicle. Relationships between the initial braking speed, acceleration of deceleration, and recovery power are determined based on the relationships between the propulsion power and energy analysis. The resulting field of values for changes in regenerative braking power allows us to get an idea of the characteristics of KERS elements. The presented diagram describing changes in the maximum braking force power depending on the initial speed and acceleration of deceleration of a vehicle provides an insight into the possible ranges of the effective operation of the energy recovery system. As a result of a theoretical experiment, it was established that the vehicle mass affects the maximum power of regenerative braking. Based on the results of theoretical research, it is possible to determine the maximum current and power absorbed by an electric energy storage unit. The obtained relationship between the speed and acceleration in the process of active deceleration allows us to get an idea of the possible modes of charging the electric energy storage unit. Tests in road conditions, conducted with the use of several types of vehicles and test models with a hybrid engine, confirm the results of the research. The approaches presented in this article and the obtained results are indicative of the regularities of regenerative braking in vehicles operated in the road network, which makes it possible to select the optimal characteristics of an electric propulsion drive and ensure high fuel energy and environmental efficiency of vehicles at a minimum cost.