Optimizing braking energy flow through charging status surface expansion

Abstract

Energy savings in electric railway transportation is essential due to the ever-rising energy cost and endeavour to reduce climate change impact. A valuable method to increase energy efficiency is to recuperate and consequently utilize the regenerative braking energy of electric railway vehicles. The system that stores and reuses the braking energy is called a regenerative braking system, consisting of an energy storage system (ESS), a bidirectional power converter, and a control system, which includes an algorithm controlling the braking energy flow. A properly designed algorithm increases energy efficiency, lessens the stress on the power grid, increases the lifetime of the energy storage system, and enables a catenary-free operation of the electric railway vehicle. The algorithm is defined by combining two algorithms with opposite features - maximum energy savings and a minimal number of cycles. The algorithm is then synthesized from those two criteria using an optimization process and then simulated while its effect on energy savings and grid stability is analyzed. Energy savings and a more stable grid are achieved with the use of the algorithm, which corroborates the inclusion of a regenerative braking system in electric railway vehicles.