Application and improvement of a direct method optimization approach for battery electric railway vehicle operation

Abstract

While the largely electrified rail network allows for direct utilization of renewable energy sources, there is still a considerable share of diesel-powered trains operating on non- and partly electrified tracks. To replace these, the more sustainable alternatives such as battery electric railway vehicles need to present a viable option with sufficient range. This paper aims to adapt and improve an existing optimization algorithm, previously used with diesel-powered trains, for the operation of battery electric railway vehicles. In this new approach, battery control is optimized alongside train control, utilizing a direct method solver to find the minimum energy trajectory. Furthermore, a detailed train model is implemented that is designed for operation on partly electrified tracks. To yield a highly accurate, yet also sufficiently fast algorithm, a numerical analysis is conducted and the parameters of the algorithm are determined accordingly. Finally, the application of the adapted algorithm on a use case in Germany shows that both velocity profile and control adapt in a way that minimizes utilization of the battery. The results indicate that the proposed algorithm presents a reliable and robust method to obtain minimum energy controls for battery electric railway vehicles with any electrification pattern.

Techno-Economic Assessment of Battery Electric Trains and Recharging Infrastructure Alternatives Integrating Adjacent Renewable Energy Sources

“…The energy demand is calculated by longitudinal simulation based on the modelling approach presented by Schenker 2020 [21]. The direct method optimization presented in [21] results in a reduced-energy trajectory compared to manual operation.…”

“…The energy demand is calculated by longitudinal simulation based on the modelling approach presented by Schenker 2020 [21]. The direct method optimization presented in [21] results in a reduced-energy trajectory compared to manual operation. The model optimizes the trajectory of a round trip of a railway line considering the route's characteristics, such as length, elevation, speed limits, schedule and vehicle characteristics, such as mass, power characteristics and resistance coefficients.…”

“…For this study, we simulated a full electrification scenario, where only traction motors and propulsion converters are subject to optimization and other drivetrain components are excluded. The simulation output comprises power demand at DC-link over the whole round trip with a maximum step-size of 100 m. The step-size is further decreased in the vicinity of stops in order to gain appropriate accuracy in the numerical discretization for solving the longitudinal equation system [21].…”

“…Sustainability 2021, 13, x FOR PEER REVIEW 7 of 30 [21] results in a reduced-energy trajectory compared to manual operation. The model optimizes the trajectory of a round trip of a railway line considering the route's characteristics, such as length, elevation, speed limits, schedule and vehicle characteristics, such as mass, power characteristics and resistance coefficients.…”

“…For the longitudinal simulation, based on [21], a generic BEMU is specified similar to Pesa Link II 2-car multiple-units with Jacobs bogie (BR632), which are currently employed at rail line RB26 [43]. The basic specification of the generic BEMU are simplified applied to the EMU longitudinal simulation, assuming a traction power of 1.2 MW for BEMU and EMU simulation for comparability reasons.…”