Abstract
Optimizing the operating speed curve of trains without adding new energy storage facilities is essential in the energy-saving operation of railways. In this paper, we propose an optimal train speed curve planning method for driving trains more energy efficiently. A refined traction energy evaluation model for induction motor propulsion systems is first presented. The proposed model considers the efficiency of the traction motor at different operating points and the efficiency of the inverter and gearbox. Then, the optimal energy-efficient speed profile problem is transformed into a multistep decision problem and solved using dynamic programming (DP). To verify the effectiveness of the proposed method, a case study was conducted on an actual subway line. The results obtained indicate that the speed curve produced by the proposed method results in a 20% energy consumption saving compared with the speed curve for actual operations. Furthermore, the results of comparison with a genetic algorithm indicate that the DP algorithm is better able to satisfy the constraints of the train traction system. Solving the optimal speed curve using the proposed method and programming the onboard controller of the train according to the optimal speed curve enables the train to be driven with greater energy efficiency.
Highlights
The main contributions of this study are as follows: (i) the development of a new model that captures motor efficiency and traction energy consumption more accurately; (ii) the development of an optimal model for solving the most energy-efficient speed profile based on dynamic programming (DP); and (iii) the implementation of our solution to estimate the energy reduction obtained for real urban rail transit line examples
This study carefully considered the model of the train traction propulsion system and the changes in motor efficiency at different operating points, which resulted in an estimated traction energy consumption that was closer to the actual value
Using the evaluated traction energy, an optimal speed profile planning method based on DP was proposed in this paper
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. This simplified method may cause the planned speed curve to deviate from the best efficiency of the TM at the operating point, resulting in greater energy losses by the motor In response to this problem, some scholars have tried combining speed planning with refined motor efficiency models. Unlike the models presented in the literature, the approach proposed in this paper considers the dynamic efficiency of the train TM to plan the speed curves, which makes the energy consumption model more economical. (ii) the development of an optimal model for solving the most energy-efficient speed profile based on DP; and (iii) the implementation of our solution to estimate the energy reduction obtained for real urban rail transit line examples.
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