The process of electric multiple units (EMUs) passing long downhill sections is inevitable in the construction of mountain railways. Moreover, huge regenerative braking energy (RBE) will be sent back to the traction network, threatening voltage safety. Due to the lack of accurate vehicle-grid integrated models considering slope parameters in studying the RBE, this article proposes a modeling scheme, taking China railway high-speed 3 (CRH3) EMUs as an example. First, based on the extended dual pulsewidth modulation (PWM) mathematical model, the quantitative formula for calculating the motor braking power of the CRH3 EMUs is established. Moreover, the slope parameters are introduced into the vehicle-grid model via force analysis and regenerative braking power calculation. Then, by substituting the calculated results into the extended dual PWM mathematical model, the target instruction parameters are solved. Next, the accurate electrical characteristics, including catenary voltage, electromagnetic torque, and converter voltage, are simulated to evaluate the voltage safety. Finally, by comparing the simulation and semi-physical experiment results with the experimental data from the Chengdu to Chongqing railway line, the feasibility, validity, and accuracy of the model are verified.

The electrical incompatibility between vehicles and traction network in railway system can result in system instability and oscillation overvoltage issues. To analyze the system stability, impedance-based frequency-domain methods are commonly used. However, the current impedance-based modeling methods face challenges in practical implementation due to the requirement of precise analytical models and detailed internal parameters for all vehicles. Moreover, multiple vehicles operate simultaneously in railway systems, each with different operating conditions and internal parameters, thereby influencing system stability to different extents. Therefore, it is crucial to accurately identify the critical vehicles to prevent resonance accidents. To address these challenges, a component connection-based modeling approach for the railway vehicle-grid system is proposed, which only requires the measured impedance results without the internal information of vehicles. In addition, a multilevel sensitivity analysis method is introduced to quantitatively identify the critical vehicles and internal parameters that influence system stability, which outperforms traditional sensitivity analysis methods in computational complexity. Furthermore, a system-level electrical compatibility test process for the railway vehicle-grid system is provided, incorporating the proposed stability and sensitivity analysis methods. Finally, case studies based on the real-world train schedule of a multivehicle-accessed railway vehicle-grid system are designed to verify the correctness of the proposed method.

Abnormal vibration can lead to frequent maintenance requirements of electric locomotives. Many factors contribute to the vibration, and the influence mechanism of pulsating torque generated by interharmonics in the traction drive system (TDS) is not clear at present. In this paper, an electromechanical coupling model is developed to investigate the influence of harmonics and interharmonics in the electric TDS on the vibration of key locomotive components. Firstly, this paper attempts to analyze the generation mechanisms of interharmonics and their resulting pulsating torque in electric TDS and derives the formulas for calculating interharmonics and pulsating torque frequencies. Then, an electromechanical coupling model is established based on the electric TDS and the multibody dynamics, and the influence of pulsating torque caused by interharmonics on the vibration of the locomotive key components is discussed in detail. It is observed that the locomotive vibrations, especially the longitudinal and vertical vibrations of bogies and wheels, can be significantly influenced by the pulsating torque. It is noticeable that the frequencies of the vibrations are consistent with those of pulsating torque, which proves that electrical parameters can affect the vibrations of key locomotive components. The research of this paper provides a new idea for restraining locomotive vibration.

Accurately characterizing wheel polygonal wear (PW) is critical for evaluating the operation status of vehicle-rail systems. While prior research has predominantly focused on employing a two-dimensional wheel profiles, it has overlooked the combined effects of circumferential and lateral wear. Furthermore, although there is evidence suggesting that interharmonics can influence wheel wear, existing studies have not thoroughly explored this aspect. Therefore, this paper examines the evolution characteristics of three-dimensional (3D) PW under the influence of interharmonics from the perspective of electromechanical coupling. Initially, an evolution model for 3D wheel PW is developed, integrating an electromechanical coupling model, a 3D wheel profile model, and the USFD wear function. Subsequently, 3D distribution characteristics of PW under multiple operating conditions are analyzed. The results reveal significant differences in the order and depth of PW across different lateral positions. Specially, on curved tracks, the order of PW is presented in distinct groupings. The dominant polygon of the locomotive running (70 km/h) on a straight track is 200 mm, attributed to ࣬5ƒ-7ƒ ₀ ࣬ interharmonic effect, whereas on the curved track, it is 316 mm, attributed to P2 resonance. Moreover, as the curve radius increases, the ratio between PW depth of 316 and 200 mm significantly decrease.

The electrified railways in high-altitude mountainous areas often feature long and steep slopes. These characteristics pose two primary challenges: traction network overvoltage caused by regenerative braking energy (RBE) in downhill and train stalls in uphill sections due to insufficient voltage supply. Configuring energy storage is feasible for recycling RBE and ensuring a stable power supply. However, existing research merely focuses on the size of energy storage systems (ESSs), failing to address the optimal siting and sizing problem adequately. To this end, this article proposes a novel hybrid ESS (HESS) configuration framework. First, the operation status of the train on long and steep slopes is analyzed, and RBE is decomposed into components suitable for the battery and supercapacitor based on a variational mode decomposition (VMD). Second, regarding the traction station, section post (SP), and overhead contact line (OCL) as HESS’s candidate locations, the types of trains are considered, and a siting and sizing optimization model is built to pursue the cost-benefit and traction network voltage. Finally, a improved combining multiobjective optimization with differential evolution (ICMODE) algorithm is proposed to solve the model. The simulation results validate the effectiveness of the method based on the actual data.