The geometry status of electric railway catenary is critical to the stability of railway power supplying. An accurate and efficient vision measurement approach for railway catenary geometry parameters (CGPs) is proposed. An image-based system using a binocular vision component composed of two line scan cameras is first described and analyzed, and then a calibration method for the vision component based on 1-D target combining with 1-D displacement platform is investigated. When the onsite inspection is performed by the test train, there are multiple degree of freedom vibrations created by onsite irregularities of railway line. The detection accuracy of CGPs is inevitably degraded due to the vibrations on the results during running. A compensation method to reduce the vibration errors is presented. Experiments carried out in real-life detections validate the effectiveness and efficiency of the proposed system.

With the increasing requirements of the railway sector for electrified railways and the development of society, the traction power supply system needs to become more flexible, economic and reliable. The traditional traction power supply system has many problems due to its own topology, such as negative sequence current, load fluctuation, low utilization rate of regenerative braking energy, and inability to use the distributed generation along the railway. In order to solve these problems and make the traction power supply system (TPSS) more flexible, efficient and reliable, a novel TPSS called flexible smart traction power supply system (FSTPSS) is proposed. This traction power supply system consists of AC-DC-AC traction substation and the microgrid along the railway. It can effectively mitigate the problems of negative sequence current, improve regenerative braking energy utilization and distributed generation utilization. A hierarchical energy management strategy is also proposed here, which can effectively improve the operating economy of FSTPSS and reduce the load fluctuation of FSTPSS. And based on the actual load measurement power of a traction substation of China’s Beijing-Shanghai high-speed railway, the proposed energy management strategy has been verified for the economic improvement and load fluctuation reduction of TPSS.

The flexible smart traction power supply system (FSTPSS) is a fully electronic traction power supply system (TPSS), which integrates ac-dc–ac traction substations, distributed generation, and hybrid energy storage system (HESS). Compared with the traditional TPSS, the power supply of FSTPSS becomes more diverse, but the randomness of power flow becomes greater. A suitable energy management strategy is needed for FSTPSS to control the power flow of the system. At present, the day-ahead energy management strategy (DAEMS) has been proposed to make an optimal plan for the whole-day operation of FSTPSS, but this energy management strategy does not consider the impact of real-time fluctuation caused by nondeterministic loads or sources on the reliable execution of DAEMS. To solve this problem, this article proposes an online energy management strategy (OEMS) based on long short-term memory (LSTM) network and deep deterministic policy gradient (DDPG) algorithm to counteract the effects of these real-time fluctuations. The proposed OEMS has the advantages of small tracking error, model-free control, and continuous action control. To verify these advantages, a series of comparative simulations is carried out, and the simulation results verify the advantages of the proposed OEMS.

A single‐phase cascaded H‐bridge multi‐level active power filter (APF) to deal with the power quality problems in the AC electric railway systems is presented. The APF can connect to the traction busbar directly without any transformer or resonance branch. The direct current control combining the current decoupling transformation is introduced in the control strategy. This strategy simplifies the control system, enabling the least amount of current measurement with the existing sensors and removing complex current reference extraction algorithms. The control system design process, especially for the parameter tuning, is mainly discussed. Finally, simulation and experimental results verify the effectiveness of the proposed APF system applied in the AC electric railway systems.

As high-speed railways develop rapidly worldwide, the problems of neutral section and power quality are becoming increasingly prominent. These problems affect the normal operation of the power grid and the electric locomotives. The co-phase power supply schemes were proposed by researchers, which can solve these problems well. Among them, the MMC-based scheme (MMC-5 L) is a representative one. The existing scheme, when applied to the auto-transformer (AT)-fed system which is usually adopted by high-speed railways, needs to install an auto-transformer on the output side. To eliminate the auto-transformer and to obtain the more suitable and superior co-phase power supply schemes to AT-fed system, two improved schemes are proposed in this paper based on the novel MMC-based scheme (MMC-6 L) we proposed before. While establishing the mathematical model, creating the control system, and carrying out simulation verification of the proposed schemes, the proposed schemes are compared with MMC-6 L and MMC-5 L in terms of topological characteristics, control system complexity, power loss, and functionality. The results show that while the proposed schemes can fulfill the functions of the co-phase power supply scheme well like the MMC-5 L and MMC-6 L, they are more suitable and superior for the AT-fed system in terms of control system complexity and power loss. Among them, MMC-5L1CB performs best in power loss, and MMC-4L2CB performs best in control system complexity.

In this article, a low computational burden model predictive control (MPC) strategy without weighting factor is proposed for the single-phase cascaded H-bridge CHB converters. To reduce the switching state candidates, a hierarchy control algorithm is proposed. The grid current is controlled by selecting a subregion from the designed 2-D control plane, instead of the entire area. Two vectors are chosen in one sampling period for more accurate tracking. Then, the voltage balancing is achieved by selecting the optimal switching state from the subregion candidates to form the above two vectors. The cost function can be constructed of one variable: load voltage. Therefore, the weighting factor can be eliminated. No tuning or retuning processes are required in the proposed method. To reduce the computational time further, the principle of eliminating the switching state candidates operating the same voltage balancing performance is proposed. Conventional and proposed MPC methods are verified by experimental tests via a laboratory setup of a three-cell connected CHB converter. Steady-state and transient operations demonstrate that the proposed method guarantees less distortion grid current and shorter execution time (reduced from 15 to 3 $\mu s$ ). Fast response speed to variations in voltage reference and load resistance can be achieved t.