Railway Traction Power Supply System Research Articles

Modeling of energy recovery processes in railway traction power supply systems

Regenerative braking of trains can provide significant energy saving and a sizeable reduction in greenhouse gas emissions. The efficiency of energy recovery can be defined using an efficiency indicator equal to the product of the free-fall acceleration and the fraction of potential energy used in the recovery. Its slope dependence is well approximated by a polynomial of the third degree. The operating conditions of the traction power supply system of the mountain pass section of the main railway were modeled. The results obtained allowed the following conclusions to arrive at: regenerative braking is accompanied by circulating currents in adjacent inter-substation areas and leads to an absolute and relative increase in electrical energy losses in the traction network; the share of active energy losses rises by several times; the energy recovery causes a change in the direction of active energy flows at traction substations with a steep increase in reactive power consumption by trains; the energy recovery produces a significant decrease in voltage on the current collectors of electric locomotives; the voltage on the section under consideration, with three trains weighing tons decreased to 23 kV due to the large reactive energy consumption. © 2024 The Authors. Published by Elsevier Ltd.

Research on Symmetric Bipolar MMC-M2Tdc-Based Flexible Railway Traction Power Supply System

Research on Symmetric Bipolar MMC-M²Tdc-Based Flexible Railway Traction Power Supply System

Harmonics suppression in high-speed railway via single-phase traction converter with an LCL filter using fuzzy logic control strategy

Introduction. The railway Traction Power Supply System (TPSS) encounters a common challenge related to high-frequency harmonic resonance, especially when employing AC-DC-AC traction drive systems in high-speed trains. This resonance issue arises when the harmonic elements introduced by the traction AC-DC converter on the grid side of trains align with the innate resonance frequency of the TPSS. The novelty the proposed work focuses on the challenges associated with resonance elevation and high-frequency harmonics in high-speed trains, while simultaneously enhancing energy quality. This is achieved by integrating a pulse-width-modulated converter on the grid side with a single-phase configuration and incorporating an LCL filter. Methodology. In order to optimize the system’s efficiency, a robust control system is employed, taking advantage of the capabilities of a fuzzy logic controller (FLC). The choice of the FLC is justified by its straightforward design and reliability, emphasizing the dedication to precise control, as fuzzy logic excels in handling complex, nonlinear systems. Through the use of linguistic variables and heuristic reasoning, the FLC adjusts to dynamic changes in the system, demonstrating its efficacy in enhancing both transient and steady-state responses. Practical value. A grid-side LCL filter-based converter was meticulously designed and rigorously simulated using the MATLAB/Simulink platform. The inclusion of an advanced FLC in the system introduced a novel approach to control strategies, surpassing the traditional PI controller. Through a comprehensive comparative analysis, the simulation results showcased the remarkable efficacy of the proposed solution in an effectively mitigating high-frequency resonance within the TPSS. This outcome underscores the potential of FLC as a sophisticated control mechanism for enhancing the performance systems in railway applications, showcasing its superiority over conventional control methods. The study contributes in shedding light on innovative approaches for optimizing the control and efficiency of grid-side LCL filter-based converters in high-speed train systems.

A Novel Interphase-Bridging Single-Phase Inverter for Photovoltaic and Energy Storage Connected to Railway Traction Power Supply System

A Novel Interphase-Bridging Single-Phase Inverter for Photovoltaic and Energy Storage Connected to Railway Traction Power Supply System

Thermal Constrained Energy Optimization of Railway Cophase Systems With ESS Integration—An FRA-Pruned DQN Approach

This paper investigates the railway co-phase traction power supply system (TPSS) with a power flow controller (PFC) to address the power quality and neutral section issues. To collect the regenerative energy and achieve a more flexible power flow, the energy storage system (ESS) is integrated into the co-phase system. As the key components, the reliability of power electronics modules in PFC and battery cells in ESS is highly related to their thermal performance. It is therefore vital to consider their operational thermal dynamics, leading to the proposal of a deep Q network (DQN) based thermal constrained energy management strategy in this paper. Firstly, the system power flow model and electrothermal models for power electronics modules and battery cells are all established. Then, a DQN method is adopted to learn an optimized policy for peak power shaving while meetings thermal constraints. Finally, an FRA-based pruning method is proposed to reshape the agent to become more compact without sacrificing its performance. Case studies confirm that the proposed strategy can effectively reduce the peak traction power supply by up to 42.0%, and achieve up to 94.1% thermal reduction. The FRA-based pruning can achieve up to 89.9% agent size reduction and 87.2% computation savings.

Quantitative Harmonic Amplification Analysis in Electric Railway Traction Power Supply Systems

Background: Harmonic resonance is one of the apprehensive power quality problems in electric railway traction power supply systems. Harmonic resonances result in big harmonic voltage distortions or harmonic currents. Different harmonic resonance frequencies existing in a power system possess varying propagation areas and amplification levels. The frequency scan analysis technique and the resonance mode analysis technique are the two most commonly used methods. The frequency scan analysis technique can reveal whether resonance exists and determine the resonance frequency. Resonance mode analysis technique can further identify the location where a resonance can be most easily initiatedand observed. However, there are still few studies on the quantitative analysis of harmonic propagation and resonance amplification in traction power supply systems. Methods: The model of the all-parallel autotransformer-fed system in the high-speed railway is built accurately, then a quantitative analysis method based on harmonic electrical distance is used to study the harmonic propagation characteristics and propagation severities caused by electric trains, and analyses in detail the influence of the number of lines, the number of trains, and the location of the train on the severity of resonance amplification. Results: The results of case studies reveal the traction power supply system harmonic propagation characteristics and amplification severities and system parameter sensitivities in a quantitative way, validating the effectiveness and superiority of the quantitative analysis method. Conclusion: Compared with the resonance mode analysis method and the frequency scan analysis method, at a harmonic resonance frequency point, the quantitative analysis method can quantitatively reveal the harmonic propagation area and amplification level at each bus of the traction power supply system. Meanwhile, it is simple and practical.

YOLOv5s-D: A Railway Catenary Dropper State Identification and Small Defect Detection Model

High-speed railway catenaries are vital components in railway traction power supply systems. To ensure stable contact between the pantograph and the catenary, droppers are positioned between the messenger wire and contact line. The failure of one or more droppers will affect the power supply of the catenary and the operation of the railway. In this paper, we modify the You Only Look Once version five (YOLOv5) model in several ways and propose a method for improving the identification of dropper status and the detection of small defects. Firstly, to focus on small target features, the selective kernel attention module is added to the backbone. Secondly, the feature graphs of different scales extracted from the backbone network are fed into the bidirectional feature pyramid network for multiscale feature fusion. Thirdly, the YOLO head is replaced by a decoupled head to improve the convergence speed and detection accuracy of the model. The experimental results show that the proposed model achieves a mean average precision of 92.9% on the dropper dataset, an increase of 3.8% over the results using YOLOv5s. The detection accuracy of small dropper defects reaches 79.2%, representing an increase of 10.8% compared with YOLOv5s and demonstrating that our model is better at detecting small defects.

Research on Low-Frequency Stability under Emergency Power Supply Scheme of Photovoltaic and Battery Access Railway Traction Power Supply System

Photovoltaics and batteries can be connected to a traction power supply system through a railway power conditioner (RPC) to switch between different control strategies. This can address power quality issues or provide emergency traction for locomotives that unexpectedly lose power and even break through traditional energy barriers in the railway field, achieving a low-carbon power supply for railway energy, and a mutual backup with substations. However, methods to coordinate the control strategies of PV and the battery locomotive traction have not been clearly revealed, nor has the actual stability of the system. In this study, to address the above issues, an emergency power supply scheme is proposed for the first time that utilizes a dual-mode RPC inverter combined with a coordinated control strategy for the PV and battery, achieving the traction of locomotives. In addition, a one-dimensional impedance model was established for the PV system, battery system, locomotive (CRH3), and RPC projected onto the dq coordinate system, and the critical amplitude margin (CAM) was defined to quantitatively analyze the sensitivity and laws of different parameters concerning the low-frequency stability of the system. At the same time, impedance ratios and passive criteria were used to reveal the stability mechanism, and parameter adjustment criteria and design suggestions were put forward. Finally, the feasibility of the emergency power supply scheme of the “PV–battery locomotive network” coupling system and the correctness of the low-frequency stability study were verified using the Starsim semi-physical experiment platform.

Improved Branch Energy Balance Control for Three-Phase to Single-Phase Modular Multilevel Converter for Railway Traction Power Supply

Maintaining the branch energy balance poses a huge challenge to controller design of many modular multilevel converter (MMC) topologies. Aiming at railway traction power supply system application of a three-phase to single-phase MMC with equal input and output frequency, this article proposes a branch energy balance control with an improved common-mode voltage selection. As a result, the capacitor voltage oscillations as well as circulating currents are reduced greatly. As the MMC is a complicated periodic time-varying system, an average theory is used to simplify the analysis and controller design. The controllability analysis of the system is carried out and the results show that the proposed branch energy balance control is controllable under most load conditions. In addition, the stability of the branch energy balance system is validated through frequency response. Finally, experimental results verify the effectiveness of the control scheme by an 18-cell model based on the RT-LAB platform.

Research on Coordinated Control Strategy of Energy Storage Type Railway Power Conditioner

In order to improve the power quality of high-speed railway traction power supply system and enhance the robust stability of railway power conditioner (RPC), a coordinated control strategy based on the energy storage system (ESS) integrated RPC (ESS-RPC) is proposed in this article. It is found that the dc impedance characteristics of the back-to-back system are different when the parameters of the ESS-RPC system are perturbed under conventional control, which will affect the dc voltage of the back-to-back system and then affect the power quality of the traction system. In this article, it is analyzed that the stability difference of the bidirectional power flow of ESS-RPC under parameter perturbation is due to the negative impedance of the dc terminal and the right shift of the dominant pole. After the analysis, a coordinated control strategy of ESS-RPC is proposed to solve this problem. The small-signal analysis of the ESS-RPC system under conventional control and coordinated control is carried out, respectively, and the robust stability of the two control strategies is judged by the Nyquist stability criterion. Simulation and experimental verification are carried out in the MATLAB/Simulink environment and semisimulation platform (Modeling Tech) to analyze the impact of the proposed coordinated control strategy on the power quality of the traction power supply system and verify the effectiveness and accuracy of this coordinated control strategy.

Функционирование релейной защиты фидеров контактной сети в условиях изменения инфраструктуры

The problem of ensuring stability of functioning of contact network feeders is an important aspect of the railway traction power supply system operation. The ability of the protection to function correctly in emergency and normal operating modes of the AC traction network operation directly affects the efficiency and continuity of a transportation process. The paper is devoted to assessing the impact of changes in the infrastructure of railway sections on functioning of the protectors of the contact network feeders. Regular circulation of trains of increased tonnage and length on electrified sections of AC railways involves a number of problems in operation of traction network protection devices. The article summarizes long-term observations of functioning of the feeder protectors of the contact network of operating sections of the AC railway. The results of field measurements at traction substations of the Far Eastern Railway are presented. The analysis of angular characteristics of operation of remote protectors of the contact network feeders is carried out. The efficiency of functioning of protectors with angular characteristics of operation of remote protectors of various forms in driving modes of trains of increased tonnage and length is estimated. The measures aimed at increasing the stability of functioning of the contact network feeders in various modes of operation of the traction network are evaluated.

Networked Protection Scheme with Feeding Section as a Unit for High-speed Railway Traction Power Supply System

Networked Protection Scheme with Feeding Section as a Unit for High-speed Railway Traction Power Supply System

Series Capacitive Compensation to Increase the Railway Traction Power Supply System Transmission Capacity

The article addresses the problem of improving the numerical analysis and operation of series capacitive compensation (SCC) units in the return wire of 25 kV power supply system traction substations to increase the railway capacity. Numerical analyses of the SCC impedance for two versions are considered: according to the condition of voltage equalization in the traction substations power supply arms and according to the condition of minimizing the negative sequence voltage. It is shown that the existing regulatory documents correctly place focus on the SCC impedances determined from the condition of ensuring equal power supply arm voltages. It is also shown that for numerical analyses of SCC impedance, the connection of the 110(220) kV power supply line impedances should be taken into account. To this end, it is proposed to connect, in the equivalent analysis circuit diagrams, two adjacent substations to the external power supply system through an equivalent delta of the impedances of 110(220) kV power lines. To effectively increase the voltage in the traction network while maintaining the minimum equalizing current values, it is advisable to connect the SCCs at both adjacent substations. In so doing, the no-load voltage values should be kept at the same level to reduce the equalizing current first component, which is determined by the difference of the transformers’ no-load voltages. It is shown that the connection of the SCC does not entail a growth in the equalizing current second component, which is determined by the difference of voltage losses at adjacent substations, including the voltages across the SCCs. If the SCC is connected at only one substation of the inter-substation zone, it is advisable to introduce automated control of the transformer OLTC at the substation without an SCC with a limited number of switching operations (up to 10 per day) with increased loads in the traction network.

Application of MMC-RPC in High-Speed Railway Traction Power Supply System Based on Energy Storage

In order to effectively improve the power quality and utilize railway regenerative braking energy in high-speed railway traction power supply system, this paper adopts the Modular Multilevel Converter type Railway Power Conditioner (MMC-RPC) with distributed super-capacitor (SC) energy storage (ES) scheme. Firstly, the single-phase MMC mathematical model is established, and the power compensation characteristics of MMC-RPC are derived. Secondly, the Virtual Synchronous Generator (VSG) control strategy is adopted to provide inertial support. Compared with the double closed loop (DCL) control, it has better anti-disturbance and dynamic performance. Then, based on the VSG control, a two-stage circulating current suppression strategy is proposed, in which Quasi-Proportional Complex Integral (QPCI) control is used to suppress the bridge arm circulating current, and integrated Proportional Integral-Quasi Proportional Resonant (PI-QPR) control is an improvement of the VSG control to further suppress the circulating current inside the VSG. Furthermore, the virtual DC motor (VDCM) strategy was proposed to control the charge and discharge of the distributed SC connected to MMC-RPC to recycle railway braking energy. Finally, simulation results of the VSG small signal model and the MMC-RPC simulation model on the Matlab/Simulink platform verify the effectiveness, stability of VDCM and improved VSG controls in the MMC-RPC.

Increasing the performance of the Far Eastern Railway traction power supply system

Introduction. The purpose of the study is to develop measures determined by the strategic programmes for the development of Russian railway transport based on the analysis of power supply schemes for the traction network of the Far Eastern Railway, a branch of Russian Railways.Materials and methods. Evaluation of the performance of the traction power supply system was made based on the analysis of the actual performance of the Far Eastern Railway section, as well as the theories of electrical engineering and power supply of the 25 kV AC electrified railway system.Results. Based on the analysis of the joint operation of the external and traction power supply systems of the Far Eastern Railway, four traction substations with low technical and economic indicators were identified. Network sections that feed the substations are a bottleneck in the traction power supply system. It is proposed to increase the efficiency by switching the connection of the windings of transformers of traction substations to the systems of external and traction power supply according to the typical star – delta scheme. Such a connection will ensure an increase in the speed of trains, a reduction in train succession time and losses of electricity, an increase in the quality of electric energy in the external power supply system and electric networks of the Far Eastern Directorate for Energy Supply (a structural subdivision of Transenergo, a branch of Russian Railways).Discussion and conclusion. Normalisation of the connection of four traction substations according to the feeding scheme is ensured by changing the phasing in such a way that the power supply of the two legs of one winding of the power transformer is transferred to two windings. Alignment of the current modules in the windings of transformers of traction substations makes it possible to reduce the voltage drop in the most loaded phase and, accordingly, increase the voltage in the traction network, which ensures an increase in the speed of trains and a reduction in passing intervals. Switching the power supply of the arms from one winding of the transformer to two reduces the loss of electrical energy in power transformers and the external power supply system. Reducing the current unbalance in the windings of the power transformer improves the quality of electrical energy in the system of external and district power supply. An increase in the service life of the power transformer is ensured by a decrease in the intensity of thermal wear of the insulation of the most loaded winding.

Power Quality Management Strategy for High-Speed Railway Traction Power Supply System Based on MMC-RPC

This paper adopts the Modular Multilevel Converter Type Railway Power Conditioner (MMC-RPC) equipment to effectively manage the power quality of the high-speed railway traction power supply system including the reactive power and negative sequence component. Firstly, the single-phase model of the MMC was established to deduce the working characteristics of the MMC-RPC and its compensation principle for the traction power supply system with the v/v wiring transformer. Secondly, the adaptive VSG control strategy was adopted for the inverter of the MMC-RPC to provide dynamic inertial and damping support for the traction power supply system based on the virtual synchronous generator (VSG) control. Compared with the traditional double closed-loop (DCL) and VSG controls, it has better anti-disturbance and dynamic performance. The root locus analysis of control parameters based on a small signal model shows that VSG control can provide more stability margin. Furthermore, Differential Flatness Control (DFC) was used in the inner-loop controller to ensure the stable control of the inverter and the stability was verified by the Lyapunov stability analysis. For the rectifier of the MMC-RPC, a hierarchical three-level control strategy with system-level control, cluster-group voltage control, and inter-cluster voltage control for keeping the voltage balance was adopted. Finally, simulation results on the Matlab/Simulink platform verified the effectiveness and stability of the joint control applied in the MMC-RPC.

Damage Detection of Insulators in Catenary Based on Deep Learning and Zernike Moment Algorithms

The intelligent damage detection of catenary insulators is one of the key steps in maintaining the safe and stable operation of railway traction power supply systems. However, traditional deep learning algorithms need to train a large number of images with damage features, which are hard to obtain; and feature-matching algorithms have limitations in anti-complex background interference, affecting the accuracy of damage detection. The current work proposes a method that combines deep learning and Zernike moment algorithms. The Mask R-CNN algorithm is firstly used to identify the catenary insulators to realize the region proposal of the insulators. After image preprocessing, the Zernike moment algorithm is used to replace the existing Hu moment algorithm to extract more detailed insulator contour features, then the similarity value and its standard deviation are further calculated, so as to complete the damage detection of the catenary insulator. The experimental results show that the mean average precision of insulator identification can reach 96.4%, and the Zernike moment algorithm has an accuracy of 93.36% in judging the damage of insulators. Compared with the existing Hu moment algorithm, the accuracy is increased by 10.94%, which provides a new method for the automatic detection of damaged insulators in catenary and even other scenarios.

Control strategy of hybrid energy storage in regenerative braking energy of high-speed railway

Regenerative braking energy (RBE) will be generated when high-speed train is in braking state, but the utilization rate of RBE is generally low. To solve this problem, based on the hybrid energy storage system (HESS), a scheme for energy storing and utilizing high-speed train RBE is proposed. In this scheme, the HESS is connected to the railway traction power supply system through the railway power conditioner (RPC) as the interface circuit. The control strategy of energy storage RPC is proposed by analyzing the compensation principle, then the power of two energy storage media is allocated. The effectiveness of the scheme is verified by simulation. The findings of the research suggest that the control strategy of energy storage RPC can not only effectively utilize RBE generated by high-speed train, but also improve the power quality and extend the service life of energy storage system.

Selection of electricity storage devices for mobile DC traction substations

The aim of the study is to review the sources covering the problems of accumulating electricity on the railways and to find new solutions to reduce the use of electricity in traction power supply system. The article analyses some existing types of electric energy storage devices (capacitive, inertial, superconducting inductive, electrochemical, fuel cells and pumped storage power plants), their common installation locations, advantages, and disadvantages. The possibility of using them in railway traction power supply systems, in particular in mobile traction substations, is also assessed. In addition, the article lists the parameters on the basis of which the optimum type of storage device can be selected for the given conditions. The study concludes that the use of some types of energy storage devices in mobile traction substations is acceptable when regenerative braking can be used at the site, and this method of energy saving can be recommended in the engineering of new or reconstruction of existing traction substations. It has been found that capacitive and inertial (flywheel) electrical energy storage units are the most suitable in terms of parameters for installation of traction power supply systems.

Research on the influence of electric railway bilateral power supply on power system and countermeasures

Bilateral power supply can improve the power supply capacity and extend the power supply distance in high-speed railway traction power supply system (TPSS). However, the balanced power generated after bilateral power supply hinders its widespread application. In order to reduce or eliminate the balanced power, in this paper, an equivalent model of the bilateral power supply system is established, and it is found that the balanced power is mainly affected by the phase deviation of the feeder voltage of the two adjacent traction substations. The influence of balanced power on the node voltage and power flow distribution of the power system is analyzed with the IEEE 14-bus test system, and then a new voltage phase shifter suitable for TPSS is proposed to reduce the balanced power. The simulation and case study show that the proposed phase shifter can effectively adjust the phase difference and significantly reduce the balanced power, which lays a foundation for the implementation of bilateral power supply in electrified railway.