Algorithm for calculating the rail-ground potential in heavy load conditions

The main problems of stray current and the low availability of the regenerative braking energy widely exist in DC traction power supply system which is currently widely used in China. The AC traction power supply system for Urban Rail Transit based on negative sequence current compensator is proposed as a kind of novel power supply scheme to solve these problems in DC system. And the construction of the AC traction power supply system is designed in detail. In the meantime, the system of negative sequence compensator based on three - phase three - level rectifier parallel is designed to compensate for the negative sequence generated by the proposed system in the paper. The negative sequence current compensation algorithm of the AC traction power supply system and the control method of the negative sequence current compensator are deeply analyzed and designed, and the proposed system is feasible to connect with three-phase power grid. Meanwhile, the equalization of the AC traction power supply system was also achieved. Finally, the performance of the power electronic compensator to eliminate the negative sequence current was verified by simulations and experiments.

Aim. Improving the efficiency of AC traction power supply systems. Solving challenges in testing technical and technological solutions using simulation modeling of their operating modes. Methods and Materials. The research is based on a simulation model designed to test algorithms for regulating the operation of electric power storage devices within the traction power supply system. The tasks are solved using the following methods: system method, analytical method, and statistical modeling method. Results. The proposed simulation model enabled the testing of an algorithm regulating an electric power storage device. The simulation provided results for active power regulation using the voltage levels in the contact network. The results included calculated oscillograms and voltages, along with their effective values for both charge and discharge modes. Conclusion. The results obtained can be used to compare the effectiveness of different methods for regulating electric power storage devices in AC traction power supply systems.

Objective: To study the problems and possible solutions in the introduction of an alternating current traction power supply system with catenary supports without rail grounding. Methods: To solve the set tasks, we used the statements and methods of the theory of power supply, experimental planning, mathematical and system analysis, and the theory of electrical measurements. In the experimental studies, the Trans-AURA Emergency Process Recorder and the Tektronix TDS 2014 Digital Oscilloscope were used, and the Aura2000 and MS Excel 2010 software products were used to process the experiment results. Results: The basic requirements for the AC traction power supply system grounding are presented. The flaws of the traditional grounding system of the catenary supports on the rail network are revealed. Two possible directions are described, which allow eliminating issues during the operation of the AC traction power supply system. The first direction requires the introduction of an additional stage into the traction network protection system, which makes it possible to identify short circuits through a high rail-to-earth resistance. The second suggests the need to revise the relay protection system itself, which includes changing the approach to grounding the catenary structures, the methodology for calculating the relay protection settings, a more detailed analysis of electrical safety conditions, etc. An equation has been formulated to determine support-groupto-earth resistance taking into account the group grounding cable and the existing requirements for ensuring the sensitivity of the main protection means, which allows ensuring reliable operation of feeders’ relay protection. The results of experimental tests of electrical safety conditions and electromagnetic influence are presented. The tasks are identified being the essential prerequisite to the widespread introduction of a system with supports without rail network grounding. Practical importance: The developed methodology for selecting the protection settings will make it possible to operate the AC catenary system without the supports’ rail grounding, as well as introduce the proposed additions to the instructions for grounding traction power supply devices at “Russian Railways”

The power supply continuity is the key factor affecting the normal operation of the load. The complex power quality problems (such as two-frequency ripple superposition, voltage sag and ripple superposition) in the dc power supply system will directly affect the continuous power supply of the load. The internal conversion control technology of the dual power switch can guarantee the continuous power supply of the load. To solve the problem of compound power quality in dc dual power supply system, this paper proposes a dual power conversion control technique based on PSO-MP. In this technique, PSO algorithm is used to perform coarse search and MP algorithm to identify the composite power quality disturbance. The example analysis not only verifies the validity and accuracy of the method proposed in this paper, but also improves the reliability of the double power switch and quickly realizes the conversion between two dc power sources.

The flexible AC traction power supply system can solve the power quality problem and realize flexible power supply of the whole line, which is an important direction of railway development. First, this paper introduces a flexible AC traction substation based on three-phase to single-phase MMC structure, which provides stable voltage support for train operation. Then, the influence of the filter capacitor on the output side is analyzed, and a damping control strategy for substation is designed to suppress potential oscillations. Aiming at the problem that the voltage amplitude and frequency deviate from the rated value in the traditional droop control, a droop control strategy with voltage amplitude and frequency recovery without communication for substation is designed, and the feasibility and effectiveness of the control strategy are verified by simulation.

Modeling and stability prediction for the static-power-converters interfaced flexible AC traction power supply system with power sharing scheme

Predicting the system behavior of traction power supply systems, earthing systems and track circuits have become of vital importance to the railway community. The availability of computer based tools is a precondition in engineering studies in the field of electrical systems compactibility (ESC) and electromagnetic compatibility (EMC). Also, the sharing of information among multiple parties involved in activities on a single segment of infrastructure has become more and more important. Multiple cases have demonstrated this need for cooperation. Since 1994 simulations and measurements on the behavior of AC traction power supply systems have been made by Holland Railconsult. Also, its influence on signaling and telecommunication systems as well as on existing railway infrastructure and third parties are studied. In the course of this process the necessity to have a dedicated simulation tool available became clear. After several years of development, a useful simulation tool is now available. The newly desgined web-implementation makes it possible to access the SimspoG tool through the Internet by a common Internet Browser. The SimspoG User application interface implementation allows for inputting or modifying different simulation model parameters and starting of simulation processing.

The article considers the problem of reactive power compensation in AC traction power supply systems, which is of particular importance in the context of the energy crisis caused by military actions, which is relevant for Ukraine. Reactive power is an important component of electric networks, which significantly affects the stability and quality of power supply. The article highlights the impact of reactive power on the efficiency of traction substations serving railway transport. Special attention is paid to the technical aspects of the problem and the analysis of the effectiveness of existing compensation methods, which is critically important for reducing electricity losses and increasing the overall efficiency of power supply systems. In conditions of outdated equipment and limited resources, the problem becomes more complicated, which requires the implementation of modern technological solutions. The paper analyzes main methods and devices for compensation of reactive power, in particular, such as capacitor units and synchronous compensators, as well as the use of modern technologies of flexible alternating current transmission systems (FACTS). Particular attention is paid to experimental studies conducted at a real traction substation, where reactive power was measured and the effectiveness of compensating devices was shown. Research results show that reactive power compensation allows to significantly reduce energy losses, improve the quality of electricity and increase the stability of the network. The article also discusses the prospects of implementing FACTS systems for dynamically regulating reactive power and improving the operation of electrical networks. The use of these systems can significantly increase the reliability and efficiency of the power system, especially in the context of the integration of renewable energy sources such as solar and wind power plants. This will ensure reliable power supply in critical conditions and increase the efficiency of Ukraine’s energy infrastructure.

The article is devoted to the experiment, what was performed on the local distribution networks with poor power quality. As a rule, these networks are subsystem of AC traction power supply system, and their design causes voltage unbalance and other power quality problems in consumers. Often, the network is powered by transformers with different vector groups, therefore their parallel operation is impossible. The purpose of the experiment is to assess the effect on energy quality of a regime with sources on both sides. The quality of electrical energy was estimated, considerable attention is devoted to unbalance voltage. Using the statistics methods measurement data are studied. During the experiment, the energy quality improved when the parallel mode was used. The concept of smart grid has been proposed to reduce energy losses for dynamic power management.

The study aimed to quantitatively assess the effectiveness of neural network-based control of dynamic reactive power compensation in the traction network of Ukrzaliznytsia. The methodology involved high-frequency monitoring of 118 substations (≈16 trillion measurements), aggregation of 52 million Supervisory Control and Data Acquisition records, Theil-Sen trend estimation, Seasonal-Trend decomposition using Loess, the Brown Forsythe test, and a deep neural network with 64-32-16 layers optimised through a Tree-structured Parzen Estimator, validated in 120 Monte Carlo scenarios in Simscape. The results demonstrated that the average daily Q increased from 309.8 to 367.2 Mvar (18.5%) with a trend of 0.95 Mvar/month (95% CI 0.82-1.08; p < 0.001). Winter peaks reached 520 Mvar, while variance after February 2022 increased 1.5-fold (F = 34.9; p < 0.001). The neural network achieved Mean Squared Error = 184 Mvar² and R² = 0.982; in testing, R² = 0.975, Mean Absolute Error = 11.2 Mvar, and the median error of winter peaks did not exceed 3%. In simulations, the algorithm maintained cos φ between 0.985 and 0.991 for loads ranging from 0.3 to 1.2 p.u., reduced daily losses by 6.1-9.4% (≈1.2 MWh/day), and decreased the number of Static Var Compensator switchings by 38%. Under failure of 20% of Insulated-Gate Bipolar Transistor modules, the duration of cos φ < 0.98 was 0.7%, compared with 19% for the Proportional Integral-Derivative controller. Quantitative comparison of compensation strategies confirmed that the simulated STATCOM-DL system achieved the lowest average cos φ deviations (0.015 vs. 0.030-0.048 for competitors) and minimal annual losses (≈ 430 MWh), outperforming all alternative approaches. The findings confirmed that the combination of deep learning and statistical validation enhances network stability and improves energy efficiency. The practical significance lies in the fact that the resulting algorithms may be employed by railway dispatch centres and energy integrators for real-time optimisation

Aiming at the problem that the existing relay protection of traction power supply system mis-operates when an out-of-phase fault occurs, based on the sum of two phase impedance, a novel distance protection method is proposed. In addition, the characteristic and settings of the proposed protection are derived in detail. Simulation results verify the effectiveness and superiority of the proposed protection method.

In this paper, a method of identifying the short-circuit fault current in DC traction power supply system based on local mean decomposition (LMD) and time-frequency entropy is proposed. Firstly, the feeder current signal of DC traction power supply system is analyzed by means of LMD, by which the LMD time-frequency distribution can be obtained. Secondly, the LMD time-frequency plane is divided into time-frequency blocks with equal area. Finally, the time-frequency entropy of the time-frequency plane is obtained, which can serve as the feature vector to distinguish the oscillation current and the short-circuit fault current in DC traction power supply system. According to the simulation analysis, it can be found out that the simulation results conform to the theoretical analysis. Moreover, the calculation results of the measured data show that the proposed method is capable of distinguishing the oscillation current and the short-circuit fault current in DC traction power supply system.

In view of the existing problems in DC traction power supply system and electric vehicle (EV) batteries charging system, a DC micro-grid is proposed: EV batteries are connected to DC traction power supply system via off-board bidirectional chargers, forming a ring DC micro-grid in a sub-region, in which EV batteries can be charged by DC traction power supply system and voltage of overhead contact system can be stabilized by the EV batteries charging and discharging system. A method that place ultra-capacitors in parallel with EV batteries is designed to improve system performance. Voltage droop control is adopted by parallel bidirectional chargers, which can achieve doublequadrant operation and avoid the circulating current as well. In the end, simulation results are presented to demonstrate the feasibility of this system.

The main trends of technical development and improvement of dc traction power supply systems are considered. Methods and programs are developed that make it possible to study the electromagnetic processes in rectifier–inverter units of traction substations and the self-excited source voltage inverter of induction traction drive and determine and predict the levels of harmonic components of the current in both dc–ac converters themselves and that in the traction network. This makes it possible to determine the electromagnetic effect of various power semiconductor converters on communication devices and railway automation and ground the choice of circuits and protection parameters ensuring electromagnetic compatibility. Analysis and synthesis of electromagnetic processes and the main characteristics of multipulse converters reveals that 24-pulse rectification circuits with serial connection of three-phase bridges are the most effective for a dc traction power supply system with a 24-kV voltage traction network. The introduction of 24-pulse rectifiers makes it possible to decrease power loss in the traction network and reduce the consumption of reactive energy from the primary power supply system. These rectifiers provide not only an increase the traction substation efficiency, but also refinement of electric energy in the primary power supply system and traction network. The latter makes it possible to use simpler and more economical smoothing filters that ensure electromagnetic compatibility of the new dc traction power supply system with communication devices, railway automation, and other infrastructure.

The article describes a problem that occurs in electrified railway transportation, involving the interaction between the earth-return circuits of different power systems. One of the analysed circuits is the earth-return circuit of a high-voltage power grid, the other is the return path of a 3 kV DC traction power supply system. The paper presents the results of the field tests carried out so far and discusses a mathematical model developed in the Matlab-Simulink environment with the aim of determining the interaction between both of the said systems. Keywords: earthing, traction substation, traction return system