TY - JOUR
AU1 - Zhang, Yu
AU2 - Zhang, Zhaoyang
AU3 - Xu, Li'en
AU4 - Ying, Ting
AU5 - Li, Jianghong
AU6 - Chen, Huaguo
AU7 - Hu, Yunqing
AU8 - Qing, Guangming
AB - Abstract In order to study the interaction among the traction power supply, the train group and the operation dispatching of urban rail transit, a coupling simulation system of power supply system, trains and dispatching management is constructed. In order to solve the problems of different timescales and difficult cooperation operation for related subsystems, a multi-bus distributed real-time network architecture based on hierarchical management of communication data is established, and simulation management software is developed to facilitate the free expansion of the simulation system. Meanwhile, the track line, train operation and other large timescale subsystems are realized by the pure digital simulation. And the time-sensitive subsystems, such as train traction system, braking system, auxiliary power supply system and network system etc., are built by the semi-physical simulation. In this article, the system structure and the main implementation principle of each simulation subsystem are given in detail, and the system is tested and verified at the end. The results show that the simulation system can meet the expected requirements. 1. Introduction With the continuous expansion of urban rail transit, its status and role in economic and social development are more prominent, and its economy, convenience and safety are also more important. Comprehensive efficiency evaluation and improvement of the rail transit system including passenger satisfaction, transportation efficiency and energy saving rate have become important research directions [1,2]. The electrified rail transit system is mainly composed of train group, traction power supply, signal system, operation dispatching system and rail line. The subsystems are coupled and restricted with each other. At the same time, they are also affected by the line operating environment, passenger flow changes and other factors. It is a random and changeable complex system. For such a complex system, the characteristic studying and comprehensive performance evaluation through a large-scale field test would bring the problems of high risk, high cost, long cycle and poor repeatability [3,4]. Therefore, it is urgent to build a coupling simulation system of the power supply system, trains and dispatching management to study the coupling evolution law of lines, trains, power supply, signal, operation scheduling and other systems, so as to provide support for the optimal design, operation optimization, function test and verification of the system and key components [5,6]. The transportation function of the urban rail transit system is mainly completed by three core systems: the power supply system, the train system and the signal and operation dispatching system, which includes a large number of subsystems and components, and forms a complex strong coupling system with the energy and information interaction, as shown in Fig. 1. Fig. 1. Open in new tabDownload slide Principle diagram of urban rail transit Fig. 1. Open in new tabDownload slide Principle diagram of urban rail transit From the perspective of system analysis, the subsystems and components of the urban rail transit system can be divided into multiple system levels, and different timescales need to be considered for the analysis of subsystems or components at different levels. For example, the performance evaluation of the operation dispatching system usually takes days, while for the power electronic circuit in the train traction system the time reaches the microsecond level. In the field of urban rail transit, extensive research has been carried out on the modelling of different levels of train traction system, braking system, train operation system, power supply system and signal dispatching system, as well as system energy consumption evaluation and operation strategy optimization based on the model, and many enlightening results have been obtained. But on the whole, these research and application results are limited to either a single specialty or a single system level, and there is a lack of simulation research to completely describe the coupling relationship of different levels of the whole large-scale system. Meanwhile, modelling and simulation are often offline, which cannot accurately reflect the real-time coupling relationship between various components. So it is difficult to evaluate and optimize the real-time operation strategy with this modelling and simulation method [7–9]. In this article, a coupling real-time simulation system of an urban rail transit large-scale system is constructed, which can be used to study not only the coupling relationship of the metro vehicle network from the macro level, but also the operation characteristics of key components in a large-scale system from the micro level, such as train traction, braking and auxiliary power supply. For large timescale subsystems such as the signal system, power supply system, track line and train operation scheduling, a pure digital simulation model with bigger simulation steps (milliseconds to seconds) is constructed; for time-sensitive subsystems such as the train traction and braking system, the auxiliary power supply system and the train control network, the hardware-in-the-loop simulation mode of physical controller and virtual controlled object is adopted (the simulation step are generally several microseconds to tens of microseconds). This system can realize a combination simulation of different subsystems and components flexibly, which can meet the requirements of various application scenarios, and comprehensively consider the simulation efficiency and scope. With the combined simulation of trains, power supply system and line operating environment, the operation law of the large-scale system could be further revealed, and some design problems such as redundancy and bad-matching of components etc. could be found, which could provide not only optimization tools for designing large-scale system and operation strategy, but also verification tools for the parameter and control algorithm design of key components of the train. In this article, the main contents are arranged as follows. Section 2 briefly introduces the simulation objects, the system structure and the function; section 3 describes the system architecture and interface, provides the decomposition of the system model and then expounds the realization of the line operating environment, power supply and train model respectively; section 4 provides the test and verification results of the simulation system; and section 5 summarizes the article and discusses possible further work based on the simulation system. 2. Overall introduction to the system The simulation system consists of the simulation management system, the simulation display system and the simulation object system, as shown in Fig. 2. Fig. 2. Open in new tabDownload slide Components of the simulation system Fig. 2. Open in new tabDownload slide Components of the simulation system The simulation management system is mainly used to realize the unified integration, management and operation control of simulation software and hardware equipment, including the project management, data management, resource management, simulation process control management, simulation data post-processing and simulation report generation. The display system is mainly used for the demonstration of the simulation process and the graphical or data output display of simulation results. The simulation object includes three simulation subsystems: the traction power supply system, the train system and the signal dispatching system. The power supply simulation subsystem includes the models of the main substation, the medium voltage power supply network and the DC catenary. It simulates the dynamic power flow distribution of AC and DC power supply network and the online dynamic conditions of the various power supply equipments in different lines with different departure densities, to provide the basis for the configuration of capacity, location and the number of power supply equipment. The train simulation subsystem is composed of the traction system, the braking system, the auxiliary power system, the network control system, the train kinematics model and the line model, etc. A hardware-in-the-loop simulation is adopted for the traction system, the braking system, the auxiliary power system and the network control system. The traction controller unit (TCU), braking controller unit (BCU), auxiliary controller unit (ACU) and train network controller are real, and their control objects are virtual. The train simulation subsystem can simulate the dynamic characteristics of the traction system, braking system, network and other key on-board components when the train is running on a specific line, and provide support for the control strategy development, key component parameter design, component reliability research, etc. The signal dispatching simulation subsystem simulates ATS (automatic train supervision), CI (computer interlocking), ZC (zone controller) and VOBC (vehicle on-board controller). It can simulate trains dispatching, operation tracking and safety protection, and provide a platform for train diagram optimization, energy-saving dispatching and train optimal operation. During the simulation operation, the traction power supply, train and signal dispatching subsystems cooperate and interact as follows. The signal dispatching simulation subsystem plans the operation schedule and organizes the trains to run on the line. At the same time, it adjusts the dispatching strategy or train control strategy in real time according to the simulation conditions of the line and train, so as to meet the operation requirements of punctuality and energy saving. The train simulation subsystem simulates the operation conditions of the vehicle level and component level in real time according to the train control instructions, power supply and line conditions, and analyses the train operation. The power supply simulation subsystem calculates the voltage, current and power flow distribution of the power grid according to the train energy information, simulates the functions of various power supply equipment and calculates the energy consumption when operating the system. To sum up, in view of the simulation system including many subsystems, different forms and different timescales, how to flexibly organize and manage these subsystems and develop subsystem models to meet various application requirements are the key issues in constructing the simulation system. 3. Realization principle of the simulation system 3.1. Design principle of the simulation system architecture In order to flexibly organize and manage simulation subsystems with different forms and timescales, a distributed system architecture based on multi-bus communication is constructed, an ‘element’ simulation system construction mechanism is proposed and a simulation management system with master-slave structure is developed. 3.1.1 Multi-bus communication The distributed system architecture based on multi-bus communication is shown in Fig. 3. Four kinds of communication buses are used to connect the subsystems—a simulation management bus, a simulation real-time data bus, a control communication bus and a display data bus. The simulation management bus is mainly used for the power management, simulation control command issuing, subsystem status monitoring, model and configuration data issuing, simulation result data uploading and human–computer interaction data transmission. The simulation real-time data bus is used for real-time data synchronization of each subsystem, and according to the simulation steps of each subsystem, the microsecond-level, millisecond-level or second-level communication cycle is adopted. The control communication bus is mainly used to simulate the operation data interaction mode between real vehicle controllers, such as the MVB (multiple vehicle bus). The display data bus is mainly used to transmit the operation information of each simulation subsystem to the display system in real time. Fig. 3. Open in new tabDownload slide Distributed architecture of the simulation system Fig. 3. Open in new tabDownload slide Distributed architecture of the simulation system The multi-bus communication mode realizes the hierarchical and synchronous management of interactive data, and meets the accuracy and timeliness of communication between various layer subsystems. For a microsecond communication cycle, data synchronization and interaction are carried out based on a special high-speed real-time communication bus to meet the needs of electromagnetic transient process simulation. The Gigalink real-time communication technology of the German dSPACE simulator is adopted here. The high-speed real-time communication network is constructed through the Gigalink bus to realize the distribution and reception of electrical quantities between converter circuit models. And for the communication cycle at the millisecond level and above, the publish subscribe mechanism based on Ethernet and DDS (data distribution service) protocol is adopted to realize synchronous communication. Through the ‘one to many’ master-slave distributed management mode, the priority is set according to the data interaction step of each subsystem. 3.1.2 Simulation elements There are differences in the form of each simulation subsystem, including a pure virtual digital model and a semi-physical simulation system composed of a virtual object model and physical controller. In order to facilitate unified management and flexible combination, the different subsystems are encapsulated into standard subsystems, which are called ‘simulation elements’. The ‘simulation element’ defined here is the basic unit of the simulation system, and it generally has four kinds of standard files: a model file, a parameter file, an interface file and a signal record file. The interface file is the file describing the interface relationship between the simulation subsystems, which is necessary for the simulation element. As shown in Fig. 4, any simulation subsystem can be packaged into a simulation element and put into storage. With the simulation management system control, the simulation element can be assembled into a specific simulation project to meet different simulation requirements. The communications between simulation subsystems are established with the standardized interface file, the parameters are uniformly configured and the simulation data is recorded by the simulation management system automatically. Fig. 4. Open in new tabDownload slide Construction of the simulation system based on simulation elements Fig. 4. Open in new tabDownload slide Construction of the simulation system based on simulation elements Based on the concept of ‘simulation elements’, the simulation management system can easily add or delete the subsystems in the simulation object, which makes the simulation platform have strong versatility and scalability. 3.1.3 Simulation management Multi-bus communication data classification and simulation elements management are realized by the simulation management system. The simulation management system consists of a master-slave software structure composed of a master console and subsystem terminals to facilitate unified management of distributed simulation subsystems. The management process is shown in Fig. 5. The terminal management software is configured to each simulation subsystem to manage the simulation resources of the subsystem. It is responsible for packaging the model, parameters, interfaces and signal records of the subsystem into simulation elements and uploading them to the main control console. The main console software collects the simulation elements uploaded by each simulation subsystem to form a simulation resource library, and creates a simulation project based on the simulation resource library to realize the functions of simulation mode configuration, simulation elements distribution, simulation parameter setting, simulation operation management, simulation data recording and processing, simulation report generation, etc. The terminal management software of each subsystem compiles and downloads the simulation primitives issued by the main console, and realizes the functions of subsystem simulation parameters' online modification, fault injection, signal observation, simulation subsystem monitoring, etc. Fig. 5. Open in new tabDownload slide Software structure of the simulation management system Fig. 5. Open in new tabDownload slide Software structure of the simulation management system The distributed real-time simulation system constructed in the above way has high generality and strong expansibility. It can realize the unified management and control of subsystem software and hardware equipment through the main console, and provide functional coupling and an information interaction platform for each subsystem, so as to effectively realize the collaborative simulation between subsystems. 3.2 Introduction to the simulation models In the simulation system, object models are divided into three parts: the signal and dispatching model, which simulates trains dispatch, train running control and line conditions; the train model, which provides simplified train models and a semi-physical train model to simulate train power, speed and running distance; and the power supply model, which provides the power environment for trains. Fig. 6 shows the coupling relations between these models. The signal and dispatching model sends the train operation command (including train conditions such as traction, brake and coast etc. and the traction/bake grade) to the train model and the physical controllers to control the simplified trains and the semi-physical train running, and the train model feeds back train speed and location for calculating the trains' given force and rail-blocking status. At the same time, the power supply model obtains the train location and power from the train model to calculate the power network nodes voltage, power flow and energy consumption. Fig. 6. Open in new tabDownload slide Model's interface of the simulation system Fig. 6. Open in new tabDownload slide Model's interface of the simulation system In addition, the semi-physical train model receives control commands from the physical controllers, and simulates detailed a working process of the traction system, brake system and auxiliary power system etc. 3.3 Simulation of signal and dispatching The signal and dispatching model organizes the train operation according to the planned timetable, and ensures operation safety at the same time. The structure of the signal and dispatching model is shown in Fig. 7. Fig. 7. Open in new tabDownload slide Structure of line signal and dispatching model Fig. 7. Open in new tabDownload slide Structure of line signal and dispatching model There are three modules in the signal and dispatching model, as follows: The train management module generates and cancels the trains according to the schedule table (including departure and arrival times, stop points, running paths); requests routines (a routine is usually a section of rail which is divided by signal lights) for the running trains; and provides trains’ running command (including trains’ departure instruction, routine distribution, next stop points etc.) to the train control module. This module ensures that trains consistently run according to schedule; when this deviates from schedule, the dwell time and running speed grade of trains will be adjusted automatically [10], as shown in Fig. 8. However, the operation adjustment would be limited by the minimum dwell time, maximum speed, as well as the minimum train track distance which guarantees safety. Fig. 8. Open in new tabDownload slide Simulation of trains running graph Fig. 8. Open in new tabDownload slide Simulation of trains running graph The line management module provides logic and function characteristics simulation for the rails, turnouts, signal lights, axle counters and responders etc., as shown in Fig. 9. By considering signal delay, confliction of different trains and other rail occupation of rails, this module distributes forward routines for running trains. The line management module also simulates conditions such as signal transferring and commands executing delay, rail abnormal occupations etc., which provides different operation scenarios. Fig. 9. Open in new tabDownload slide Equipment layout in a line Fig. 9. Open in new tabDownload slide Equipment layout in a line The train control module calculates train movement authorities (MAs, which indicates the current movement end point for a train) according to routine distribution results; then calculates train protection and operation speed given curves based on MAs, speed limitations and stop points; and finally generates train operation commands based on the feedback train speed. This module ensures the train tracking distances to avoid crash accidents. 3.4 Simulation of the power supply system The power supply of urban rail transit usually includes two parts—the AC and DC systems. The former obtains energy from the public grid through main stations and distributes energy to the substation for traction and station loads with a medium voltage power network, and the latter transforms the AC power to DC 1500 V or 750 V and sends it to the trains with catenary, as shown in Fig. 10. Fig. 10. Open in new tabDownload slide Principle diagram of the power supply system Fig. 10. Open in new tabDownload slide Principle diagram of the power supply system The steady state model is built for analysis of the voltage and current distributions of the power supply system considering the trains’ moving, in which the power supply devices are treated as voltage sources series with impedance and trains are treated as power loads generally. The power supply model is divided into AC and DC network modules, as described below. 3.4.1 The AC network module Normally, a distributed power supply is adopted for an urban rail transit AC network [11], that is, there are multiple main stations and every main station supplies power for N substations, as shown in Fig. 11. In the figure, Us is a known quantity as public net voltage; S1∼SN represent substation power, which is also assumed to be known according to station loads and the DC network module; and Zi (i = 1,2,3,4,…) represents impedance of the transmission line. With node voltage equations and iterative computation, the station voltages and branch currents could be obtained, as well as the power flow and energy consumption. Fig. 11. Open in new tabDownload slide AC network modelling for urban rail transit Fig. 11. Open in new tabDownload slide AC network modelling for urban rail transit 3.4.2 The DC network module The DC network module mainly considers the traction substations, trains, catenaries and current returning circuits (including track and ground), as shown in Fig. 12, in which traction substations are described as switched between a voltage source, a voltage source and a turn-off resistor, and the trains are described as switched between a power load, a voltage source and a turn-off resistor [12]. With the equivalent circuit, the node voltage equations can be built and the voltage, power flow and energy consumption can be calculated. It should be noted that because of the moving of trains, the equivalent circuit will vary continuously, so the node voltage equations should be updated at every simulation step. Fig. 12. Open in new tabDownload slide DC network modelling for urban rail transit Fig. 12. Open in new tabDownload slide DC network modelling for urban rail transit Modelling of the traction substations and trains is introduced below. 3.4.2.1 Modelling of traction substations Traction substations complete the conversion of AC to DC power, and there are mainly two types of converter: the traditional diode-based non-controlled converter and the full-controlled converters based on IGBTs, IGCTs or GTOs etc., which includes the energy feedback and storage equipment. The former can only realize power flowing from the AC side to the DC side, but the latter can support power bi-direction flowing and fulfill the requirement of train brake regenerated power feedback to the AC side or storing into the batteries. Taking a 12-pulse diode-based rectifier as an example, when it is working, its DC output voltage can be expressed approximately by [13]: $$\begin{equation*} {U_d} = {f_1}(k){U_{d0}} - {f_2}(k){x_c}{I_d} \end{equation*}$$(1) where |${U_{d0}} = 2.42{U_{2t}}$|⁠, |${U_{2t}}$| is the secondary output phase voltage of the rectifier transformer; |$k = \frac{{{x_s} + 2{x_k} - {x_b}}}{{{x_s} + {x_b}}}$|⁠, |${x_c} = {x_s} + {x_b}$|⁠, xs is the AC power network internal impedance, and xk, xb are the crossing impedance and the half-crossing impedance of the rectifier transformer, respectively; f1(k), f2(k) are piecewise functions related to the different range of output current Id. So, a diode-based rectifier could be equivalent to a series branch of a voltage source Usub = f1(k)Ud0 and resistor Ron = f1(k)xc. When substation voltage exceeds Ud0, the rectifier is turned off, which is equivalent to a turn-off resistor Roff. The simulation waveform of voltage and current of traction substation is provided in Fig. 13. Fig. 13. Open in new tabDownload slide Simulation of a diode-based traction substation Fig. 13. Open in new tabDownload slide Simulation of a diode-based traction substation For a bi-direction converter, because its main function is to stabilize the catenary voltage, it also could be regarded as a voltage source with an internal resistor normally; but when the power turns too high to supply for it, it could only output a maximal power, so it would be treated as a power source. The simulation waveform of voltage and current of traction substation is provided in Fig. 14. Fig. 14. Open in new tabDownload slide Simulation of bi-direction traction substation Fig. 14. Open in new tabDownload slide Simulation of bi-direction traction substation An energy storage converter is usually cooperated used with a diode-based rectifier or a bi-direction converter, and it could be treated as a varied voltage source or power source, and its work status is determined by device capacity and SOC (state of change). 3.4.2.2 Modelling of trains In the power supply system, a train is usually regarded as a power load, but when over voltage occurs the braking resistance of the train is switched in to stabilize the net voltage, and the train will be considered as a voltage source. 3.5 Simulation of trains To simulate multiple train operation conditions and the internal component interactions of a train at the same time, two types of train model are developed—a simplified train model and a semi-physical train system, as shown in Fig. 15. Fig. 15. Open in new tabDownload slide Diagram of a train simulation system Fig. 15. Open in new tabDownload slide Diagram of a train simulation system 3.5.1 The simplified train model The simplified train model simulates a train's motive and power characteristics. To obtain a fast calculation, only three parts are included in the model, i.e. the traction/brake characteristics module, train kinematics module and traction and auxiliary consumption module. The traction/brake characteristics module provides the actual traction or brake force according to train characteristic curves which are limited by traction motor, converter and air-brake parameters, as shown in Fig. 16. Fig. 16. Open in new tabDownload slide Train characteristics curves of traction and brake Fig. 16. Open in new tabDownload slide Train characteristics curves of traction and brake The train kinematics module can be expressed by the following deferential equations [14]: $$\begin{equation*} {F_t} - {F_b} - {F_r} = {m_t}\frac{{dv}}{{dt}} \nonumber\\ v = \frac{{ds}}{{dt}} \end{equation*}$$(2) where Ft and Fb are the traction force and brake force, respectively; Fr is the resistance, v and s are the train speed and moving distance respectively; and mt is the mass of the train. For the resistance calculation, it should be noted that the gradient resistance Fg should consider the gravity components of every car respectively to obtain an accurate value, as shown in Fig. 17. $$\begin{equation*} {F_g} = \sum\limits_{i = 1}^n {{F_{gi}}} \end{equation*}$$(3) Fig. 17. Open in new tabDownload slide Analysis of gradient resistance Fig. 17. Open in new tabDownload slide Analysis of gradient resistance The traction and auxiliary consumption module calculates the train's energy consumption according to traction efficiency and auxiliary power loads, and provides net-side power for the trains, which was transferred to the power supply simulation. 3.5.2 The semi-physical train system The hardware-in-loop (HIL) simulation is adopted for the semi-physical train system to simulate the real-time coupling relationships between the train control network, the traction system and the auxiliary power system [15]. Shown as Fig. 15, the detailed electrical and mechanical models for the controlled objects are built and downloaded to a real-time simulator (in this article, the German dSPACE simulator is adopted), and connected to the physical controller (including auxiliary controller, brake controller and traction controller). Fig. 18 shows the HIL simulation of the traction system. In the figure, the simulation values of motor current and DC voltage of each motor car are provided. Because the traction electrical circuit model was described with differential equation and solved in steps of a microsecond, the voltage and current transient process can be obtained. Fig. 18. Open in new tabDownload slide Hardware-in-the-loop simulation of a traction system Fig. 18. Open in new tabDownload slide Hardware-in-the-loop simulation of a traction system The losses of the key components such as converters, motors and brake shoes are calculated and sent to a thermal model for temperature calculation in a high-performance computer. Besides this, the semi-physical train shares the kinematics module with the simplified train model. 4. Test and validation of the simulation system 4.1 Function test of the simulation system According to the above simulation system architecture and modelling method, the simulation system including the subway power supply, train and signal and dispatching of the urban rail transit is built, as shown in Fig. 19. The simulation system consists of 10 parts, which forms a coupled real-time simulation system with multiple levels and multiple timescales. The components of the system include: the main console; the power supply simulation; the signal and dispatching simulation; the train kinematics simulation; the virtual train network object (with physical train network controller); the train traction simulation (with physical contorller); the train brake simulation (with physical contorller); the train auxiliary simulation (with physical contorller); the thermal simulation of train traction components. Fig. 19. Open in new tabDownload slide Coupled real-time simulation system for urban rail transit Fig. 19. Open in new tabDownload slide Coupled real-time simulation system for urban rail transit In order to test the function of the simulation system, taking Changsha Metro Line 2 as the research object, the signal system and line model are established, as shown in Fig. 20. Fig. 20. Open in new tabDownload slide Line model of Changsha Metro Line 2 Fig. 20. Open in new tabDownload slide Line model of Changsha Metro Line 2 By importing the planned operation schedule of the metro system, the line information (including the slope, curve information, etc.), the power supply information (including the distribution and power capacity of the substation, the impedance coefficient of the contact line, etc.), the train parameters (including the length, weight, resistance coefficient, traction and braking characteristics of the train, etc.) and the train component parameters (such as the traction circuit parameters, etc.), the train operation on the line is simulated. Fig. 21 shows the train operation speed curve; the curves of the line ramp, the line speed limit and the emergency braking curve are also given. Fig. 21. Open in new tabDownload slide Speed curves of trains Fig. 21. Open in new tabDownload slide Speed curves of trains Fig. 22 shows the train operation timetable. In the figure, the dotted line is the planned train timetable and the solid line is the train timetable generated by simulated trains. In the figure, some trains are delayed at first, and the measures are taken to resume the planned operation under the premise of the train tracking safety. Fig. 22. Open in new tabDownload slide Train operation timetable Fig. 22. Open in new tabDownload slide Train operation timetable Fig. 23 shows the power supply simulation in the condition of multiple trains running. Fig. 23 (a) provides the DC bus voltage of each power supply substation; Fig. 23 (b) shows the output power of each power supply substation; Fig. 23 (c) shows the catenary voltage of each train on the line. Fig. 23. Open in new tabDownload slide Simulation of the power supply system: (a) DC voltage of substations; (b) Power distribution of substations; (c) Catenary voltage of each train. Fig. 23. Open in new tabDownload slide Simulation of the power supply system: (a) DC voltage of substations; (b) Power distribution of substations; (c) Catenary voltage of each train. Fig. 24 shows the catenary voltage, running speed, traction force and motor rotational speed, current and torque in the same time axis for the semi-physical train, which reflects the real-time coupling relationship between the simulation models of power supply, train operation and traction converter at different levels and timescales. Fig. 24. Open in new tabDownload slide Coupling real-time simulation of a semi-physical train Fig. 24. Open in new tabDownload slide Coupling real-time simulation of a semi-physical train Fig. 25 simulates the influence of a traction substation disconnection on the train running speed and traction. When the train passes by the disconnected substation, the voltage of the power supply network will be reduced, making the train unable to run to the predetermined speed. Finally, the train running will be delayed. Fig. 25. Open in new tabDownload slide Disconnection simulation of a substation Fig. 25. Open in new tabDownload slide Disconnection simulation of a substation From the above results, it can be seen that the simulation platform proposed in this article can simulate the coupling operation relationship of signal, power supply, train and components at different levels. 4.2 Verification of the simulation system In order to verify the rationality of the simulation results, the field operation data of Changsha Metro Lines 2 and 4 are collected, and the comparison is carried out for the train running speed, train traction/braking force, train running time, train traction energy, motor torque and current, etc. Fig. 26 shows the comparison of train running speed in the whole process of Changsha Metro Line 4, and Fig. 27 shows the comparison of train traction/braking force in this course. The simulation process of the train operation is consistent with the reality. Fig. 26. Open in new tabDownload slide Train speed comparison of simulation and field test Fig. 26. Open in new tabDownload slide Train speed comparison of simulation and field test Fig. 27. Open in new tabDownload slide Train traction and brake force comparison of simulation and field test Fig. 27. Open in new tabDownload slide Train traction and brake force comparison of simulation and field test Figs. 28 and 29 show the running time and traction energy consumption of the train in each station interval. Through the comparison of the running time and traction energy in the whole line, the deviation between the simulation and the measured value of the total running time is 1.93%, and the deviation of the total traction energy is 4.38%, so there is a high degree of coincidence between them. Fig. 28. Open in new tabDownload slide Train running time comparison of simulation and field test Fig. 28. Open in new tabDownload slide Train running time comparison of simulation and field test Fig. 29. Open in new tabDownload slide Train traction energy comparison of simulation and field test Fig. 29. Open in new tabDownload slide Train traction energy comparison of simulation and field test Furthermore, the operation data of the traction system are compared. Taking the traction system data of Changsha Metro Line 2 as reference, Fig. 30 shows the motor current comparison of a train in a certain station interval. The simulation waveform is in good agreement with the actually measured waveform, too. Fig. 30. Open in new tabDownload slide Motor current comparison of a train Fig. 30. Open in new tabDownload slide Motor current comparison of a train By comparing the simulation data and the measured data of a train in the simulation system, the credibility of the simulation system is proved from the train operation level to the traction motor level, which provides a guarantee for the simulation system as a tool to study the coupling operation law of power supply, train, signal dispatching and its components. Of course, due to the randomness of many parameters of the actual system, or the inability to obtain accurate parameters, such as of the passengers on the train, line resistance and many uncertain interference factors in the actual operation, there will inevitably be errors between the simulation results and the measured values. 5. Conclusions In this article, a coupling real-time simulation system of power supply, train and dispatching for urban rail transit is constructed. This article introduces the working principle of the simulation system, puts forward the multi system, multi-level, multi timescale real-time simulation architecture and simulation management implementation method; at the same time, for the signal system, power supply system, trains and its components, it introduces the simulation modelling, simulation interface and implementation method in detail. Finally, the coupling simulation functions of dispatching, power supply, train and components are verified for the simulation system. Based on the field data, the simulation data of the train and traction system are verified, which proves the credibility of the simulation. In the future, we will further study the verification method of the simulation system on the basis of a large number of field operation data, continuously improve the simulation system, promote the application of the simulation system in the design, operation and maintenance of the train, power supply and signal system, improve the safety, reliability and energy saving performance of urban rail transit and help promote its digitization and intellectualization. Conflict of interest statement None declared. References 1. Francesco C , Lingyun M. A review of online dynamic models and algorithms for railway traffic management . IEEE Trans Intell Transp Syst . 2016 ; 16 : 1274 – 84 . Google Scholar OpenURL Placeholder Text WorldCat 2. Wang P . Train Trajectory Optimization Methods for Energy-Efficient Railway Operations . Thesis. Delft University of Technology , 2017 . Google Scholar Google Preview OpenURL Placeholder Text WorldCat COPAC 3. Douglas H , Roberts C, Hillmansen S et al. 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This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse, distribution, and reproduction in any medium, provided the original work is properly cited.
TI - Coupling real-time simulation of power supply, trains and dispatching for urban rail transit
JF - Transportation Safety and Open Environment
DO - 10.1093/tse/tdab010
DA - 2021-07-21
UR - https://www.deepdyve.com/lp/oxford-university-press/coupling-real-time-simulation-of-power-supply-trains-and-dispatching-wT0cx6z45P
SP - 1
EP - 1
VL - Advance Article
IS - 
DP - DeepDyve
ER -