RAILROAD CONVERTER STATION LINKED TO MVDC DISTRIBUTION SYSTEM AND ITS SIMULATION METHOD

Abstract

To provide a simulation system of a railway system for a Medium-Voltage Direct Current (MVDC) distribution network.SOLUTION: In the simulation system, a converter station model simulates a converter station included in the MVDC distribution network, a train operation model simulates an operation state of a train, and a converter controller controls a DC / DC converter included in the converter station model. The simulation system includes a Hardware In the Loop Simulation (HILS) device which performs a simulation based on the converter station model, the train operation model and the converter controller. The converter station model and the train operation model are executed in software by the HILS device, and the converter controller is connected to the HILS device and driven to control the converter station model.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The present invention relates to a railway converter station connected to an MVDC power distribution system and a simulation method thereof. [Background technology]

[0002] Figure 1 shows a conventional DC railway system.

[0003] Korea's standard DC railway system is connected to the AC 22.9kV bus of the distribution system supplied by Korea Electric Power Corporation. This system steps down AC 22.9kV to AC 1180V through a rectifier-type transformer, and then converts this to DC 1620V on a no-load basis using a rectifier such as a silicon diode to supply the railway system.

[0004] However, recently, as the proportion of renewable energy sources has increased, the need to increase the capacity of distribution lines has been raised, but due to complaints and other reasons, it is not easy to expand the distribution lines.

[0005] As a result, research is being conducted into methods that can apply DC rather than AC methods to distribution systems, making it possible to expand voltage from the perspective of insulation level, and increase current capacity by eliminating the skin effect.

[0006] Currently, Korea has three standard voltages: transmission voltage 765KV, 345KV, and 154KV, while distribution voltages are 22.9KV (extra high voltage) and 380V and 220V (low voltage). MVDC (Medium-Voltage Direct Current) technology converts AC to DC before transmitting electricity through the distribution network, or supplies DC power directly to users. High-voltage DC distribution is defined as DC 1500V or higher and 100KV or lower. Therefore, the MVDC voltage range is linked to the 22.9KV distribution system before the transformer on the consumer side.

[0007] 1.Necessity of a virtual simulation system for DC railway converter stations

[0008] Since this DC railway system is connected as a load to the 22.9 kV bus of the distribution system supplied by Korea Electric Power Corporation, when applying MVDC technology to the distribution system, the railway substation, which is the connection point with the DC railway system, must also be converted into MVDC connection infrastructure. In other words, to convert the high-voltage DC voltage of the KEPCO distribution system to railway operating voltages (3000V, 1500V, 750V) and ensure operational flexibility, a DC / DC converter-based DC railway converter station capable of converter-based active voltage control is required to be developed.

[0009] Therefore, the present invention provides a method for configuring a railway converter station required to connect a railway system to an MVDC power distribution network, and a method for virtually simulating a core component, a train, as a moving load in a software environment using only controller hardware in order to pre-verify the converter station without on-site testing.

[0010] 2. The need for improved simulation algorithms

[0011] Meanwhile, the algorithm used to simulate a DC rail converter station also needs to be improved. In other words, to implement virtual operation based on real-time simulation without using actual railcars, real-time performance must be guaranteed, and a high-speed calculation-based power simulation technique is required to simulate a DC railroad system including rolling stock, which is a moving load.

[0012] Looking at conventional power simulation technology, tractive force and braking force curves created based on the design performance values ​​of the electric motors used in railway vehicle design have been used, and batch processing-based train running simulations have been used in which all vehicle data, operation data, and track data (curves, gradients, and stop station position information) are input and calculated all at once for the entire given route using a time accumulation, distance accumulation, or speed accumulation method.

[0013] The general application method of conventional technology is to input the results of this batch processing type train running simulation (speed profile and power profile) again and perform a power simulation that calculates the current and voltage of each node using programming or simulation tools.

[0014] In other words, the biggest feature of the conventional technology is sequential data processing, which means collecting bounded data for a certain period (by route or by several hours or minutes) and processing it sequentially at a certain point in time.

[0015] FIG. 2 is a flow chart showing a conventional power simulation process.

[0016] As shown in Figure 2, the overall power simulation process is roughly divided into a train running calculation process and a power simulation process, which operate as separate calculation algorithms.

[0017] First, when train running calculations begin, all train data input information, such as vehicle data, operation data, and track data (curves, gradients, and stop station location information), is input and parameterized, and then pre-processing of train operations is performed. The pre-processing of train operations utilizes the above train data input information in the process of pre-calculating reverse-to-turnaround switching points and turnaround-to-braking switching points.

[0018] First, the reverse-to-opposite switching point is selected taking into account the train's operational requirements and environment, but is not selected separately for sections with short inter-station distances (meaning a set of starting and ending stations). The opposite-to-opposite braking point is determined by taking into account the location of each station, which is the train's starting and ending point, obtaining a train speed trajectory through forward travel in consideration of the tractive force curve, and obtaining a train speed trajectory through reverse travel in consideration of the characteristics of the braking force curve, and then obtaining the opposite-to-opposite braking switching point at the intersection of these two trajectories.

[0019] Next, train running calculations are started based on the results of the calculated train operation pre-processing. First, acceleration is calculated taking into account tractive force or braking force and running resistance, and the time and values ​​are simultaneously saved in table / array format. Next, speed and position are calculated using acceleration and a preset unit time (sample time), and simultaneously saved in lookup table or array format. Finally, power consumption values ​​are calculated and saved using these values. Power consumption can be calculated based on the product of tractive force and speed or the product of braking force and speed.

[0020] Then, by referring to the lookup table derived in the pre-processing of train operation, if a switch in reverse / alternate / braking mode occurs, the mode is switched and the tractive force is set to a positive value when reversed, 0 when alternate, and negative when braking, and recalculated; otherwise, the process is repeated. If an interruption condition occurs or the value of the train's current position is exactly the same as the value of the stop station, the algorithm ends.

[0021] Next, a power simulation process is performed using a separate algorithm. Power simulation can involve both using a simulation tool that is modeled and driven separately, or solving differential equations numerically to obtain a solution. First, initial values ​​and conditions are set, and the values ​​of the power consumption lookup table (array) derived previously during train running calculations are loaded and parameterized, or loaded over time. The current consumed by the train is then converted and input into an equivalent model (including mathematical models) expressed in current circular or impedance form. A coefficient matrix is ​​then calculated through the construction of state-space equations. Finally, the voltage, current, and power values, which are the outputs of a continuous or discrete-time system, are derived through the calculation of the state-space equations and saved, completing the process. In summary, conventional technology is characterized by having three modes (states)—reverse, reverse, and braking—that can be switched, and all of these require calculations to be performed in advance for each section between stations.

[0022] The conventional batch or single-processing train running simulation method has a problem in that it is difficult to query data in real time. In other words, the batch processing method makes it impossible to perform other tasks, such as a power simulation, before the train running calculation process is completed. In particular, when this processing method is used for real-time railway power simulation, it may affect the accuracy and the size of input data.

[0023] On the other hand, when the batch method is used for real-time simulation, the results of the batch processing train running simulation are temporarily stored in cache memory before the simulation and then used during the real-time simulation. Therefore, in the case of large amounts of data, there are limitations to the storage and use of the data, and there are also limitations to the high-speed calculation of the real-time simulation.

[0024] 3. The need to improve DC / DC converters in converter stations

[0025] DAB (Dual Active Bridge) converters are widely used for bidirectional power conversion in various industrial fields, such as railway vehicles, electric vehicles, and solar power generation systems, which require the reuse of regenerative power. DAB converters, which have a symmetrical dual bridge switching stack with a series inductor in between, have advantages such as a simple structure, ZVS turn-on characteristics for all switches on the primary and secondary sides, and natural direction change.

[0026] However, typical DAB converters have the problem that they tend to lose their ZVS characteristics when the load is small, and when the load increases, the conduction loss increases due to the reactive power components present in the circuit.

[0027] To solve this problem, a series-resonant DAB converter (SRDAB) has been proposed, which adds a series inductor and a tuned resonant capacitor. Like conventional DAB converters, the SRDAB has many advantages, such as being able to easily adjust the magnitude and flow of power by adjusting the phase difference between the two bridges, and maintaining ZVS characteristics over a wide range.

[0028] However, currently known resonant and non-resonant DAB converters are generally constructed based on a full-bridge (FB) or half-bridge (HB) topology, and the switching voltage that can be handled by a two-level topology is low, at a few hundred volts or less. To switch high voltages of DC 1500V or more, such as those used in railway vehicles, a modular structure with an input-series-output-parallel (ISOP) structure is required, in which such DAB converters are stacked in series and the outputs are bundled in parallel. However, this structure requires a large number of switching elements, and passive elements are added to each module, increasing the number of active and passive elements structurally.

[0029] Figure 3 shows a typical two-level FB-based SRDAB converter, and Figure 4 shows a typical SRDAB converter combined in an ISOP structure.

[0030] The converter in Figure 3 is a two-level converter, so the switching voltage that each switch can withstand is the input source voltage, Vdc. The converter circuit shown is composed of four input switches, four output switches, a resonant inductor Lr, a resonant capacitor Cr, a transformer with a turns ratio of n:1, input / output filter capacitors, and a load resistor R.

[0031] As mentioned above, since the input terminal is configured in a two-level based FB configuration, it needs to have an ISOP (Input-Series-Output-Parallel) structure in order to be applied to a power conversion system with a high input source voltage such as a railway vehicle.

[0032] As shown in Figure 4, an ISOP structure can be used in which two unit converters from Figure 3 are stacked in series on the input side and two are connected in parallel on the output side. The entire circuit consists of eight input-side switches, eight output-side switches, four resonant elements (inductors and capacitors), two transformers, two input capacitors, and one output capacitor. When configuring this type of ISOP, it can be seen that the number of input switches and resonant elements doubles. Furthermore, because the input is configured in series, it can be seen that a separate control means is required to control the neutral point fluctuations of the capacitor. [Prior art documents] [Patent documents]

[0033] [Patent Document 1] Korean Patent No. 10-2213266 (Name of invention: Method and system for arranging regenerative braking energy recovery device for urban railway traffic) Summary of the Invention [Problem to be solved by the invention]

[0034] An object of the present invention is to provide an MVDC distribution system-connected railway converter station used in a DC railway system and a simulation system therefor.

[0035] Another object of the present invention is to provide a train running simulation device and method that can be used in an MVDC distribution system-connected railway converter station used in a direct current railway system.

[0036] Another object of the present invention is to provide a series resonant DAB converter that can be used in a railway converter station connected to an MVDC distribution system used in a DC railway system, and a control method thereof.

[0037] However, the technical problem that this embodiment aims to achieve is not limited to the above-mentioned technical problem, and other technical problems may exist. [Means for solving the problem]

[0038] As a technical means for achieving the above technical object, according to one aspect of the present invention, a simulation system for a railway system for an MVDC power distribution network includes: a computing device storing a simulation program including a converter station model that simulates a converter station included in the MVDC power distribution network and a train running model that simulates the running state of a train that operates using power supplied from the converter station; a converter controller that controls a DC / DC converter included in the converter station model; and a Hardware In the Loop Simulation (HILS) device that performs a simulation based on the converter station model, the train running model, and the converter controller, wherein the converter station model and the train running model are executed by software in the HILS device, and the converter controller is connected to the HILS device and driven to control the converter station model.

[0039] In accordance with another aspect of the present invention, a method for simulating a railway system for an MVDC distribution network includes the steps of: executing, as software, a simulation program in a Hardware-In-the-Loop Simulation (HILS) device; the simulation program includes a converter station model that simulates a converter station included in the MVDC distribution network; and a train running model that simulates the running state of a train that operates using power supplied from the converter station; and connecting a converter controller that controls a DC / DC converter included in the converter station model to the HILS device and driving the converter controller to control the converter station model. [Effects of the Invention]

[0040] According to the above-described means for solving the problems, the present invention proposes a configuration and method for performing a railway system HILS verification method using an actual controller, thereby enabling operational algorithms for a railway system to be verified in advance without on-site testing or a final completed product. By analyzing the results of the virtual simulation obtained in this way and utilizing them in the production and performance testing of actual rolling stock, efficient optimization can be achieved.

[0041] Furthermore, by applying the present invention, it is possible to easily establish a system operation plan by introducing multiple railway vehicles with similar operation patterns. Furthermore, there is no need to consider the time interval between train operation simulations, and time synchronization with the power simulation environment is possible. While conventional train operation and power simulation technologies require input of a train schedule to simulate the operation of multiple vehicles, the present invention makes it possible to output and generate a train schedule. Furthermore, since the input data itself is small enough to be variable, it is possible to create and install the present state-machine-based stream-based high-speed train running calculation module in the traction inverter controller, thereby creating a configuration similar to an actual railway operation environment. Furthermore, because it is driven by a state machine, it is highly stable. In other words, a train can only have one state at a time, and the flow always follows the design, with state transitions occurring only in response to predetermined events.

[0042] In addition, the configuration of the series resonant DAB converter proposed in this invention has the effect of reducing the number of active and passive elements of the primary bridge by half compared to the conventional FB under the same withstand voltage conditions. Meanwhile, to realize the proposed method, a special switching sequence is required, but this invention solves this by presenting a special sequence for neutral point balancing control using a switching pattern of voltage magnitude modulation method instead of the conventional phase transition method. [Brief explanation of the drawings]

[0043] Figure 1 shows a conventional DC railway system.

[0044] FIG. 2 is a flow chart showing a conventional power simulation process.

[0045] Figure 3 shows a typical two-level FB-based SRDAB converter.

[0046] Figure 4 shows a typical SRDAB converter connected in an ISOP structure.

[0047] FIG. 5 is a diagram illustrating the configuration of a railway system for an MVDC power distribution network according to an embodiment of the present invention.

[0048] FIG. 6 is a block diagram showing the configuration of a simulation system for a railway system with respect to an MVDC power distribution network according to an embodiment of the present invention.

[0049] FIG. 7 is a block diagram showing the configuration of a computing device included in a simulation system according to an embodiment of the present invention.

[0050] FIG. 8 is a flowchart showing the operation of a train running model based on a stream processing method according to an embodiment of the present invention.

[0051] 9 to 12 are diagrams illustrating a train running calculation process based on a state machine according to an embodiment of the present invention.

[0052] FIG. 13 is a diagram showing the calculation results of the train running model according to one embodiment of the present invention.

[0053] FIG. 14 is an illustration of an equivalent model of a railway system used in a train running model according to one embodiment of the present invention.

[0054] FIG. 15 shows the analysis process of an equivalent model of a railway system used in a train running model according to one embodiment of the present invention.

[0055] FIG. 16 shows a series resonant DAB converter applied to a converter station model according to one embodiment of the present invention.

[0056] FIG. 17 shows an ISOP connection state of a series resonant DAB converter to which a converter station model according to an embodiment of the present invention is applied.

[0057] FIG. 18 is a diagram illustrating the operation of the series resonant DAB converter according to one embodiment of the present invention.

[0058] FIG. 19 shows primary / secondary leg voltage waveforms of a series resonant DAB converter according to an embodiment of the present invention.

[0059] FIG. 20 shows a case where a switching sequence of a general phase transition method is applied to the present invention.

[0060] 21 and 22 show switching sequences of a pulse magnitude modulation method for driving a series resonant DAB converter according to the present invention.

[0061] FIG. 23 shows the relationship between the carrier and the PWM command value in the method for driving a series resonant DAB converter according to one embodiment of the present invention.

[0062] FIG. 24 shows a process of selecting a command mode (CM) in a method of driving a series resonant DAB converter according to an embodiment of the present invention.

[0063] 25 to 27 are block diagrams of control logic for outputting control signals of a series resonant DAB converter according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0064] Hereinafter, with reference to the accompanying drawings, embodiments of the present application will be described in detail so that those skilled in the art can easily carry out the present application. However, the present application may be embodied in various different forms and is not limited to the embodiments described herein. In order to clearly explain the present application in the drawings, parts that are not relevant to the description will be omitted, and similar parts will be designated by similar reference numerals throughout the specification.

[0065] Throughout this specification, when a part is "coupled" to another part, it includes not only when it is "directly coupled" to another part, but also when it is "electrically coupled" to another part via another element therebetween.

[0066] Throughout this specification, when an element is said to be "on" another element, "located" includes not only when the element is in contact with another element, but also when there is another element between the two elements.

[0067] Throughout this specification, when a part "comprises" a certain element, it does not mean that it excludes other elements, but that it may further include other elements, unless otherwise specified. Terms of degree such as "about," "substantially," etc., used throughout this specification are used to mean a numerical value or a close approximation of a numerical value when inherent manufacturing and material tolerances are presented, and are used to facilitate understanding of this application and to prevent unscrupulous infringers from unfairly exploiting disclosures in which precise or absolute numerical values ​​are recited. Terms of degree such as "(a) step of" or "a step of" used throughout this specification do not mean "a step for."

[0068] As used herein, the term "module" includes units implemented using hardware or software, as well as units implemented using both hardware and software. One unit may be implemented using two or more pieces of hardware, or two or more units may be implemented by a single piece of hardware. However, the term "module" is not limited to software or hardware; a "module" may reside on an addressable storage medium or execute one or more processors. Thus, by way of example, a "module" includes components such as software components, object-oriented software components, class components, and task components, processes, functions, attributes, procedures, subroutines, program code segments, drivers, firmware, microcode, circuits, data, databases, data structures, tables, arrays, and variables. The components and functionality provided within a "module" may be combined into fewer components and "modules" or further separated into additional components and "modules."

[0069] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will now be described in detail with reference to the accompanying drawings and the following description. However, the present invention is not limited to the embodiments described herein and may be embodied in other forms. Like reference numerals refer to like elements throughout the specification.

[0070] FIG. 5 is a diagram illustrating the configuration of a railway system for an MVDC power distribution network according to an embodiment of the present invention.

[0071] In FIG. 5, the left side shows a conventional DC railway system, and the right side shows a DC railway system according to the present invention.

[0072] The DC railway system according to the present invention converts the DC voltage of the distribution system into railway operating voltage through a DC / DC converter-based DC railway converter station, which uses a DC / DC converter capable of converter-based active control.

[0073] On the other hand, testing of the newly developed DC railway converter station requires on-site testing using actual railway infrastructure during the power equipment development process. However, this poses a significant risk of train disruption or personal injury if an accident occurs during the testing process, while also posing problems of low efficiency due to the difficulty of repeated testing.

[0074] In addition, verifying and optimizing system performance using actual railway vehicles requires a lot of time and financial support, and there are limitations to various tests and iterative tests depending on the testbed environment.

[0075] Therefore, in order to conduct safe repeated testing and analysis to confirm the performance of new systems (power equipment), it is necessary to build a HILS platform based on a laboratory-scale real-time simulator and controller hardware, and then develop virtual operation technology that can evaluate the performance of the operational efficiency of the target power equipment according to the purpose of use of the electrical equipment.

[0076] That is, the dc / dc converter controller of the converter station is implemented in hardware, and the other parts are implemented in a software-based virtual environment, enabling virtual operation.

[0077] To realize virtual operation based on real-time simulation without using actual railway vehicles, real-time performance must be guaranteed, and a high-speed calculation-based power simulation technique is required to simulate a DC railway system including vehicles, which are moving loads.

[0078] FIG. 6 is a block diagram showing the configuration of a simulation system for a railway system with respect to an MVDC power distribution network according to an embodiment of the present invention.

[0079] The illustrated simulation system (10) includes a computing device (100), a HILS device (200), and a converter controller (300).

[0080] The computing device (100) stores a simulation program including a converter station model that simulates a converter station included in an MVDC power distribution network and a train running model that simulates the running state of a train that operates using power supplied from the converter station.

[0081] The Hardware In the Loop Simulation (HILS) device (200) is a device that enables various simulations to be performed during the development process of a real-time embedded system. The HILS device (200) mathematically models the operating environment and system of the equipment to be tested and performs simulations. The HILS device (200) itself corresponds to conventional technology, but in this invention, the HILS device (200) is used to simulate a converter station. For the HILS device (200), the converter controller (300), which is the actual hardware controller of the railway system to be tested, must operate under the illusion that it is in the real environment, so a real-time simulation environment is required.

[0082] The converter controller 300 includes a processor equipped with control logic for controlling the DC / DC converter, which is the core component of the converter station to be tested. The converter controller 300 controls the DC / DC converter in cooperation with the real-time simulator IO (e.g., DI (PWM) card) of the HILS device 200. The converter controller 300 may include a processor such as an MCU or FPGA, and the specific configuration of the control logic will be described later.

[0083] FIG. 7 is a block diagram showing the configuration of a computing device included in a simulation system according to an embodiment of the present invention.

[0084] The computing device (100) includes a processor (110) and a memory (120), and may further include a communication module (130) and a database (140).

[0085] A simulation program is recorded in the memory 120. The simulation program includes a converter station model that simulates a converter station included in the MVDC power distribution network and a train running model that simulates the running state of a train that operates with power supplied from the converter station.

[0086] The memory 120 also functions to temporarily or permanently store data processed by the processor 110. The memory 120 may include a volatile storage medium or a non-volatile storage medium, but the scope of the present invention is not limited thereto.

[0087] The processor 110 executes a simulation program stored in the memory 120. The processor 110 also performs various control operations for the operation of the computing device 100. The processor 110 may refer to a data processing device embedded in hardware, having a circuit physically structured to perform functions expressed by code or commands contained in a program. Examples of such data processing devices embedded in hardware include a microprocessor, a central processing unit (CPU), a processor core, a multiprocessor, an application-specific integrated circuit (ASIC), a field programmable gate array (FPGA), a graphics processing unit (GPU), etc., but the scope of the present invention is not limited thereto.

[0088] The communications module 130 may include one or more components for transmitting and receiving various types of data to and from external computing devices. The communications module 130 may be a device that includes the necessary hardware and software to transmit and receive signals, such as control or data signals, to and from other network devices via wired or wireless connections.

[0089] The database (140) can manage various data required for executing the simulation program.

[0090] Now, let's look at the detailed configuration of the simulation program.

[0091] As described above, the simulation program includes a converter station model and a train running model, and is uploaded to the HILS device (200) in response to a user request, and the train running model and the converter station model are executed, respectively. The train running simulation program operates when the train running model is executed, and the converter station simulation program operates when the converter station model is executed. Then, assuming that the converter station model is installed in a DC railway system, a train running simulation is performed according to the train running model.

[0092] Offline simulation requires tens of hours of calculation to simulate a few minutes at most. In contrast, real-time simulation using a real-time simulator shows the same simulated time as the actual time (1 second in the simulation is the same as 1 second in the actual time) and can simulate from tens of minutes to several hours, making it highly useful for pre-verification.

[0093] 1. Train running simulation program configuration

[0094] The train running model is implemented as a moving load in a real-time simulator according to train running calculation logic, and a high-speed calculation-based power simulation technique is required to simulate the virtual operation of a DC railway system.

[0095] First, when considering the accuracy of the train running model, if the simulation results have a calculation interval (Ttps) of around one second, which is very long compared to the power system response (time constant, in the range of tens of microseconds), the control sampling frequency or control time interval (Tc) of the converter station controller can also be included as a major control variable. Therefore, depending on the relationship between the calculation interval (Ttps), the time interval (Ts) of the discrete-time system, and the control time interval (Tc), the problem of finding a solution for the entire power system becomes stiffer. Depending on the size of the calculation interval (Ttps), this may ultimately cause numerical instability and may reduce the robustness of the results obtained through numerical analysis.

[0096] Furthermore, if the calculation interval (Ttps) is set very small to improve accuracy in terms of the size of input data, the size of the data from the batch processing train running simulation results will become very large, and the large amount of data will have to be saved in the form of a text file, divided or read (input) again, and processed again for power simulation, which can reduce calculation efficiency.

[0097] To solve these problems, the stream processing method that is a feature of this invention can be applied to reduce the time interval to the minimum time interval level (several hundred microseconds or less) that can guarantee real-time performance of the entire power system, including the train running model. To apply the stream processing method to the train running model, the concept of a state machine is introduced, which solves all of the problems of the size and accuracy of the input data mentioned above.

[0098] FIG. 8 is a flowchart showing the operation of a train running model based on a stream processing method according to an embodiment of the present invention.

[0099] First, the initial value x(0) and input value u(t) of the system are set (S810).

[0100] In this case, x(0) is the initial value of the system and can include initial speed (0 km / h), initial position (0 km), initial train torque (0 kN), initial acceleration (0 km / h / s), initial consumed / regenerated power (0 kW), etc. u(t) represents the train's power value that changes over time, and x(t) is a system state variable that changes over time and represents speed, position, acceleration, train torque, consumed power, or regenerated power. u(t) is determined in the train running calculation step (S820), and x(t) is determined in the power simulation step (S830).

[0101] Next, train running calculations are performed according to a state machine-based stream processing method (S820).

[0102] More specifically, it may include a step (S822) of calculating acceleration taking into account tractive force and running resistance or braking force and running resistance, a step (S824) of calculating speed and position using acceleration and unit time (time interval (Ts) of a discrete time system), and a step (S826) of performing a state machine-based stream-based train running calculation and returning the final value notch and train power consumption value.

[0103] In the step of calculating acceleration (S822), acceleration is calculated using the tractive force, braking force, and running resistance determined according to the speed and a notch value determined by the train running state machine, as shown in Fig. 12, which will be described later. The notch value is used to select one of the tractive force and braking force curves. Once the tractive force and braking force curves are selected, the current speed is mapped to one of the two curves, the current train torque is converted, and the converted torque is divided by the train mass to calculate the acceleration / deceleration.

[0104] The step of calculating velocity and position (S824) utilizes acceleration and unit time (time interval (Ts) of a discrete time system). The unit time (time interval) is used to calculate the next calculated value (velocity, position, acceleration, etc.) based on the current calculated value (velocity, position, acceleration, etc.). For example, when calculating the next velocity from the current velocity, it can be used in the form of v=v0+a*Ts.

[0105] The notch value output in step S826 may be returned to the previous step S822, and the train power consumption value may be returned to the step in step S832.

[0106] Then, the notch value and the train power consumption value are returned, and the train running calculation is repeated again, and the train power consumption value output as a result is input to the power simulation step (S830). For reference, a notch is a controller used by the engineer to adjust the speed when the train is running, and refers to the notch state value (e.g., P4~, P1, N, B1~B7) when the train is running.

[0107] Next, the train power consumption output in the previous step (S820) is received as an input, and a power simulation is performed using a state space equation (S830).

[0108] More specifically, this may include a step of dividing the train's power consumption by the voltage and inputting the result into an equivalent model in the form of a current source (S832), a step of constructing the entire power system including the current source (train load) as a state space equation and calculating a coefficient matrix (S834), and a step of deriving a discrete-time system output through the state space equation calculation and starting the power simulation again (S836).

[0109] Meanwhile, the train running calculation (S820) and the power simulation (S830) can be repeatedly performed in parallel until an interruption condition is met (S840), and when the interruption condition is met, the results of each calculation are saved and the process is terminated. One of the features of the present invention is that it is possible to perform a simulation without interruption, but when a user requests to interrupt the entire simulation, it is determined that the interruption condition is met.

[0110] Meanwhile, the train running calculation process (S820) of the stream method based on the state machine described above will be examined in more detail.

[0111] 9 to 12 are diagrams illustrating a train running calculation process based on a state machine according to an embodiment of the present invention.

[0112] First, in the train running calculation step (S826), the state information is confirmed based on the speed calculated in the previous step (S824), and a notch value corresponding to the state information is output.

[0113] As shown in Figure 9, the state machine consists of four states: a stopped state, a reverse state, a sideways state, and a braking state. First, the vehicle enters the stopped state section via an entry point. This does not apply initially, but after a specific stopping time has elapsed, the state transitions to the reverse state section. The state machine then determines whether the calculated speed satisfies the speed limit arrival condition of the following equation 1, and if the speed limit arrival condition is met, the state transitions to the sideways state section.

[0114] [Formula 1] TIFF0007778888000001.tif827

[0115] In other words, it determines whether the difference between the current driving speed (V) and the speed limit (VLIM) is smaller than the threshold, and if the condition is met, it enters the opposite state. In this case, the entry point is the 0 notch (N) state. However, the opposite state suppresses excessive notch control and provides a speed deadband (δ) as shown in Equation 2 for gear control, reducing the sensitivity of the state transition.

[0116] [Formula 2] TIFF0007778888000002.tif841

[0117] That is, the state machine includes the train's stopped state, reverse state, oncoming state, and braking state, and transitions between states of the state machine depending on whether the speed has reached the speed limit, and outputs a notch value matching each state.

[0118] Figure 10 (a), (b), and (c) are diagrams of the mascon notch's state machine in the reverse, forward, and braking states, respectively. In the reverse state, if Equation 1 is satisfied, the value is 1, otherwise it is 0. When it is 1, the state transition is in the direction of increasing speed, and when it is 0, the state transition is in the direction of decreasing speed. At this time, the arbitrary value ε can be reduced counterclockwise.

[0119] As shown in (b), in the case of the other state part, if formula 2 is satisfied, it has a value of 1, otherwise it has a value of 0. When it is 1, the state transition is in the direction of increasing the speed, and when it is 0, the state transition is in the direction of decreasing the speed. At this time, the arbitrary value ε can decrease the standard in the counterclockwise direction.

[0120] As shown in (c), in the braking state section, the target operating time for one section when operating at the scheduled speed and the braking point when braking with maximum torque at the current operating point are calculated first, and when the arrival conditions are met, a state transition is performed, and the approach point is set to handle the notch for B7 maximum braking force. In the stopping state section, a state transition occurs when speed = 0, and at this time, only the stopping time starts counting, and the train moves between the current stop station and the next stop station set one section at a time.

[0121] Using the example in Figure 11, to derive the train operating speed profile, a speed limit is set for each section, and a state transition occurs when the conditions for satisfying the speed limit are met, as shown in Equation 1 and Equation 2. That is, when departing from Station 1, the train starts at notch (P4) with maximum tractive force, reaches the initial speed limit (speed limit n), and transitions to the next state (P3) when Equation 1 or 2 is met. The speed continues to increase, and when it reaches the maximum speed limit (speed limit 1), the state transitions to notch (N) which is in a crossing state. After that, when the speed decelerates below the speed limit, the state transitions to notch (B1) with braking force, and the state transitions in the braking state are repeated until the train brakes at the exact point at Station 2, the final stop. In this way, train operation can be calculated using only state transitions, without the need for prior calculations such as estimating braking points.

[0122] Meanwhile, the embodiment can be modified by objectifying the driver's patterns and reflecting the train's notch handling sensitivity factor in the train operation state machine. This allows for more realistic train operation calculations, adds randomness to train operation, and adds probabilistic optimal efficiency operation factors to the system operation of future power simulations (power system numerical calculations). In particular, this can be differentiated from the conventional batch processing train operation simulation format, which shows deterministic results through extreme operational handling of P4 notch (reverse), 0 notch (alternate), and B7 (braking), but shows somewhat unrealistic operational patterns (electrical load models).

[0123] In addition, for routes with frequently fluctuating speed limits, the driver's perception of the speed limit can be reflected in the train operation state machine. During train operation calculations, the speed limit may suddenly change. For example, if a train traveling at 70 km / h with an 80 km / h speed limit suddenly encounters a 50 km / h speed limit, even if it suddenly accelerates, the calculation results may still exceed the speed limit. To solve this problem, a speed limit-distance table can be made into a variable and reflected in the state machine diagram. This can be applied by transitioning to a braking state at a specific distance to reduce speed.

[0124] FIG. 12 shows an example of an algorithm for calculating the power consumption of a train in the train running calculation process.

[0125] The train running model calculates the acceleration / deceleration and power consumption through the acceleration / deceleration calculation block and the power consumption calculation block to calculate the train power consumption. The values ​​input to the acceleration / deceleration calculation block and the power consumption calculation block are the output of the traction / brake selection block, the output of the running resistance calculation block, the output of the grade resistance lookup block, and the output of the curve resistance lookup block.

[0126] First, the tractive force lookup block or braking force lookup block stores information about tractive force or braking force that has been previously matched and stored according to the vehicle speed value. When a speed value is input, the matching tractive force or braking force is output. Then, the tractive force and braking force are calculated taking into account the notch value calculated in the previous step (S826).

[0127] The running resistance calculation block inputs the speed value into a preset mathematical formula and outputs the running resistance.

[0128] In addition, the grade resistance lookup block and the curve resistance lookup block store information on grade resistance and curve resistance that have been previously matched and stored according to the location. When the vehicle's location information is input, the corresponding grade resistance or curve resistance is output. At this time, the location information can be calculated based on the speed and travel time calculated in the previous step (S824), or the location information can be confirmed using GPS, etc.

[0129] Based on the information collected as described above, the acceleration / deceleration calculation block and the power consumption calculation block calculate and output acceleration, deceleration, and power consumption according to preset formulas. For example, acceleration / deceleration can be calculated using a = F / m (where a is acceleration or deceleration, F is tractive force or braking force, and m is the train's mass). Power consumption (regenerative power) can be calculated using P = Fv (where P is power consumption or regenerative power, F is tractive force or braking force, and V is the current train speed).

[0130] Through this process, when operation of a certain section is completed, the route information is updated, and when the upbound operation is completed, the upbound vehicle position calculation block is switched to the downbound vehicle position calculation block, so that calculations are performed continuously.

[0131] FIG. 13 is a diagram showing the calculation results of the train running model according to one embodiment of the present invention.

[0132] FIG. 13(a) shows the output of the notch values ​​calculated by the state machine on a time axis.

[0133] FIG. 13(b) shows the results of vehicle speed calculation on the time axis.

[0134] FIG. 13(c) shows the vehicle position on the time axis.

[0135] FIG. 13(d) shows the train power consumption calculation results along the time axis.

[0136] Next, we will look at the process of performing power simulation using state space equations (S830).

[0137] FIG. 14 is an illustration of an equivalent model of a railway system used in a train running model according to one embodiment of the present invention.

[0138] Figure 14(a) shows a single-formation vehicle moving load model, Figure 14(b) shows a multi-formation vehicle moving load model with parallel impedance configuration, Figure 14(c) shows a multi-formation vehicle moving load model with series impedance configuration, and Figure 14(d) shows a rearranged and aligned multi-formation vehicle moving load model.

[0139] A switch-free configuration can be derived by starting with a single-car moving load model. First, when one impedance is configured as a parallel equivalent with the same impedance, it becomes multiplied by N impedance values. Then, since the car load (current source) is also connected at the same node, it can be configured as a parallel current source. By rearranging and aligning this, it can be changed to a form that is easy to apply to the train diagram, as shown in (d).

[0140] FIG. 15 shows the analysis process of an equivalent model of a railway system used in a train running model according to an embodiment of the present invention.

[0141] In the multi-vehicle movement load model shown in Figure 14(d), the model can be divided into each element. The magnitude of each resistance is the same in each diagram, but the operating headway differs for each train, so the changing behavior may differ.

[0142] Figure 15(a) shows a parallel configuration when railway system model decomposition is applied, Figure 15(b) shows a series configuration when railway vehicle model decomposition is applied, and Figure 15(c) shows a system decomposition method that utilizes the model reduction method.

[0143] Such an equivalent model can be expressed as a state space equation and solved.

[0144] For example, matrices and vectors of the following form may be derived:

[0145] TIFF0007778888000003.tif2064

[0146] In this case, the number of elements required to configure the state space matrix of the existing DC railway system model as a single group is assumed to be, for example, 37 inputs, 74 state values, 94 outputs, and 94 switches. For real-time calculations, the simulator must pre-calculate and allocate cache memory on a scale that is 274 times larger than the memory storage capacity. Even if the number of switch contacts is reduced, it is impossible to perform a simulation with a sampling time of approximately 50 μs.

[0147] TIFF0007778888000004.tif2081

[0148] However, when using the method of the present invention, the capacity stored in the cache memory before real-time calculation is 393.626 Mb. The total calculation groups are divided into 67 groups, most of which are groups consisting of only inputs and outputs. The remaining group consists of three substations, each with 28 states, 35 inputs, 20 outputs, and 12 switches. For reference, these 12 switches correspond to 12 pulse diodes, and the diodes are classified as switches and included in the calculation. However, the amount of calculation required for pre-calculation before real-time simulation is significantly reduced to 212*3 times the sum of the number of elements in the state-space matrix, rather than 236 times. Therefore, during real-time simulation, the calculations consumed for the inputs and outputs of the system model stored in the cache memory within the same time interval are reduced, ensuring real-time performance. However, the number of diodes or switches in a substation may vary depending on the substation configuration. For example, in the case of a bidirectional thyristor converter, one substation would contain 24 thyristors.

[0149] 2. Converter Station Simulation Program Configuration

[0150] The DC / DC converter of the converter station model is composed of switching elements, inductors, capacitors, etc., and its configuration is realized using the element model provided by the real-time simulator. The DC / DC converter that supplies the power required for train operation at the converter station can be configured as follows:

[0151] DC / DC converter configurations can be categorized based on whether the distribution system is a two-circuit or three-circuit system. When a distribution system has two circuits, it is configured with positive and negative poles. For example, if the distribution system voltage is connected at ±20 kV, the input of the DC / DC converter in the converter station can be configured with a magnitude of 40 kV. Furthermore, the output is at a railway operating voltage of 3000 V, 1500 V, or 750 V. In this case, assuming a unit capacity of one converter station is 2 MW, it may be necessary to add two or three converter stations in parallel, taking into account the maximum capacity depending on the train schedule and capacity. When converter stations are added in parallel, balancing control may be required within the converter stations.

[0152] If the distribution system has three circuits, each consisting of positive and negative poles and a neutral line, and the distribution system voltage is linked at ±20KV, for example, the DC / DC converters in the converter station can be configured with one 20KV converter whose input is the positive pole and neutral line, and another 20KV converter whose input is the negative pole and neutral line.If the converter has the same topology as in the two-circuit case, two 1MW DC / DC converters are required to meet the unit capacity of one converter station of 2MW.

[0153] In addition, depending on the train schedule and capacity, it may be necessary to add two or three converter stations in parallel, taking into account maximum capacity. Even when converter stations are added in parallel, overall balancing can be maintained by each converter performing its own balancing control. This balancing control selects a reference voltage on the series-connected side, performs PI control to eliminate the error between this reference voltage and the actual voltage measured, and performs a control logic that balances by adjusting the amount of power (P). It is desirable to design such DC / DC converter topologies taking into account the following railway characteristics.

[0154] - Considering a wide range of load fluctuations from light to medium loads (vehicle configuration, operating intervals / speed, acceleration / deceleration, etc.) (maintaining high efficiency over a wide load range)

[0155] - Considering large moving load (approximately 1MW per M Car)

[0156] - Regenerative energy generation (taking into account bidirectional power flow)

[0157] - By applying the isolated type, it can be separated from the Korean power grid.

[0158] - Balancing control ensures control stability

[0159] FIG. 16 shows a series resonant DAB converter applied to a converter station model according to one embodiment of the present invention, and FIG. 17 shows the ISOP connection state of the series resonant DAB converter applied to a converter station model according to one embodiment of the present invention.

[0160] First, referring to FIG. 16, the structure of a two-series HB-based series resonant DAB converter can be seen as a DC / DC converter.

[0161] The series resonant DAB converter 400 includes an input circuit 410, an output circuit 430, a transformer 440, and a resonant circuit 450. In this case, the series resonant DAB converter 400 includes not only elements in the form of a physical circuit, but also all elements embodied in the form of software that constitute a DC / DC converter in a converter station model.

[0162] The input circuit (410) includes a power supply, a first capacitor (415) and a second capacitor (416) connected in series to the power supply, and first to fourth switching elements (411, 412, 413, 414) connected in series to the power supply in a half-bridge configuration. The first capacitor (415) is connected in parallel to the first switching element (410) and the second switching element (412), and the second capacitor (416) is connected in parallel to the third switching element (414) and the fourth switching element (416). A connection node (N3) connecting the first capacitor (415) and the second capacitor (416) and a connection node (N4) connecting the second switching element (412) and the third switching element (413) are connected to each other, and a neutral point current (Inp) flows between the connection node (N3) and the connection node (N4).

[0163] A resonant circuit 450 and a transformer 440 are coupled between the input circuit 410 and the output circuit 430. The resonant circuit 450 is coupled between a connection node N1 between the first switching element 411 and the second switching element 412 and a connection node N2 between the third switching element 413 and the fourth switching element 414, and includes a capacitor Cr and an inductor Lr connected in series.

[0164] The transformer (440) has one primary terminal connected to the output end (terminal of the inductor (Lr)) of the resonant circuit (450), and the other primary terminal connected to the connection node (N2).

[0165] The output circuit 430 includes a first switching element 431, a second switching element 432, a third switching element 433, and a fourth switching element 434 connected in a full-bridge configuration. The output circuit 430 is connected to the secondary side of the transformer 440, with one terminal of the secondary side connected to a connection node N5 between the first switching element 431 and the second switching element 432, and the other terminal of the secondary side connected to a connection node N6 between the third switching element 433 and the fourth switching element 434.

[0166] As described above, the series resonant DAB converter according to the present invention differs from the converter shown in Figure 3 in that the input side is configured in a two-series configuration based on a half-bridge. Therefore, the switching withstand voltage that the unit switches must withstand can be half the input power supply voltage Vdc. Therefore, it can be seen that the number of elements required on the input side under the same withstand voltage conditions is half that of a full-bridge.

[0167] Furthermore, as shown in Figure 17, a series resonant DAB converter can be extended to an ISOP structure for application to MVDC. Because the input voltage for MVDC can reach several tens of kV, a conventional full-bridge configuration would require a significant increase in the number of active and passive components, leading to additional control requirements, such as current balancing between the increased number of submodules. However, when an ISOP is configured based on the half-bridge series resonant DAB converter proposed in this invention, the number of active and passive components is reduced by half, and the current balancing controller configuration is also reduced by half, simplifying the configuration. In other words, while the switching voltage of the unit switches in the conventional two-level FB structure circuit in Figure 4 is Vdc, the proposed method in Figure 17 has a HB-based switching voltage of 0.5 Vdc, which is half the switching voltage. This is expected to reduce the number of passive components by half for the same switching voltage.

[0168] FIG. 18 is a diagram for explaining the operation of the series resonant DAB converter according to one embodiment of the present invention.

[0169] Specifically, it shows the output leg voltage and neutral point (NP) current depending on the switching state of the input circuit. The first switching element (QA1, 411) and the second switching element (QA2, 412) operate complementarily, and the third switching element (QA3, 413) and the fourth switching element (QA4, 414) also operate complementarily. The primary leg voltage (VA), which represents the voltage between the connection node (N1) and the connection node (N2), is output in three stages: 0, E, and 2E. Here, E represents the unit voltage of the capacitors (Cdc1, Cdc2).

[0170] Additionally, it can be seen that the neutral point current (Inp) between the connection node (N3) and the connection node (N4) is ILr or -ILr depending on the switching state of the circuit under the condition that VA = E. Here, it can be seen that the neutral point current is related to the direction of the resonant current.

[0171] The converter 400 of the present invention also has two input capacitors 415 and 416 connected in series, so it is necessary to carefully control the voltages of the capacitors to prevent voltage deviations. For this reason, the present invention applies a new switching sequence, and by using this, a separate controller is not required.

[0172] FIG. 19 shows primary / secondary leg voltage waveforms of a series resonant DAB converter according to one embodiment of the present invention.

[0173] As mentioned above, the primary leg voltage (VA) indicates the voltage between connection node (N1) and connection node (N2), and the secondary leg voltage (VB) indicates the voltage between connection node (N5) and connection node (N6). Because the E level is essential for controlling the voltage balancing between the capacitors, the overall voltage waveform is designed to have a stepped shape of 0 -> E -> 2E. For reference, this type of control method can also be useful for ZVS switching of the secondary switch.

[0174] The duration of the E voltage level is π(1-k1), and the primary leg voltage (VA) and secondary leg voltage (VB) have a phase difference of φ. Here, k1 is a modulation index ranging from 0 to 1, but in the present invention, its value is fixed (for example, 0.9) and the output voltage is adjusted by the phase difference (φ). The output power Po and output voltage Vo are all smoothly adjusted in proportion to the phase difference sinφ.

[0175] The following equations 3 to 5 show the relationship between the output power (Po) and the output voltage (Vo) of the converter according to the present invention. X represents the equivalent impedance of the resonant circuit (450, Lr-Cr) at the switching frequency ωsw. Here, ωr corresponds to the resonant frequency of the resonant circuit (450), and R represents the output resistance.

[0176] [Formula 3] TIFF0007778888000005.tif1038

[0177] [Formula 4] TIFF0007778888000006.tif1038

[0178] [Formula 5] TIFF0007778888000007.tif1931

[0179] We will now look at the switching sequence for driving a series resonant DAB converter according to the invention.

[0180] FIG. 20 shows a case where a switching sequence of a general phase transition method is applied to the present invention.

[0181] A typical phase transition switching technique adjusts the gates to adjust the turn-on / turn-off timing of a 50% duty signal in the order of A1 → A4 → A2 → A3 → A1 → ... as shown in Figure 20. With this phase transition method, as shown in Figure 20, Inp becomes positive in the switching pairs (2E,E) and (E,0) that make up the E level, causing Cdc1 to continuously charge and Cdc2 to continuously discharge, resulting in a problem of voltage balancing being impossible. This is because not all switching modes that express the E level are utilized. To solve this problem, the present invention proposes a new switching sequence that applies voltage magnitude modulation and clamp mode.

[0182] 21 and 22 show switching sequences of a pulse magnitude modulation method for driving a series resonant DAB converter according to the present invention.

[0183] For reference, in the following drawings, Gate A, Carrier A, Vampl_a, Vcmd_a, etc. refer to signals on the primary side of the transformer (440) or the input circuit (410) side, respectively, and Gate B, Carrier B, Vampl_b, Vcmd_b, etc. refer to signals on the secondary side of the transformer (440) or the output circuit (430) side, respectively.

[0184] The first switching sequence applied to the first switching element (411, Gate A1) periodically repeats a first pulse having a pulse width and a first level amplitude during a reference time (T / 2), a second pulse having a pulse width and a second level amplitude during a time (T / 2-ΔT) obtained by subtracting a predetermined time from the reference time, a third pulse having a pulse width and a first level amplitude during the reference time (T / 2), and a fourth pulse having a pulse width and a second level amplitude during a time (T / 2+ΔT) obtained by adding a predetermined time to the reference time.

[0185] Similarly, the second switching sequence applied to the third switching element (413, Gate A3) periodically repeats the following: a first pulse having a pulse width and a second level amplitude during a reference time (T / 2), a second pulse having a pulse width and a first level amplitude during a time (T / 2+ΔT) obtained by adding a predetermined time to the reference time, a third pulse having a pulse width and a second level amplitude during the reference time (T / 2), and a fourth pulse having a pulse width and a first level amplitude during a time (T / 2-ΔT) obtained by subtracting a predetermined time from the reference time. In this case, the first level may be a high level, and the second level may be a low level that is distinct from the first level.

[0186] That is, the first switching element (411, Gate A1) is turned on / off in the order of T / 2 -> T / 2 - ΔT -> T / 2 -> T / 2 + ΔT -> T / 2 -> ..., and the third switching element (413, Gate A3) is turned on / off in the order of T / 2 -> T / 2 + ΔT -> T / 2 -> T / 2 - ΔT -> T / 2 -> .... This special switching pattern utilizes both the positive and negative polarities of the neutral point current, naturally achieving the purpose of voltage balancing of the input capacitor. Meanwhile, the second switching element (412, Gate A2) and the fourth switching element (414, Gate A4) have complementary characteristics, and therefore their switching sequences are determined to be opposite to those of the first switching element (411, Gate A1) and the third switching element (413, Gate A3), respectively.

[0187] With this configuration, as shown in FIG. 22, the neutral point current (Inp) has negative and positive sections in the (E,0) and (2E,E) switching pairs that make up the E level, and Cdc1 and Cdc2 alternately charge and discharge. As a result, it can be seen that the voltage of Cdc1 (Vdc1) and the voltage of Cdc2 (Vdc2) alternately rise and fall, thereby enabling voltage balancing between the capacitors.

[0188] As a result, during one cycle of the first switching sequence and the second switching sequence, the first neutral point current (Inp) includes both a section having a negative value and a section having a positive value.

[0189] In this case, the pulse widths of the first pulse of the first switching sequence and the first pulse of the second switching sequence are the same, but the first pulse of the second switching sequence is arranged to be earlier than the first pulse of the first switching sequence by a predetermined time (ΔT), i.e., the rising edge of the first pulse of the first switching sequence is later than the falling edge of the first pulse of the second switching sequence by a predetermined time (ΔT).

[0190] In addition, the pulse width of the second pulse of the first switching sequence is set to (T / 2-ΔT), and the pulse width of the second pulse of the second switching sequence is set to (T / 2+ΔT), and the rising edge of the second pulse of the second switching sequence is arranged to be earlier than the falling edge of the first pulse of the first switching sequence by the predetermined time (ΔT), and the falling edge of the second pulse of the second switching sequence is arranged to be later than the rising edge of the second pulse of the first switching sequence by the predetermined time (ΔT).

[0191] Furthermore, the pulse widths of the third pulse of the first switching sequence and the third pulse of the second switching sequence are the same, but the rising edge of the third pulse of the first switching sequence is arranged to be earlier than the falling edge of the third pulse of the second switching sequence by a predetermined time (ΔT). At the initial start point, the second switching sequence is arranged to be earlier by the predetermined time (ΔT), but during the operation time of the second pulse, the second pulse width of the second switching sequence is set to be longer by twice the predetermined time (2ΔT), so that the third pulse of the second switching sequence is delayed by the predetermined time (ΔT).

[0192] In addition, the pulse width of the fourth pulse of the first switching sequence is set to (T / 2+ΔT), and the pulse width of the fourth pulse of the second switching sequence is set to (T / 2-ΔT), and they are arranged so that the falling edge of the fourth pulse of the first switching sequence is earlier than the rising edge of the fourth pulse of the second switching sequence by the predetermined time (ΔT), and so that the rising edge of the fourth pulse of the first switching sequence is later than the falling edge of the fourth pulse of the second switching sequence by the predetermined time (ΔT).

[0193] With this configuration, a negative neutral current (Inp) flows for the time interval (ΔT) between the falling edge of the first pulse of the second switching sequence and the rising edge of the first pulse of the first switching sequence, and a negative neutral current (Inp) flows for the time interval (ΔT) between the rising edge of the second pulse of the second switching sequence and the falling edge of the second pulse of the first switching sequence.

[0194] In addition, a positive neutral current (Inp) flows for the time interval (ΔT) between the rising edge of the third pulse of the first switching sequence and the falling edge of the third pulse of the second switching sequence, and a positive neutral current (Inp) flows for the time interval (ΔT) between the falling edge of the fourth pulse of the first switching sequence and the rising edge of the fourth pulse of the second switching sequence.

[0195] On the other hand, Figure 21 shows the switching pattern design of the proposed pulse magnitude modulation method. Vcmd_A represents the command voltage whose amplitude alternates between ±Vampl_a every half cycle. In the first cycle, the clamping mode (CM) is set to 1, and in the next cycle, CM is set to -1.

[0196] A down-counting triangular wave is used as the carrier wave, and the command values ​​(Vcmd_a1 and Vcmd_a3) for the first switching element (411, QA1) and the third switching element (413, QA3) are set as follows according to CM.

[0197] When CM=1, Vcmd_a1 has a value of 0.5Vcmd_a and Vcmd_a3 has a value of -0.5Vcmd_a. The offset voltage (Voffset) is set to Vdc_ref / 4-max(Vcmd_a1, Vcmd_a3), where max(a, b) is a function that outputs the larger of a and b.

[0198] Conversely, when CM=-1, the polarity of Vcmd_a1 and Vcmd_a3 is set to the opposite of when CM=1, and the offset voltage (Voffset) is calculated in the same way. Then, the offset voltage and Vdc_ref / 4 are added to the original command values ​​Vcmd_a1 and Vcmd_a3 to calculate the PWM command value, and finally, this is divided by Vdc_ref / 2 to calculate the final normalized PWM command value that can be used to plot N_max and compare it to the triangular carrier wave.

[0199] Calculating the PWM command value according to CM as described above allows for the special switching sequence shown in Figure 21 to be expressed, where the first switching element (Gate A1) is turned on / off in the order of T / 2 -> T / 2 -> T / 2 + ΔT -> T / 2 -> ..., and the third switching element (Gate A3) switches in the order of T / 2 -> T / 2 + ΔT -> T / 2 -> T / 2 -> T / 2 -> .... This special switching pattern utilizes both the positive and negative polarities of the neutral point current, naturally achieving the purpose of balancing the voltage of the input capacitor.

[0200] Figure 22 shows the main waveforms from the simulation results of a series resonant DAB converter. PWM_CMD_a1 determines the on / off state of GateA1 relative to the primary carrier, while PWM_CMD_a3 determines the on / off state of GateA3 relative to the primary carrier. Meanwhile, the second switching element (412, GateA2) and the fourth switching element (414, GateA4) have complementary characteristics, which determine the switching behavior opposite to that of the first switching element (411, GateA1) and the third switching element (413, GateA3), respectively. While Figure 20, which uses a conventional phase transition method, only uses positive values ​​of the neutral point current (Inp), this example utilizes both positive and negative values ​​of the neutral point current (Inp), naturally eliminating the voltage deviation of the input capacitor. Both the positive and negative values ​​of the neutral point current (Inp) are utilized, eliminating the capacitor voltage deviation. Both the positive and negative values ​​of the neutral point current (Inp) are utilized, and both the positive and negative values ​​of the neutral point current (Inp) are utilized.

[0201] FIG. 23 shows the relationship between the carrier and the PWM command value in the method for driving a series resonant DAB converter according to one embodiment of the present invention.

[0202] In order to output a symmetric leg waveform, the initial value and count direction of the carrier are reversed according to the CM (FIG. 23(a)). Then, during the interval in which the PWM command value (PWM-CMD) is greater than the carrier, a signal (Gate A or Gate B) that turns on the corresponding switch is output, as shown in FIGS. 21 and 22, and during the remaining interval, a signal that turns off the corresponding switch is output. In the case of FIG. 23(a), during the first pulse interval of the carrier, PWM_CMD_a1 (dotted line signal) is always greater than the carrier, so a signal (Gate A1) that turns on the first switching element (411) is output, and during the interval in which PWM_CMD_a2 (solid line signal) is temporarily greater than the carrier, a signal (Gate A3) that turns on the third switching element (413) is output.

[0203] On the other hand, a method can also be implemented in which the carrier remains unchanged and the relationship between the command value and the carrier is inverted according to CM (FIG. 23(b)), and this method is more suitable for a method that utilizes the primary / secondary phase difference. That is, when CM=-1, a signal (GateA or GateB) that turns on the corresponding switch is output during the period when the PWM command value (PWM-CMD) is smaller than the carrier, and a signal that turns off the corresponding switch is output during the remaining period.

[0204] When calculating the offset voltage (Voffset), if CM=-1, Voffset should normally be equal to Vdc_ref / 4-min(Vcmd_a1, Vcmd_a3). However, if you select the method shown in Figure 23(b), you can achieve the same effect by setting the max value instead of min when CM=-1 and reversing the polarity of Vcmd_a1 and Vcmd_a3.

[0205] FIG. 24 shows a process of selecting a command mode (CM) in a method of driving a series resonant DAB converter according to an embodiment of the present invention.

[0206] The voltages of the input capacitors (Vdc1, Vdc2) are input, and the flow of power (Power) (positive: direction of power flow from source to load, negative: direction of power flow from load to source) is determined. The command mode (CM) is determined based on the magnitude relationship between the voltages of the first capacitor (Vdc1) and the second capacitor (Vdc2). For example, if power flows from the source to the load and the voltage of the first capacitor (Vdc1) is greater than the voltage of the second capacitor (Vdc2), CM = 1; if the voltage of the first capacitor (Vdc1) is less than the voltage of the second capacitor (Vdc2), CM = -1. Also, if power flows from the load to the source and the voltage of the first capacitor (Vdc1) is greater than the voltage of the second capacitor (Vdc2), CM = -1; if the voltage of the first capacitor (Vdc1) is less than the voltage of the second capacitor (Vdc2), CM = 1.

[0207] 25 to 27 are block diagrams of control logic for outputting control signals of a series resonant DAB converter according to an embodiment of the present invention.

[0208] The control logic shown can be implemented in the converter controller 300 in the form of hardware.

[0209] First, FIG. 25 shows the control logic for determining the phase difference between the primary and secondary sides of a transformer, or between the input circuit and the output circuit.

[0210] The phase difference is determined by integrating the difference between the output (Vo) and the initial value (Vo*) of the series resonant DAB converter through a PI controller, and upper and lower limits are set. Through this process, the primary side carrier (Carrier_A) and secondary side carrier (Carrier_B) are output, respectively.

[0211] Next, FIG. 26 shows the control logic that outputs the switching sequence on the primary side or input circuit side.

[0212] As described in the explanation of FIG. 21, Vcmd_A indicates a command voltage whose amplitude alternates between ±Vampl_a every half period, and the offset voltage (Voffset) is determined according to the clamp mode.

[0213] When CM=1, Vcmd_a1 has a value of 0.5*Vcmd_A, and Vcmd_a3 has a value of -0.5*Vcmd_A. The offset voltage is calculated as 0.25*Vdc-max(Vcmd_a1,Vcmd_a3) based on CM_a, Vcmd_a1, and Vcmd_a3. These offset voltages are added equally to the original command values ​​Vcmd_a1 and Vcmd_a3, respectively, to calculate VCMD_a1 and VCMD_a3. Here, max(a,b) is a function that outputs the larger of a and b. VCMD_a1 and VCMD_a3 are normalized by dividing them by 0.5*Vdc, and then multiplied by N_max to output the PWM command voltages (PWM_CMD_a1, PWM_CMD_a3).

[0214] Conversely, when CM=-1, the polarity of Vcmd_a1 and Vcmd_a3 is set to the opposite of when CM=1 (Vcmd_a1=-0.5*Vcmd_A, Vcmd_a3=0.5*Vcmd_A), and the offset voltage is calculated in the same way. Then, the offset voltage is added equally to the original command values ​​Vcmd_a1 and Vcmd_a3, respectively, to calculate VCMD_a1 and VCMD_a3. Finally, the offset voltage is normalized by dividing by 0.5Vdc, and then multiplied by N_max to calculate the final PWM command values ​​(PWM_CMD_a1, PWM_CMD_a3) that can be compared to the triangular carrier wave.

[0215] The dead time block prevents the first switching element (411) and the second switching element (412) from being turned on at the same time, allowing them to operate complementarily, and similarly prevents the third switching element (413) and the fourth switching element (414) from being turned on at the same time, allowing them to operate complementarily.

[0216] Next, FIG. 27 shows the control logic for outputting the switching sequence on the secondary side or the output circuit side.

[0217] Looking specifically at the operation of the secondary side, Vcmd_B indicates a command voltage whose amplitude alternates between ±Vampl_b every half cycle, and the offset voltage (Voffset) is determined by the clamp mode.

[0218] When CM=1, Vcmd_b1 has a value of 0.5Vcmd_B and Vcmd_b3 has a value of -0.5Vcmd_B. The offset voltage is then calculated based on CM_b, Vcmd_b1, and Vcmd_b3 as 0.5*Vo-max(Vcmd_b1,Vcmd_b3). These offset voltages are added equally to the original command values ​​Vcmd_b1 and Vcmd_b3, respectively, to calculate VCMD_b1 and VCMD_b3. VCMD_b1 and VCMD_b3 are normalized by dividing them by Vo, and then multiplied by N_max to output the PWM command voltages (PWM_CMD_b1, PWM_CMD_b3).

[0219] Conversely, when CM=-1, the polarity of Vcmd_b1 and Vcmd_b3 is set to the opposite of when CM=1 (Vcmd_b1=-0.5*Vcmd_B, Vcmd_b3=0.5*Vcmd_B), and the offset voltage is calculated in the same way.The offset voltage is then added equally to the original command values ​​Vcmd_b1 and Vcmd_b3, respectively, to calculate VCMD_b1 and VCMD_b3.Finally, it is normalized by dividing by Vo, and then multiplied by N_max to calculate the final PWM command values ​​(PWM_CMD_b1, PWM_CMD_b3) that can be compared to the triangular carrier wave.

[0220] The dead time block prevents the first switching element (431) and the second switching element (432) from being turned on at the same time, allowing them to operate in a complementary manner, and similarly prevents the third switching element (433) and the fourth switching element (434) from being turned on at the same time, allowing them to operate in a complementary manner.

[0221] An embodiment of the present invention may also be embodied in the form of a recording medium containing computer-executable commands, such as program modules executed by a computer. A computer-readable medium may be any available medium accessible by a computer, including both volatile and nonvolatile media, removable and non-removable media. Computer-readable media may also include computer storage media. Computer storage media includes all volatile and nonvolatile, removable and non-removable media embodied in any method or technology for storing information, such as computer-readable commands, data structures, program modules, or other data.

[0222] Although the method and system of the present invention have been described with reference to particular embodiments, some or all of their components or operations may be implemented using a computer system having a general-purpose hardware architecture.

[0223] The above description of the present invention is for illustrative purposes only, and those skilled in the art will understand that the present invention can be easily modified into other specific forms without changing the technical spirit or essential characteristics of the present invention. Therefore, it should be understood that the above-described embodiments are illustrative in all respects and not limiting. For example, each component described as a single component can be implemented in a distributed form, and similarly, each component described as a distributed form can be implemented in a combined form.

[0224] The scope of the present invention is indicated by the claims that follow rather than by the above detailed description, and all modifications and variations that fall within the meaning and scope of the claims and their equivalents should be construed as being included within the scope of the present invention. [Explanation of symbols]

[0225] 100: Computing equipment 110: Processor 120:Memory 130: Communication module 140: Database

Claims

1. In a simulation system for railway systems on MVDC (Medium-Voltage Direct Current) distribution networks, a computing device storing a simulation program including a converter station model that simulates a converter station included in the MVDC power distribution network and a train running model that simulates the running state of a train that operates by receiving power from the converter station; a converter controller for controlling a DC / DC converter included in the converter station model; and The system includes a Hardware In the Loop Simulation (HILS) device that performs a simulation based on the converter station model, train running model, and converter controller. A simulation system for a railway system, wherein the converter station model and the train running model are executed as software in the HILS device, and the converter controller is connected to the HILS device and driven to control the converter station model.

2. Claim 1: The described simulation program uses the train running model to perform a stream processing train running simulation. The train running model is configured to perform a power simulation by calculating the acceleration of the train based on the tractive force and running resistance or the braking force and running resistance of the train, calculating the speed and position using the calculated acceleration and the time interval of a discrete-time system, performing a state-machine-based stream-type train running calculation using the speed and position, and outputting a notch value and train power consumption, converting the train power consumption into a current source and inputting it into an equivalent model, calculating a coefficient matrix from a state-space equation representing the equivalent model, and outputting a discrete-time system through the calculation of the state-space equation.

3. Claim 2: The train running model described is A railway system simulation system that inputs the speed into a state machine that includes the train's stopped state, reversing state, oncoming state, and braking state, transitions the state of the state machine based on whether the speed has reached the speed limit, and outputs a notch value that matches each state.

4. Claim 2: The train running model described is outputting a tractive force or a braking force corresponding to the speed, and outputting a running resistance corresponding to the speed; A railway system simulation system that calculates the acceleration and power consumption of the train based on the notch value output by the state machine according to the speed, the tractive force or braking force, the running resistance, and the gradient resistance or curve resistance corresponding to the position of the train.

5. Claim 1: The converter station model described uses a series resonant DAB converter as a DC / DC converter, The series resonant DAB converter comprises: an input circuit including a first switching element, a second switching element, a third switching element, and a fourth switching element connected in series according to a half-bridge configuration, a first capacitor connected in parallel to the first switching element and the second switching element, and a second capacitor connected in parallel to the third switching element and the fourth switching element; an output circuit including a first switching element, a second switching element, a third switching element, and a fourth switching element connected according to a full bridge configuration; A railway system simulation system including a resonant circuit and a transformer connected between the input circuit and the output circuit.

6. Claim 1: The converter station model described uses multiple series resonant DAB converters connected in an ISOP (Input-Series-Output-Parallel) structure as DC / DC converters. Each series resonant DAB converter has: The series resonant DAB converter comprises: an input circuit including a first switching element, a second switching element, a third switching element, and a fourth switching element connected in series according to a half-bridge configuration, a first capacitor connected in parallel to the first switching element and the second switching element, and a second capacitor connected in parallel to the third switching element and the fourth switching element; an output circuit including a first switching element, a second switching element, a third switching element, and a fourth switching element connected according to a full bridge configuration; A railway system simulation system including a resonant circuit and a transformer connected between the input circuit and the output circuit.

7. In claim 5 or claim 6, the resonant circuit and the transformer are coupled between a connection node of the first switching element and the second switching element of the input circuit and a connection node of the third switching element and the fourth switching element, the resonant circuit includes a capacitor and an inductor connected in series with each other; one primary terminal of the transformer is connected to the resonant circuit, and the other primary terminal is connected to a connection node of a third switching element and a fourth switching element of the input circuit; A simulation system for a railway system, wherein one terminal of the secondary side of the transformer is connected to a connection node of a first switching element and a second switching element of the output circuit, and the other terminal of the secondary side is connected to a connection node of a third switching element and a fourth switching element of the output circuit.

8. In claim 5 or claim 6, The converter controller includes control logic for applying a first switching sequence to the first and second switching elements of the input circuit in a complementary manner, and for applying a second switching sequence to the third and fourth switching elements in a complementary manner, the first switching sequence is a sequence of a first pulse having a pulse width and a first level amplitude during a reference time (T / 2), a second pulse having a pulse width and a second level amplitude during a time (T / 2-ΔT) obtained by subtracting a predetermined time from the reference time, a third pulse having a pulse width and a first level amplitude during the reference time (T / 2), and a fourth pulse having a pulse width and a second level amplitude during a time (T / 2+ΔT) obtained by adding a predetermined time to the reference time, which are periodically repeated; The second switching sequence periodically repeats a first pulse having a pulse width and a second level amplitude during a reference time (T / 2), a second pulse having a pulse width and a first level amplitude during a time (T / 2+ΔT) obtained by adding a predetermined time to the reference time, a third pulse having a pulse width and a second level amplitude during the reference time (T / 2), and a fourth pulse having a pulse width and a first level amplitude during a time (T / 2-ΔT) obtained by subtracting a predetermined time from the reference time; A simulation system for a railway system, wherein the first level is a high level and the second level is a low level as distinguished from the first level.

9. Simulation method for railway systems on MVDC (Medium-Voltage Direct Current) distribution networks. (a) executing a simulation program including a converter station model simulating a converter station included in the MVDC power distribution network and a train running model simulating the running state of a train running with power supplied from the converter station in a software manner using a Hardware In the Loop Simulation (HILS) device; (b) A method for simulating a railway system, comprising a step of connecting a converter controller that controls a DC / DC converter included in the converter station model to the HILS device and driving the converter controller to control the converter station model.

10. In claim 9, The step (a) described above includes a step of performing a stream processing train running simulation using the train running model, The step of performing the train running simulation includes: (a-1) calculating the acceleration of the train based on the tractive force and running resistance or braking force and running resistance of the train; (a-2) calculating velocity and position using the calculated acceleration and the time interval of the discrete-time system; (a-3) performing a state machine-based stream-based train running calculation using the speed and position, and outputting a notch value and train power consumption; (a-4) converting the train power consumption into a current source and inputting the converted current source into an equivalent model; (a-5) calculating a coefficient matrix from the state space equations representing the equivalent model; (a-6) A method for simulating a railway system, comprising the step of performing a power simulation in a manner of outputting a discrete-time system through calculation of the state space equation.

11. In claim 10, The step (a-3) described is A simulation method for a railway system, which inputs the speed into a state machine including the train's stopped state, reverse state, oncoming state, and braking state, transitions the state of the state machine based on whether the speed has reached the speed limit, and outputs a notch value that matches each state.

12. In claim 10, The step (a-3) described is outputting a tractive force or a braking force corresponding to the speed, and outputting a running resistance corresponding to the speed; A railway system simulation method for calculating the acceleration and power consumption of the train based on the notch value output by a state machine according to the speed, the tractive force or braking force, the running resistance, and the gradient resistance or curve resistance corresponding to the position of the train.

13. In claim 9, The step (a) described above involves running a simulation program in software on a HILS device using the converter station model. The converter station model uses a series resonant DAB converter as a DC / DC converter, The series resonant DAB converter comprises: an input circuit including a first switching element, a second switching element, a third switching element, and a fourth switching element connected in series according to a half-bridge configuration, a first capacitor connected in parallel to the first switching element and the second switching element, and a second capacitor connected in parallel to the third switching element and the fourth switching element; an output circuit including a first switching element, a second switching element, a third switching element and a fourth switching element connected according to a full bridge configuration; A method for simulating a railway system, comprising: a resonant circuit and a transformer connected between the input circuit and the output circuit.

14. In claim 9, The step (a) described above involves running a simulation program in software on a HILS device using the converter station model. The converter station model uses multiple series resonant DAB converters connected in an ISOP (Input-Series-Output-Parallel) structure as DC / DC converters, Each series resonant DAB converter has: The series resonant DAB converter comprises: an input circuit including a first switching element, a second switching element, a third switching element, and a fourth switching element connected in series according to a half-bridge configuration, a first capacitor connected in parallel to the first switching element and the second switching element, and a second capacitor connected in parallel to the third switching element and the fourth switching element; an output circuit including a first switching element, a second switching element, a third switching element and a fourth switching element connected according to a full bridge configuration; A method for simulating a railway system, comprising: a resonant circuit and a transformer connected between the input circuit and the output circuit.

15. In claim 13 or claim 14, The step (a) described above may include connecting one terminal of the transformer to a connection node of the first switching element and the second switching element described above; The other terminal of the transformer is connected to the connection node of the third switching element and the fourth switching element described above. The resonant circuit is connected between a connection node of the first switching element and the second switching element and one terminal of the transformer.

16. In claim 13 or claim 14, The step (b) described is A control method is performed in which a first switching sequence is applied to the first and second switching elements in a complementary manner through the converter controller, and a second switching sequence is applied to the third and fourth switching elements in a complementary manner, the first switching sequence is a sequence of a first pulse having a pulse width and a first level amplitude during a reference time (T / 2), a second pulse having a pulse width and a second level amplitude during a time (T / 2-ΔT) obtained by subtracting a predetermined time from the reference time, a third pulse having a pulse width and a first level amplitude during the reference time (T / 2), and a fourth pulse having a pulse width and a second level amplitude during a time (T / 2+ΔT) obtained by adding a predetermined time to the reference time, which are periodically repeated; The second switching sequence periodically repeats a first pulse having a pulse width and a second level amplitude during a reference time (T / 2), a second pulse having a pulse width and a first level amplitude during a time (T / 2+ΔT) obtained by adding a predetermined time to the reference time, a third pulse having a pulse width and a second level amplitude during the reference time (T / 2), and a fourth pulse having a pulse width and a first level amplitude during a time (T / 2-ΔT) obtained by subtracting a predetermined time from the reference time; A method for simulating a railway system, wherein the first level is a high level and the second level is a low level as distinguished from the first level.

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