Railway converter station connected with MVDC power distribution system and simulation method thereof

Abstract

A simulation system of a railway system for a medium voltage direct current (MVDC) power distribution network according to an embodiment of the present invention comprises: a calculation device storing a simulation program, the simulation program includes: a converter station model that simulates a converter station included in the MVDC power distribution network; and a train travel model that simulates a travel state of a train that is operated by supplying power from the converter station. A converter controller that controls a DC / DC converter included in the converter station model; and a hardware-in-loop simulation (HILS) device, the hardware-in-loop simulation device performing simulation based on the converter station model, a train driving model, and a converter controller, the converter station model and the train driving model being executed in software in the HILS device, the converter controller is connected to the HILS device and is driven to control the converter station model.

Description

Technical Field

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

[0002] Figure 1 An existing DC railway system is shown.

[0003] The usual DC railway system in the country is connected to the AC 22.9kV busbar of the distribution system provided by Korea Electric Power Corporation. This system steps down the AC 22.9kV to AC 1180V through a rectifier transformer, converts it to DC 1620V under no-load conditions using a rectifier such as diode silicon, and supplies it to the railway system.

[0004] However, recently, with the increase in the proportion of new energy and renewable energy connected to the grid, the demand for expanding the capacity of distribution lines has been proposed, but due to civil complaints and other reasons, it is not easy to expand the distribution lines.

[0005] Therefore, research is being conducted to improve the voltage in terms of insulation level by applying a direct current method (rather than an alternating current method) to the power distribution system and to increase the current capacity by eliminating the skin effect.

[0006] Currently, South Korea has three standard voltages: transmission voltages of 765KV, 345KV, and 154KV, and distribution voltages of UHV 22.9KV, low voltage 380V, and 220V. Medium voltage direct current (MVDC) technology is a technology that converts AC power into DC power and then transmits it when transmitting power in the distribution network, or directly provides DC power to users, and is defined as (UHV) DC power distribution within the range of DC above 1500V and below 100KV. Accordingly, the voltage range of MVDC is linked to the 22.9KV distribution system before the transformer on the user side.

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

[0008] Since the DC railway system is connected as a load to the 22.9kV busbar of the distribution system provided by Korea Electric Power Corporation, when MVDC technology is applied to the distribution system, the DC railway system also needs to change the substation as the connection point of the distribution system to the MVDC connection infrastructure. That is, it is necessary to develop DC railway commutation based on DC / DC converters that can convert the high-voltage DC voltage of the Korea Electric Power distribution system into the railway operating voltage (3000V, 1500V, 750V), and can perform active voltage control based on the converter to ensure operational flexibility.

[0009] Therefore, the present invention proposes a method for configuring a railway converter station required for connecting a railway system to an MVDC distribution network and a virtual simulation method for implementing a train as a core component of a mobile load in a software environment using only controller hardware in order to pre-verify the converter station without field testing.

[0011] 2. The need to improve simulation algorithms

[0012] In addition, in the process of simulating DC railway converter stations, the algorithm also needs to be improved. That is, in order to realize virtual operation based on real-time simulation without actual railway vehicles, real-time performance must be guaranteed, and power simulation technology based on fast calculation is needed to simulate the DC railway system including vehicles as mobile loads.

[0013] Looking at the existing power simulation technology, the following batch processing (batch processing) based train operation simulation is used: based on the traction / braking force curve created using the design performance values ​​of the electric motor used in the design of the railway vehicle, all vehicle data, driving data and line data (curve, gradient and station location information) are received as input, and batch operations are performed on a given total line in the form of time accumulation, distance accumulation or speed accumulation.

[0014] A common method using the prior art is as follows: re-receive the results of the batch vehicle driving simulation (speed curve and power curve) as input, and use a programming or simulation tool to perform an electrical simulation of the current / voltage of each node.

[0015] That is, the biggest feature of the existing technology is sequential data processing. Sequential data processing refers to a method of collecting bounded data in a certain period of time (in units of routes or in units of hours or minutes) and processing them sequentially at a certain point in time.

[0016] Figure 2 is a flowchart showing a conventional power simulation process.

[0017] like Figure 2 As shown, the entire power simulation process is mainly divided into a train driving operation process and a power simulation process, and is operated as a separate operation algorithm.

[0018] First, when the train operation operation starts, all the train data input information such as vehicle data, driving data, route data (curves, gradients, station location information) is received as input for parameterization, and the train operation pre-batch processing is performed in advance. The train operation pre-batch processing is the process of using the above train data input information to calculate the reverse-coasting transition point and the coasting-braking transition point in advance.

[0019] First, the reverse-sliding conversion point is appropriately selected considering the train driving requirements and environment, but the section with a short distance between stations (the starting station and the terminal station, that is, the next target station is a group) is not selected separately. In addition, for the sliding-braking point, the position of each station (that is, the starting and ending point of the train) is considered and the traction curve is considered. The speed trajectory of the train is obtained by forward driving, and the characteristics of the braking force curve are considered. The speed trajectory of the train is obtained by reverse driving, and the sliding-braking conversion point is obtained by the intersection of these two trajectories.

[0020] Next, the train operation calculation is started based on the calculated results of the train operation pre-batch processing. First, the acceleration is calculated considering the traction or braking force and the running resistance, and the corresponding time and value are stored in the form of a table / array. Then, the speed and position are calculated using the acceleration and the preset unit time (sampling time), and stored in the form of a lookup table or array. Then, these values ​​are used to calculate and store the power consumption value. At this time, the power consumption can be calculated based on the product of the traction and the speed or the product of the braking force and the speed.

[0021] In addition, if the switching between reverse / coast / brake modes is performed by referring to the lookup table derived from the train operation pre-batch processing, the mode is switched, and the traction force in reverse is set to a positive number, the traction force in coasting is set to 0, and the traction force in braking is set to a negative number, and recalculated. If it is not the case above, the process is repeated. If the interruption condition or the current position value of the train is exactly the same as the station value, the algorithm ends.

[0022] Next, the power simulation process as a separately prepared algorithm is executed. The power simulation includes the case where a simulation tool that is separately modeled and driven is used and the case where a solution is obtained by solving differential equations through numerical analysis. First, the initial values ​​and conditions are set, and the values ​​of the power consumption lookup table (array) previously derived during the train driving operation are read and parameterized, or read at each accumulated time. Then, the current of the train power consumption is converted and input into an equivalent model (including a mathematical model) represented in the form of a current circle or impedance. Then, the coefficient matrix is ​​calculated by constructing a state space equation. Finally, through the state space equation calculation, it is derived, stored and ended in the form of voltage, current and power values ​​as the output of a continuous or discrete time system. In summary, the prior art has the characteristics of switching between three modes (states): reversing, coasting and braking, which all require pre-calculations for each section between stations.

[0023] This existing batch processing or batch mode train running simulation method has the problem of difficulty in viewing data in real time. In other words, in the batch processing mode, other tasks, namely the power simulation process, cannot be performed until the train running calculation process is completed. In particular, when this processing mode is used for real-time railway power simulation, it may affect the accuracy and input data size.

[0024] On the other hand, when batch processing is used for real-time simulation, the train running simulation results using batch processing are temporarily stored in a cache memory before simulation and then used in real-time simulation. Therefore, in the case of big data, storage and utilization are limited, and high-speed computing of real-time simulation is also limited.

[0026] 3. Necessity of improving DC / DC converters in converter stations

[0027] 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 that require the reuse of renewable power. The DAB converter with a symmetrical dual-bridge switch stack with a series inductor in the middle has the advantages of simple structure, ZVS conduction characteristics of all switches on the primary and secondary sides, and natural direction switching.

[0028] However, a general DAB converter tends to lose the ZVS characteristic when the load is light, and when the load increases, there is a problem of increased conduction loss due to the presence of reactive power components in the circuit.

[0029] To solve this problem, a series resonant DAB converter (SRDAB) with a series inductor and a tuned resonant capacitor added is proposed. Like the existing DAB converter, SRDAB has many advantages, such as being able to easily adjust the power size and flow rate by adjusting the phase difference between the two bridges, and maintaining ZVS characteristics over a wide range.

[0030] However, the resonant / non-resonant DAB known so far are all based on a general full bridge (FB) or half bridge (HB), and the switching voltage that can be handled with a 2-level-based topology is low (below a few hundred volts). In order to switch high voltages above DC 1500V (such as in railway vehicles), a modular structure with an ISOP (input-series-output-parallel) structure is required, which stacks these DAB converters in series and connects the outputs in parallel. However, this structure requires a large number of switching elements and increases the number of active / passive elements in the structure, such as adding passive elements for each unit module.

[0031] Figure 3 shows a typical 2-level FB based SRDAB converter, Figure 4 A conventional SRDAB converter is shown connected into an ISOP configuration.

[0032] because Figure 3 The converter in is based on 2 levels, so the switching voltage withstand voltage of one switch is Vdc, which is the input source voltage. The converter circuit shown consists of 4 input side switches, 4 output side switches, resonant inductor Lr, resonant capacitor Cr, transformer with a turns ratio of n:1, input / output filter capacitors and load resistor R.

[0033] As described above, since the input terminal is configured in a 2-level FB form, in order to be applied to a power conversion system with a high input source voltage such as a railway vehicle, it is necessary to have an ISOP (input-series-output-parallel) structure.

[0034] like Figure 4 As shown, an ISOP structure can be used, where Figure 3 Two unit converters are stacked in series on the input side, and two unit converters are stacked in parallel on the output side. The entire circuit consists of 8 input-side switches, 8 output-side switches, 4 resonant elements (inductors, capacitors), 2 transformers, 2 input capacitors, and 1 output capacitor. When configuring this ISOP, it can be seen that the number of input-side switches or resonant elements doubles. In addition, it can be seen that since the input is configured in series, a separate control device is required to control the change of the neutral point of the capacitor. [Prior art literature] [Patent Literature]

[0035] Korean Patent No. 10-2213266 (Invention Title: Arrangement Method and System of Regenerative Braking Energy Recovery Device for Urban Rail Transit) Summary of the invention [Issues to be resolved]

[0036] An object of the present invention is to provide a railway converter station connected to an MVDC power distribution system for a DC railway system and a simulation system thereof.

[0037] Furthermore, another object of the present invention is to provide a train travel simulation device and method that can be used in a railway converter station connected to an MVDC power distribution system used in a DC railway system.

[0038] Furthermore, another object of the present invention is to provide a series resonant DAB converter and a control method thereof that can be used in a railway converter station connected to an MVDC power distribution system used in a DC railway system.

[0039] However, the technical problems that this embodiment aims to solve are not limited to the above-mentioned technical problems, and there may be other technical problems.

Solution to the problem

[0040] As a technical solution to the above technical problems, a simulation system for a railway system of a medium voltage direct current (MVDC) distribution network according to one aspect of the present invention includes: a computing device storing a simulation program, the simulation program including: a converter station model simulating a converter station included in the MVDC distribution network and a train travel model simulating the travel state of a train running with power supplied from the converter station; a converter controller, the converter controller controlling a DC / DC converter included in the converter station model; and a hardware-in-the-loop simulation (HILS) device, the hardware-in-the-loop simulation device performing simulation based on the converter station model, the train travel model and the converter controller, the converter station model and the train drive model being executed in the HILS device in software, the converter controller being connected to the HILS device and being driven to control the converter station model.

[0041] In addition, in a simulation method of a railway system for a medium voltage direct current (MVDC) distribution network according to another aspect of the present invention, the simulation method of the railway system includes the following steps: executing a simulation program by software on a high-in-the-loop (HILS) device, the simulation program including: a converter station model simulating a converter station included in the MVDC distribution network and a train travel model simulating a travel state of a train running with power supplied from the converter station; and connecting a converter controller for controlling a DC / DC converter included in the converter station model to the HILS device and driving it to control the converter station model. [Effects of the invention]

[0042] According to the above-mentioned solution to the problem of the present invention, by proposing a configuration and method of verifying the HILS of a railway system using an actual controller, the operation algorithm can be verified in advance without field testing or final product of the railway system. If the virtual simulation results obtained in this way are analyzed and used for actual vehicle production and performance testing, efficient optimization can be achieved.

[0043] In addition, by applying the present invention, it is possible to easily establish a system operation plan by deploying a large number of railway vehicles with similar driving modes. In addition, time synchronization with the power simulation environment can be performed without considering the time interval of the train operation simulation. In addition, the existing train operation and power simulation technology simulates the operation of multiple vehicles by receiving a train operation diagram as input, but through the present invention, a train operation diagram can be output / generated. In addition, since the input data itself can be small enough to be variable, the train drive high-speed computing module based on the state machine stream processing method of the present invention can be created and installed in the propulsion inverter controller to configure it to be the same as the actual railway operation environment. In addition, since it is driven based on a state machine, it has high stability. In other words, a train can only have one state at a time, the process must be carried out strictly according to the design, and the state can only be changed through prescribed events.

[0044] In addition, the configuration of the series resonant DAB converter proposed according to the present invention has the following effects under the same internal voltage condition compared with the existing FB: the number of active components and passive components of the primary side bridge is reduced by half. In addition, a special switching sequence is required to implement the proposed method, but the present invention solves this problem by proposing a special sequence for neutral point balance control using a voltage amplitude modulation switching mode (rather than the existing phase shift method). BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 An existing DC railway system is shown.

[0046] Figure 2 is a flowchart showing a conventional power simulation process.

[0047] Figure 3 A conventional 2-level FB based SRDAB converter is shown.

[0048] Figure 4 Connect conventional SRDAB converters into an ISOP configuration.

[0049] Figure 5 is a diagram showing a configuration of a railway system for an MVDC power distribution network according to an embodiment of the present invention.

[0050] Figure 6 is a block diagram showing a configuration of a simulation system of a railway system for an MVDC distribution network according to an embodiment of the present invention.

[0051] Figure 7 is a block diagram showing a configuration of a computing device included in a simulation system according to an embodiment of the present invention.

[0052] Figure 8Detailed description is a flowchart showing the operation of a train driving model in a stream processing manner according to an embodiment of the present invention.

[0053] Figures 9 to 12 It is a diagram for explaining a train travel calculation process based on a state machine according to an embodiment of the present invention.

[0054] Fig.13 2 is a diagram showing calculation results of a train travel model according to an embodiment of the present invention.

[0055] Fig.14 is an example of an equivalent model of a railway system used in a train travel model according to an embodiment of the present invention.

[0056] Fig.15 The analysis process of the railway system equivalent model used in the train travel model according to the embodiment of the present invention is shown.

[0057] Fig.16 A series resonant DAB converter applied to a converter station model according to an embodiment of the present invention is shown.

[0058] Fig.17 The ISOP connection state of the series resonant DAB converter applied to the converter station model according to the embodiment of the present invention is shown.

[0059] Fig.18 is a diagram for explaining the operation of the series resonance type DAB converter according to the embodiment of the present invention.

[0060] Fig.19 FIG. 4 shows the primary-side / secondary-side bridge arm voltage waveforms of a series resonant DAB converter according to an embodiment of the present invention.

[0061] Fig. 20 The case where a switching sequence in a general phase shift manner is applied to the present invention is shown.

[0062] Fig.21 and 22 The switching sequence of the pulse size modulation method for driving a series resonant DAB converter according to the present invention is shown.

[0063] Fig.23 The relationship between the carrier and the PWM command value in the driving method of the series resonance type DAB converter according to the embodiment of the present invention is shown.

[0064] Fig.24 A process of selecting a command mode (CM) in a driving method of a series resonance type DAB converter according to an embodiment of the present invention is shown.

[0065] Figure 25 to Figure 27is a block diagram of a control logic for outputting a control signal of a series resonant DAB converter according to an embodiment of the present invention. DETAILED DESCRIPTION

[0066] The embodiments of the present application will be described in detail below in conjunction with the accompanying drawings so that those skilled in the art can easily implement them. However, the present application can be implemented in various forms and is not limited to the embodiments described herein. In order to clearly describe the present application in the accompanying drawings, parts not related to the description are omitted, and similar parts are given similar reference numerals throughout the specification.

[0067] Throughout the specification of the present application, when a component is referred to as being “connected” to another component, this includes not only the case where they are “directly connected” but also the case where they are “electrically connected” with other elements interposed therebetween.

[0068] Throughout the specification of the present application, when it is said that a member is located “on” another member, this includes not only a case where one member is in contact with another member but also a case where other members exist between the two members.

[0069] Throughout the specification of the present application, when a component "includes" a certain component, it means that it may also include other components rather than exclude other components, unless explicitly stated to the contrary. As used throughout the specification, the degree terms "about", "substantially" and the like are used to indicate being equal to or close to the value when given the manufacturing and material tolerances inherent in the mentioned meaning, and are used to prevent unscrupulous infringers from taking unfair advantage of the disclosure that mentions precise or absolute values ​​for the purpose of facilitating the understanding of the present application. As used throughout the specification, the term "to step" or "step of to" does not mean "step for to".

[0070] In this specification, "part" includes a unit implemented by hardware or software, and a unit implemented using both. One unit can be implemented using more than two hardwares, or more than two units can be implemented using one hardware. In addition, "part" is not limited to software or hardware, and "part" can be configured to reside in an addressable storage medium or can be configured to reproduce one or more processors. Therefore, as an example, "part" includes: components such as software components, object-oriented software components, class components and task components, processes, functions, properties, procedures, subroutines and program code segments, drivers, firmware, microcodes, circuits, data, databases, data structures, tables, arrays and variables. The functions provided in components and "parts" can be combined into a smaller number of components and "parts", or can be further divided into additional components and "parts".

[0071] Hereinafter, the preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings and the contents described below. However, the present invention is not limited to the embodiments described herein and can be implemented in other forms. Throughout the specification, the same reference numerals refer to the same components.

[0072] Figure 5 is a diagram showing a configuration of a railway system for an MVDC power distribution network according to an embodiment of the present invention.

[0073] exist Figure 5 In the figure, the left side shows an existing DC railway system, and the right side shows a DC railway system according to the present invention.

[0074] The DC railway system according to the present invention converts the DC voltage of the power distribution system into the railway operating voltage through a DC railway converter station based on a DC / DC converter. The DC railway converter station adopts a DC / DC converter capable of active converter control.

[0075] In addition, in order to test the newly developed DC railway converter stations, field testing using actual railway infrastructure is required during the development of power facilities. If an accident occurs during the testing process, there is a significant risk of train operation interruption and casualties, but due to the difficulty of repeated testing, there is a problem of inefficiency.

[0076] In addition, confirming and optimizing system performance using actual railway vehicles requires a lot of time and financial support. In addition, there are limitations on various tests and repeated tests depending on the test bench environment.

[0077] Therefore, in order to safely repeat tests and analyses to confirm the performance of new systems (electrical equipment), after building a HILS platform based on laboratory-scale real-time simulators and controller hardware, virtual operation technology capable of evaluating the operating efficiency of power facilities needs to be developed according to the purpose of power equipment utilization.

[0078] That is, the dc / dc converter controller of the converter station is implemented in hardware, and the other parts are implemented in a SW-based virtual environment to achieve virtual operation.

[0079] In order to realize virtual operation based on real-time simulation without actual railway vehicles, real-time performance must be guaranteed, and power simulation technology based on fast calculations is needed to simulate the DC railway system including vehicles as mobile loads.

[0080] Figure 6 is a block diagram showing a configuration of a simulation system of a railway system for an MVDC distribution network according to an embodiment of the present invention.

[0081] The simulation system 10 shown includes a computing device 100 , a HILS device 200 , and a converter controller 300 .

[0082] The computing device 100 stores a simulation program including a converter station model for simulating a converter station included in an MVDC power distribution network and a train travel model for simulating a travel state of a train running with power supplied from the converter station.

[0083] The hardware-in-the-loop simulation (HILS) device 200 is a device that allows various simulations to be performed during the development process of a real-time embedded system. The HILS device 200 performs simulations by mathematically modeling the operating environment or system of the device as a test object. The HILS device 200 itself corresponds to the prior art, and in the present invention, the HILS device 200 is used to simulate a converter station. For the HILS device 200, it is necessary to build a real-time simulation environment because the converter controller 300, which is an actual hardware controller of the railway system as a test object, must operate under the illusion that it is in a real environment.

[0084] The converter controller 300 includes a processor equipped with a control logic for performing control on a DC / DC converter, which is a core component of a converter station as a test object. The converter controller 300 is connected to a real-time simulator IO (e.g., a DI (PWM) card) of the HILS device 200 and performs a control operation of the DC / DC converter. For example, a processor such as an MCU or an FPGA may be included in the converter controller 300, and a specific configuration of the control logic will be described later.

[0085] Figure 7 is a block diagram showing a configuration of a computing device included in a simulation system according to an embodiment of the present invention.

[0086] The computing device 100 includes a processor 110 and a memory 120 , and may further include a communication module 130 and a database 140 .

[0087] The memory 120 records the simulation program. The simulation program includes: a converter station model for simulating a converter station included in the MVDC power distribution network and a train travel model for simulating the travel state of a train running with power supplied from the converter station.

[0088] In addition, the memory 120 performs a function of temporarily or permanently storing data processed by the processor 110. Here, the memory 120 may include a volatile storage medium or a nonvolatile storage medium, but the scope of the present invention is not limited thereto.

[0089] The processor 110 executes the simulation program stored in the memory 120. In addition, the processor 110 performs various control operations for running the computing device 100. The processor 110 may refer to, for example, a data processing device built into hardware, which has a physical structured circuit to execute functions expressed as codes or instructions included in the program. Examples of data processing devices built into hardware include processing devices such as 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 device (GPU: Graphics Processing Unit), etc., but the scope of the present invention is not limited thereto.

[0090] The communication module 130 may include one or more components that transmit and receive various types of data with an external computing device. The communication module 130 may be a device including the hardware and software necessary to transmit and receive signals such as control signals or data signals through a wired or wireless connection with other network devices.

[0091] The database 140 may manage various data required to execute the simulation program.

[0092] Now, the detailed structure of the simulation program is described.

[0093] As described above, the simulation program includes a converter station model and a train travel model. According to a user's request, the train travel model and the converter station model are uploaded to the HILS device 200, and the train travel model and the converter station model are respectively executed. When the train travel model is executed, the train travel simulation program runs, and when the converter station model is executed, the converter station simulation program runs. In addition, assuming that a converter station model is provided in the DC railway system, the train travel simulation is performed according to the train travel model.

[0094] Offline simulation requires dozens of hours of calculation to achieve a simulation time of at most a few minutes. On the other hand, real-time simulation using a real-time simulator has an execution time that is the same as the actual time (1 second in the simulation is the same as 1 second in reality), and can simulate for dozens of minutes to several hours, so it is very useful for pre-verification.

[0096] 1. Composition of train driving simulation program

[0097] The train operation model is implemented as a mobile load in the real-time simulator according to the train operation logic, and power simulation technology based on fast calculation is needed to simulate the virtual operation of the DC railway system.

[0098] First, considering the accuracy of the train travel model, when the simulation results show that the operation interval (Ttps) is about 1 second, which is very long compared with the response of the power system (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 in the main control variable. Therefore, the difficulty of solving the problem of the entire power system increases, depending on the relationship between the operation interval (Ttps), the time step (Ts) of the discrete time system, and the control time step (Tc), the stiffness of the problem of finding a solution for the entire power system increases, so depending on the size of the operation interval (Ttps), numerical instability may eventually occur, and the robustness of the results obtained by numerical analysis may also be reduced.

[0099] In addition, if the operation interval (Ttps) is set small in order to improve accuracy in terms of input data size, the data size of the train operation simulation results in batch processing will be very large. Large data is stored sequentially in the form of text files, then re-divided or batch-read (input), and processed again for power simulation, so the calculation efficiency may be reduced.

[0100] To solve this problem, when the stream processing method that is a feature of the present invention is applied, the time step can be reduced to the minimum time step level (below hundreds of microseconds) that can ensure the real-time performance of the entire power system (including the train driving model). In order to apply the stream processing method to the train driving model, the concept of a state machine is introduced, which can solve the above-mentioned input data size problem and accuracy problem at the same time.

[0101] Figure 8 Detailed description is a flowchart showing the operation of a train driving model in a stream processing manner according to an embodiment of the present invention.

[0102] First, the initial value x(0) and input value u(t) of the system are set (S810).

[0103] At this time, x(0) is the initial value of the system, including the initial speed (0km / h), initial position (0km), initial train torque (0kN), initial acceleration (0km / h / s) and initial consumption / regeneration power (0kW), etc. u(t) represents the power value of the train that changes with time, and x(t) represents the system state variable that changes with time, representing speed, position, acceleration, train torque, power consumption or regeneration power. u(t) is determined by the train driving calculation step (S820), and x(t) is determined by the power simulation step (S830).

[0104] Next, train travel calculation is performed according to the stream processing method based on the state machine (S820).

[0105] More specifically, the following steps may be included: a step of calculating acceleration by taking into account traction and running resistance or braking force and running resistance (S822); a step of calculating speed and position using acceleration and unit time (time interval (Ts) of discrete time system) (S824); and a step of performing train running operations in a state machine-based stream processing manner to return the final value gear position and train power consumption value (S826).

[0106] In the step of calculating the acceleration (S822), as follows Fig.12 As shown, acceleration is calculated using the traction, braking force and running resistance determined according to the speed and the gear value determined by the train operation state machine. The gear value is used to select between the traction curve and the braking force curve. Once the traction and braking force curves are selected, the current train torque is converted by matching the current speed to one of the two curves, and the acceleration / deceleration is calculated by dividing the converted torque by the mass of the train.

[0107] The step of calculating the speed and position (S824) uses acceleration and unit time (time interval (Ts) of discrete time system). The unit time (time interval) is used to calculate the next calculated value (speed, position, acceleration, etc.) based on the current calculated value (speed, position, acceleration, etc.). For example, when calculating the next speed based on the current speed, the form of v=v0+a*Ts can be adopted.

[0108] The gear value output in step S826 can be returned to the previous step (S822), and the train power consumption value can be returned to step S832.

[0109] Then, while returning the gear value and the train power consumption value, the train running operation is repeatedly performed, and the train power consumption power value outputted thereby is input into the power simulation step (S830). For reference, the gear is a controller used by engineers to adjust the speed during the operation of the train, and refers to the gear state value (e.g., P4~, P1, N, B1~B7) when the train is running.

[0110] 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).

[0111] More specifically, the following steps may be included: a step of dividing the train power consumption by the voltage and inputting the result into an equivalent model in the form of a current source (S832); a step of configuring the entire power system including the corresponding current source (train load) into a state space equation and calculating the coefficient matrix (S834); and a step of deriving the discrete time system output through the state space equation calculation and starting the power simulation again (S836).

[0112] In addition, the train travel operation (S820) and the power simulation (S830) can be repeated in parallel until the interruption condition (S840) is met, and when the interruption condition is met, the result of each operation is saved and ended. One of the features of the present invention is that the simulation can be performed without interruption, and when the user receives a request to interrupt the entire simulation, it is determined that the interruption condition is met.

[0113] In addition, the train travel calculation process (S820) based on the stream processing method of the above-mentioned state machine will be understood in more detail.

[0114] Figures 9 to 12 It is a diagram for explaining a train travel calculation process based on a state machine according to an embodiment of the present invention.

[0115] First, in the train travel calculation process (S826), the state information is confirmed based on the speed calculated in the previous step (S824), and the gear value corresponding thereto is output.

[0116] like Fig. 9 As shown, the state machine has four states, including a stop state, a reverse state, a coasting state, and a braking state. First, the stop state portion is entered through an entry point. This does not apply initially, but after a certain stop time, the state is changed to a reverse state portion. Then, the state machine determines whether the calculated speed satisfies the speed limit reaching condition of the following mathematical formula 1, and if the speed limit reaching condition is satisfied, it is changed to a coasting state portion.

[0117] [Mathematical formula 1]

[0118] VV LIM <∈

[0119] That is, it is determined whether the difference between the current driving speed (V) and the speed limit (VLIM) is less than a threshold value, and if the condition is satisfied, the coasting state is entered. In this case, the entry point is the 0 gear (N) state. However, the reverse state portion can suppress excessive notch control and reduce the sensitivity of state transition by providing a speed dead zone (δ) as shown in Mathematical Formula 2 for sawtooth control.

[0120] [Mathematical formula 2]

[0121] VV LIM <∈+δ

[0122] That is, the state machine includes the parking state, reversing state, coasting state and braking state of the train, and changes the state of the state machine according to whether the speed reaches the speed limit, and outputs the gear value matching each state.

[0123] Fig.10(a), (b) and (c) show the state machine diagram of the Mascone gear in the reverse, coasting and braking states, respectively. In the reverse state, if equation 1 is satisfied, the value is 1, if not satisfied, the value is 0, when it is 1, the state transition occurs in the direction of increasing speed, when it is 0, the state transition occurs in the direction of decreasing speed. At this time, the arbitrary value ε can decrease in the counterclockwise direction of the reference value.

[0124] like Fig.10 (b), in the case of the coasting state, if the mathematical formula 2 is satisfied, the value is 1, and if it is not satisfied, the value is 0. When it is 1, the state transition occurs in the direction of increasing speed, and when it is 0, the state transition occurs in the direction of decreasing speed. At this time, the arbitrary value ε can decrease in the counterclockwise direction relative to the reference value.

[0125] like Fig.10 (c), in the case of the braking state, first calculate the target driving time for one section when driving at a constant speed and the braking point when braking with maximum torque at the current driving point, if the arrival condition is met, a state transition occurs, and the entry point is set to the gear position that handles the maximum braking force of B7. In the case of the stop state, when the speed = 0, a state transition occurs, at which time, the start count is the same as the stop time, and the current station and the next station move one section at a time.

[0126] by Fig.11 Take the case of as an example, when deriving the train running speed curve, a speed limit is set for each part, and when the speed limit conditions such as Mathematical Formula 1 and Mathematical Formula 2 are met, the state is changed. That is, when starting from station 1, starting from the gear (P4) with the largest traction force, when the first speed limit (speed limit n) is reached and Mathematical Formula 1 or Formula 2 is met, it is changed to the next state (P3), and when the speed continues to increase and reaches the maximum speed limit (speed limit 1), the state is changed to the gear (N) to have a coasting state. Thereafter, when the speed drops below the speed limit, the state is changed to a gear (B1) with braking force, and the state transition in the braking state is repeated to brake at the precise position of station 2 as the final station. In this way, the operation of the train can be calculated only by state transition, which is characterized in that the operation of the train can be calculated without prior estimation of the braking point and other calculations.

[0127] In addition, the embodiment can be modified by objectifying the driver's mode and reflecting the gear control sensitivity element of the train in the train driving state machine. As a result, a train driving operation closer to reality can be performed, and by giving randomness to the train operation, a random optimal efficiency operation element can be given in the system operation of future power simulation (power system numerical calculation). In particular, in the form of existing batch processing (batch processing) train operation simulation, through extreme driving controls of P4 gear (reverse), 0 gear (coasting), B7 (braking), the results can be distinguished from those that show deterministic but somewhat unrealistic driving forms (electric load models).

[0128] In addition, for lines with many speed limit changes, the driver's speed limit recognition condition can be reflected in the train travel state machine. In the train travel calculation, there may be a situation where the speed limit changes suddenly. For example, a train with a speed limit of 80 km / h and running at 70 km / h suddenly encounters a speed limit of 50 km / h. Even if it accelerates quickly, the calculation result may exceed the speed limit. To solve this problem, the speed limit-distance table can be changed in advance, reflected in the state machine diagram, and applied by transitioning to the braking state at a specific distance to reduce the speed.

[0129] Fig.12 An example of an algorithm for calculating train power consumption during train travel calculation is shown.

[0130] In order to calculate the train power consumption, the train travel model calculates acceleration / deceleration and power consumption through the acceleration / deceleration calculation block and the power consumption calculation block. 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 driving resistance calculation block, the output of the gradient resistance search block, and the output of the curve resistance search block.

[0131] First, the traction force lookup block or the braking force lookup block stores information about the traction force or braking force that is pre-matched and stored according to the speed value of the vehicle. Therefore, when the speed value is input, the traction force or braking force matched therewith is output. Then, the traction force and the braking force are calculated considering the gear value calculated in the previous step (S826).

[0132] Then, the running resistance calculation block inputs the speed value into a preset mathematical formula and outputs the running resistance.

[0133] In addition, the gradient resistance browsing block or the curve resistance browsing block stores information about the gradient resistance and the curve resistance that are pre-matched and stored according to the position, respectively. Therefore, when the position information of the vehicle is input, the gradient resistance or the curve resistance matched therewith is output. At this time, the position information can be calculated based on the speed and travel time calculated in the previous step (S824), or the position information can be confirmed by GPS, etc.

[0134] Based on the information collected as described above, the acceleration / deceleration calculation block and the power consumption calculation block each calculate acceleration or deceleration and power consumption according to a preset mathematical formula and output them. For example, acceleration / deceleration can be calculated by a=F / m (a is acceleration or deceleration, F is traction or braking force, and m is the mass of the train). In addition, power consumption (regenerative power) can be calculated by P=Fv (P is power consumption or regenerative power. F is traction or braking force. V is the current speed of the train).

[0135] Through the above process, when the operation of a section is completed, the route information is updated, the upward operation is completed, and the upward vehicle position calculation block is switched to the downward vehicle position calculation block to continue the calculation.

[0136] Fig.13 2 is a diagram showing calculation results of a train travel model according to an embodiment of the present invention.

[0137] Fig.13 (a) shows the output of the gear value calculated by the state machine along the time axis.

[0138] Fig.13 (b) shows the vehicle speed calculation result along the time axis.

[0139] Fig.13 (c) shows the vehicle position along the time axis.

[0140] Fig.13 (d) shows the calculation results of train power consumption along the time axis.

[0141] Next, a process of performing power simulation using the state-space equation (S830) will be understood.

[0142] Fig.14 is an example of an equivalent model of a railway system used in a train travel model according to an embodiment of the present invention.

[0143] (a) shows a single-way vehicle moving load model, (b) shows an impedance parallel configuration as a multi-way vehicle moving load model, (c) shows an impedance series configuration as a multi-way vehicle moving load model, and (d) shows the rearrangement and alignment of the multi-way vehicle moving load model.

[0144] The form without switches can be derived starting from the basic single-trip train moving load model. First, when an impedance is configured in parallel with the same impedance, it becomes the product of N impedance values ​​multiplied together. And since the vehicle load (current source) is also connected to the same node, it can be configured as a parallel current source. By rearranging and aligning, as shown in (d), the train operation diagram can be changed to a form that is easy to apply.

[0145] Fig.15 The analysis process of the railway system equivalent model used in the train travel model according to the embodiment of the present invention is shown.

[0146] exist Fig.14 In the multi-pass train moving load model shown in (d), the model can be divided for each element. In each figure, the magnitude of each resistance is the same, but since the running time interval of each train is different, the change pattern may also be different.

[0147] (a) shows a parallel configuration applying railway system model decomposition, (b) shows a serial configuration applying railway vehicle model decomposition, and (c) shows a system decomposition manner using a model simplification method.

[0148] This equivalent model can be solved by expressing it as a state-space equation.

[0149] For example, matrices and vectors of the following form can be derived.

[0150]

[0151] At this time, 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. In order to perform real-time operations, the simulator must calculate in advance to ensure that the scale of the cache memory is 274 times the level, making memory storage impossible, and even if the number of switch contacts is reduced, it is impossible to perform simulation with a time sampling of about 50μs.

[0152]

[0153] However, when the method of the present invention is used, the capacity stored in the cache memory before real-time operation is 393.626Mb. The entire operation group can be divided into 67 groups, most of which are groups consisting of inputs and outputs only, and the rest are 3 substations, each of which consists of 28 states, 35 inputs, 20 outputs and 12 switches. For reference, these 12 switches all correspond to 12 pulse diodes, and the diodes are also classified as switches and included in the operation. However, in the end, the calculation scale pre-calculated before real-time simulation is greatly reduced to 212*3 times, rather than twice the sum of 236 state space matrix elements. Therefore, when performing real-time simulation, real-time performance can be guaranteed by reducing the amount of calculation required for the input and output of the system model stored in the cache memory in the same time interval. However, the number of 12 diodes or switches used in a substation may vary depending on the type of substation. For example, in the case of a bidirectional converter thyristor converter, 24 thyristors are used in a substation.

[0155] 2. Configuration of converter station simulation program

[0156] The DC / DC converter of the converter station model consists of switching elements, inductors, capacitors, etc., and is configured using the component models provided by the real-time simulator. The DC / DC converter that provides the power required for train operation at the converter station can be configured as follows.

[0157] The configuration of the DC / DC converter can be classified according to whether the distribution system is a two-wire or three-wire system. If the distribution system has a two-wire system, it consists of a + pole and a - pole, and according to the example, if the distribution system voltage is connected to ±20KV, the input of the converter station DC / DC converter can be configured to be 40KV. In addition, the output is output at the railway operating voltage of 3000V / 1500V / 750V. At this time, assuming that the unit capacity of a converter station is 2MW, depending on the time interval (schedule) or capacity of the running vehicles, considering the capacity at the maximum, it may be necessary to add two or three converter stations in parallel. In this way, when adding converter stations in parallel, balance control within the converter station may be required.

[0158] If the distribution system is a three-wire system, it consists of a + pole, a - pole and a neutral line, and according to the example, if the distribution system voltage is connected to ±20KV, the DC / DC converter of the converter station can be composed of a 20KV converter with an input consisting of a + pole and a neutral line and another 20KV converter with an input consisting of a - pole and a neutral line. If the topology of the converter is the same as the two-wire case, two DC / DC converters of 1MW are required to meet a unit capacity of 2MW of the converter station.

[0159] In addition, depending on the time interval (schedule) or capacity of the running vehicles, it may be necessary to add two or three converter stations in parallel, taking into account the capacity at the maximum. Even if the converter stations are added in parallel, the overall balance can be maintained because each converter performs its own balance control. This balance control selects a voltage as a reference on the serial configuration side, and performs PI control to eliminate the error between the reference voltage and the actual voltage measured, and a control logic of a balanced form can be performed by adjusting the amount of power (P). Preferably, the topology design of the DC / DC converter takes into account the following railway characteristics.

[0160] - Considering a wide range of load variations from light to medium loads (vehicle configuration, driving interval / speed, acceleration / deceleration, etc.) (maintaining high efficiency over a wide load range)

[0161] - Consider large capacity mobile loads (approximately 1MW per vehicle)

[0162] - Consider regenerative energy generation (consider bidirectional power flow)

[0163] - Differentiated from the Korean power system by adopting an insulation type

[0164] -Ensure control stability through balance control

[0165] Fig.16 The series resonant DAB converter applied to the converter station model according to the embodiment of the present invention is shown. Fig.17 The ISOP connection state of the series resonance type DAB display converter applied to the converter station model according to the embodiment of the present invention is shown.

[0166] First, refer to Fig.16 , the structure of the series resonant DAB converter based on two series HBs as a DC / DC converter can be confirmed.

[0167] The series resonant DAB converter 400 includes an input circuit 410, an output circuit 430, a transformer 440, and a resonant circuit 450. At this time, the series resonant DAB converter 400 includes not only elements in the form of actual circuits but also elements implemented in the form of software constituting a DC / DC converter in a converter station model.

[0168] 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, and 414 connected in series to the power supply according to a half-bridge structure. Also, 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.

[0169] The resonant circuit 450 and the 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) of the first switching element 411 and the second switching element 412 and a connection node N2 of the third switching element 413 and the fourth switching element 414, and may include a capacitor Cr and an inductor Lr connected in series to each other.

[0170] In addition, one end of the primary side of the transformer 440 is connected to the output end (the terminal of the inductor Lr) of the resonance circuit 450 , and the other end of the primary side is connected to the connection node N2 .

[0171] 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 according to a full-bridge structure. At this time, the output circuit 430 is connected to the secondary side of the transformer 440, one end of the secondary side is connected to a connection node N5 of the first switching element 431 and the second switching element 432, and the other end of the secondary side is connected to a connection node N6 of the third switching element 433 and the fourth switching element 434.

[0172] In this way, Figure 3 Unlike the converter of the present invention, the series resonant DAB converter of the present invention is configured such that the input side is composed of two series connections based on a half bridge. Therefore, the switch withstand voltage that the unit switch needs to withstand can be half of Vdc, which is the input side power supply voltage. Therefore, it can be seen that under the same withstand voltage condition, the number of components required on the input side is half of that of the full bridge.

[0173] In addition, if Fig.17As shown, the series resonant DAB converter can be expanded to an ISOP structure for application in MVDC. The input voltage of MVDC reaches tens of kV, so if it is configured based on the existing full bridge, the number of active / passive components increases significantly, and the individual control requirements such as current balance between the added sub-modules also increase. However, when ISOP is configured based on the half-bridge-based series resonant DAB converter proposed in the present invention, the number of active / passive components is reduced by half, and the current balance controller configuration is also reduced by half, making it simpler. That is, in Figure 4 In the case of the conventional two-level FB structure circuit, the switch withstand voltage of the unit switch is Vdc, and Fig.17 The proposed method is based on HB, and the switch withstand voltage of a unit switch is halved to 0.5Vdc, so the effect of reducing the number of passive components to half can be expected under the same switch withstand voltage condition.

[0174] Fig.18 is a diagram for explaining the operation of the series resonance type DAB converter according to the embodiment of the present invention.

[0175] Specifically, the pattern of the output bridge arm voltage and the neutral point NP current according to the switching state of the input circuit is shown. The first switch element (QA1, 411) and the second switch element (QA2, 412) operate complementarily, and the third switch element (QA3, 413) and the fourth switch element (QA4, 414) also operate complementarily. The primary side bridge arm voltage VA representing the voltage between the connection node (N1) and the connection node (N2) can output a three-level step voltage of 0, E, and 2E. At this time, E represents the unit voltage of the capacitor (Cdc1, Cdc2).

[0176] In addition, it can be seen that under the condition of VA=E, the neutral point current Inp between the connection node N3 and the connection node N4 becomes ILr or -ILr according to the switching state of the circuit. It can be seen that the neutral point current is related to the direction of the resonant current.

[0177] Since the converter 400 of the present invention also includes two series-connected input capacitors 415 and 416, good control must be performed to prevent voltage deviation of the capacitors. To this end, the present invention applies a new switching sequence, and using this sequence does not require a separate controller.

[0178] Fig.19 FIG. 4 shows the primary-side / secondary-side bridge arm voltage waveforms of a series resonant DAB converter according to an embodiment of the present invention.

[0179] As described above, the primary-side bridge arm voltage VA represents the voltage between the connection node N1 and the connection node N2, and the secondary-side bridge arm voltage VB represents the voltage between the connection node N5 and the connection node N6. Since the E level is necessary to control the voltage balance between the capacitors, a step-like voltage pattern of 0->E->2E is generally formed. For reference, this control method may also contribute to the ZVS of the secondary-side switch. (Zero Voltage Switching).

[0180] The duration of the voltage level E is π(1-k1), and the primary side bridge arm voltage VA and the secondary side bridge arm voltage VB have Here, k1 is the modulation index and is in the range of 0 to 1. In the present invention, this value is fixed (e.g., 0.9), and the output voltage is modulated by the phase difference The output power Po and output voltage Vo are both different from the phase difference Proportional and smooth adjustment.

[0181] The following Mathematical Formulas 3 to 5 represent 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.

[0182] [Mathematical formula 3]

[0183]

[0184] [Formula 4]

[0185]

[0186] [Mathematical formula 5]

[0187]

[0188] Next, a switching sequence for driving a series resonant DAB converter according to the present invention will be studied.

[0189] Fig. 20 The case where a switching sequence in a general phase shift manner is applied to the present invention is shown.

[0190] The switching method of the general phase shift mode adjusts the gate to adjust the on / off timing of the 50% duty cycle signal in the manner of A1->A4->A2->A3->A1->... as shown in the figure. In this phase shift mode, as shown in the figure, the problem existing in the (2E, E) and (E, 0) switch pairs constituting the E level is that Inp all becomes positive, Cdc1 continues to charge, and Cdc2 continues to discharge, resulting in the inability to achieve voltage balance. This is because all switching forms representing the E level are not utilized. In order to solve this problem, the present invention proposes a new switching sequence using a voltage modulation method and a clamping mode.

[0191] Fig.21 and 22 The switching sequence of the pulse size modulation method for driving a series resonant DAB converter according to the present invention is shown.

[0192] For reference, in the following figures, Gate A, Carrier A, Vampl_a, Vcmd_a, etc. respectively represent signals on the primary side of the transformer 440 or the input circuit 410 side, and Gate B, Carrier B, Vampl_b, Vcmd_b, etc. respectively represent signals on the secondary side of the transformer 440 or the output circuit 430 side.

[0193] A first switching sequence applied to the first switching element (411, GateA1) is a periodic repetition of a first pulse, a second pulse, a third pulse and a fourth pulse, wherein the first pulse has a pulse width and an amplitude of a first level during a reference time (T / 2), the second pulse has a pulse width and an amplitude of a second level during a time (T / 2-ΔT) obtained by subtracting a predetermined time from the reference time, the third pulse has a pulse width and an amplitude of the first level during the reference time (T / 2), and the fourth pulse has a pulse width and an amplitude of the second level during a time (T / 2+ΔT) obtained by adding a predetermined time to the reference time.

[0194] Similarly, the second switching sequence of the first pulse, the second pulse, the third pulse and the fourth pulse applied to the third switching element (413, GateA3) are periodically repeated, the first pulse having a pulse width during the reference time (T / 2) and an amplitude of the second level, the second pulse having a pulse width during the time (T / 2+ΔT) obtained by adding the predetermined time to the reference time and an amplitude of the first level, the third pulse having a pulse width during the reference time (T / 2) and an amplitude of the second level, and the fourth pulse having a pulse width during the time (T / 2-ΔT) obtained by subtracting the predetermined time from the reference time and an amplitude of the first level. At this time, the first level may be a high level and the second level may be a low level to be distinguished from the first level.

[0195] That is, the first switch element (411, GateA1) is turned on / off according to T / 2->T / 2-ΔT->T / 2->T / 2+ΔT->T / 2->..., and the third switch element (413, GateA3) is turned on / off according to T / 2->T / 2+ΔT->T / 2->T / 2-ΔT->T / 2->..., and this special switching mode utilizes the positive polarity / negative polarity of the neutral current, thereby naturally achieving the purpose of input capacitor voltage balance. In addition, the second switch element (412, GateA2) and the fourth switch element (414, GateA4) respectively determine the switching order opposite to the first switch element (411, GateA1) and the third switch element (413, GateA3) due to complementary characteristics.

[0196] With this configuration, Fig. 22 As shown, it can be seen that the neutral point current Inp in the (E, 0,) and (2E, E) switch pairs constituting the E level has both negative and positive segments, Cdc1 and Cdc2 are charged and discharged alternately, and the voltage Vdc1 of Cdc1 and the voltage Vdc2 of Cdc2 repeatedly rise and fall with each other, thereby enabling voltage balance between the capacitors.

[0197] Therefore, during one cycle of the first switching sequence and the second switching sequence, the first neutral point current Inp includes an interval having a negative value and an interval having a positive value.

[0198] At this time, the pulse widths of the first pulse of the first switching sequence and the first pulse of the second switching sequence are the same, and the first pulse of the second switching sequence is arranged to be earlier by a predetermined time (ΔT). That is, the rising edge of the first pulse of the first switching sequence is arranged to be later than the falling edge of the first pulse of the second switching sequence by a predetermined time (ΔT).

[0199] In addition, the pulse width of the second pulse of the first switching sequence is set to (T / 2-ΔT), the pulse width of the second pulse of the second switching sequence is set to (T / 2+ΔT), 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 a 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 a predetermined time (ΔT).

[0200] In addition, 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 starting point, the second switching sequence is arranged to be earlier by a 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 than twice the predetermined time (2ΔT), so the third pulse of the second switching sequence is delayed by a predetermined time (ΔT).

[0201] In addition, the pulse width of the fourth pulse of the first switching sequence is set to (T / 2+ΔT), the pulse width of the fourth pulse of the second switching sequence is set to (T / 2-ΔT), the falling edge of the fourth pulse of the first switching sequence is set to be a predetermined time (ΔT) earlier than the rising edge of the fourth pulse of the second switching sequence, and the rising edge of the fourth pulse of the first switching sequence is arranged to be a predetermined time (ΔT) later than the falling edge of the fourth pulse of the second switching sequence.

[0202] According to this configuration, the flow of the negative neutral point current Inp is as long as 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 the flow of the negative neutral point current Inp is as long as 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.

[0203] In addition, the flow of the positive neutral point current Inp is as long as 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 the flow of the positive neutral point current Inp is as long as 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.

[0204] also, Fig.21 The switching mode design of the proposed pulse size modulation method is shown. Vcmd_A represents the command voltage, whose amplitude alternates with ±Vampl_a every half cycle, and makes the clamp mode (CM) work at 1 during the first cycle and at -1 during the next cycle.

[0205] The carrier wave adopts a triangular wave in a decreasing manner, and according to CM, the command values ​​(Vcmd_a1 and Vcmd_a3) of the first switching element (411, QA1) and the third switching element (413, QA3) are set as follows.

[0206] When CM=1, Vcmd_a1 has a value of 0.5 Vcmd_a, and Vcmd_a3 has a value of -0.5 Vcmd_a. Also, the offset voltage (Voffse) is set to Vdc_ref / 4-max(Vcmd_a1, Vcmd_a3). Here, max(a, b) is a function that outputs the larger of two numbers a and b.

[0207] On the contrary, when CM=-1, the polarity of Vcmd_a1 and Vcmd_a3 is set to be opposite to that when CM=1, and the offset voltage (Voffset) is obtained similarly. The offset voltage and Vdc_ref / 4 are then added to the original command values ​​Vcmd_a1 and Vcmd_a3 to calculate the PWM command value, which is finally divided by Vdc_ref / 2 and multiplied by N_max to calculate the final normalized PWM command value that can be compared with the triangular carrier waveform.

[0208] If the PWM command value is calculated according to CM as described above, it can be expressed as Fig.21 In the special switching sequence shown, the first switching element (GateA1) is turned on / off according to T / 2->T / 2-ΔT->T / 2->T / 2+ΔT->T / 2->..., and the third switching element (GateA3) is turned on / off according to T / 2->T / 2+ΔT->T / 2->T / 2-ΔT->T / 2->... This special switching mode utilizes the positive / negative polarity of the neutral current and naturally achieves the purpose of input capacitor voltage balance.

[0209] Fig. 22 The main waveforms of the simulation results of the series resonant DAB converter are shown. PWM_CMD_a1 determines the on / off of GateA1 by comparing with the primary side carrier, and PWM_CMD_a3 determines the on / off of GateA3 by comparing with the primary side carrier. In addition, the second switching element (412, GateA2) and the fourth switching element (414, GateA4) respectively determine the switching opposite to the first switching element (411, GateA1) and the third switching element (413, GateA3) due to their complementary characteristics. In the case of using the general phase shift method Fig. 20In the example, only the positive value of the neutral point current Inp is used, but here, both the positive and negative values ​​of the neutral point current Inp can be used, so it can be seen that the voltage deviation of the input capacitor is naturally eliminated. It can be seen that in both cases, CM = 1 or CM = -1, the capacitor voltage deviation is eliminated by using the positive and negative neutral point current Inp.

[0210] Fig.23 The relationship between the carrier and the PWM command value in the driving method of the series resonance type DAB converter according to the embodiment of the present invention is shown.

[0211] In order to output a symmetrical bridge arm waveform, the initial value of the carrier and the counting direction are opposite according to CM ( Fig.23 (a)). In addition, in the interval where the PWM command value (PWM-CMD) is greater than the carrier, as Fig.21 and Fig. 22 As shown, a signal (GateA or GateB) that turns on the corresponding switch is output, and in the remaining intervals, a signal that turns off the corresponding switch is output. In case (a), since PWM_CMD_a1 (green signal) is always greater than the carrier during the first pulse portion of the carrier, a signal (GateA1) that turns on the first switching element 411 is output, and in the interval where PWM_CMD_a2 (red signal) is temporarily greater than the carrier, a signal (GateA3) that turns on the third switching element 413 is output.

[0212] On the other hand, a method can also be implemented to keep the carrier unchanged and apply the relationship between the command value and the carrier according to the CM reverse application ( Fig.23 (b) in FIG. 1 , and this method may be more suitable for utilizing the primary / secondary phase difference. That is, when CM=-1, in the portion where the PWM command value (PWM-CMD) is less than the carrier, a signal (GateA or GateB) that turns on the corresponding switch is output, and in the remaining interval, a signal that turns off the corresponding switch is output.

[0213] When calculating the offset voltage (Voffset), when CM = -1, Voffset = Vdc_ref / 4-min(Vcmd_a1, Vcmd_a3), but if you choose Fig.23 In the method (b) of FIG. 1 , the same effect can be expected by setting the maximum value instead of the minimum value at CM=-1 and reversing the polarity of Vcmd_a1 and Vcmd_a3.

[0214] Fig.24 A process of selecting a command mode (CM) in a driving method of a series resonance type DAB converter according to an embodiment of the present invention is shown.

[0215] The voltage (Vdc1, Vdc2) of the input capacitor is received as an input, the power flow (positive: the direction in which power flows from the power supply to the load, negative: the direction in which power flows from the load to the power supply) is determined, and the command mode (CM) is determined based on the magnitude relationship between the voltage (Vdc1) of the first capacitor and the voltage (Vdc2) of the second capacitor. For example, when power flows from the power supply to the load, if the voltage (Vdc1) of the first capacitor is greater than the voltage (Vdc2) of the second capacitor, CM=1, and if the voltage (Vdc1) of the first capacitor is less than the voltage (Vdc2) of the second capacitor, CM=-1. In addition, when power flows from the load to the power supply, if the voltage (Vdc1) of the first capacitor is greater than the voltage (Vdc2) of the second capacitor, CM=-1, and if the voltage (Vdc1) of the first capacitor is less than the voltage (Vdc2) of the second capacitor, CM=1.

[0216] Figure 25 to Figure 27 is a block diagram of a control logic for outputting a control signal of a series resonant DAB converter according to an embodiment of the present invention.

[0217] The control logic shown may be implemented as converter controller 300 in hardware form.

[0218] first, Fig.25 Control logic is shown that determines the phase difference between the primary and secondary sides of a transformer or the input and output circuits.

[0219] The phase difference is determined by integrating the difference between the output (Vo) of the series resonant DAB converter and the initial value (Vo*) through the PI controller, and the upper and lower limits are set. Through this process, the primary side carrier (Carrier_A) and the auxiliary carrier (Carrier_B) are output respectively.

[0220] Next, Fig.26 It is the control logic that outputs the switching sequence on the primary side or input circuit side.

[0221] like Fig.21 As mentioned in the description, Vcmd_A represents a command voltage whose amplitude alternates with ±Vampl_a every half cycle, and an offset voltage (Voffset) is determined according to a clamping mode.

[0222] When CM=1, Vcmd_a1 has a value of 0.5*Vcmd_A, and Vcmd_a3 has a value of -0.5*Vcmd_A. And, the offset voltage is calculated as 0.25*Vdc-max(Vcmd_a1, Vcmd_a3) based on CM_a and Vcmd_a1, Vcmd_a3. This offset voltage is added equally to Vcmd_a1 and Vcmd_a3, which are original command values, to calculate VCMD_a1 and VCMD_a3. Here, max(a, b) is a function that outputs the larger of the two numbers a and b. VCMD_a1 and VCMD_a3 are normalized by dividing by 0.5*Vdc, and then multiplied by the value of N_max and output as PWM command value voltages (PWM_CMD_a1, PWM_CMD_a3).

[0223] Conversely, when CM=-1, the polarity of Vcmd_a1 and Vcmd_a3 is set to be opposite to that when CM=1 (Vcmd_a1=-0.5*Vcmd_A, Vcmd_a3=0.5*Vcmd_A), and the offset voltage is similarly obtained. Then, VCMD_a1 and VCMD_a3 are calculated by adding the offset voltages to Vcmd_a1 and Vcmd_a3, which are the original command values, respectively. Finally, the final PWM command values ​​(PWM_CMD_a1, PWM_CMD_a3) that can be compared with the triangular carrier waveform are calculated by dividing by 0.5Vdc for normalization and then multiplying by N_max.

[0224] Also, the dead time block allows the first switching element 411 and the second switching element 412 to operate complementarily without being turned on at the same time, and similarly, the third switching element 413 and the fourth switching element 414 are not turned on at the same time and allow complementary operation.

[0225] Next, Fig. 27 The control logic for outputting the switching sequence on the secondary side or output circuit side is shown.

[0226] Looking at the operation of the secondary side in detail, Vcmd_B represents the command voltage, whose amplitude alternates with ±Vampl_b every half cycle, and the offset voltage (Voffset) is determined according to the clamping mode.

[0227] When CM=1, Vcmd_b1 has a value of 0.5Vcmd_B and Vcmd_b3 has a value of -0.5Vcmd_B. And, the offset voltage is calculated as 0.5*Vo-max(Vcmd_b1, Vcmd_b3) based on CM_b and Vcmd_b1, Vcmd_b3. These offset voltages are added equally to Vcmd_b1 and Vcmd_b3, which are original command values, respectively, to calculate VCMD_b1 and VCMD_b3. After VCMD_b1 and VCMD_b3 are divided by Vo for normalization, the values ​​multiplied by N_max are output as PWM command value voltages (PWM_CMD_b1, PWM_CMD_b3).

[0228] Conversely, when CM=-1, the polarities of Vcmd_b1 and Vcmd_b3 are set opposite to those when CM=1 (Vcmd_b1=-0.5*Vcmd_B, Vcmd_b3=0.5*Vcmd_B), and the offset voltage is similarly obtained. Then, VCMD_b1 and VCMD_b3 are calculated by adding the offset voltages to Vcmd_b1 and Vcmd_b3, which are the original command values, respectively. Finally, the final normalized final PWM command values ​​(PWM_CMD_b1, PWM_CMD_b3) are calculated by dividing by Vo for normalization and then multiplying by N_max to calculate the final normalized final PWM command values ​​(PWM_CMD_b1, PWM_CMD_b3) that can be compared with the triangular carrier waveform.

[0229] Also, the dead time block allows the first switching element 431 and the second switching element 432 to operate complementarily without being turned on at the same time, and similarly, the third switching element 433 and the fourth switching element 434 are not turned on at the same time and allow complementary operation.

[0230] Embodiments of the present invention may also be implemented in the form of a recording medium containing computer-executable instructions (such as a program module executed by a computer). Computer-readable media can be any available media that can be accessed by a computer, and include volatile and non-volatile media, removable and non-removable media. In addition, computer-readable media may include computer storage media. Computer storage media include volatile and non-volatile, removable and non-removable media implemented in any method or technology for storing information such as computer-readable instructions, data structures, program modules, or other data.

[0231] Although the methods and systems of the present invention have been described with respect to specific embodiments, some or all of their components or operations may be implemented using a computer system having a general hardware architecture.

[0232] The above description of the present invention is for illustrative purposes, and those skilled in the art will appreciate that it can be easily modified into other specific forms without changing the technical ideas or basic features of the present invention. Therefore, the above embodiments should be understood in all respects as illustrative rather than restrictive. For example, each component described as a single component can be implemented in a distributed manner, and similarly, components described as distributed components can also be implemented in a combined form.

[0233] The scope of the present invention is indicated by the claims described later rather than the detailed description above, and the meaning and scope of the claims and all changes or modifications derived from the equivalent concepts thereof should be construed as being included in the scope of the present invention.

Explanation of symbols

Claims

1. A simulation system for a railway system for a medium voltage direct current (MVDC) distribution network, the simulation system for the railway system comprising: A computing device storing a simulation program, the simulation program comprising: a converter station model simulating a converter station included in the MVDC power distribution network and a train travel model simulating a travel state of a train running with power supplied from the converter station; a converter controller, the converter controller controlling a DC / DC converter included in the converter station model; and A hardware-in-the-loop simulation (HILS) device is provided, wherein the hardware-in-the-loop simulation device performs simulation based on the converter station model, the train travel model and the converter controller, The converter station model and the train driving model are executed in software in the HILS device, and the converter controller is connected to the HILS device and driven to control the converter station model.

2. The simulation system of a railway system according to claim 1, wherein: The simulation program uses the train travel model to perform a train travel simulation in a stream processing manner. The train driving model is configured as follows: calculating the acceleration of the train based on the traction and driving resistance or braking force and driving resistance of the train; calculating the speed and position using the calculated acceleration and the time interval of the discrete time system; using the speed and position, performing train driving operations based on the stream processing method of the state machine, and outputting the gear value and train power consumption; converting the train power consumption into a current source and inputting it into the equivalent model; calculating the coefficient matrix from the state space equation representing the equivalent model; and performing power simulation by outputting a discrete time system through the calculation of the state space equation.

3. The simulation system of a railway system according to claim 2, wherein: The train travel model is used for: The speed is input into a state machine including a stop state, a reverse state, a coasting state and a braking state of the train, the state of the state machine is transformed based on whether the speed reaches a speed limit, and a gear value matching each state is output.

4. The simulation system of a railway system according to claim 2, wherein: The train travel model is used for: outputting traction force or braking force corresponding to the speed, and outputting running resistance corresponding to the speed; The acceleration and train power consumption of the train are calculated based on the gear value output by the state machine according to the speed, the traction force or braking force, the running resistance, and the gradient resistance or curve resistance corresponding to the train position.

5. The simulation system of a railway system according to claim 1, wherein: The converter station model uses a series resonant DAB converter as a DC / DC converter. The series resonant DAB converter comprises: an input circuit, the input circuit comprising 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 structure, a first capacitor connected in parallel with the first switching element and the second switching element, and a second capacitor connected in parallel with 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 structure; and A resonant circuit and a transformer are connected between the input circuit and the output circuit.

6. The simulation system of a railway system according to claim 1, wherein: The converter station model is a DC / DC converter that connects multiple series resonant DAB converters into an input-series-output-parallel (ISOP) structure. Each series resonant DAB converter consists of: The series resonant DAB converter comprises: an input circuit, the input circuit comprising 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 structure, a first capacitor connected in parallel with the first switching element and the second switching element, and a second capacitor connected in parallel with 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 structure; and A resonant circuit and a transformer are connected between the input circuit and the output circuit.

7. The simulation system of a railway system according to claim 5 or 6, wherein: The resonant circuit and the transformer are connected between a connection node between the first switching element and the second switching element of the input circuit and a connection node between 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 end of the primary side of the transformer is connected to the resonant circuit, and the other end of the primary side is connected to a connection node of a third switching element and a fourth switching element of the input circuit. One end of the secondary side of the transformer is connected to a connection node between the first switching element and the second switching element of the output circuit, and the other end of the secondary side is connected to a connection node between the third switching element and the fourth switching element of the output circuit.

8. The simulation system of a railway system according to claim 5 or 6, wherein: The converter controller includes control logic that complementarily applies a first switching sequence to the first and second switching elements of the input circuit and that complementarily applies a second switching sequence to the third and fourth switching elements, The first switching sequence is a periodic repetition of a first pulse, a second pulse, a third pulse, and a fourth pulse, the first pulse having a pulse width and an amplitude of a first level during a reference time (T / 2), the second pulse having a pulse width and an amplitude of a second level during a time (T / 2-ΔT) obtained by subtracting a predetermined time from the reference time, the third pulse having a pulse width and an amplitude of the first level during the reference time (T / 2), the fourth pulse having a pulse width and an amplitude of the second level during a time (T / 2+ΔT) obtained by adding a predetermined time to the reference time, The second switching sequence is a periodic repetition of a first pulse, a second pulse, a third pulse, and a fourth pulse, the first pulse having a pulse width during a reference time (T / 2) and an amplitude of a second level, the second pulse having a pulse width during a time (T / 2+ΔT) obtained by adding a predetermined time to the reference time and an amplitude of the first level, the third pulse having a pulse width during the reference time (T / 2) and an amplitude of the second level, the fourth pulse having a pulse width during a time (T / 2-ΔT) obtained by subtracting a predetermined time from the reference time and an amplitude of the first level, The first level is a high level, and the second level is a low level to be distinguished from the first level.

9. A method for simulating a railway system for a medium voltage direct current (MVDC) distribution network, the method comprising the following steps: (a) executing a simulation program by software on a loop simulation (HILS) device, the simulation program comprising: a converter station model simulating a converter station included in the MVDC power distribution network and a train travel model simulating a travel state of a train running with power supplied from the converter station; and (b) A converter controller for controlling a DC / DC converter included in the converter station model is connected to the HILS device and driven to control the converter station model.

10. The method for simulating a railway system according to claim 9, wherein: The step (a) comprises using the train travel model to perform a train travel simulation in a stream processing manner, The steps of performing the train travel simulation include: (a-1) Calculating the acceleration of the train based on the traction and running resistance or the braking force and running resistance of the train; (a-2) Calculate velocity and position using the calculated acceleration and time interval of the discrete time system; (a-3) using the speed and position, performing train travel calculations in a stream processing manner based on a state machine, and outputting a gear value and train power consumption; (a-4) converting the train power consumption into a current source and inputting it into an equivalent model; (a-5) calculating a coefficient matrix from the state space equations representing the equivalent model; and (a-6) By calculating the state space equations, power simulation is performed in the form of outputting a discrete time system.

11. The method for simulating a railway system according to claim 10, wherein: In the step (a-3), The speed is input into a state machine including a stop state, a reverse state, a coasting state and a braking state of the train, the state of the state machine is transformed based on whether the speed reaches a speed limit, and a gear value matching each state is output.

12. The method for simulating a railway system according to claim 10, wherein: In the step (a-3), outputting traction or braking force corresponding to the speed, outputting running resistance corresponding to the speed, The acceleration and train power consumption of the train are calculated based on the gear value output by the state machine according to the speed, the traction force or braking force, the running resistance, and the gradient resistance or curve resistance corresponding to the train position.

13. The method for simulating a railway system according to claim 9, wherein: In said step (a), a simulation program is executed in software on a HILS device using said 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, the input circuit comprising 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 structure, a first capacitor connected in parallel with the first switching element and the second switching element, and a second capacitor connected in parallel with 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 structure; and A resonant circuit and a transformer are connected between the input circuit and the output circuit.

14. The method for simulating a railway system according to claim 9, wherein: In said step (a), a simulation program is executed in software on a HILS device using said converter station model, The converter station model is a DC / DC converter that connects multiple series resonant DAB converters into an input-series-output-parallel (ISOP) structure. Each series resonant DAB converter consists of: The series resonant DAB converter comprises: an input circuit, the input circuit comprising 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 structure, a first capacitor connected in parallel with the first switching element and the second switching element, and a second capacitor connected in parallel with 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 structure; and A resonant circuit and a transformer are connected between the input circuit and the output circuit.

15. The method for simulating a railway system according to claim 13 or 14, wherein: One end of the transformer is connected to a connection node between the first switching element and the second switching element, The other end of the transformer is connected to a connection node between the third switching element and the fourth switching element, The resonance circuit is connected between a connection node between the first switching element and the second switching element and one end of the transformer.

16. The method for simulating a railway system according to claim 13 or 14, wherein: In the step (b), applying a first switching sequence complementarily to the first switching element and the second switching element and applying a second switching sequence complementarily to the third switching element and the fourth switching element by the converter controller, The first switching sequence is a periodic repetition of a first pulse, a second pulse, a third pulse, and a fourth pulse, the first pulse having a pulse width and an amplitude of a first level during a reference time (T / 2), the second pulse having a pulse width and an amplitude of a second level during a time (T / 2-ΔT) obtained by subtracting a predetermined time from the reference time, the third pulse having a pulse width and an amplitude of the first level during the reference time (T / 2), the fourth pulse having a pulse width and an amplitude of the second level during a time (T / 2+ΔT) obtained by adding a predetermined time to the reference time, The second switching sequence is a periodic repetition of a first pulse, a second pulse, a third pulse, and a fourth pulse, the first pulse having a pulse width during a reference time (T / 2) and an amplitude of a second level, the second pulse having a pulse width during a time (T / 2+ΔT) obtained by adding a predetermined time to the reference time and an amplitude of the first level, the third pulse having a pulse width during the reference time (T / 2) and an amplitude of the second level, the fourth pulse having a pulse width during a time (T / 2-ΔT) obtained by subtracting a predetermined time from the reference time and an amplitude of the first level, The first level is a high level, and the second level is a low level to be distinguished from the first level.

17. A simulation device for a railway system, the simulation device for the railway system comprising: A memory storing a simulation program, wherein the simulation program includes a train running model for simulating a train running state; as well as comprising a processor for executing said simulation program, The simulation program uses the train travel model to perform a train travel simulation in a stream processing manner. The train driving model is configured as follows: calculating the acceleration of the train based on the traction and driving resistance or braking force and driving resistance of the train; calculating the speed and position using the calculated acceleration and the time interval of the discrete time system; using the speed and position, performing train driving operations based on the stream processing method of the state machine, and outputting the gear value and train power consumption; converting the train power consumption into a current source and inputting it into the equivalent model; calculating the coefficient matrix from the state space equation representing the equivalent model; and performing power simulation by outputting a discrete time system through the calculation of the state space equation.

18. The simulation device for a railway system according to claim 17, wherein: The train travel model is used for: The speed is input into a state machine including a stop state, a reverse state, a coasting state and a braking state of the train, the state of the state machine is transformed based on whether the speed reaches a speed limit, and a gear value matching each state is output.

19. The simulation device for a railway system according to claim 17, wherein: The train travel model is used for: outputting traction force or braking force corresponding to the speed, and outputting running resistance corresponding to the speed; The acceleration and train power consumption of the train are calculated based on the gear value output by the state machine according to the speed, the traction force or braking force, the running resistance, and the gradient resistance or curve resistance corresponding to the train position.

20. A train running simulation method using a stream processing method of a simulation device of a railway system, the train running simulation method comprising the following steps: (a) Calculating the acceleration of the train based on the traction and running resistance or the braking force and running resistance of the train; (b) Calculate velocity and position using the calculated acceleration and time interval of the discrete time system; (c) using the speed and position, performing train travel calculations in a stream processing manner based on a state machine, and outputting a gear value and train power consumption; (d) converting the train power consumption into a current source and inputting it into an equivalent model; (e) calculating a coefficient matrix from the state-space equations representing the equivalent model; and (f) Performing power simulation by calculating the state space equations to output a discrete time system.

21. The train running simulation method according to claim 20, wherein: In the step (c), The speed is input into a state machine including a stop state, a reverse state, a coasting state and a braking state of the train, the state of the state machine is transformed based on whether the speed reaches a speed limit, and a gear value matching each state is output.

22. The train running simulation method according to claim 20, wherein: In the step (c), outputting traction or braking force corresponding to the speed, outputting running resistance corresponding to the speed, The acceleration and train power consumption of the train are calculated based on the gear value output by the state machine according to the speed, the traction force or braking force, the running resistance, and the gradient resistance or curve resistance corresponding to the train position.

23. A computer-readable recording medium having a computer program recorded thereon, the computer program being used to execute the train travel simulation method according to any one of claims 20 to 22.

24. A series resonant DAB converter, comprising: an input circuit, the input circuit comprising 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 structure, a first capacitor connected in parallel with the first switching element and the second switching element, and a second capacitor connected in parallel with the third switching element and the fourth switching element; an output circuit comprising a first switching element, a second switching element, a third switching element, and a fourth switching element connected according to a full-bridge structure; as well as A resonant circuit and a transformer are connected between the input circuit and the output circuit.

25. The series resonant DAB converter according to claim 24, wherein: The resonant circuit and the transformer are connected between a connection node between the first switching element and the second switching element of the input circuit and a connection node between 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 end of the primary side of the transformer is connected to the resonant circuit, and the other end of the primary side is connected to a connection node of a third switching element and a fourth switching element of the input circuit. One end of the secondary side of the transformer is connected to a connection node between the first switching element and the second switching element of the output circuit, and the other end of the secondary side is connected to a connection node between the third switching element and the fourth switching element of the output circuit.

26. The series resonant DAB converter according to claim 24, wherein: The series resonant DAB converter is driven by a control logic that complementarily applies a first switching sequence to a first switching element and a second switching element of the input circuit and complementarily applies a second switching sequence to a third switching element and a fourth switching element, The first switching sequence is a periodic repetition of a first pulse, a second pulse, a third pulse, and a fourth pulse, the first pulse having a pulse width and an amplitude of a first level during a reference time (T / 2), the second pulse having a pulse width and an amplitude of a second level during a time (T / 2-ΔT) obtained by subtracting a predetermined time from the reference time, the third pulse having a pulse width and an amplitude of the first level during the reference time (T / 2), the fourth pulse having a pulse width and an amplitude of the second level during a time (T / 2+ΔT) obtained by adding a predetermined time to the reference time, The second switching sequence is a periodic repetition of a first pulse, a second pulse, a third pulse, and a fourth pulse, the first pulse having a pulse width during a reference time (T / 2) and an amplitude of a second level, the second pulse having a pulse width during a time (T / 2+ΔT) obtained by adding a predetermined time to the reference time and an amplitude of the first level, the third pulse having a pulse width during the reference time (T / 2) and an amplitude of the second level, the fourth pulse having a pulse width during a time (T / 2-ΔT) obtained by subtracting a predetermined time from the reference time and an amplitude of the first level, The first level is a high level, and the second level is a low level to be distinguished from the first level.

27. A DC / DC converter comprising a plurality of series resonant DAB converters according to any one of claims 24 to 26 connected in an input-series-output-parallel (ISOP) structure.

28. A DC / DC converter, comprising: Series resonant DAB converter; as well as a converter controller for controlling the series resonant DAB converter, The series resonant DAB converter comprises: an input circuit, the input circuit comprising 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 structure, a first capacitor connected in parallel with the first switching element and the second switching element, and a second capacitor connected in parallel with 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 structure; and A resonant circuit and a transformer are connected between the input circuit and the output circuit.

29. The DC / DC converter according to claim 28, wherein: The resonant circuit and the transformer are connected between a connection node between the first switching element and the second switching element of the input circuit and a connection node between 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 end of the primary side of the transformer is connected to the resonant circuit, and the other end of the primary side is connected to a connection node of a third switching element and a fourth switching element of the input circuit. One end of the secondary side of the transformer is connected to a connection node between the first switching element and the second switching element of the output circuit, and the other end of the secondary side is connected to a connection node between the third switching element and the fourth switching element of the output circuit.

30. The DC / DC converter according to claim 28, wherein: The converter controller includes control logic, The control logic applies a first switching sequence complementarily to the first switching element and the second switching element of the input circuit, and applies a second switching sequence complementarily to the third switching element and the fourth switching element, The first switching sequence is a periodic repetition of a first pulse, a second pulse, a third pulse, and a fourth pulse, the first pulse having a pulse width and an amplitude of a first level during a reference time (T / 2), the second pulse having a pulse width and an amplitude of a second level during a time (T / 2-ΔT) obtained by subtracting a predetermined time from the reference time, the third pulse having a pulse width and an amplitude of the first level during the reference time (T / 2), the fourth pulse having a pulse width and an amplitude of the second level during a time (T / 2+ΔT) obtained by adding a predetermined time to the reference time, The second switching sequence is a periodic repetition of a first pulse, a second pulse, a third pulse, and a fourth pulse, the first pulse having a pulse width during a reference time (T / 2) and an amplitude of a second level, the second pulse having a pulse width during a time (T / 2+ΔT) obtained by adding a predetermined time to the reference time and an amplitude of the first level, the third pulse having a pulse width during the reference time (T / 2) and an amplitude of the second level, the fourth pulse having a pulse width during a time (T / 2-ΔT) obtained by subtracting a predetermined time from the reference time and an amplitude of the first level, The first level is a high level, and the second level is a low level to be distinguished from the first level.

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