Control architecture for flexible direct-current traction power supply system based on energy routers

Abstract

The present invention belongs to the field of direct-current traction power supply systems. Disclosed is a control architecture for a flexible direct-current traction power supply system based on energy routers. The flexible direct-current traction power supply system comprises a plurality of traction substations, and external power sources connected to the plurality of traction substations, wherein locomotives are connected to the traction substations by means of a catenary system, each traction substation comprises a plurality of energy routers, and each energy router comprises at least three ports, a first port being connected to the external power source by means of a traction substation alternating-current bus, a second port being connected to the catenary system by means of a traction bus, and the other ports being connected to one or more of photovoltaics, wind power, energy storage, a direct-current load and an alternating-current load. The solution of the present invention overcomes the defects of existing direct-current traction power supply systems using a diode rectifier unit as a core power supply device and existing direct-current traction power supply systems based on energy routers in the aspect of system structure design, and provides a corresponding collaborative control technical solution.

Description

Control architecture of flexible DC traction power supply system based on energy router

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to Chinese patent application number "202310660727.1" filed by Tsinghua University on June 6, 2023, entitled "Flexible DC traction power supply system based on energy router and its control architecture". Technical Field

[0003] The present invention relates to the technical field of direct current (DC) traction power supply systems, and in particular to a control architecture of a flexible DC traction power supply system based on an energy router. Background Art

[0004] Traditional DC traction power supply systems utilize diode rectifiers as their core power supply equipment. However, with the rapid development of urban rail transit, traction power supply systems face new challenges. With the rapid growth in the carrying capacity and mileage of urban rail transit systems like subways and light rail, the supply capacity and distance of DC traction power supply systems are also increasing. This places higher demands on the external power supply capacity of DC traction power supply systems, severely impacting the economic viability of external power grid construction. Furthermore, DC traction power supply systems are experiencing increasing energy consumption, necessitating improved energy efficiency to support the "green development" concept. To overcome the shortcomings of traditional DC traction power supply systems, it is necessary to regulate the power flow distribution within the DC traction power supply system and optimize the voltage and energy distribution. However, the lack of controllability of diode rectifiers makes it impossible to control the power flow distribution within the system. Therefore, it is necessary to develop a highly controllable flexible DC traction power supply system. This flexible DC traction power supply solution utilizes highly controllable converters as the primary power supply equipment, eliminating the uncontrollable diode rectifiers. This reduces the external power supply requirements of the DC traction power supply system, improves the utilization of locomotive regenerative braking energy, and improves the power quality of the AC / DC system, offering numerous advantages for the traction power supply system.

[0005] Current research on flexible DC traction power supply solutions primarily focuses on flexible DC traction power supply systems based on bidirectional converters. While traditional bidirectional converters can only connect to the grid and traction networks, multi-port energy routers can connect to external power sources, the traction network, and integrate photovoltaic, energy storage, and power lighting loads. The energy router-based flexible DC traction power supply system replaces the bidirectional converter with a multi-port energy router. This further improves system reliability, affordability, and energy efficiency, building on the foundation of a flexible DC traction power supply system based on bidirectional converters. It also facilitates the integration and consumption of new energy sources, optimizes traction energy consumption, and reduces the size of power supply equipment.

[0006] Although relevant literature has introduced energy routers within DC traction power supply systems to facilitate the integration of new equipment such as renewable energy and energy storage, diode rectifiers remain the core power supply device. Because the diode rectifier's operating characteristics follow a fixed volt-ampere characteristic curve, its operating point is not controllable, making it difficult to flexibly regulate the system's power flow. Relying on the frequent charging and discharging of energy storage devices to regulate system power flow reduces the device's lifespan and results in high economic costs. Due to the limited ability to regulate system power flow, the economic and energy-saving benefits of this type of technology are limited. This technology still requires designing an external power supply configuration based on the inherent characteristics of the diode uncontrolled rectifier, making it difficult to reduce external power supply construction costs. Furthermore, the system's locomotive regenerative energy and renewable energy output cannot be efficiently and effectively absorbed.

[0007] Related literature has used energy routers to replace existing traction station transformers and diode rectifiers. This power electronics topology includes a high-voltage conversion module, a medium-voltage transformer module, and a low-voltage conversion module, resulting in high equipment costs. Retaining the transformer within the traction station and replacing only the diode rectifier with an energy router significantly reduces the complexity and system cost of the energy router. However, this design requires too many energy routers to convert high voltage to low voltage, which increases the system cost.

[0008] Summary of the Invention

[0009] The present invention provides a control architecture for a flexible DC traction power supply system based on an energy router, which overcomes the shortcomings of the existing DC traction power supply system using a diode rectifier unit as the core power supply equipment and the existing DC traction power supply system based on an energy router in terms of system structure design, and provides a corresponding collaborative control technical solution.

[0010] An embodiment of the present invention provides a control architecture for a flexible DC traction power supply system based on an energy router. The flexible DC traction power supply system includes multiple traction stations, an external power source connected to the multiple traction stations, a locomotive connected to the traction station via a contact network, the traction station including multiple energy routers, and the energy router including at least three ports, a first port connected to the external power source via a traction station AC bus, a second port connected to the contact network via a traction bus, and the remaining ports connected to one or more of photovoltaic, wind power, energy storage, DC load, and AC load;

[0011] The control architecture of the flexible DC traction power supply system based on the energy router includes: a system-level collaborative control layer, a traction station-level collaborative control layer, and a port-level collaborative control layer;

[0012] The system-level collaborative control layer is connected to the traction station-level collaborative control layer, and is used to obtain measurement information from the traction station-level collaborative control layer and send the generated control instructions to the traction station-level collaborative control layer;

[0013] The traction station-level collaborative control layer is connected to the port-level collaborative control layer, and is used to obtain measurement information from the port-level collaborative control layer and send generated control instructions to the port-level collaborative control layer;

[0014] The port-level collaborative control layer is connected to the energy router, and is used to obtain measurement information from the energy router and send generated control instructions to the energy router.

[0015] Optionally, in the flexible DC traction power supply system, the energy router internally includes multiple discrete independent converters. The energy router has both a distributed and a centralized structure. The converters of the distributed energy router do not share power electronic devices or bridge arms. The energy conversion processes corresponding to the converter ports of the centralized energy router share the same power electronic devices or bridge arms.

[0016] Optionally, in the flexible DC traction power supply system, the traction station AC busbar and the energy router device form two paths to the AC load, so that the AC load is supplied with power only through the energy router or only through the traction station AC busbar.

[0017] Optionally, the port-level collaborative control layer directly controls multiple ports of the energy router, and performs constant voltage control on energy router ports connected to DC loads and AC loads;

[0018] Under normal operating conditions, the maximum power point tracking control is performed on the energy router ports connected to photovoltaic and wind power;

[0019] Under normal operating conditions, the energy router port connected to the traction busbar is subjected to constant voltage control. The voltage reference instruction is provided by the traction station-level collaborative control layer. When the difference between the power of the energy router and the maximum capacity is less than a preset threshold, the energy router is controlled according to the constant power.

[0020] Under normal operating conditions, the energy router port connected to the external power supply is controlled according to the fixed AC voltage and fixed reactive power;

[0021] For the energy router port connected to the energy storage, the output power of the energy storage device is regulated according to the constant power control, and the power reference instruction is provided by the traction station-level collaborative control layer.

[0022] Optionally, the system-level collaborative control layer is further used to perform energy management and operation optimization at the flexible DC traction power supply system level, regulate the voltage and power of each traction station, and further regulate the power flow distribution of the flexible DC traction power supply system.

[0023] Optionally, the control instructions of the system-level collaborative control layer include DC voltage reference instructions on the traction network side, power reference instructions for energy storage, and reactive power reference instructions on the external power supply side. When the number of energy routers in a traction station is greater than 1, the traction station-level collaborative control layer is used as an intermediate control layer to enable the energy routers in the same traction station to operate at the same working point.

[0024] The control architecture of the flexible DC traction power supply system based on the energy router according to the embodiment of the present invention has the following beneficial effects:

[0025] Compared with the existing DC traction power supply system that uses a diode rectifier unit as the core power supply equipment, the solution of the present invention can more flexibly and economically regulate the system flow, optimize the economic and energy-saving benefits of the traction power supply system, and reduce the demand for external power supply construction.

[0026] Compared with the existing flexible DC traction power supply system based on bidirectional converters, the energy router is easier to connect to new energy and energy storage, and is convenient for providing power to the station's DC loads. It can save redundant components, optimize the control effect of power electronic devices, reduce equipment size, and reduce energy consumption.

[0027] Compared with the existing DC traction power supply system based on energy routers, the transformer structure is retained, thereby reducing the complexity and equipment cost of a single energy router; the structural design of the traction depot is optimized to avoid an excessive number of energy routers in the traction depot.

[0028] Additional aspects and advantages of the present invention will be set forth in part in the description which follows and, in part, will be obvious from the description which follows, or may be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the following description of the embodiments in conjunction with the accompanying drawings, in which:

[0030] FIG1 is a schematic structural diagram of a flexible DC traction power supply system based on an energy router according to an embodiment of the present invention;

[0031] FIG2 is a schematic diagram of a control architecture of a flexible DC traction power supply system based on an energy router according to an embodiment of the present invention. DETAILED DESCRIPTION

[0032] The following describes embodiments of the present invention in detail, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, and are not to be construed as limiting the present invention.

[0033] FIG1 is a schematic structural diagram of a flexible DC traction power supply system based on an energy router according to an embodiment of the present invention.

[0034] As shown in FIG1 , the flexible DC traction power supply system based on the energy router includes multiple traction stations 100 , an external power source 200 connected to the multiple traction stations 100 , and a locomotive 300 connected to the traction station 100 via a contact network.

[0035] The traction station 100 includes multiple energy routers 101, and the energy router 101 includes at least three ports. The first port is connected to the external power supply 200 through the traction station AC bus, the second port is connected to the contact network through the traction bus, and the remaining ports are connected to one or more of photovoltaic, wind power, energy storage, DC load, and AC load.

[0036] The traction power supply system includes several traction stations 100. The locomotive is powered by a catenary or third rail, which is connected to the traction busbar within the traction station 100. The voltage levels of the traction busbar, catenary, and third rail include but are not limited to 750V, 1500V, and 3000V. Each traction station 100 has several traction station AC busbars. Let the number of traction station AC busbars in the i-th traction station be X. i (The number of AC busbars in the traction station includes but is not limited to 2. i =2). The AC busbar of the traction station connects the external power supply and the traction station, and its voltage levels include but are not limited to 35kV and 10kV.

[0037] Each traction station AC busbar is connected to an energy router 101. The energy router 101 has at least one port for connecting to the traction station AC busbar and one port for connecting to the traction busbar. It may also have ports for connecting to photovoltaic power, wind power, energy storage, DC loads, and AC loads. The voltage levels of different energy storage, DC loads, and AC loads may vary. To accommodate energy storage, DC loads, and AC loads of varying voltage levels, the energy router 101 may have more than one port for connecting to energy storage, DC loads, and AC loads.

[0038] Energy router 101 internally includes multiple discrete, independent converters. Energy router 101 can have both distributed and centralized architectures. In a distributed energy router, converters do not share power electronic components or bridge arms. In a centralized energy router, the energy conversion processes corresponding to each converter port share the same power electronic components or bridge arms. The energy router can be designed using the distributed architecture shown in Figure 1, with multiple converters designed separately and operating independently, or a centralized architecture, with multiple ports integrated and sharing power electronic components. The centralized architecture reduces component redundancy and further optimizes device losses and size.

[0039] In traditional DC traction power supply systems, the AC loads within the traction station are powered by the station's AC busbar. In this technical solution, different power supply pathways for the AC loads can be selected: using the station's AC busbar and energy router to form two pathways for supplying power to the AC loads, relying solely on the energy router to supply power to the AC loads, or relying solely on the traction station's AC busbar to supply power to the AC loads. If the traction station's AC busbar is used to supply power to the AC loads, it will take a long time to restore power if the external power supply fails. However, if the traction station's AC busbar and energy router are used to form two pathways for supplying power to the AC loads, the two pathways can serve as backup for each other, improving the reliability of power supply to the AC loads.

[0040] The flexible DC traction power supply system based on the energy router of the embodiment of the present invention can more flexibly and economically regulate the system flow, optimize the economic and energy-saving benefits of the traction power supply system, and reduce the demand for the construction of external power supplies. The energy router is more convenient for connecting to new energy and energy storage, facilitating the provision of power for the station's DC loads, saving redundant components, optimizing the control effect of power electronic devices, reducing the size of the equipment, and reducing energy consumption. The DC traction power supply system based on the energy router retains the transformer structure, thereby reducing the complexity and equipment cost of a single energy router; it optimizes the structural design of the traction depot, avoiding an excessive number of energy routers in the traction depot.

[0041] Next, the control architecture of the flexible DC traction power supply system based on the energy router proposed in the embodiment of the present invention will be described with reference to the accompanying drawings.

[0042] FIG2 is a schematic diagram of a control architecture of a flexible DC traction power supply system based on an energy router according to an embodiment of the present invention.

[0043] As shown in Figure 2, the control architecture of the flexible DC traction power supply system based on the energy router includes: a system-level collaborative control layer, a traction station-level collaborative control layer, and a port-level collaborative control layer.

[0044] Among them, the system-level collaborative control layer is connected to the traction station-level collaborative control layer, and is used to obtain measurement information from the traction station-level collaborative control layer and send the generated control instructions to the traction station-level collaborative control layer; the traction station-level collaborative control layer is connected to the port-level collaborative control layer, and is used to obtain measurement information from the port-level collaborative control layer and send the generated control instructions to the port-level collaborative control layer; the port-level collaborative control layer is connected to the energy router, and is used to obtain measurement information from the energy router and send the generated control instructions to the energy router.

[0045] The measurement information required for system-level collaborative control is provided by the lower-level traction station-level collaborative control, which sends control commands to the lower-level traction station-level collaborative control. The measurement information required for traction station-level collaborative control is provided by the lower-level port-level collaborative control, which sends control commands to the lower-level port-level collaborative control. The port-level collaborative control requires real-time measurement information from the energy router and related equipment, and sends control commands to the energy router.

[0046] Optionally, in one embodiment of the present invention, the port-level collaborative control layer directly controls multiple ports of the energy router and performs constant voltage control on the energy router ports connected to the DC load and the AC load;

[0047] Under normal operating conditions, the maximum power point tracking control is performed on the energy router ports connected to photovoltaic and wind power;

[0048] Under normal operating conditions, the energy router port connected to the traction busbar is controlled at a constant voltage. The voltage reference instruction is provided by the traction station-level collaborative control layer. When the difference between the power of the energy router and the maximum capacity is less than the preset threshold, the energy router is controlled at a constant power.

[0049] Under normal operating conditions, the energy router port connected to the external power supply is controlled according to the fixed AC voltage and fixed reactive power;

[0050] For the energy router port connected to the energy storage, the output power of the energy storage device is regulated according to the constant power control, and the power reference instruction is provided by the traction station-level collaborative control layer.

[0051] Specifically, port-level coordinated control directly controls each port of the multi-port energy router. For ports supplying DC and AC loads within stations and traction depots, under normal operation, constant voltage control is implemented to ensure stable voltages for the DC and AC loads and that energy demands are met. In emergency or fault conditions, some ports can lock and disconnect circuit breakers, removing Class 3 loads. For ports connected to photovoltaic and wind power, MPPT control is implemented under normal operation to ensure that photovoltaic and wind power can maximize their power output. In emergency or fault conditions, some ports can curtail wind and solar power, ensuring safe and reliable system operation. For ports connected to the traction grid, under normal operation, the energy router is controlled at a constant voltage, with voltage reference instructions provided by the traction depot-level coordinated control. When the power of the energy router approaches or equals its maximum capacity, constant power control is implemented to ensure that the energy router does not violate capacity limits. For ports connected to external power sources, under normal operation, the Energy Router operates according to a fixed AC voltage and fixed reactive power control scheme. The reactive power command can be simply set to 0, or it can accept control commands from the traction station-level coordinated control to optimize the voltage-reactive power balance of the AC network. For ports connected to energy storage, the output power of the energy storage device is regulated using a fixed power control scheme, with the power reference command provided by the traction station-level coordinated control scheme.

[0052] The top layer is system-level collaborative control. This layer manages energy and optimizes operations across the entire traction power supply system, regulating the voltage and power of each traction station and, consequently, the power flow distribution across the entire system. System-level collaborative control employs optimization-based methods to determine optimal control decisions for system state variables, achieving optimal control across the entire system. System-level collaborative control can also employ simplified control methods to reduce implementation complexity, such as droop control and master-slave control.

[0053] The output control instructions of system-level collaborative control are instructions for each traction station. These instructions include the DC voltage reference instruction on the traction grid side, the power reference instruction for the energy storage, and the reactive power reference instruction on the external power supply side. A traction station contains several energy routers. When the number of energy routers in a traction station exceeds one, traction station-level collaborative control is required as an intermediate control layer to connect the upper and lower levels. The control purpose of traction station-level collaborative control is to ensure that the energy routers in the same traction station operate at the same operating point, that is, to ensure that multiple energy routers in the same traction station have the same energy flow relationship and output voltage.

[0054] It should be noted that the above explanation of the embodiment of the flexible DC traction power supply system based on the energy router is also applicable to the control architecture of the flexible DC traction power supply system based on the energy router in this embodiment, and will not be repeated here.

[0055] The control architecture of the flexible DC traction power supply system based on the energy router proposed in an embodiment of the present invention provides a three-level collaborative control architecture to achieve optimal control of the entire system.

[0056] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or N embodiments or examples in a suitable manner. In addition, those skilled in the art can combine and combine different embodiments or examples described in this specification and the features of different embodiments or examples without contradiction.

[0057] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be understood to indicate or imply relative importance or implicitly specify the number of technical features indicated. Thus, a feature specified as "first" or "second" may explicitly or implicitly include at least one such feature. In the description of the present invention, "N" means at least two, such as two, three, etc., unless otherwise specifically defined.

Claims

1. A control architecture of a flexible DC traction power supply system based on an energy router, the flexible DC traction power supply system comprising a plurality of traction stations, an external power source connected to the plurality of traction stations, a locomotive connected to the traction stations via a contact network, It is characterized in that In a flexible DC traction power supply system based on an energy router, the traction station includes a plurality of energy routers, the energy router includes at least three ports, a first port is connected to the external power source through an AC busbar of the traction station, a second port is connected to the contact network through a traction busbar, and the remaining ports are connected to one or more of photovoltaic, wind power, energy storage, DC load, and AC load. The control architecture of the flexible DC traction power supply system based on the energy router includes: a system-level collaborative control layer, a traction station-level collaborative control layer, and a port-level collaborative control layer; The system-level collaborative control layer is connected to the traction station-level collaborative control layer, and is used to obtain measurement information from the traction station-level collaborative control layer and send the generated control instructions to the traction station-level collaborative control layer; The traction station-level collaborative control layer is connected to the port-level collaborative control layer, and is used to obtain measurement information from the port-level collaborative control layer and send the generated control instructions to the port-level collaborative control layer; The port-level collaborative control layer is connected to the energy router, and is used to obtain measurement information from the energy router and send generated control instructions to the energy router.

2. According to the control architecture of the flexible DC traction power supply system based on the energy router in claim 1, It is characterized in that In a flexible DC traction power supply system based on an energy router, the energy router includes a plurality of discrete independent converters, and the energy router includes a distributed structure and a centralized structure. The converters of the energy router with the distributed structure do not share power electronic devices or bridge arms, and the energy conversion processes corresponding to the various ports of the converters of the energy router with the centralized structure share the same power electronic devices or bridge arms.

3. According to the control architecture of the flexible DC traction power supply system based on the energy router in claim 1, It is characterized in that In the flexible DC traction power supply system based on the energy router, the traction station AC bus and the energy router device form two paths to the AC load, so that the AC load is powered only through the energy router or only through the traction station AC bus.

4. According to the control architecture of the flexible DC traction power supply system based on the energy router in claim 1, It is characterized in that The port-level collaborative control layer directly controls the multiple ports of the energy router, and performs constant voltage control on the energy router ports connected to the DC load and the AC load; Under normal operation, the maximum power point tracking control is performed on the energy router ports connected to photovoltaic and wind power; Under normal operation, the energy router port connected to the traction busbar is controlled at a constant voltage, and the voltage reference instruction is provided by the traction station-level collaborative control layer. When the difference between the power of the energy router and the maximum capacity is less than a preset threshold, the energy router is controlled at a constant power; Under normal operation, the energy router port connected to the external power source is controlled according to the fixed AC voltage and fixed reactive power; For the energy router port connected to the energy storage, the output power of the energy storage device is regulated according to the constant power control, and the power reference instruction is provided by the traction station-level collaborative control layer.

5. According to the control architecture of the flexible DC traction power supply system based on the energy router in claim 1, It is characterized in that The system-level collaborative control layer is further used to perform energy management and operation optimization at the flexible DC traction power supply system level, regulate the voltage and power of each traction station, and further regulate the power flow distribution of the flexible DC traction power supply system.

6. According to the control architecture of the flexible DC traction power supply system based on the energy router in claim 1, It is characterized in that The control instructions of the system-level collaborative control layer include DC voltage reference instructions on the traction network side, power reference instructions for energy storage and reactive power reference instructions on the external power supply side. When the number of energy routers in a traction station is greater than 1, the traction station-level collaborative control layer is used as an intermediate control layer to enable the energy routers in the same traction station to operate at the same working point.

Images