Flexible mutual assistance topology structure of rail transit traction power supply system and control method thereof

Abstract

Embodiments of the present application provide a kind of rail transit traction power supply system flexible mutual aid topology structure and its control method, belong to rail transit power supply technical field.The topology structure includes: traction power supply system, including multiple traction power supply subarea and corresponding main station;Three-port power electronic converter, first AC port and second AC port are connected to corresponding traction power supply subarea respectively, the third AC port of three-port power electronic converter is connected to city distribution network;Power mutual aid dispatching center, through communication link with three-port power electronic converter, city grid and traction power supply system connection, for collecting the multi-source data of city grid and traction power supply system, and based on multi-source data, three-port power electronic converter is controlled.The present application scheme realizes the electric energy two-way flexible mutual aid between rail transit traction power supply system and city grid, improves distributed photovoltaic consumption capacity and promotes grid collaborative operation stability.

Description

Technical Field

[0001] This invention relates to the field of rail transit power supply technology, specifically to a flexible mutual assistance topology for rail transit traction power supply system and a control method for the flexible mutual assistance topology for rail transit traction power supply system. Background Technology

[0002] Traditional rail transit traction power supply systems draw 110kV power from the city power grid through two main substations, which is then stepped down to supply power to the traction network. A tie switch is usually installed between the power supply zones of the two main substations, but this switch is mostly a mechanical circuit breaker that only closes in the event of a power failure or other fault in one of the main substations to provide fault support. During normal operation, it is in the open state, making them two independent power supply islands.

[0003] With the advancement of the "dual carbon" target, more and more rail transit stations (such as depots and parking lots) are using rooftops for distributed photovoltaic (PV) installations. However, the load characteristics of rail transit and the characteristics of PV power generation do not perfectly match in time. When there is sufficient sunlight during the day and the train operation density is not high, PV power generation may be excessive and cannot be fully absorbed by the traction load, resulting in "curtailment" of solar power.

[0004] Due to rapid load growth and unbalanced development, some load-center cities are experiencing problems such as tight distribution corridors, excessively high feeder load rates, and uneven distribution in their medium-voltage distribution networks. Urban power grids face supply pressure during peak hours, while rail transit traction power supply systems have surplus power during off-peak hours or periods of high photovoltaic power generation. The existing architecture lacks a flexible interaction mechanism with the urban power grid, resulting in resource waste. Simultaneously, existing urban medium-voltage distribution networks are prone to insufficient reactive power and excessive voltage fluctuations under peak load or distributed power source integration scenarios, leading to a decline in power quality. Urban rail transit flexible DC traction power supply systems are typically designed with a certain amount of redundant capacity. When traction load levels are low, this redundant capacity cannot be fully utilized, and it has the potential to participate in grid reactive power compensation. Summary of the Invention

[0005] The purpose of this invention is to provide a flexible mutual support topology for rail transit traction power supply system and its control method, so as to at least solve the problems of lack of flexible interaction mechanism between existing rail transit traction power supply system and urban power grid, difficulty in effectively absorbing distributed photovoltaic power, and insufficient utilization of redundant capacity of traction power supply system.

[0006] To achieve the above objectives, the first aspect of the present invention provides a flexible mutual assistance topology for a rail transit traction power supply system. The topology includes: a traction power supply system comprising multiple traction power supply zones and corresponding substations; a three-port power electronic converter disposed at a tie switch between adjacent traction power supply zones, wherein the first and second AC ports of the three-port power electronic converter are respectively connected to the corresponding traction power supply zones, and the third AC port of the three-port power electronic converter is connected to the urban power distribution network; and a power mutual assistance dispatch center connected to the three-port power electronic converter, the urban power grid, and the traction power supply system via a communication link, for collecting multi-source data from the urban power grid and the traction power supply system, and controlling the three-port power electronic converter based on the multi-source data.

[0007] Optionally, at least one traction power supply section of the traction power supply system is equipped with a distributed photovoltaic power generation unit; the distributed photovoltaic power generation unit is connected to the power supply network of the corresponding traction power supply section and is used to generate electrical energy within the traction power supply section.

[0008] Optionally, the electrical energy generated by the distributed photovoltaic power generation unit is preferentially consumed within the traction power supply system; when the traction power supply system has traction load demand, the electrical energy generated by the distributed photovoltaic power generation unit is directly supplied to the traction power supply zone.

[0009] Optionally, when the electrical energy generated by the distributed photovoltaic power generation unit exceeds the internal absorption capacity of the traction power supply system, the surplus electrical energy generated by the distributed photovoltaic power generation unit is fed into the urban power distribution network through the third AC port of the three-port power electronic converter.

[0010] Optionally, the three-port power electronic converter is constructed using a modular multilevel converter topology or a voltage source converter combined topology. The modular multilevel converter topology includes multiple power sub-modules arranged in series and bridge arm circuits connected to the corresponding power sub-modules. Each bridge arm circuit is connected to the first AC port, the second AC port, and the third AC port, respectively. The voltage source converter combined topology includes converter units connected to the first AC port, the second AC port, and the third AC port, respectively. Each converter unit is electrically connected to the DC side to form a converter structure to realize power exchange between the three ports.

[0011] Optionally, the power mutual assistance dispatch center collects urban power grid operation status information and traction power supply system operation information through a communication link; the urban power grid operation status information includes any one or more of the following: urban power grid load rate, bus voltage, and power factor; the traction power supply system operation information includes any one or more of the following: the load status of each main substation transformer, photovoltaic power generation status, and the operation status of the three-port power electronic converter.

[0012] Optionally, the power mutual assistance dispatch center is configured to: acquire the urban power grid operation status information and the traction power supply system operation information, and construct a load change sequence based on the urban power grid operation status information and the traction power supply system operation information; calculate a consistency index of the change direction between the urban power grid load change trend and the traction power supply system load change trend based on the load change sequence; when the change direction consistency index meets a preset consistency condition, generate power change constraint parameters for limiting the port power change rate of the three-port power electronic converter, and generate a control strategy based on the power change constraint parameters; when the change direction consistency index does not meet the preset consistency condition, generate power allocation adjustment parameters for adjusting the port power allocation ratio of the three-port power electronic converter, and generate a control strategy based on the power allocation adjustment parameters.

[0013] Optionally, before generating the control strategy, the power mutual assistance dispatch center is further configured to: perform load fluctuation coupling analysis on the urban power grid operation status information and the traction power supply system operation information, and construct load coupling parameters to characterize the degree of influence of traction power supply system load changes on the urban power grid operation status; identify transient load fluctuation sections in the traction power supply system caused by train starting or braking based on the load coupling parameters; limit the port power regulation rate of the three-port power electronic converter within the transient load fluctuation section, and restore the power regulation range of the three-port power electronic converter after the transient load fluctuation section ends.

[0014] A second aspect of this invention provides a control method for a flexible mutual-assistance topology structure of a rail transit traction power supply system. The method is applied to the aforementioned flexible mutual-assistance topology structure of the rail transit traction power supply system. The method includes: acquiring urban power grid operating status information and traction power supply system operating information; constructing an operating status dataset based on the urban power grid operating status information and the traction power supply system operating information to characterize the load changes of the urban power grid and the traction power supply system; performing operating status correlation analysis based on the operating status dataset to determine the power mutual-assistance demand between the traction power supply system and the urban power grid, and generating a control strategy for controlling the operating status of a three-port power electronic converter; determining the power distribution relationship between each AC port of the three-port power electronic converter based on the control strategy, and generating corresponding converter control commands; and sending the converter control commands to the three-port power electronic converter to control the three-port power electronic converter to perform power exchange between the traction power supply system and the urban power grid.

[0015] On the other hand, the present invention provides a computer-readable storage medium storing instructions that, when executed on a computer, cause the computer to perform the above-described flexible mutual assistance topology control method for rail transit traction power supply system.

[0016] Through the above technical solution, this invention installs a three-port power electronic converter at the interconnection switch of adjacent traction power supply zones, connecting its third AC port to the urban distribution network. Simultaneously, a power mutual assistance dispatch center collects and controls multi-source operational data from both the traction power supply system and the urban power grid, creating a controllable energy mutual assistance channel between the previously relatively independent traction power supply zones and establishing a power interaction path between the traction power supply system and the urban distribution network. Based on this, the traction power supply system, while meeting its own traction load requirements, can output surplus power to the urban distribution network or participate in power regulation when the urban power grid's operating status changes. This enhances the absorption capacity of distributed photovoltaic power and effectively utilizes the redundant capacity of the traction power supply system, thereby improving overall power utilization efficiency and the grid's operating status.

[0017] Other features and advantages of the embodiments of the present invention will be described in detail in the following detailed description section. Attached Figure Description

[0018] The accompanying drawings are provided to further illustrate embodiments of the present invention and form part of the specification. They are used together with the following detailed description to explain the embodiments of the present invention, but do not constitute a limitation thereof. In the drawings: Figure 1 This is a schematic diagram of the flexible mutual assistance topology of a rail transit traction power supply system provided in one embodiment of the present invention; Figure 2 This is an application example diagram of the flexible mutual assistance topology structure of the rail transit traction power supply system provided in one embodiment of the present invention; Figure 3 This is a schematic diagram of the operation model switching provided by one embodiment of the present invention; Figure 4 This is a flowchart illustrating the steps of a flexible mutual support topology control method for a rail transit traction power supply system according to one embodiment of the present invention. Detailed Implementation

[0019] The specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0020] Figure 1This is a schematic diagram of a flexible mutual assistance topology for rail transit traction power supply provided in one embodiment of the present invention. Figure 1 As shown, this invention provides a flexible mutual support topology for rail transit traction power supply. The topology includes: a traction power supply, comprising multiple traction power supply zones and corresponding substations; a three-port power electronic converter, installed at the interconnection switch between adjacent traction power supply zones, wherein the first and second AC ports of the three-port power electronic converter are respectively connected to the corresponding traction power supply zones, and the third AC port of the three-port power electronic converter is connected to the urban power distribution network; and a power mutual support dispatch center, connected to the three-port power electronic converter, the urban power grid, and the traction power supply via a communication link, for collecting multi-source data from the urban power grid and the traction power supply, and controlling the three-port power electronic converter based on the multi-source data.

[0021] In this embodiment of the invention, the present invention provides a controllable energy exchange channel between traction power supplies by setting a three-port power electronic converter at the connection point between adjacent traction power supply zones, and establishes an energy interaction path between traction power supply and urban power distribution network through the third AC port.

[0022] Based on this, the power mutual assistance dispatch center obtains the operation status information of the urban power grid and traction power supply through the communication link, and controls the three-port power electronic converter based on the acquired multi-source data, thereby realizing the power exchange and operation coordination between the various power supply zones of the traction power supply and between the traction power supply and the urban distribution network.

[0023] The above-mentioned structural design enables the traction power supply to exchange energy with the urban power distribution network while meeting the traction power supply requirements, thereby improving operational flexibility and providing technical support for the coordinated operation between the traction power supply and the urban power grid.

[0024] In a specific application scenario, such as Figure 2 As shown, a certain urban rail transit line adopts a dual-substation traction power supply structure. The first and second substations respectively draw AC high-voltage power from the urban power grid, which, after voltage reduction, provides traction power to their corresponding traction power supply sections. The traction power supply sections powered by the first and second substations are connected by a tie line. A three-port power electronic converter is installed at this tie line location to replace the traditional mechanical tie switch, thus forming a controllable flexible tie structure. The first AC 35kV port of the three-port power electronic converter is connected to the AC bus side of the traction power supply section powered by the first substation, the second AC 35kV port is connected to the AC bus side of the traction power supply section powered by the second substation, and the third AC 10kV port is connected to the urban medium-voltage distribution network, thereby establishing a power exchange channel between the traction power supply and the urban distribution network.

[0025] In this example, the power mutual assistance dispatch center interacts with the three-port power electronic converter, the urban power grid, and the traction power supply via a communication link. It acquires real-time information on the urban power grid's operating status and the traction power supply's operating status, and controls the operation of the three-port power electronic converter based on the acquired multi-source data. When a load difference occurs between the first and second main power supply zones, the three-port power electronic converter can perform power exchange between the two traction power supply zones to achieve power mutual assistance within the traction power supply. When the traction power supply has surplus power, it can transmit power to the urban medium-voltage distribution network through the third port of the three-port power electronic converter. When the urban distribution network's operating status changes and requires power support, the converter can also supply power from the traction power supply to the urban distribution network, thus achieving coordinated operation between the traction power supply and the urban distribution network.

[0026] In one embodiment of the present invention, multiple three-port power electronic converters may be configured and arranged at the connection points between different traction power supply zones to establish flexible power exchange channels between adjacent traction power supply zones.

[0027] Specifically, each three-port power electronic converter is installed at the interconnection switch of adjacent traction power supply zones. The first AC port of each three-port power electronic converter is connected to the power supply network of one of the traction power supply zones, the second AC port is connected to the power supply network of another adjacent traction power supply zone, and the third AC port is connected to the urban distribution network. By setting up multiple three-port power electronic converters between multiple traction power supply zones, a multi-point flexible interconnection structure is formed between different zones in the traction power supply system, thereby enabling power mutual assistance between zones according to load changes in each traction power supply zone. At the same time, under the unified dispatch and control of the power mutual assistance dispatch center, each three-port power electronic converter can also transmit surplus power from the traction power supply system to the urban distribution network through the third AC port, or provide power from the traction power supply system to the urban power grid when the urban power grid needs support.

[0028] When the traction power supply system includes only two adjacent traction power supply zones, a three-port power electronic converter can be installed at the interconnection switch between the two traction power supply zones. The first AC port of the three-port power electronic converter is connected to traction power supply zone 1, the second AC port is connected to traction power supply zone 2, and the third AC port is connected to the urban power distribution network, thereby forming a controllable power mutual assistance channel between the two traction power supply zones.

[0029] When a traction power supply system comprises multiple traction power supply zones, it can be deployed by configuring three-port power electronic converters segment by segment between adjacent traction power supply zones. For example, when the traction power supply system includes traction power supply zone 1, traction power supply zone 2, traction power supply zone 3, and traction power supply zone 4, a three-port power electronic converter 1 can be installed between traction power supply zone 1 and traction power supply zone 2, a three-port power electronic converter 2 between traction power supply zone 2 and traction power supply zone 3, and a three-port power electronic converter 3 between traction power supply zone 3 and traction power supply zone 4. The third AC port of each three-port power electronic converter is connected to the urban power distribution network. Through this segment-by-segment deployment method, the traction power supply system forms a distributed power mutual assistance structure along the line direction, consisting of multiple three-port power electronic converters. This enables dynamic power allocation between adjacent traction power supply zones and allows power exchange with the urban power distribution network through the third AC port when needed.

[0030] Preferably, at least one traction power supply zone of the traction power supply is provided with a distributed photovoltaic power generation unit; the distributed photovoltaic power generation unit is connected to the power supply network of the corresponding traction power supply zone and is used to generate electricity within the traction power supply zone.

[0031] Furthermore, the electrical energy generated by the distributed photovoltaic power generation unit is preferentially consumed within the traction power supply; when there is a traction load demand in the traction power supply, the electrical energy generated by the distributed photovoltaic power generation unit is directly supplied to the traction power supply zone.

[0032] Furthermore, when the electrical energy generated by the distributed photovoltaic power generation unit exceeds the internal absorption capacity of the traction power supply, the surplus electrical energy generated by the distributed photovoltaic power generation unit is fed into the urban power distribution network through the third AC port of the three-port power electronic converter.

[0033] In this embodiment of the invention, at least one traction power supply section is equipped with a distributed photovoltaic power generation unit. The distributed photovoltaic power generation unit is connected to the power supply network of the corresponding traction power supply section and is used to generate electricity within the traction power supply section. By arranging distributed photovoltaic power generation units in areas such as rail transit stations, depots, or parking lots, clean energy can be introduced into the traction power supply while meeting the train operation load requirements, thereby forming a power supply structure in which traction load and distributed power sources operate in coordination.

[0034] During operation, the electricity generated by the distributed photovoltaic (PV) power generation units is preferentially absorbed within the traction power supply system. When the traction power supply system has traction load demand, the electricity generated by the distributed PV power generation units directly supplies power to the traction power supply zone, thereby reducing the electricity demand introduced from the urban power grid. Furthermore, when the electricity generated by the distributed PV power generation units exceeds the internal absorption capacity of the traction power supply system, the surplus electricity generated by the distributed PV power generation units is fed into the urban distribution network through the third AC port of the three-port power electronic converter.

[0035] In one embodiment, the power mutual assistance dispatch center continuously monitors the relationship between photovoltaic (PV) power generation and the load of the traction power supply zone. When the PV output exceeds the load demand of the traction power supply zone, the PV grid feeding mode is triggered. After detecting the surplus PV power, the power mutual assistance dispatch center controls the three-port power electronic converter to transmit the excess power to the urban distribution network through the third AC port. During the PV grid feeding process, the power mutual assistance dispatch center simultaneously monitors and controls the power quality of the grid feed to ensure that the power fed into the urban distribution network meets the power quality standards, such as the total harmonic distortion rate and power factor being within preset ranges.

[0036] In another implementation, when the urban power distribution network experiences excessively high load and the traction power supply has a capacity margin, the urban power grid active power support mode can be triggered. At this time, the power mutual assistance dispatch center assesses the traction power supply operation status based on the support request sent by the urban power grid dispatch center, and controls the three-port power electronic converter to absorb power from the traction power supply zone and deliver active power to the urban power distribution network through the third port. During the execution of urban power grid support, the power mutual assistance dispatch center continuously monitors changes in the traction power supply load. When a sudden increase in traction load is detected, the three-port power electronic converter is controlled to reduce the support power at a preset rate, thereby prioritizing the stable operation of the traction power supply.

[0037] Furthermore, when the power factor or voltage deviation of the urban power grid becomes abnormal and there is a capacity margin in traction power supply, the reactive power support mode of the urban power grid can be triggered. The power mutual assistance dispatch center controls the three-port power electronic converter to output or absorb reactive power according to the operating status of the urban power grid, thereby regulating the voltage or compensating the power factor of the urban power grid. The various operating modes are switched according to preset priorities, thereby ensuring stable operation and energy mutual assistance under different operating conditions.

[0038] In a specific application example, such as Figure 3As shown, the power mutual assistance dispatch center continuously collects urban power grid operating status information and traction power supply operating information during operation, and performs operating mode judgment and switching control based on the collected data. After startup, the power mutual assistance dispatch center first monitors the urban power grid power factor, urban power grid load rate, main substation load rate, and photovoltaic power generation in real time. When the urban power grid power factor is detected to be less than or equal to 0.9, or the urban power grid voltage deviation exceeds ±5%, and the traction power supply load rate does not exceed 60%, the power mutual assistance dispatch center triggers the urban power grid reactive power support mode, outputting or absorbing reactive power to the urban distribution network through three-port power electronic converters to regulate the voltage or compensate the power factor of the urban power grid. During the reactive power support process, the urban power grid operating status is continuously monitored. When the urban power grid power factor recovers to above 0.93 and the voltage deviation is less than or equal to ±3%, the operating mode is exited.

[0039] Furthermore, when the 10kV distribution network of the urban power grid experiences excessively high load rates, and the traction power supply load rate does not exceed 60%, the urban power grid dispatch center sends an active power support request to the power mutual assistance dispatch center. After assessing the capacity margin, the power mutual assistance dispatch center controls the three-port power electronic converter to absorb power from the first and second traction power supply zones and transmit active power to the urban distribution network through the third AC port. During the execution of active power support for the urban power grid, the power mutual assistance dispatch center continuously monitors changes in the traction power supply load. When a train starts or a sudden increase in traction load is detected, the three-port power electronic converter is controlled to rapidly reduce the support power at a preset rate to prioritize the stability of the traction power supply.

[0040] In another operating scenario, when the distributed photovoltaic (PV) power generation exceeds the load demand of the traction power supply zone, the power mutual assistance dispatch center triggers the PV feed-to-grid mode. After detecting surplus PV power, the power mutual assistance dispatch center controls the three-port power electronic converter to transmit the excess power to the urban distribution network through the third AC10kV port. During the PV feed-to-grid process, the power quality of the feed-to-grid is monitored and adjusted to ensure that the power fed into the urban distribution network meets power quality requirements, including a total harmonic distortion (THD) of no more than 5% and a power factor of no less than 0.95.

[0041] In this embodiment, the operating modes of the three-port power electronic converter are switched according to a preset priority. The reactive power support mode for the urban power grid has the highest priority, followed by the active power support mode for the urban power grid, then the main substation power mutual assistance mode, and finally the photovoltaic feeder mode. When multiple triggering conditions are met simultaneously, the highest priority operating mode is executed first, thereby ensuring the power quality of the urban power grid and the stability of traction power supply.

[0042] Preferably, the three-port power electronic converter is constructed using a modular multilevel converter topology or a voltage source converter combined topology. The modular multilevel converter topology includes multiple power sub-modules connected in series and bridge arm circuits connected to the corresponding power sub-modules. Each bridge arm circuit is connected to the first AC port, the second AC port, and the third AC port, respectively. The voltage source converter combined topology includes converter units connected to the first AC port, the second AC port, and the third AC port, respectively. Each converter unit is electrically connected to the DC side to form a converter structure to realize power exchange between the three ports.

[0043] In this embodiment of the invention, the three-port power electronic converter is constructed using a modular multilevel converter topology or a voltage source converter combination topology to meet the operational requirements of multi-port power exchange and rapid power regulation between traction power supply and urban distribution network. In one embodiment, the three-port power electronic converter adopts a modular multilevel converter topology, which includes multiple power sub-modules connected in series and corresponding bridge arm circuits connected to the power sub-modules. Each power sub-module can achieve voltage superposition output through a half-bridge or full-bridge structure, thereby forming a multi-level voltage waveform. The bridge arm circuits are respectively connected to the first AC port, the second AC port, and the third AC port. Through the activation or bypass control of each power sub-module in the bridge arm circuit, energy transmission and voltage and current regulation between the ports are realized. Through this structure, the three-port power electronic converter can establish stable power exchange channels between different power supply zones of the traction power supply and between the traction power supply and the urban distribution network.

[0044] In another embodiment, the three-port power electronic converter adopts a voltage source converter combined topology. The voltage source converter combined topology includes converter units respectively connected to the first, second, and third AC ports, and each converter unit is electrically connected via a DC-side bus to form a unified converter structure. Through DC-side energy coupling, power exchange and regulation can be achieved between the converter units, thereby completing the power conversion and distribution between the three ports. The power mutual assistance dispatch center can regulate the active and reactive power between the ports by controlling the switching state of each converter unit, realizing bidirectional power transmission between traction power supply zones and between traction power supply and the urban distribution network. Through the above structural configuration, the three-port power electronic converter can achieve multi-port power exchange under different operating conditions and provide a power electronic interface for flexible mutual assistance between traction power supply and the urban distribution network.

[0045] Preferably, the power mutual assistance dispatch center collects urban power grid operation status information and traction power supply operation information through a communication link; the urban power grid operation status information includes any one or more of the following: urban power grid load rate, bus voltage, and power factor; the traction power supply operation information includes any one or more of the following: the load status of each main substation transformer, photovoltaic power generation status, and the operation status of the three-port power electronic converter.

[0046] Furthermore, the power mutual assistance dispatch center is configured to: acquire the urban power grid operation status information and the traction power supply operation information, and construct a load change sequence based on the urban power grid operation status information and the traction power supply operation information; calculate the consistency index of the change direction between the urban power grid load change trend and the traction power supply load change trend based on the load change sequence; when the change direction consistency index meets the preset consistency condition, generate power change constraint parameters for limiting the port power change rate of the three-port power electronic converter, and generate a control strategy based on the power change constraint parameters; when the change direction consistency index does not meet the preset consistency condition, generate power allocation adjustment parameters for adjusting the port power allocation ratio of the three-port power electronic converter, and generate a control strategy based on the power allocation adjustment parameters.

[0047] In this embodiment of the invention, the power mutual assistance dispatch center collects urban power grid operation status information and traction power supply operation information through a communication link. The urban power grid operation status information includes any one or more of the following: urban power grid load rate, bus voltage, and power factor. The traction power supply operation information includes the load status of each main substation transformer, photovoltaic power generation status, and the operation status of the three-port power electronic converter. The power mutual assistance dispatch center collects and processes the above operation data in real time and constructs an operation status data sequence between the urban power grid and the traction power supply to reflect the load changes of both over time.

[0048] In one embodiment, the power mutual assistance dispatch center constructs a time series from the collected urban power grid load rate sequence and traction power supply load rate sequence to form a load change sequence:

[0049] in, This represents the load change sequence of the urban power grid within a time window. This represents the load change sequence of traction power supply within the same time window. By performing differential processing on the above load change sequence, the load change trends of the urban power grid and the traction power supply load can be obtained:

[0050] Based on the above trends, a consistency index between the changing directions of urban power grid load and traction power supply load can be further calculated:

[0051] in, This indicates an index representing consistency in the direction of change. When... Greater than the preset consistency threshold This indicates a high degree of consistency between the urban power grid load change trend and the traction power supply load change trend. In this case, the power mutual assistance dispatch center generates power change constraint parameters to limit the rate of power change at the ports of the three-port power electronic converter, in order to avoid shocks caused by sudden power changes. For example, in this situation, the rate of power change at the converter ports can be limited:

[0052] in, This is a preset power change rate limit value.

[0053] When the consistency index of the change direction does not meet the preset consistency condition, it indicates that there is a significant difference between the urban power grid load change trend and the traction power supply load change trend. At this time, the power mutual assistance dispatch center generates power allocation adjustment parameters for adjusting the port power allocation ratio of the three-port power electronic converter, so as to achieve power coordination between traction power supply and urban power grid.

[0054] In another embodiment, when the operation enters the active power support mode of the urban power grid, the power allocation between the first port and the second port can be calculated according to the following formula:

[0055] in, The rated capacity of the main transformer, and These represent the current power requirements of the corresponding traction power supply zones. To the maximum power that can be supported, This represents the supporting power required by the urban power grid. Based on the above proportions, the supporting power allocation results for the first and second ports can be obtained. When At that time, then order To ensure the safe operation of traction power supply.

[0056] Furthermore, during the operation of the urban power grid in active power support mode, the power mutual assistance dispatch center continuously monitors the total active load of traction power supply. When a sudden increase in traction load is detected, the support power of the urban power grid needs to be adjusted rapidly. A sudden increase in traction load needs to meet the following two conditions: Rate of change condition:

[0057] Absolute value condition:

[0058] in, This is a preset threshold. When the above conditions are met, the power mutual assistance dispatch center immediately sends a control command to the three-port converter, with a slope not lower than the preset threshold. The rate of reduction of the urban power grid support power is reduced, and the active power support mode of the urban power grid is automatically exited after the support power is reduced to zero, thereby prioritizing the stable operation of traction power supply.

[0059] Furthermore, when switching between different operating modes, to avoid shocks caused by sudden changes in power commands, a smooth transition strategy based on power reference values ​​can be adopted. The mathematical model is as follows:

[0060] in, , These are the active and reactive power reference values ​​before the mode switch. , This is a reference value for the target pattern. Weighting function. satisfy:

[0061] in, It is a time constant that is adaptively adjusted according to the mode switching type; The transition time between modes typically satisfies 。

[0062] The above control strategy can achieve smooth switching between different operating modes, thereby avoiding the impact of sudden power command changes and improving the stability of traction power supply and urban power grid coordinated operation.

[0063] Preferably, before generating the control strategy, the power mutual assistance dispatch center is further configured to: perform load fluctuation coupling analysis on the urban power grid operation status information and the traction power supply operation information, and construct load coupling parameters to characterize the degree of influence of traction power supply load changes on the urban power grid operation status; identify transient load fluctuation sections in traction power supply caused by train starting or braking based on the load coupling parameters; limit the port power regulation rate of the three-port power electronic converter within the transient load fluctuation section, and restore the power regulation range of the three-port power electronic converter after the transient load fluctuation section ends.

[0064] In this embodiment of the invention, the power mutual assistance dispatch center collects operational status data such as urban power grid load rate, bus voltage, and power factor through a communication link, and simultaneously collects data such as the load power of each main transformer in traction power supply, load changes in traction power supply zones, and the operational status of three-port power electronic converters. Based on the above data, an urban power grid load sequence is constructed. With traction power supply load sequence :

[0065] Based on this, the power mutual assistance dispatch center calculates the coupling relationship between changes in traction power supply load and changes in the urban power grid operating status, and constructs load coupling parameters. :

[0066] in:

[0067] The load coupling parameters Used to characterize the impact of changes in traction power supply load on the operation of the urban power grid. Greater than the preset threshold When this occurs, it indicates that changes in traction power supply load have a significant impact on the urban power grid. At this point, the power mutual assistance dispatch center will further execute the transient load identification process.

[0068] Furthermore, the power distribution dispatch center identifies transient load fluctuation sections caused by train starting or regenerative braking based on the traction power supply load change rate. The traction load change rate is defined as:

[0069] in This represents the total active power of traction power supply. The system is considered to have entered the transient load fluctuation zone when the following conditions are met:

[0070] Simultaneously satisfy the absolute value condition:

[0071] in, The load change rate threshold, Main transformer rated capacity, This is a proportional coefficient used to prevent false triggering under low load conditions.

[0072] When the transient load fluctuation segment is detected, the power mutual assistance dispatch center limits the port power regulation rate of the three-port power electronic converter to prevent sudden changes in traction load from being transmitted to the urban power grid through the converter. At this time, the converter port power change rate satisfies:

[0073] in This indicates the port output power of the three-port power electronic converter. This is the power regulation rate limit value.

[0074] When the transient load fluctuation period ends, that is, when the load change rate satisfies:

[0075] And the duration exceeds the preset stable time window. At this time, the power mutual assistance dispatch center determines that the stable operation state has been restored and restores the normal power regulation range of the three-port power electronic converter. At this time, the converter port power regulation constraint is restored to:

[0076] in This represents the maximum allowable power regulation rate under normal operating conditions. Through the aforementioned load fluctuation coupling analysis and transient load identification mechanism, the power regulation behavior of the three-port power electronic converter can be constrained under typical operating conditions such as train start-up or regenerative braking. This avoids the adverse effects of transient fluctuations in traction power supply load on the stability of the urban power grid, and improves the stability and reliability of the coordinated operation between rail transit traction power supply and the urban power grid.

[0077] In one possible implementation, the power balance dispatch center obtains train operation plan data within a future preset time window by interacting with the rail transit operation control system. This data includes train departure times, operating sections, and train density. Based on this train operation plan data, a traction load prediction sequence is constructed. When forecasts indicate that multiple trains will start simultaneously or in quick succession within a future time window, the power balance dispatch center identifies potential sections of concentrated traction load growth in advance and pre-adjusts the power regulation strategy of the three-port power electronic converter before the arrival of such sections.

[0078] For example, when a rapid increase in traction load is predicted, the power balance dispatch center can reduce the supporting power of the urban power grid or adjust the power balance ratio between traction power supply zones in advance to reserve capacity margin for the traction power supply system. When it is predicted that trains will enter sections with intensive regenerative braking, the power supply capacity of the three-port power electronic converter to the urban distribution network can be increased in advance to absorb the regenerative energy that may appear in the traction system.

[0079] In this way, the power mutual assistance dispatch center can not only respond to load changes that have already occurred, but also make forward-looking adjustments to traction load changes based on train operation patterns, thereby reducing the impact of transient load fluctuations on the urban power grid and improving the overall stability and energy utilization efficiency of the system.

[0080] Figure 4 This is a flowchart illustrating the steps of a flexible mutual-assistance topology control method for a rail transit traction power supply system according to one embodiment of the present invention. Figure 4 As shown, this invention provides a flexible mutual assistance topology control method for a rail transit traction power supply system, the method comprising: Step S10: Obtain urban power grid operation status information and traction power supply system operation information, and construct an operation status dataset to characterize urban power grid load changes and traction power supply system load changes based on the urban power grid operation status information and the traction power supply system operation information.

[0081] Step S20: Perform operational status correlation analysis based on the operational status dataset to determine the power mutual assistance demand between the traction power supply system and the urban power grid, and generate a control strategy for controlling the operational status of the three-port power electronic converter.

[0082] Step S30: Determine the power distribution relationship between each AC port of the three-port power electronic converter based on the control strategy, and generate the corresponding converter control command.

[0083] Step S40: Send the converter control command to the three-port power electronic converter to control the three-port power electronic converter to perform power exchange between the traction power supply system and the urban power grid.

[0084] The present invention also provides a computer-readable storage medium storing instructions that, when executed on a computer, cause the computer to perform the above-described flexible mutual assistance topology control method for rail transit traction power supply system.

[0085] Those skilled in the art will understand that all or part of the steps in the methods of the above embodiments can be implemented by a program instructing related hardware. This program is stored in a storage medium and includes several instructions to cause a microcontroller, chip, or processor to execute all or part of the steps of the methods described in the various embodiments of the present invention. The aforementioned storage medium includes various media capable of storing program code, such as a USB flash drive, a portable hard drive, a read-only memory (ROM), a random access memory (RAM), a magnetic disk, or an optical disk.

[0086] The optional embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the embodiments of the present invention are not limited to the specific details described above. Within the scope of the technical concept of the embodiments of the present invention, various simple modifications can be made to the technical solutions of the embodiments of the present invention, and these simple modifications all fall within the protection scope of the embodiments of the present invention. It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. To avoid unnecessary repetition, the embodiments of the present invention will not further describe the various possible combinations.

[0087] Furthermore, various different embodiments of the present invention can be combined in any way, as long as they do not violate the spirit of the embodiments of the present invention, they should also be regarded as the content disclosed by the embodiments of the present invention.

Claims

1. A flexible mutual-assistance topology for a rail transit traction power supply system, characterized in that, The topology includes: The traction power supply system includes multiple traction power supply zones and corresponding main substations; A three-port power electronic converter is installed at the interconnection switch between adjacent traction power supply zones. The first AC port and the second AC port of the three-port power electronic converter are respectively connected to the corresponding traction power supply zones, and the third AC port of the three-port power electronic converter is connected to the urban power distribution network. The power mutual assistance dispatch center is connected to the three-port power electronic converter, the urban power grid, and the traction power supply system via a communication link. It is used to collect multi-source data from the urban power grid and the traction power supply system, and to control the three-port power electronic converter based on the multi-source data.

2. The flexible mutual assistance topology structure of the rail transit traction power supply system according to claim 1, characterized in that, At least one traction power supply zone of the traction power supply system is equipped with a distributed photovoltaic power generation unit. The distributed photovoltaic power generation unit is connected to the power supply network of the corresponding traction power supply zone and is used to generate electricity within the traction power supply zone.

3. The flexible mutual assistance topology structure of the rail transit traction power supply system according to claim 2, characterized in that, The electrical energy generated by the distributed photovoltaic power generation unit is preferentially consumed within the traction power supply system; When the traction power supply system has traction load demand, the electrical energy generated by the distributed photovoltaic power generation unit is directly supplied to the traction power supply zone.

4. The flexible mutual assistance topology structure of the rail transit traction power supply system according to claim 2, characterized in that, When the electrical energy generated by the distributed photovoltaic power generation unit exceeds the internal absorption capacity of the traction power supply system, the surplus electrical energy generated by the distributed photovoltaic power generation unit is fed into the urban power distribution network through the third AC port of the three-port power electronic converter.

5. The flexible mutual assistance topology structure of the rail transit traction power supply system according to claim 1, characterized in that, The three-port power electronic converter is constructed using a modular multilevel converter topology or a voltage source converter combined topology. The modular multilevel converter topology includes multiple power sub-modules arranged in series and bridge arm circuits connected to the corresponding power sub-modules. Each bridge arm circuit is connected to the first AC port, the second AC port, and the third AC port, respectively; The voltage source converter combined topology includes converter units that are respectively connected to the first AC port, the second AC port and the third AC port. Each converter unit is electrically connected to the DC side to form a converter structure to realize power exchange between the three ports.

6. The flexible mutual assistance topology structure of the rail transit traction power supply system according to claim 1, characterized in that, The power mutual assistance dispatch center collects urban power grid operation status information and traction power supply system operation information through communication links; The urban power grid operation status information includes: Any one or more of the following: urban power grid load rate, bus voltage, and power factor; The traction power supply system operation information includes: Any one or more of the following: the load status of each main transformer, the photovoltaic power generation status, and the operating status of the three-port power electronic converter.

7. The flexible mutual assistance topology structure of the rail transit traction power supply system according to claim 1, characterized in that, The power mutual assistance dispatch center is configured as follows: The system acquires the urban power grid operation status information and the traction power supply system operation information, and constructs a load change sequence based on the urban power grid operation status information and the traction power supply system operation information. Based on the load change sequence, calculate the consistency index of the change direction between the urban power grid load change trend and the traction power supply system load change trend; When the consistency index of the change direction meets the preset consistency condition, a power change constraint parameter is generated to limit the port power change rate of the three-port power electronic converter, and a control strategy is generated based on the power change constraint parameter. When the consistency index of the change direction does not meet the preset consistency condition, a power allocation adjustment parameter is generated to adjust the port power allocation ratio of the three-port power electronic converter, and a control strategy is generated based on the power allocation adjustment parameter.

8. The flexible mutual assistance topology structure of the rail transit traction power supply system according to claim 7, characterized in that, Before generating the control strategy, the power mutual assistance scheduling center is also configured as follows: A load fluctuation coupling analysis is performed on the urban power grid operation status information and the traction power supply system operation information to construct load coupling parameters to characterize the degree of influence of traction power supply system load changes on the urban power grid operation status. Based on the load coupling parameters, identify transient load fluctuation sections in the traction power supply system caused by train starting or braking; The port power regulation rate of the three-port power electronic converter is limited during the transient load fluctuation period, and the power regulation range of the three-port power electronic converter is restored after the transient load fluctuation period ends.

9. A control method for a flexible mutual-assist topology structure in a rail transit traction power supply system, characterized in that, The method is applied to the flexible mutual assistance topology of the rail transit traction power supply system according to any one of claims 1-8, and the method includes: Obtain urban power grid operation status information and traction power supply system operation information, and construct an operation status dataset to characterize urban power grid load changes and traction power supply system load changes based on the urban power grid operation status information and the traction power supply system operation information; Based on the aforementioned operating status dataset, an operating status correlation analysis is performed to determine the power mutual assistance demand between the traction power supply system and the urban power grid, and a control strategy for controlling the operating status of the three-port power electronic converter is generated. Based on the control strategy, the power distribution relationship between each AC port of the three-port power electronic converter is determined, and corresponding converter control commands are generated. The converter control command is sent to the three-port power electronic converter to control the three-port power electronic converter to perform power exchange between the traction power supply system and the urban power grid.

10. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores instructions that, when executed on a computer, cause the computer to perform the flexible mutual assistance topology control method for rail transit traction power supply system as described in claim 9.

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