Energy optimization scheduling method for car-station-network flexible through-type railway power supply system

Abstract

The application discloses a kind of car-station-net flexible through type railway power supply system energy optimization scheduling method, belong to railway traction power supply and power system flexible interconnection technical field.The application adopts 3AC (grid side)-DC-1AC (railway train side) full-through flexible topology, the core is the double-sided network type flexible converter station of built-in battery energy storage, realize the energy two-way free flow between grid, energy storage, railway train;Propose double-sided independent network + DC bus collaborative voltage stabilizing control strategy, realize seamless switching of grid-connected / off-grid;Build "day-ahead-intraday-real-time" three-level multi-time scale multi-objective optimization scheduling system, give consideration to train reliable power supply, braking energy efficient recovery, grid auxiliary service and energy storage economic operation.The application solves the problems of single target scheduling, energy unidirectional flow and no network construction capability in the prior art, and can be widely applied to various railway power supply scenes such as high-speed, heavy-load and urban rail.

Description

Technical Field

[0001] This invention belongs to the field of railway traction power supply and flexible interconnection technology of power system. Specifically, it relates to an energy optimization scheduling method for a railway flexible power supply system that connects rail train, flexible converter station and power grid. It is applicable to power supply scenarios for various types of rail trains such as high-speed trains, heavy-haul trains and urban rail transit, and can achieve coordinated optimization of reliable power supply for trains, efficient recovery of braking energy and active support from the power grid. Background Technology

[0002] The railway traction power supply system is the core guarantee for the safe and stable operation of rail trains, and its performance directly affects train operating efficiency, power quality, and grid security. Traditional railway traction power supply systems use traction transformers to convert three-phase grid power into single-phase traction loads, which presents several intractable technical challenges: First, single-phase traction loads inject large amounts of negative-sequence current and harmonics into the grid, leading to severe voltage fluctuations, significantly substandard power quality, and increased burden on the grid. Second, the large amount of regenerative braking energy generated during train braking cannot be effectively recovered and can only be consumed through braking resistors, resulting in serious energy waste and reduced overall system efficiency. Third, the system relies on grid voltage phase-locking and adopts a following control mode, lacking independent grid connection capabilities; once a grid failure occurs, the entire power supply system immediately... The system suffers from several drawbacks: first, train shutdowns lead to train paralysis and extremely low power supply reliability; second, the system can only achieve unidirectional energy flow with the grid, passively receiving power from the grid and unable to provide auxiliary services such as active power support, reactive power regulation, and inertial response to the grid, resulting in poor grid friendliness; and third, existing flexible traction power supply schemes with energy storage mostly adopt a single-sided external energy storage mode, which can only achieve simple recovery of braking energy and has not constructed a fully connected, bidirectional energy interaction architecture between the grid, energy storage, and train. The scheduling strategy is simplistic and cannot simultaneously meet multiple needs such as reliable power supply for trains, economical operation of energy storage, and grid auxiliary services, resulting in insufficient overall system economy and adaptability.

[0003] In existing technologies, while continuous in-phase power supply systems can eliminate phase separation and balance negative sequence in the grid, they lack energy storage units, making it impossible to achieve braking energy recovery and emergency power supply during grid failures. Conventional flexible traction power supply systems, although incorporating simple energy storage (mostly supercapacitors), lack dual-sided grid-connection capabilities, allowing only passive charging and discharging and preventing active participation in grid regulation. Photovoltaic-storage integrated railway power supply systems, focusing on renewable energy consumption, fail to prioritize train power supply and grid support, resulting in limited bidirectional energy flow capabilities. In summary, existing railway traction power supply technologies cannot simultaneously address the four core pain points of power quality, energy utilization, power supply reliability, and grid adaptability. There is a lack of a scheduling scheme capable of achieving bidirectional energy flow across all three ends, independent operation of dual-sided grids, and multi-objective collaborative optimization. Therefore, a creative technical solution is urgently needed to fill this technological gap. Summary of the Invention

[0004] This invention provides an energy optimization scheduling method for a flexible through-train power supply system, which aims to address the problems of severe negative sequence, harmonics, and voltage fluctuations in the power grid caused by single-phase traction loads in existing railway traction power supply systems.

[0005] A method for energy optimization scheduling of a flexible through-train power supply system, characterized in that: the system adopts a fully through-flexible flexible topology from the grid side (3AC-DC-1AC) to the track train side; the flexible converter station's built-in battery energy storage system uses a dual-sided grid control, allowing energy to flow freely bidirectionally between the grid, the battery storage system, and the track train; the scheduling method includes the following steps: (1) Constructing the system topology: Three-phase grid-type AC / DC converters are installed on the grid side, and single-phase grid-type DC / AC converters are installed on the train side. The common DC bus in the middle is connected in parallel to the battery energy storage system accessed through the bidirectional DC / DC converter. An energy management system (EMS) is configured to coordinate the operation of the converters and battery energy storage system on both sides. (2) Adopting a dual-side grid-connection control strategy: The three-phase grid-connected AC / DC converter on the grid side adopts VF grid-connection or droop grid-connection control to independently establish the three-phase voltage amplitude and frequency, and can realize grid-connected and off-grid dual-mode operation; the single-phase grid-connected DC / AC converter on the train side adopts single-phase synchronous grid-connection control to stabilize the traction grid voltage and dynamically adapt to sudden changes in train traction / braking power; the battery energy storage system adopts coordinated voltage regulation control to respond in real time to the power difference between the two converters and suppress DC bus voltage fluctuations by rapidly charging and discharging levels. (3) Implement multi-timescale energy optimization scheduling: Establish a three-level multi-timescale multi-objective optimization scheduling system of "day-to-day-real-time", adopt targeted innovative methods to adapt to impact loads, mainly through three-level scheduling constraints to adapt to impact loads, namely: instantaneous high power change of train traction / braking, and the entire scheduling system incorporates the recovery and utilization of train regenerative braking energy into the core consideration. The constraints at each level are clearly defined as follows to achieve efficient energy coordination and stable operation under impact loads.

[0006] The technical effects of this invention are significantly improved compared to existing technologies, as detailed below: (1) Power quality: The present invention achieves negative sequence imbalance <1%, total harmonic distortion (THD) <3%, and voltage deviation ≤±2%, which fully complies with the national power quality standards. In the prior art, the traditional system has negative sequence >10% and THD >15%. The through-type in-phase power supply system only improves the negative sequence, but harmonics and voltage fluctuations still exist. The conventional flexible system only partially improves the power quality.

[0007] (2) Energy utilization rate: The braking energy recovery rate of the present invention is ≥95%, the overall energy efficiency is improved by ≥30%, and the off-peak electricity can be fully utilized to reduce the power supply cost; in the prior art, the braking energy recovery rate of the traditional system is 0, the recovery rate of the through-type in-phase power supply system is ≤50%, the recovery rate of the conventional flexible system is ≤70%, and none of them have the ability to utilize off-peak electricity.

[0008] (3) Power supply reliability: The present invention can be independently powered off the grid for ≥2 hours when the grid fails, and the train will not stop running. The power supply reliability is ≥99.99%; the existing technologies all rely on the grid, and the power supply will stop when the grid fails. The power supply reliability is <99.7%.

[0009] (4) Power grid interaction capability: This invention can actively provide auxiliary services such as frequency regulation, voltage regulation, inertial response, peak shaving and valley filling to the power grid, so that the railway system can be transformed from "power grid load" to "power grid friendly flexible resource", and the power grid acceptance capacity is increased by ≥40%; existing technologies are all passive power receiving, which cannot provide any support to the power grid, but instead increase the burden on the power grid.

[0010] (5) System adaptability: This invention is compatible with all types of trains, including high-speed, heavy-load, and urban rail, and is compatible with all scenarios, including strong power grid, weak power grid, and off-grid. It can be expanded to access new energy sources such as photovoltaic and wind power. Existing technologies are only compatible with a single type of train, rely on strong power grids, and have difficulty accessing new energy sources. Attached Figure Description

[0011] Figure 1 Overall architecture of a flexible power supply system for railways that integrates train, station, and network. Detailed Implementation

[0012] Exemplary embodiments of the present invention will now be described in more detail with reference to the accompanying drawings.

[0013] An energy optimization scheduling method for a railway flexible power supply system with integrated rail-flexible converter station-grid connection is disclosed. The system employs a fully integrated flexible topology of 3AC (grid side) - DC - 1AC (rail train side), and the flexible converter station incorporates a battery energy storage system and uses dual-sided grid control, allowing energy to flow freely bidirectionally among the grid, battery energy storage system, and rail train. The scheduling method includes the following steps: (1) Constructing the system topology: Three-phase grid-type AC / DC converters are installed on the grid side, and single-phase grid-type DC / AC converters are installed on the train side. The common DC bus in the middle is connected in parallel to the battery energy storage system accessed through the bidirectional DC / DC converter. An energy management system (EMS) is configured to coordinate the operation of the converters and battery energy storage system on both sides. (2) Adopting a dual-side grid-connection control strategy: The three-phase grid-connected AC / DC converter on the grid side adopts VF grid-connection or droop grid-connection control to independently establish the three-phase voltage amplitude and frequency, and can realize grid-connected and off-grid dual-mode operation; the single-phase grid-connected DC / AC converter on the train side adopts single-phase synchronous grid-connection control to stabilize the traction grid voltage and dynamically adapt to sudden changes in train traction / braking power; the battery energy storage system adopts coordinated voltage regulation control to respond in real time to the power difference between the two converters and suppress DC bus voltage fluctuations by rapidly charging and discharging levels. (3) Implement multi-timescale energy optimization scheduling: Establish a three-level multi-timescale multi-objective optimization scheduling system of "day-ahead-intraday-real-time", adopt targeted innovative methods to adapt to impact loads, mainly through three-level scheduling constraint innovation to adapt to impact loads (instantaneous high power change of train traction / braking), and the entire scheduling system incorporates the recovery and utilization of train regenerative braking energy into the core consideration. The constraints at each level are clearly defined as follows to achieve efficient energy coordination and stable operation under impact loads; the specific scheduling process and constraint innovation are as follows: a. Day-ahead optimized scheduling (time scale: 1 day, step size: 1 hour): Incorporate train regenerative braking load into the load forecasting system and clarify constraints; specifically: based on train operation plans, traction / regenerative braking load forecasts, new energy (photovoltaic / wind power) output forecasts, time-of-use pricing, and grid dispatching plans, establish an optimization model with the objectives of minimizing power supply costs, minimizing energy storage losses, maximizing grid ancillary service revenue, and maximizing new energy absorption rate, and solve it using mixed integer linear programming (MILP); constraints include: ① Energy storage constraints: (1) (2) in This is the minimum state of charge for energy storage. At the maximum state of charge of energy storage, For minimum charge and discharge power of energy storage, This represents the maximum charging and discharging power for energy storage.

[0014] ② Constraints on the absorption of new energy sources: (3) in, Providing real-time power for new energy sources To maximize the power output of new energy sources that the power grid can accommodate, For energy storage charging power, To ensure the local consumption of new energy sources and reduce wind and solar curtailment, train traction load is guaranteed.

[0015] ③ Regenerative braking constraint: (4) in, To ensure real-time recovery of regenerative braking energy for trains, regenerative braking power is provided. To maximize the power grid's capacity to receive feedback, ensuring that regenerative braking energy is not wasted.

[0016] ④ Power balance constraints: (5) The daily charging and discharging plan (charging period, discharging period, charging and discharging power) of the battery energy storage system, the power boundary of the grid-side converter, the power supply priority of the train side, and the new energy consumption plan are finally determined to form the dispatching benchmark scheme for the next day.

[0017] b. Intraday Rolling Optimization Scheduling (Time Scale: 1 day, Step Size: 5-15 minutes): Based on the day-ahead scheduling scheme, a two-way energy flow balance constraint is designed to dynamically adapt to impulsive load fluctuations, while simultaneously tracking real-time changes in regenerative braking energy and correcting constraint parameters; specifically: the EMS collects real-time operating data every 5-15 minutes (real-time train traction / regenerative braking load, grid voltage / frequency, energy storage SOC, grid AGC / AVC commands, and real-time renewable energy output), and performs rolling corrections to load forecasts, grid demand, and renewable energy output; model predictive control (MPC) is used to adjust the day-ahead scheduling scheme, correcting energy storage charging and discharging power, operating parameters of the two converters, and renewable energy consumption plans; constraints include: ① Two-way energy flow balance constraint: (6) in, (Positive values ​​represent traction load, and negative values ​​represent regenerative braking energy.) To ensure a balanced bidirectional energy flow between the power grid, energy storage, and train, and to mitigate the impact of load fluctuations, the system sets a permissible power fluctuation threshold (to adapt to impulsive loads).

[0018] ② Dynamic constraints on energy storage: (7) Based on real-time SOC, the charging and discharging power is adjusted to prioritize the absorption of regenerative braking energy; ③ Real-time constraints for regenerative braking: (8) in, The available charging power for energy storage ensures real-time recovery of regenerative braking energy.

[0019] c. Real-time closed-loop control (time scale: milliseconds): The EMS collects the operating parameters of each component in real time, designs bidirectional power balance constraints, and quickly responds to impact loads (sudden changes in train traction / braking power) to ensure system stability while maximizing the recovery of regenerative braking energy; it adopts sliding mode variable structure control to quickly adjust the power output of the grid-side converter, train-side converter, and energy storage; the constraints include: ① Bidirectional flow power balance constraint: (9) Among them, each parameter is a real-time instantaneous value to ensure that the energy flow in both directions at the three terminals is instantly balanced during sudden changes in impact load, and to avoid voltage and frequency fluctuations exceeding the standard.

[0020] ② Impact load adaptation constraints: When the train's traction / braking power changes abruptly, the energy storage compensates for the power difference in real time.

[0021] (10) in, This represents the sudden change in train power. To compensate for energy storage power, This is the allowable power surge threshold for the converter, used to suppress the impact of impulsive loads on the power grid and system.

[0022] ③ Regenerative braking fast constraint: After the train braking signal is triggered, the energy storage starts charging within 10ms, prioritizing the absorption of regenerative braking energy. The remaining energy is fed back to the grid through the grid-side converter. The braking energy recovery response time is ≤10ms and the recovery rate is ≥95%.

[0023] ④ Power quality constraints: Negative sequence imbalance <1%, THD <3%, voltage deviation ≤±2%, voltage fluctuation ≤±1% during sudden load changes.

[0024] Specific operation control: In traction mode, the power supply of the grid, new energy sources and energy storage is optimized and distributed, and energy storage is given priority to smooth load impact and reduce grid load fluctuations; in braking mode, the train-side converter is controlled to quickly absorb braking energy and store it in energy storage first, and the surplus energy is fed back to the grid through the grid-side converter; in the event of a grid fault, the grid-side connection is immediately disconnected and switched to off-grid mode, and the energy storage independently supports the operation of the converters on both sides to ensure uninterrupted power supply to the train; at the same time, reactive power is adjusted in real time to suppress harmonics and negative sequence and ensure that the power quality meets the standards.

[0025] Furthermore, preferably, the battery energy storage system uses a lithium iron phosphate battery pack, and its charge / discharge power and state of charge (SOC) are both incorporated into the optimization constraints of the energy management system (EMS).

[0026] Preferably, the grid-side three-phase grid-type AC / DC converter adopts an MMC topology or a two-level topology, and has reactive power compensation, harmonic control, and negative sequence balancing functions. When operating in grid-connected mode, it automatically synchronizes with the grid frequency and phase, and when operating off-grid mode, it maintains the stability of three-phase voltage and frequency.

[0027] Preferably, the single-phase grid-type DC / AC converter on the train side can stabilize the traction grid voltage at 27.5kV, control voltage fluctuations within ±1%, and can quickly respond to large power surges during train traction / braking without voltage overshoot or drop.

[0028] Preferably, the objective function for the multi-timescale energy optimization scheduling is: (11) in, For the cost of purchasing electricity from the power grid, For energy storage loss costs, For system loss costs, Revenue from ancillary services for the power grid.

[0029] Preferably, the constraints of the optimized scheduling also include power balance constraints and power quality constraints: the power balance constraints are as follows: (12) in, Power on the grid side For energy storage power, For train-side power, This refers to system losses.

[0030] The power quality constraints are negative sequence imbalance <1%, total harmonic distortion (THD) <3%, and voltage deviation ≤±2%.

[0031] Preferably, the day-ahead scheduling is solved using mixed integer linear programming (MILP), the intraday rolling scheduling is solved using model predictive control (MPC), and the real-time closed-loop control is solved using sliding mode variable structure control, thereby achieving a balance between global optimization and real-time response.

[0032] Preferably, the system has multiple operating modes, including: in train traction mode, the power grid and energy storage jointly supply power, with priority given to using energy storage to mitigate load surges; in train braking mode, braking energy is preferentially stored in energy storage, with surplus energy fed back to the power grid; in peak-valley mode, energy storage charges during off-peak hours and discharges during peak hours to supply power to the train and transmit power to the power grid; in grid support mode, it responds to grid AGC frequency regulation, AVC voltage regulation, and inertia response commands; in grid fault mode, the system switches to off-grid mode, with energy storage independently supporting the voltage frequencies on both sides to ensure uninterrupted train operation.

[0033] Preferably, the system is also equipped with a detection and protection system that collects parameters such as voltage, current, power, SOC, and frequency in real time, and has protection functions such as overvoltage, overcurrent, short circuit, islanding, and insulation fault to ensure the safe and stable operation of the system.

[0034] Preferably, the system can be expanded to connect to distributed photovoltaic, wind power and other new energy sources, and the output of new energy sources is incorporated into a multi-time-scale optimized scheduling system to realize the local consumption of new energy sources and the coordinated utilization of energy.

[0035] The present invention will be discussed from multiple perspectives below: 1. The system has multiple working modes; Based on the above topology and control scheduling strategy, the system of the present invention has the following 5 working modes, which can be automatically switched according to the actual operating scenario to achieve full scenario adaptation: (1) Train traction mode: When the train is in traction mode, the EMS controls the grid-side converter to output active power, and the energy storage provides auxiliary power supply according to the load fluctuation, smoothing the high power impact during train traction, reducing grid voltage fluctuation, and ensuring stable supply of train traction power.

[0036] (2) Train braking mode: When the train is in braking state, the regenerative braking energy generated by the train is converted into DC power by the train-side converter. The EMS prioritizes the energy storage to absorb the braking energy. When the energy storage reaches the maximum SOC, the excess braking energy is fed back to the public grid through the grid-side converter, so as to achieve a braking energy recovery rate of ≥95%.

[0037] (3) Grid peak-valley arbitrage mode: During the grid valley electricity price period (when the electricity price is low), the EMS controls the grid-side converter to charge the energy storage and store low-priced electricity; during the grid peak electricity price period (when the electricity price is high), the EMS controls the energy storage to discharge and supply power to the train, while outputting active power to the grid to obtain peak-valley arbitrage benefits and reduce the system power supply cost.

[0038] (4) Grid support mode: When the grid experiences frequency fluctuations or voltage deviations, the EMS responds to the grid's AGC (Automatic Generation Control) and AVC (Automatic Voltage Control) commands, controls the grid-side converter and energy storage to output / absorb active and reactive power in coordination, participates in grid frequency regulation, voltage regulation, and inertia response, improves grid stability, and obtains grid ancillary service revenue.

[0039] (5) Power grid fault mode: When a fault occurs in the public power grid (such as power outage or voltage collapse), the EMS quickly detects the power grid fault signal and immediately controls the grid-side converter to disconnect from the power grid. The system switches to the off-grid mode. The energy storage provides a stable voltage to the public DC bus through the bidirectional DC / DC converter. The converters on both sides operate independently to provide uninterrupted power supply to the train and ensure normal train operation for ≥2 hours. After the power grid is restored to normal, it automatically switches back to the grid-connected mode.

[0040] 2. Detection and protection system; The system is equipped with a comprehensive detection and protection system that collects parameters such as voltage, current, power, SOC, frequency, and insulation status from the grid side, train side, DC bus, and energy storage system in real time. It has the following protection functions: overvoltage protection (when the DC bus or traction network voltage exceeds 115% of the rated value, the corresponding strain gauge is cut off), overcurrent protection (when the current exceeds 120% of the rated value, current limiting measures are triggered), short circuit protection (when a short circuit fault is detected, the faulty circuit is quickly cut off), islanding protection (when the grid islanding operation is detected, the system operation mode is adjusted in a timely manner), and insulation fault protection (when the insulation resistance is detected to be lower than the threshold, an alarm is issued and the power supply is cut off), ensuring the safe and stable operation of all system components and preventing the fault from escalating.

[0041] 3. Comparison with existing technologies This invention differs significantly from existing railway traction power supply technologies in terms of technical problems, technical solutions, and technical effects. A detailed comparison is provided below to highlight the inventiveness and technological advancement of this invention: (1). Comparison of technical issues Existing technologies can only address single technical pain points and cannot achieve comprehensive optimization: traditional AT / BT traction power supply systems cannot solve any core problems such as negative sequence, harmonics, braking energy waste, and grid failure outages; continuous in-phase power supply systems can only solve negative sequence and phase separation problems, but lack energy storage and grid construction capabilities; conventional flexible traction power supply systems can only achieve partial recovery of braking energy, but cannot support the grid or operate off-grid; and photovoltaic-storage integrated railway power supply systems only focus on new energy consumption, resulting in an imbalance between the priority of train power supply and grid support.

[0042] This invention solves all the core pain points of existing technologies simultaneously through a single system, including excessive negative sequence and harmonics, wasted braking energy, power grid failure and outage, inability to support the power grid, and single dispatch target. It achieves comprehensive optimization of train power supply, energy storage operation, and power grid support, and its technical coverage and problem-solving capabilities far exceed those of existing technologies.

[0043] (2). Comparison of technical solutions The core limitations of existing technologies are "unidirectional power supply, no energy storage or energy storage only externally connected, follower-type control, and single-objective scheduling": traditional systems have no converters or energy storage, and energy flows in one direction; through-type in-phase power supply systems only have back-to-back converters and no energy storage; conventional flexible systems have energy storage only externally connected on one side, and the converters are follower-type controlled and have no grid-building capability; photovoltaic-energy storage integrated systems have no dual-sided grid-building for energy storage, and scheduling only focuses on the consumption of new energy.

[0044] The technical solution of this invention has a fundamental difference: it is the first to create a fully connected 3AC-DC-1AC dual-sided grid topology with built-in battery energy storage, realizing full bidirectional energy flow between the power grid, energy storage and train; it adopts dual-sided grid control, breaking through the limitations of follower-type control, and realizing seamless switching between grid connection and off-grid; it proposes a three-level multi-time scale multi-objective collaborative scheduling, taking into account train power supply, energy storage economy and grid support. The overall technical solution is a completely new design, not a simple combination or improvement of existing technologies.

[0045] (3). Comparison of technical effects; The technical effects of this invention are significantly improved compared to existing technologies, as detailed below: (a) Power quality: The present invention achieves negative sequence imbalance of <1%, total harmonic distortion (THD) of <3%, and voltage deviation of ≤±2%, which fully complies with the national power quality standards. In the prior art, the negative sequence of traditional systems is >10% and THD is >15%. The through-type in-phase power supply system only improves the negative sequence, but harmonics and voltage fluctuations still exist. Conventional flexible systems only partially improve power quality.

[0046] (b) Energy utilization rate: The braking energy recovery rate of the present invention is ≥95%, the overall energy efficiency is improved by ≥30%, and the off-peak electricity can be fully utilized to reduce the power supply cost; in the prior art, the braking energy recovery rate of the traditional system is 0, the recovery rate of the through-type in-phase power supply system is ≤50%, the recovery rate of the conventional flexible system is ≤70%, and none of them have the ability to utilize off-peak electricity.

[0047] (c) Power supply reliability: The present invention can be independently powered off the grid for ≥2 hours when the grid fails, and the train will not stop running, with a power supply reliability of ≥99.99%; the existing technologies all rely on the grid, and the power supply will stop when the grid fails, with a power supply reliability of <99.7%.

[0048] (d) Power grid interaction capability: This invention can actively provide auxiliary services such as frequency regulation, voltage regulation, inertial response, peak shaving and valley filling to the power grid, so that the railway system can be transformed from "power grid load" to "power grid friendly flexible resource", and the power grid acceptance capacity can be increased by ≥40%; existing technologies are all passive power receiving, which cannot provide any support to the power grid, but instead increase the burden on the power grid.

[0049] (e) System adaptability: This invention is compatible with all types of trains, including high-speed, heavy-load, and urban rail, and is compatible with all scenarios, including strong power grid, weak power grid, and off-grid. It can be expanded to connect to new energy sources such as photovoltaic and wind power. Existing technologies are only compatible with a single type of train, rely on strong power grids, and have difficulty connecting to new energy sources.

[0050] 4. Creative conclusions This invention possesses outstanding substantive features and significant progress, fully meeting the inventiveness requirements of the Patent Law, as specifically demonstrated below: (1) Topological innovation: Existing technologies do not adopt the topological architecture of "3AC-DC-1AC full connection + built-in battery energy storage double-sided grid". This invention is the first to deeply couple the double-sided grid-type converter with the built-in energy storage, realize the free flow of energy in both directions between the power grid, energy storage and train, break the limitation of the unidirectional energy flow of the traditional railway power supply system. The topological architecture is a brand-new design with outstanding substantive features.

[0051] (2). Control innovation: Existing railway traction converters all adopt follow-type control, rely on external voltage phase-locked loop, and have no independent grid construction capability; This invention is the first to create a dual-side independent grid construction + energy storage coordinated voltage stabilization control strategy, realize the independent grid construction operation of the grid-side and train-side converters, and seamless switching between grid-connected and off-grid, solve the technical problems of existing technologies that cannot operate independently and cannot support the grid, and the control method is not obvious, with significant progress.

[0052] (3) Scheduling innovation: Existing scheduling strategies only focus on a single objective (such as braking energy recovery and new energy consumption), without achieving multi-objective coordination, and do not design targeted constraints for train traction / braking impact loads, making them unable to adapt to impact load fluctuations; This invention proposes a three-level multi-timescale optimization scheduling system of "day-intraday-real-time", and designs a targeted innovative method to adapt to impact loads. The core innovation lies in the breakthrough of the three-level scheduling constraints: day-intraday optimization adds new energy consumption constraints, intraday optimization adds bidirectional energy flow balance constraints, and real-time control adds bidirectional flow power balance constraints. Moreover, the entire scheduling system incorporates the recovery and utilization of train regenerative braking energy into the core considerations, clarifies the constraints at each level, and achieves multi-objective coordination of bidirectional energy balance between the power grid, energy storage and train under impact loads, efficient consumption of new energy and maximization of regenerative braking energy recovery. It constructs a brand-new scheduling model and solution method, achieves optimal comprehensive benefits, and the scheduling strategy has outstanding substantive characteristics.

[0053] (4). Creative effect: The present invention has achieved effects far exceeding those of the prior art in terms of power quality, energy utilization rate, power supply reliability and grid interaction capability. It has solved the comprehensive pain points that the prior art cannot solve, achieved technological progress that the prior art could not expect, and has significant practical value.

[0054] In summary, this invention represents a groundbreaking breakthrough in topology architecture, control strategy, and scheduling method, and is fundamentally different from existing technologies. It possesses novelty, inventiveness, and practicality, and meets the requirements for invention patent application.

Claims

1. An energy optimization scheduling method for a flexible through-train power supply system, characterized in that: The system adopts a fully continuous flexible topology from the grid side (3AC-DC-1AC) to the rail train side. The flexible converter station's built-in battery energy storage system uses a dual-sided grid control, allowing energy to flow freely bidirectionally between the grid, battery energy storage system, and rail train. The scheduling method includes the following steps: (1) Constructing the system topology: Three-phase grid-type AC / DC converters are installed on the grid side, and single-phase grid-type DC / AC converters are installed on the train side. The common DC bus in the middle is connected in parallel to the battery energy storage system accessed through the bidirectional DC / DC converter. An energy management system (EMS) is configured to coordinate the operation of the converters and battery energy storage system on both sides. (2) Adopting a dual-side grid-connection control strategy: The three-phase grid-connected AC / DC converter on the grid side adopts VF grid-connection or droop grid-connection control to independently establish the three-phase voltage amplitude and frequency, and can realize grid-connected and off-grid dual-mode operation; the single-phase grid-connected DC / AC converter on the train side adopts single-phase synchronous grid-connection control to stabilize the traction grid voltage and dynamically adapt to sudden changes in train traction / braking power; the battery energy storage system adopts coordinated voltage regulation control to respond in real time to the power difference between the two converters and suppress DC bus voltage fluctuations by rapidly charging and discharging levels. (3) Implement multi-timescale energy optimization scheduling: Establish a three-level multi-timescale multi-objective optimization scheduling system of "day-to-day-real-time", adopt targeted innovative methods to adapt to impact loads, mainly through three-level scheduling constraints to adapt to impact loads, namely: instantaneous high power change of train traction / braking, and the entire scheduling system incorporates the recovery and utilization of train regenerative braking energy into the core consideration. The constraints at each level are clearly defined as follows to achieve efficient energy coordination and stable operation under impact loads.

2. The energy optimization scheduling method for the flexible through-train power supply system of the train-station-network as described in claim 1, characterized in that, The battery energy storage system uses lithium iron phosphate battery packs, and its charge / discharge power and state of charge (SOC) are both incorporated into the optimization constraints of the energy management system.

3. The energy optimization scheduling method for the flexible through-train power supply system of the train-station-network as described in claim 1, characterized in that, The grid-side three-phase grid-type AC / DC converter adopts MMC topology or two-level topology and has reactive power compensation, harmonic control and negative sequence balancing functions. When operating in grid-connected mode, it automatically synchronizes with the grid frequency and phase, and when operating off-grid mode, it maintains the stability of three-phase voltage and frequency.

4. The energy optimization scheduling method for the flexible through-train power supply system of the train-station-network as described in claim 1, characterized in that, The single-phase grid-type DC / AC converter on the train side can stabilize the traction grid voltage at 27.5kV, control voltage fluctuations within ±1%, and can quickly respond to large power surges during train traction / braking without voltage overshoot or drop.

5. The energy optimization scheduling method for a flexible through-train power supply system based on the train-station-network as described in claim 1, characterized in that, The objective function for the multi-timescale energy optimization scheduling is: （11） in, For the cost of purchasing electricity from the power grid, For energy storage loss costs, For system loss costs, Revenue from ancillary services for the power grid.

6. The energy optimization scheduling method for a flexible through-train railway power supply system according to claim 5, characterized in that, The constraints of the optimized scheduling also include power balance constraints and power quality constraints: the power balance constraints are as follows: （12） in, Power on the grid side For energy storage power, For train-side power, For system losses; The power quality constraints are negative sequence imbalance <1%, total harmonic distortion (THD) <3%, and voltage deviation ≤±2%.

7. The energy optimization scheduling method for a flexible through-type railway power supply system based on the train-station-network as described in claim 1, characterized in that, The daytime scheduling is solved using mixed integer linear programming, the intraday rolling scheduling is solved using model predictive control, and the real-time closed-loop control uses sliding mode variable structure control to achieve a balance between global optimization and real-time response.

8. The energy optimization scheduling method for a flexible through-type railway power supply system based on the train-station-network as described in claim 1, characterized in that, The system has multiple operating modes, including: in train traction mode, the power grid and energy storage work together to supply power, with priority given to using energy storage to mitigate load surges; in train braking mode, braking energy is preferentially stored in energy storage, with surplus energy fed back to the power grid; in peak-valley mode, energy storage charges during off-peak hours and discharges during peak hours to supply power to the train and transmit power to the power grid; in grid support mode, it responds to grid AGC frequency regulation, AVC voltage regulation, and inertia response commands; in grid fault mode, the system switches to off-grid mode, with energy storage independently supporting the voltage and frequency on both sides to ensure uninterrupted train operation.

9. The energy optimization scheduling method for a flexible through-type railway power supply system based on the train-station-network as described in claim 1, characterized in that, The system is also equipped with a detection and protection system that collects parameters such as voltage, current, power, SOC, and frequency in real time. It has protection functions such as overvoltage, overcurrent, short circuit, islanding, and insulation fault to ensure the safe and stable operation of the system.

10. The energy optimization scheduling method for a flexible through-train power supply system based on the train-station-network as described in claim 1, characterized in that, The system can be expanded to include distributed photovoltaic, wind power and other new energy sources. The output of new energy sources is incorporated into a multi-time-scale optimized scheduling system to achieve local consumption of new energy sources and coordinated energy utilization.

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