Magnetic-levitation train traction power supply system and method based on medium-voltage direct-current bus

Abstract

The invention belongs to the technical field of magnetic-levitation train traction power supply, and discloses a medium-voltage direct-current bus-based magnetic-levitation train traction power supply system and method. The system comprises a high-voltage alternating-current power grid, a four-quadrant rectification system, a full-line through medium-voltage direct-current bus, a high-power traction conversion system, a stator switching station, a long-stator linear synchronous motor and a distributed renewable energy source and energy storage system. The four-quadrant rectification system rectifies the high-voltage alternating current and then transmits the rectified high-voltage alternating current to a medium-voltage direct-current bus; the distributed renewable energy source and energy storage system is connected to a bus through a multi-port converter to realize electric energy injection or absorption; the high-power traction conversion system converts direct current into variable-frequency and variable-voltage alternating current, and the variable-frequency and variable-voltage alternating current is switched by the stator switching station and conveyed to a corresponding stator section of the long-stator linear synchronous motor so as to drive the maglev train. According to the invention, distributed energy is integrated through the medium-voltage direct-current bus, so that the system energy efficiency and the power supply reliability are improved.

Description

Technical Field

[0001] This invention belongs to the field of traction power supply technology for maglev trains, specifically relating to a traction power supply system and method for maglev trains based on a medium-voltage DC bus. Background Technology

[0002] Traditional maglev train traction power supply systems typically employ AC power, resulting in a large amount of feeder cables and high transmission losses. Furthermore, existing systems struggle to efficiently integrate and utilize distributed renewable energy sources, and cannot flexibly recover and reuse train braking energy. In addition, to drive a long-stator linear synchronous motor, the system requires rapid and reliable power switching between stator segments; however, the dynamic response and coordinated control capabilities of traditional solutions need improvement, hindering further enhancements to the system's overall energy efficiency and operational flexibility. Summary of the Invention

[0003] This invention aims to solve the problems of high power supply loss, difficulty in accessing renewable energy, and insufficient power supply flexibility of the stator section in traditional maglev train traction power supply systems. By constructing a new system architecture based on a medium-voltage DC bus, it aims to reduce energy consumption, improve energy utilization efficiency, and enhance the reliability of system power supply.

[0004] Therefore, the present invention provides a maglev train traction power supply system based on a medium-voltage DC bus, the system comprising:

[0005] High-voltage AC power grid;

[0006] The four-quadrant rectifier system has its input terminal connected to the high-voltage AC power grid via an input step-down transformer.

[0007] A medium-voltage DC busbar, laid along the entire maglev line, is connected to the output of the four-quadrant rectifier system, serving as the system's sole main trunk for power collection and distribution.

[0008] A high-power traction converter system, the DC side of which is connected to the medium-voltage DC bus;

[0009] The stator switch station is connected to the AC output terminal of the high-power traction converter system.

[0010] A long stator linear synchronous motor, wherein the segmented stator segments are connected to the high-power traction converter system via corresponding stator switch stations; and:

[0011] The distributed renewable energy and energy storage system is connected to the medium-voltage DC bus through a converter with multi-port coordination control function to achieve bidirectional energy flow and power coordination.

[0012] The high-power traction converter system, the distributed renewable energy and energy storage system, and the stator switch station are arranged in a distributed manner along the maglev track.

[0013] The high-power traction converter system is used to convert the DC power on the medium-voltage DC bus into a frequency- and voltage-changing three-phase AC power to drive a long stator linear synchronous motor.

[0014] The stator switching station is used to realize the dynamic switching and series power supply of adjacent high-power traction converter systems to the corresponding stator sections, thereby driving the long stator linear synchronous motor and the maglev train.

[0015] The present invention also provides a traction power supply method for maglev trains based on a medium-voltage DC bus, the method comprising:

[0016] The high-voltage AC power from the high-voltage AC grid is rectified into DC power by the four-quadrant rectifier system and then transmitted to the medium-voltage DC bus.

[0017] The distributed renewable energy and energy storage system injects electrical energy into the medium-voltage DC bus according to the medium-voltage DC bus voltage and dispatch instructions, and / or absorbs electrical energy from the medium-voltage DC bus for storage.

[0018] The high-power traction converter system converts the DC power on the medium-voltage DC bus into three-phase AC power with adjustable frequency and voltage. The output frequency and voltage of the three-phase AC power are adjusted according to the real-time position and power requirements of the train.

[0019] The stator switching station dynamically switches the converted three-phase AC power according to the train's running position and delivers it to the corresponding stator section of the long stator linear synchronous motor to drive the maglev train.

[0020] This invention significantly reduces the amount of feeder cables and power transmission losses by employing a continuous medium-voltage DC bus. The integration of distributed renewable energy and energy storage systems enhances the capacity for clean energy absorption and the flexibility of system operation. The coordinated control of the high-power traction converter system and the stator switch station enables precise and dynamic power supply to the stator section of the long stator linear synchronous motor, thereby effectively improving the energy efficiency and reliability of the entire traction power supply system. Attached Figure Description

[0021] Figure 1 This is the system described in this invention.

[0022] Figure 2 This is the four-quadrant rectifier system described in this invention.

[0023] Figure 3 This is the high-power traction converter system described in this invention.

[0024] Figure 4 This is a typical multi-port converter structure diagram according to the present invention. Detailed Implementation

[0025] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0026] The system of the present invention is as follows Figure 1 As shown, the system mainly includes a high-voltage AC grid, a four-quadrant rectifier system, a medium-voltage DC bus, a high-power traction converter system, a distributed renewable energy and energy storage system, a stator switchyard (composed of multiple sets of high-speed switching equipment), and a long-stator linear synchronous motor. The system uses the medium-voltage DC bus as the core for power collection and distribution, significantly reducing the amount of feeder cables and supporting the integration of distributed energy and energy storage systems. The system adopts a hierarchical control structure, with the bottom layer consisting of power electronic converter control equipment and the upper layer being an embedded centralized control system. Communication is achieved through fiber optic Ethernet to ensure real-time coordination.

[0027] The high-voltage AC grid serves as the external power source, typically a 20kV or 35kV three-phase AC power supply. The four-quadrant rectifier system connects to the high-voltage AC grid via an input step-down transformer, which reduces the AC voltage to a suitable rectification level, such as 3kV or 5kV. The four-quadrant rectifier system comprises multiple parallel four-quadrant rectifier units, each consisting of one input step-down transformer and at least one four-quadrant rectifier. The four-quadrant rectifiers utilize fully controlled power devices (such as IGCTs) to form a three-phase bridge circuit, achieving unity power factor operation and rectifying AC to DC while suppressing harmonics and enabling bidirectional energy flow. The parallel design of multiple units improves system reliability; if some units fail, the remaining units can continue operating. The DC output from the four-quadrant rectifier system is supplied to the medium-voltage DC bus. The medium-voltage DC bus is fully connected and laid along the maglev line. Its rated voltage level is preferably 5kV to 10kV to reduce DC transmission loss and meet the input voltage requirements of subsequent converters. Figure 2 The topology of two parallel four-quadrant rectifier systems based on a midpoint clamping three-level converter is shown.

[0028] The high-power traction converter system and the distributed renewable energy and energy storage system are distributedly connected via a medium-voltage DC bus. The main function of this high-power traction converter system is to convert the DC power from the medium-voltage DC bus into three-phase AC power with adjustable frequency and voltage to drive a long-stator linear synchronous motor. In high-power applications, the traction converter can adopt a modular cascaded multilevel topology or a midpoint-clamped three-level topology. The modular cascaded multilevel converter consists of multiple power submodules connected in series, capable of outputting high-quality multilevel voltage waveforms and reducing voltage variation rate and harmonic content; the midpoint-clamped three-level converter has a relatively simple structure and higher efficiency. To meet the high voltage required for high-speed train operation, two adjacent high-power traction converter systems are connected in series to jointly supply power to the long stator. Figure 3 A schematic diagram of series power supply for a long stator linear motor based on a midpoint clamping three-level converter is shown.

[0029] Distributed renewable energy and energy storage systems include one or more combinations of photovoltaic power generation units, wind power generation units, supercapacitor energy storage units, and battery energy storage units. These units are connected to a medium-voltage DC bus via a multi-port converter. A typical multi-port converter structure is shown below. Figure 4 As shown, the system features multiple decoupled power interfaces, enabling coordinated control and power management of different energy units. Specifically, photovoltaic and wind power generation units feed power to the medium-voltage DC bus when energy is abundant, supplementing traction power supply needs; supercapacitor energy storage units respond quickly to power fluctuations, suppressing sudden changes in bus voltage; and battery energy storage units participate in energy time-shifting, storing energy during low-load periods and releasing it during high-load periods, improving system energy efficiency and renewable energy absorption capacity. By integrating distributed energy through the medium-voltage DC bus, the system achieves coordinated operation of source-grid-load-storage, effectively improving the utilization efficiency of renewable energy and power supply reliability. Simultaneously, the system optimizes renewable energy output and energy storage charging and discharging processes through intelligent scheduling strategies, balancing the dynamic demand of traction loads and reducing dependence on the traditional power grid. The system also possesses fault isolation and rapid recovery capabilities; when a unit fails, the multi-port converter can dynamically adjust the power path to ensure traction power supply continuity. Combined with real-time communication and predictive algorithms, the system can pre-schedule energy storage output, smoothing renewable energy fluctuations and improving overall operational stability.

[0030] The stator switching station is located between the high-power traction converter system and the long-stator linear synchronous motor. The stator windings of the long-stator linear synchronous motor are arranged in segments along the line, with each segment powered by a corresponding traction converter. The stator switching station contains multiple sets of high-speed switching equipment to enable switching and series power supply to stator segments from adjacent traction converters. When the maglev train is running, the centralized control system, based on the train's position, controls the stator switching station to connect the current stator segment to the power supply circuit while simultaneously disconnecting any stator segments that have already passed behind, ensuring continuous power supply to the train during operation.

[0031] The centralized control system communicates with the four-quadrant rectifier system, high-power traction converter system, stator switch station, and distributed renewable energy and energy storage system, for example, via fiber optic Ethernet or industrial bus. The centralized control system collects real-time information on train operating status (such as position, speed, and power demand), grid status, renewable energy generation capacity, and energy storage unit state of charge, and performs optimization calculations based on this information.

[0032] The centralized control system dynamically controls the output frequency and voltage of the high-power traction converter system to match the train's needs, controls the switching operation of the stator switch station to achieve timely switching of the stator section, and regulates the energy exchange between the four-quadrant rectifier system and the distributed renewable energy and energy storage system, giving priority to the consumption of renewable energy, and recovering energy to the energy storage unit when the train brakes, so as to achieve the optimal overall energy efficiency of the system.

[0033] This invention also provides a method applied to the aforementioned system. The method includes: First, rectifying high-voltage AC power from the high-voltage AC grid into DC power using a four-quadrant rectifier system and transmitting it to a medium-voltage DC bus. Simultaneously, a distributed renewable energy and energy storage system injects electrical energy into the medium-voltage DC bus (when photovoltaic or wind power is generated) or absorbs and stores electrical energy from the bus (when energy storage units are charging or train braking energy is recovered), depending on actual conditions. Then, a high-power traction converter system converts the DC power on the medium-voltage DC bus into frequency and voltage adjustable three-phase AC power, with its output frequency and voltage precisely adjusted according to the train's real-time speed and power requirements. Finally, the converted three-phase AC power is switched and transmitted to the corresponding stator section of a long-stator linear synchronous motor via a stator switching station to drive the maglev train. Throughout the process, a centralized control system continuously monitors the system status and dynamically coordinates the power allocation of each unit based on the train's operating position, power requirements, and the power generation and storage status of the distributed renewable energy and energy storage system, ensuring the continuity, stability, and economy of power supply.

[0034] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A traction power supply system for maglev trains based on a medium-voltage DC bus, characterized in that, The system includes: High-voltage AC power grid; The four-quadrant rectifier system has its input terminal connected to the high-voltage AC power grid via an input step-down transformer. A medium-voltage DC busbar, laid along the entire maglev line, is connected to the output of the four-quadrant rectifier system, serving as the system's sole main trunk for power collection and distribution. A high-power traction converter system, the DC side of which is connected to the medium-voltage DC bus; The stator switch station is connected to the AC output terminal of the high-power traction converter system. A long stator linear synchronous motor, wherein the segmented stator segments are connected to the high-power traction converter system via corresponding stator switch stations; and: The distributed renewable energy and energy storage system is connected to the medium-voltage DC bus through a converter with multi-port coordination control function to achieve bidirectional energy flow and power coordination. The high-power traction converter system, the distributed renewable energy and energy storage system, and the stator switch station are arranged in a distributed manner along the maglev track. The high-power traction converter system is used to convert the DC power on the medium-voltage DC bus into a frequency- and voltage-changing three-phase AC power to drive a long stator linear synchronous motor. The stator switching station is used to realize the dynamic switching and series power supply of adjacent high-power traction converter systems to the corresponding stator sections, thereby driving the long stator linear synchronous motor and the maglev train.

2. The system according to claim 1, characterized in that, The four-quadrant rectifier system comprises multiple sets of parallel four-quadrant rectifier units, each set of which consists of one input step-down transformer and at least one four-quadrant rectifier.

3. The system according to claim 1, characterized in that, The rated voltage of the medium-voltage DC bus is 5kV to 10kV.

4. The system according to claim 1, characterized in that, The distributed renewable energy and energy storage system includes one or more combinations of photovoltaic power generation units, wind power generation units, supercapacitor energy storage units, and battery energy storage units.

5. The system according to claim 4, characterized in that, The photovoltaic power generation unit, wind power generation unit, supercapacitor energy storage unit, and battery energy storage unit are connected to the medium-voltage DC bus through a unified multi-port converter; the multi-port converter contains multiple decoupled power interfaces, which can coordinate and control the power of each energy unit and manage its power.

6. The system according to claim 1, characterized in that, The high-power traction converter system adopts a modular cascaded multilevel converter topology or a midpoint clamped three-level converter topology.

7. The system according to claim 6, characterized in that, The two adjacent high-power traction converter systems are connected in series through the stator switch station to supply power to meet the voltage requirements of the train when it is running at high speed.

8. The system according to claim 1, characterized in that, The system also includes a centralized control system, which is communicatively connected to the four-quadrant rectifier system, the high-power traction converter system, the stator switch station, and the distributed renewable energy and energy storage system, and is used to coordinate and control the power flow, stator segment switching, and energy management of the entire power supply system.

9. A traction power supply method for maglev trains based on a medium-voltage DC bus, applied to the system described in any one of claims 1 to 8, characterized in that, The method includes: The high-voltage AC power from the high-voltage AC grid is rectified into DC power by the four-quadrant rectifier system and then transmitted to the medium-voltage DC bus. The distributed renewable energy and energy storage system injects electrical energy into the medium-voltage DC bus according to the medium-voltage DC bus voltage and dispatch instructions, and / or absorbs electrical energy from the medium-voltage DC bus for storage. The high-power traction converter system converts the DC power on the medium-voltage DC bus into three-phase AC power with adjustable frequency and voltage. The output frequency and voltage of the three-phase AC power are adjusted according to the train's operating position and power requirements. The stator switching station dynamically switches the converted three-phase AC power according to the train's running position and delivers it to the corresponding stator section of the long stator linear synchronous motor to drive the maglev train.

10. The method according to claim 9, characterized in that, The method further includes: dynamically controlling the output power of the high-power traction converter system, controlling the switching operation of the stator switch station, and adjusting the energy exchange between the four-quadrant rectifier system and the distributed renewable energy and energy storage system through a centralized control system, based on the train's operating location, power demand, and the power generation and energy storage status of the distributed renewable energy and energy storage system.

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