Electrified railway bilateral power supply system

Abstract

The embodiment of the invention provides an electrified railway bilateral power supply system, and belongs to the technical field of alternating current electrified railway traction power supply. The power supply and transformation system comprises two power substations, two main substations adopting three-phase and two-phase traction transformers, n voltage reduction substations adopting single-phase wiring traction transformers, a single-phase high-voltage transmission line and a traction network. Wherein the two main substations are connected with a three-phase bus of the power transformer through power transmission lines; the n step-down substations are respectively connected with the single-phase high-voltage transmission line and the traction network; the circuit breaker is arranged between the three-phase bus and the single-phase bus, and bilateral power supply of the traction network is realized through a left-closing and right-opening or left-opening and right-closing control mode. According to the bilateral power supply system, three-phase balance of a superior power grid is realized, and a negative sequence compensation device can be prevented from being arranged; the single-phase high-voltage transmission line and the traction network are erected in parallel, system impedance is reduced, and the traction network power supply distance is effectively prolonged.

Description

Technical Field

[0001] This invention relates to the field of AC electrified railway traction power supply technology, and more specifically to a bilateral power supply system for electrified railways. Background Technology

[0002] As a crucial component of modern transportation systems, the reliability, economy, and power quality of electrified railways' traction power supply systems directly impact the efficiency and safety of railway operations. Currently, traditional electrified railways generally employ a single-sided power supply method, meaning trains draw power from only one traction substation on one side. While this power supply structure is simple, its inherent technical bottlenecks are becoming increasingly apparent as railway transportation develops towards high speeds, heavy loads, and long distances.

[0003] First, when a single-phase traction load is connected to a three-phase power system, it will generate a significant negative sequence current in the upstream power grid, causing generator rotor heating, relay protection malfunction, and a decline in power quality for nearby users, which seriously restricts the access capacity of the traction power supply system and the safe and stable operation of the power grid.

[0004] Secondly, in long-distance power supply scenarios, the line impedance voltage drop in the single-sided power supply mode is large, resulting in a low voltage level at the end of the traction network, which is difficult to meet the voltage requirements of high-power loads such as high-speed trains. At the same time, since the current is concentrated from one end, the overall power loss of the traction network is high, and the operating economy is poor.

[0005] To address these issues, dual-phase power supply technology has emerged. Chinese invention patent CN109217330A, "A Same-Phase Power Supply System for Electrified Railways," discloses a solution that uses a traction substation for centralized negative sequence compensation and extends the power supply distance using single-phase high-voltage transmission lines. While this technology eliminates phase separation and compensates for negative sequence, its core reliance on additional negative sequence compensation devices (including three-phase compensation transformers and SVG, etc.) undoubtedly increases system complexity, equipment costs, and maintenance burden. Furthermore, the system's operational efficiency and compensation effect largely depend on the capacity and response speed of these additional devices.

[0006] Another common approach to bilateral power supply involves directly connecting the power supply arms of two traction substations. While this theoretically increases voltage and balances load, in practice, especially in complex structures with multiple substations and long lines, the voltage amplitude and phase differences between the two power sources can lead to circulating currents. These circulating currents not only increase system losses and reduce economic efficiency but can also cause malfunctions in protection devices, threatening power supply reliability. Furthermore, optimizing substation layout and wiring, and effectively coordinating the opening and closing of multiple circuit breakers to precisely control power supply sections and suppress negative sequence remain unresolved challenges in current technology.

[0007] Therefore, there is an urgent need in this field for a new type of bilateral power supply system that can fundamentally suppress negative sequence, eliminate circulating current, and achieve flexible and efficient power supply without the need for additional compensation devices, but only through innovative system architecture and collaborative control. Summary of the Invention

[0008] The purpose of this invention is to provide a bilateral power supply system for electrified railways, addressing at least three core challenges inherent in existing electrified railway traction power supply systems, particularly traditional single-sided power supply and existing bilateral power supply technologies: 1. Negative sequence current pollution: Single-phase traction loads connected to a three-phase public power grid generate negative sequence currents, jeopardizing grid safety and power quality. 2. Insufficient long-distance power supply capacity: Severe voltage drops at the power supply end restrict the development of high-speed and heavy-haul railways. 3. System operational economy and reliability issues: These include high traction network losses and the generation of balancing circulating currents in existing bilateral power supply modes, leading to additional losses and protection risks.

[0009] To achieve the above objectives, the first aspect of the present invention provides a bilateral power supply system for electrified railways, comprising a first power substation PS1, a second power substation PS2, a first main traction substation SS1, a second main traction substation SS2, and a single-phase step-down traction substation; the system is laterally connected to the traction network OCS via a single-phase high-voltage transmission line HL, characterized in that: the first main traction substation SS1 includes a first three-phase high-voltage busbar HB1 and a first main transformer TT1 connected to the first three-phase high-voltage busbar HB1; the second main traction substation SS2 includes a second three-phase high-voltage busbar HB2 and a second main transformer TT2 connected to the second three-phase high-voltage busbar HB2; the primary side of the single-phase step-down traction substation SSn is connected across the single-phase high-voltage transmission line HL, and the secondary side is connected to the traction network OCS; a circuit breaker QF1 is installed between the three-phase busbar connected to the first main traction substation SS1 and the single-phase high-voltage transmission line; a circuit breaker QF2 is installed between the three-phase busbar connected to the second main traction substation SS2 and the single-phase high-voltage transmission line.

[0010] Optionally, both the first main transformer TT1 and the second main transformer TT2 are traction transformers with a three-phase to two-phase connection, including any one of the Vv connection method, Scott connection method, and impedance matching balance connection traction transformers.

[0011] Optionally, all traction transformers in the step-down traction substation SSn adopt a single-phase connection method.

[0012] Optionally, on the traction network OCS, n+1 segmented insulating joints GJ are provided between the ends of the power supply arms of each traction substation. Each segmented insulating joint GJ is connected in parallel with a circuit breaker QF. Circuit breaker QF1-1 is provided at the end of the right power supply arm of the first main traction substation SS1, and circuit breaker QF1-2 is provided at the end of the left power supply arm. Circuit breaker QF2-1 is provided at the end of the left power supply arm of the second main traction substation SS2, and circuit breaker QF2-2 is provided at the end of the right power supply arm. Circuit breaker QFn is provided at the end of the power supply arm of the step-down traction substation.

[0013] Optionally, the left power supply arm of the first main transformer TT1 of the first main traction substation SS1 is connected to phase BC, and the right power supply arm is connected to phase AC.

[0014] Optionally, the left power supply arm of the second main transformer TT2 of the second main traction substation SS2 is connected to the AC phase, and the right power supply arm is connected to the AB phase.

[0015] Optionally, switching between the following modes can be achieved by controlling the opening and closing of the circuit breakers: Traction network bilateral power supply mode 1: Close circuit breakers QF1, QF1-1 and the corresponding switch QFn at the end of the power supply arm of the step-down traction substation adjacent to the first main traction substation SS1, and open circuit breakers QF2 and QF2-1, so that the first power substation PS1 becomes the main power supply; Bilateral power supply mode 2: Close circuit breakers QF2, QF2-1 and the corresponding switch QFn at the end of the power supply arm of the step-down traction substation adjacent to the second main traction substation SS2, and open circuit breakers QF1 and QF1-1, so that the second power substation PS2 becomes the main power supply.

[0016] Optionally, the single-phase high-voltage transmission line HL is erected in parallel along the traction network OCS, and the single-phase high-voltage transmission line HL and the traction network OCS form an electrical correspondence at each single-phase step-down traction substation, so that the single-phase high-voltage transmission line HL serves as a centralized transmission channel for traction power, providing a unified power input to each single-phase step-down traction substation.

[0017] Optionally, the segmented insulating joint GJ and the circuit breaker QF connected in parallel together constitute the segmented power supply structure of the traction network OCS. By selectively opening or closing the corresponding circuit breaker, the traction network OCS can form mutually electrically isolated power supply sections under different power supply modes, thereby limiting the transmission of traction current within the preset power supply section.

[0018] Optionally, in any of the aforementioned bilateral power supply modes of the traction network, only one of the main traction substations establishes an electrical connection with the single-phase high-voltage transmission line HL through a corresponding circuit breaker, while the other main traction substation disconnects its corresponding circuit breaker to electrically isolate itself from the single-phase high-voltage transmission line HL, so as to avoid different power sources simultaneously supplying power to the single-phase high-voltage transmission line HL and forming a circulating current.

[0019] The beneficial effects of the present invention through the above technical solution are: 1. The main substation adopts a traction transformer with a three-phase to two-phase connection. In the dual-side power supply mode, by reasonably configuring the load of the two power supply arms of the main traction transformer, the three-phase voltage imbalance at the power system assessment point PCC can be effectively reduced without the need for additional negative sequence compensation devices (or the capacity of negative sequence compensation devices can be effectively reduced), thus addressing negative sequence pollution from the structural perspective.

[0020] Second, the traction network is powered by a single power transformer in a two-sided power supply mode, without equal current injection into the power system.

[0021] Third, the dual power supply point, consisting of two power transformers, allows the system to flexibly and quickly switch between single-sided and double-sided power supply modes during faults or maintenance through the logical combination of circuit breakers. This enables rapid isolation of faulty sections and self-healing of power supply to non-faulty sections, significantly improving system availability and resilience.

[0022] Fourth, a dedicated single-phase transmission line is connected in parallel with the traction network to reduce the impedance of the traction network, effectively reduce traction network losses, and extend the power supply distance.

[0023] V. This power supply structure can be used for the renovation of existing lines or for the construction of new lines.

[0024] 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

[0025] 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 structure of a bilateral power supply system for electrified railways, taking the Vv connection of the first and second main traction substations as an example. Figure 2 This is a schematic diagram of the structure of a bilateral power supply system for an electrified railway, taking the Scott connection of the first and second main traction substations as an example. Figure 3(a) shows the circuit breaker status and power flow direction in bilateral power supply mode 1 (PS1 main supply); Figure 3(b) shows the circuit breaker status and power flow in bilateral power supply mode 2 (PS2 main supply). Detailed Implementation

[0026] 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.

[0027] like Figure 1 As shown in the figure, this embodiment provides a bilateral power supply system for electrified railways, which is suitable for a long-distance electrified railway trunk line.

[0028] The system draws two independent three-phase high-voltage power supplies from the power grid through the first power substation PS1 and the second power substation PS2. These two power supplies provide strong power support and power supply reliability for the entire traction power supply system. The first main traction substation SS1 is connected to PS1 through its three-phase high-voltage bus HB1. Its core equipment is the first main transformer TT1, which, in this embodiment, adopts a Vv connection. Specifically, its primary winding is connected to phases BC and AC of HB1, respectively. The second main traction substation SS2 is connected to PS2 through its three-phase high-voltage bus HB2. Its core equipment is the second main transformer TT2, which also adopts a Vv connection. Its primary winding is connected to phases AC and AB, respectively. Between SS1 and SS2, several intermediate step-down traction substations SS3, SS4, ..., SSn are distributed along the railway line. These step-down traction substations all use traction transformers with single-phase connection. The primary side is directly connected across phases A and C of the single-phase high-voltage transmission line HL, while the secondary side is connected to the traction network OCS at one end and grounded at the other end. The traction network OCS is laid along the railway line, providing 27.5kV single-phase AC power to electric locomotives. The system is equipped with key circuit breakers to achieve power supply mode switching: circuit breaker QF1 is installed between the three-phase high-voltage busbar HB1 and the single-phase high-voltage transmission line HL at the first main traction substation SS1; circuit breaker QF2 is installed between the three-phase high-voltage busbar HB2 and the single-phase high-voltage transmission line HL at the second main traction substation SS2. In addition, on the traction network OCS, n+1 segmented insulated joints GJ are installed between the ends of the power supply arms of each substation. Each GJ has a circuit breaker connected in parallel, including QF1-1 on the right side of SS1, QF1-2 on the left side of SS1, QF2-1 on the left side of SS2, QF2-2 on the right side of SS2, and switch QFn at the end of the power supply arm of the intermediate step-down traction substation. The control system monitors voltage and current signals to control the opening and closing of these circuit breakers. These circuit breakers, such as QF1-1, QF1-2, QF1, ..., QFn, QF2-1, and QF2-2, are the core actuators for achieving flexible switching of power supply modes.

[0029] Specifically, the single-phase high-voltage transmission line HL serves as a centralized transmission channel for traction power. During system operation, it transmits the single-phase traction power output from the main traction substation along the line direction to each single-phase step-down traction substation SSn. By controlling the opening and closing of circuit breakers QF1 and QF2 located at the main traction substation, at any given operating time, the single-phase high-voltage transmission line HL establishes an electrical connection with only one main traction substation, thereby ensuring that the single-phase high-voltage transmission line HL is powered by a single power source and avoiding a state of multiple power sources operating in parallel.

[0030] like Figure 2 This paper provides an embodiment of a bilateral power supply system for electrified railways, taking the first and second main traction substations connected in a Scott configuration as an example. In this embodiment, the three-phase power supply is converted into a two-phase traction power supply through the Scott configuration, and power is supplied to the left and right power supply arms respectively, so as to achieve a balanced distribution of traction load on the three-phase power grid side. It should be understood that the present invention is not limited to... Figure 1 The Vv wiring embodiment shown or Figure 2 The Scott connection embodiment shown herein, and any other equivalent three-phase to two-phase connection traction transformer configurations, fall within the protection scope of this invention.

[0031] The collaborative control method is implemented through a central controller and specifically includes multiple power supply modes: The dual-side power supply mode 1 is shown in Figure 3(a): When the PS1 side power supply needs to be used as the main power supply, the control system closes circuit breakers QF1 and QF1-1, as well as the corresponding switches at the end of the power supply arm of the intermediate traction substation adjacent to SS1. At the same time, circuit breaker QF2 and circuit breaker QF2-1 on the left side of SS2 are disconnected.

[0032] The dual-side power supply mode 2 is shown in Figure 3(b): When the PS2 side power supply needs to be used as the main power supply, the control system closes circuit breakers QF2 and QF2-1, as well as the corresponding switches at the end of the power supply arm of the intermediate traction substation adjacent to SS2. At the same time, circuit breaker QF1 and circuit breaker QF1-1 on the right side of SS1 are disconnected.

[0033] The control system includes a monitoring unit for collecting voltage and current status information of each main traction substation, step-down traction substation, and key nodes of the traction network, and a control unit for generating circuit breaker control commands according to a preset power supply mode. Based on the monitored operating status information, the control unit coordinates the opening and closing states of circuit breakers QF1, QF2, QF1-1, QF1-2, QF2-1, QF2-2, and each QFn to achieve switching between different power supply modes.

[0034] In another possible implementation, at different sections of the single-phase high-voltage transmission line HL, the circuit breakers QFn at the corresponding segment insulation joints GJ are dynamically combined and controlled based on the load status of each single-phase step-down traction substation SSn. When the traction load in a certain section increases significantly or local voltage fluctuations occur, the control system can temporarily shorten the equivalent power supply distance of that section by adjusting the opening and closing states of adjacent segment circuit breakers without changing the power supply direction of the main traction substation, so that the traction current is borne more by the adjacent step-down traction substation. This implementation does not require changing the wiring structure of the main traction substation or adding new compensation equipment, and can achieve flexible reconfiguration of the traction network power supply sections under uneven load distribution along the line, thereby improving the system's adaptability to changes in operating conditions.

[0035] In another possible implementation, when the first main traction substation SS1 or the second main traction substation SS2 is under planned maintenance or de-capacity operation, the control system, while maintaining the single-injection point characteristic of the single-phase high-voltage transmission line HL, adjusts the power supply boundary of the circuit breaker corresponding to the segmented insulation joint GJ in the traction network OCS through a preset circuit breaker switching sequence. This allows all single-phase step-down traction substations SSn to be temporarily supplied with centralized power from the main traction substations on the non-maintained side. This implementation does not rely on direct parallel operation between main traction substations, nor does it require changes to the wiring method of the traction transformers. It can maintain continuous power supply to the traction network during the maintenance of the main traction substations, thereby improving the operational flexibility and maintainability of the system under maintenance conditions.

[0036] In summary, this embodiment successfully implemented a flexible, efficient, and reliable bilateral power supply system through the specific system construction and control methods described above, providing an excellent solution for addressing many challenges in long-distance power supply for electrified railways.

Claims

1. A bilateral power supply system for an electrified railway, the system comprising: The system comprises a first power substation (PS1), a second power substation (PS2), a first main traction substation (SS1), a second main traction substation (SS2), and a single-phase step-down traction substation; the system is laterally connected via a single-phase high-voltage transmission line (HL) and a traction network (OCS), characterized in that: The first main traction substation (SS1) includes a first three-phase high-voltage busbar (HB1) and a first main transformer (TT1) connected to the first three-phase high-voltage busbar (HB1). The second main traction substation (SS2) includes a second three-phase high-voltage busbar (HB2) and a second main transformer (TT2) connected to the second three-phase high-voltage busbar (HB2). The primary side of the single-phase step-down traction substation (SSn) is connected across the single-phase high-voltage transmission line (HL), and the secondary side is connected to the traction network (OCS). A circuit breaker (QF1) is installed between the three-phase busbar connected to the first main traction substation (SS1) and the single-phase high-voltage transmission line. A circuit breaker (QF2) is installed between the three-phase busbar connected to the second main traction substation (SS2) and the single-phase high-voltage transmission line.

2. The bilateral power supply system for electrified railways according to claim 1, characterized in that, Both the first main transformer (TT1) and the second main transformer (TT2) are traction transformers with a three-phase to two-phase connection, including any one of the Vv connection method, Scott connection method, and impedance matching balance connection traction transformer.

3. The bilateral power supply system for electrified railways according to claim 1, characterized in that, The traction transformers in the step-down traction substation (SSn) all adopt a single-phase connection method.

4. The bilateral power supply system for electrified railways according to claim 3, characterized in that, On the traction network (OCS), there are a total of n+1 segmented insulating joints (GJ) between the ends of the power supply arms of each traction substation. Each segmented insulating joint (GJ) is connected in parallel with a circuit breaker (QF). Circuit breaker QF1-1 is installed at the end of the right power supply arm of the first main traction substation (SS1), and circuit breaker QF1-2 is installed at the end of the left power supply arm. Circuit breaker QF2-1 is installed at the end of the left power supply arm of the second main traction substation (SS2), and circuit breaker QF2-2 is installed at the end of the right power supply arm. A circuit breaker (QFn) is installed at the end of the power supply arm of the step-down traction substation.

5. The bilateral power supply system for electrified railways according to claim 2, characterized in that, The first main transformer (TT1) of the first main traction substation (SS1) has its left power supply arm connected to phase BC and its right power supply arm connected to phase AC.

6. The bilateral power supply system for electrified railways according to claim 2, characterized in that, The second main transformer (TT2) of the second main traction substation (SS2) has its left power supply arm connected to phase AC and its right power supply arm connected to phase AB.

7. The electrified railway bilateral power supply system according to claim 1, characterized in that, Switching between the following modes can be achieved by controlling the opening and closing of the circuit breaker: Traction network bilateral power supply mode 1: Close circuit breaker QF1, circuit breaker QF1-1 and the corresponding switch (QFn) at the end of the power supply arm of the step-down traction substation adjacent to the first main traction substation (SS1), and open circuit breaker QF2 and circuit breaker QF2-1, so that the first power substation (PS1) becomes the main power supply. Dual-sided power supply mode 2: Close circuit breaker QF2, circuit breaker QF2-1 and the corresponding switch (QFn) at the end of the power supply arm of the step-down traction substation adjacent to the second main traction substation (SS2), and open circuit breaker QF1 and circuit breaker QF1-1, so that the second power substation (PS2) becomes the main power supply.

8. The bilateral power supply system for electrified railways according to claim 1, characterized in that, The single-phase high-voltage transmission line (HL) is erected in parallel along the traction network (OCS), and the single-phase high-voltage transmission line (HL) and the traction network (OCS) form an electrical correspondence at each single-phase step-down traction substation, so that the single-phase high-voltage transmission line (HL) serves as a centralized transmission channel for traction power, providing a unified power input to each single-phase step-down traction substation.

9. The electrified railway bilateral power supply system according to claim 4, characterized in that, The segmented insulating joint (GJ) and the parallel circuit breaker (QF) together constitute the segmented power supply structure of the traction network (OCS). By selectively opening or closing the corresponding circuit breaker, the traction network (OCS) forms mutually electrically isolated power supply sections under different power supply modes, thereby limiting the transmission of traction current within the preset power supply section.

10. The bilateral power supply system for electrified railways according to claim 7, characterized in that, In any traction network bilateral power supply mode, only one of the main traction substations establishes an electrical connection with the single-phase high-voltage transmission line (HL) through the corresponding circuit breaker, while the other main traction substation disconnects its corresponding circuit breaker to electrically isolate itself from the single-phase high-voltage transmission line (HL), so as to avoid different power sources supplying power to the single-phase high-voltage transmission line (HL) at the same time and forming a circulating current.

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