Train three-phase electric transmission system and optimized operation control method

Abstract

The invention discloses a train three-phase electric transmission system and a system optimization operation control method, and belongs to the technical field of rail transit train electric transmission. The system comprises a traction network, a current collection device, a leakage reactance transformer, a traction converter, a traction motor and a traction controller, the traction network comprises three rails, and two current collecting shoes and a rail connecting device of the current collecting device are electrically connected with the leakage reactance variable primary side from the three rails respectively; a plurality of isolated and ungrounded three-phase traction windings are arranged on the secondary side of the leakage reactance transformer, and the equivalent leakage reactance of the three-phase traction windings serves as the grid-connected reactance of the converter; each traction winding is correspondingly connected with a rectification end of a traction converter, and an inversion end of the converter is connected with a traction motor; the traction controller controls the working condition of the converter according to current transformer signals. The system is compact in structure, can restrain rectification harmonic waves, optimizes electric energy quality, realizes self-adaptive stable regulation and control of operation conditions, and adapts to different power supply scenes.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of electric transmission technology of rail transit train, and particularly relates to a three-phase electric transmission system of train and an optimized operation control method. BACKGROUND

[0002] The electric transmission system of the existing electrified railway and urban rail transit train mainly adopts two kinds of traction power supply systems: DC 1500V (or 750V system) and power frequency single-phase AC 25kV system. Both of the two systems have inherent defects in practical application:

[0003] 1. Problems of DC system:

[0004] Stray current corrosion: DC leakage current (stray current) can cause long-term electrochemical corrosion to the metal structures in tunnels and bridges and underground pipelines, which is difficult to protect and has high maintenance cost.

[0005] Low utilization efficiency of regenerative energy: about 30%-50% of the regenerative electric energy generated by train braking cannot be directly utilized by adjacent vehicles, and usually needs to be recycled through the addition of energy feeding devices or energy storage devices, which is complex and poor in economy.

[0006] Safety problem of regenerative braking: in the energy absorption dead zone, regenerative braking may fail and be forced to mechanical braking, which increases the risk of train overturning at high speed.

[0007] 2. Problems of power frequency single-phase AC 25kV system:

[0008] Electric phase separation and no-electric zone: in order to reduce the unbalanced influence of single-phase large load on three-phase public power grid, electric phase separation device needs to be set in the traction network to form no-electric zone. The train needs to be powered off and coasting when passing through, which affects the continuity of operation. The interval between urban rail transit stations is short, the start and stop are frequent, and the train density is large. Frequent passing through no-electric zone will cause significant speed drop, restrict the transport capacity, increase the burden of driver operation, and even may cause parking accident.

[0009] High engineering cost: AC 25kV voltage level requires the overhead line to have larger insulation gap and tunnel section, which significantly increases the investment of civil engineering.

[0010] In addition, the existing train electric transmission system generally adopts the topology structure of "single-phase rectifier-intermediate DC-three-phase inverter", which will cause significant secondary ripple of DC bus voltage at the input side of single-phase rectifier, affecting the power quality and system efficiency.

[0011] In order to solve the above problems, a new type of train electric transmission system scheme is needed, which can consider power supply efficiency, engineering economy, operation safety and environmental friendliness.

[0012] The application provides a train three-phase power transmission system, which can effectively overcome the defects of DC 1500V system and single-phase AC 25kV system, and provides a more economical and reliable traction power supply and train power transmission solution. SUMMARY

[0013] The application aims to overcome the defects of the existing DC system and single-phase AC system, and provide a train power transmission system which can effectively suppress stray current, efficiently utilize regenerated energy, prevent safety risks of regenerative braking, eliminate the influence of no power area, reduce engineering cost, and has better power quality.

[0014] The application aims to overcome the defects of the existing DC system and single-phase AC system, and provide a train power transmission system which can effectively suppress stray current, efficiently utilize regenerated energy, prevent safety risks of regenerative braking, eliminate the influence of no power area, reduce engineering cost, and has better power quality.

[0015] In some embodiments, the secondary side of the leakage reactance transformer is further provided with a three-phase Y-connected winding, and the three-phase Y-connected winding outputs 400V / 220V voltage; in some embodiments, the primary side voltage of the leakage reactance transformer is 3kV; and the secondary side three-phase traction winding voltage of the leakage reactance transformer is 0.8kV-1.0kV.

[0016] In some embodiments, the primary side winding and the secondary side winding of the leakage reactance transformer are respectively connected in delta / Y mode, and one of the terminals of the primary side winding of the leakage reactance transformer is connected to the steel rail through the rail connector.

[0017] In some embodiments, the leakage-reactance-variable primary winding and the leakage-reactance-variable secondary winding are respectively connected in a delta / delta configuration, and one terminal of the leakage-reactance-variable primary winding is connected to the rail via a rail connector.

[0018] In some embodiments, the leakage-reactance-variable primary winding and the leakage-reactance-variable secondary winding are respectively connected in a Y / Y configuration, and one terminal of the leakage-reactance-variable primary winding is connected to the rail via a rail connector.

[0019] In some embodiments, the leakage-reactance-variable primary winding and the leakage-reactance-variable secondary winding are respectively connected in a Y / △ configuration, and one terminal of the leakage-reactance-variable primary winding is connected to the rail via a rail connector.

[0020] In some embodiments, the traction converter is a three-level converter.

[0021] In some embodiments, the current collection device supports a single-phase current collection mode, and when the current collection device switches to the single-phase current collection mode, the three-phase traction converter operates in a single-phase working condition.

[0022] In some embodiments, the equivalent leakage reactance of each three-phase traction winding of the leakage-reactance-variable secondary winding is greater than or equal to 25%.

[0023] In some embodiments, the traction motor is an asynchronous motor, a group of asynchronous motors, or a synchronous motor.

[0024] The plurality of embodiments of the present specification also provide a method for optimizing operation control of a three-phase electric drive system of a train. The traction controller controls the working conditions of each traction converter according to the currents of the first current transformer and the second current transformer, and specifically includes: when the traction controller detects that the currents of the first current transformer and the second current transformer are both 0, the traction controller controls the traction converter to stop inverting output; when the traction controller detects that the current of one of the first current transformer and the second current transformer is 0, the traction controller controls the traction converter to make the rectified power of the phase corresponding to the non-0 current be 2 / 3 and the rectified power of the other two phases be 1 / 3; and when the traction controller detects that the currents of the first current transformer and the second current transformer are both non-0, the traction controller controls the traction converter to make the rectified power of the three phases be 1 / 3.

[0025] In some embodiments, when the traction motor is an asynchronous motor, the slip frequency control is adopted on the inverting side of the traction converter, and when the zero-speed start is performed, in order to improve the motor torque, the control slip frequency is ω sctl =kω scla ; wherein ω scla is a theoretical calculation value of the slip frequency, ω sctl is an actual control value of the slip frequency, and k=f(ω r ) (0<k<1), k varies with ω rGradually increase from 0.5 to 1; when k = 1, the slip frequency carries out the flux linkage q axis component closed loop control, ω sctl =ω scla +k p1 Φ q +k i1 ∫Φ q dt; wherein, Φ q It is the actual value of motor flux linkage q axis component, k p1 It is the slip frequency flux linkage q axis component closed loop PI control proportion parameter, k i1 Slip frequency flux linkage q axis component closed loop PI control integral parameter; when motor speed reaches the rated speed, the modulation mode is switched to square wave modulation, the slip frequency is switched to torque current control, ω sctl =ω scla +k p2 (I qref -I q )+k i2 ∫(I qref -I q )dt; wherein, I qref It is the motor torque current reference value, I q It is the actual value of motor torque current, k p2 It is the slip frequency torque current closed loop PI control proportion parameter, k i2 It is the slip frequency torque current closed loop PI control integral parameter.

[0026] The working principle of the application is: the system obtains electric energy from the three-phase traction network (preferably AC 3kV) through the two current collecting shoes and a rail adapter of the current collecting device, and stably transmits the three-phase electric energy to the leakage reactance transformer primary side. The leakage reactance transformer realizes two key functions in this process: first, the reactor voltage transformation and electromagnetic isolation, which reduces the high voltage of 3kV on the network side to a voltage level suitable for the direct rectification input of the traction converter (TCV1~n), and matches the voltage level of the traction motor; second, according to the equivalent transformation principle of delta connection and Y connection, the required equivalent grid-connected reactance is provided to suppress the harmonic current generated by rectification and improve the input power factor. The traction converter (TCV1~n) converts the three-phase alternating current adapted by the leakage reactance transformer through a series of controllable transformations such as four-quadrant rectification, DC filtering, and three-phase inversion, and finally outputs the variable frequency and variable voltage (VVVF) three-phase alternating current required to drive the traction motor (M1~n). By selecting a variable frequency converter output that matches the voltage of the existing traction motor (M1~n), the traction motor (M1~n) can be directly utilized or minimized, protecting existing assets and reducing manufacturing costs. In addition, by judging the input current, the operating conditions of the traction converter (TCV1~n) are controlled for operation optimization, and even single-phase power supply can ensure train operation.

[0027] Compared with the prior art, the application has the following advantages:

[0028] 1. This invention adopts the national standard voltage level, which is beneficial for using standard power supply and transformation equipment, improving reliability and reducing system costs.

[0029] 2. This invention proposes a three-phase electric drive implementation scheme. The leakage reactance transformer has the dual functions of voltage reduction and grid-connected reactor, making the equipment more compact and saving limited space in the train. At the same time, the primary side of the leakage reactance transformer has the function of connecting the rail (ground) to the terminal, which is well coordinated with the grounding of the traction power supply system.

[0030] 3. This invention proposes a train operation optimization control method that can ensure train operation even in the event of a single-phase failure, allowing the train to reach the next station or the end of the line and evacuate passengers.

[0031] 4. This invention has a high degree of standardization, good equipment compatibility, low cost, and is easy to mass-produce and implement in engineering.

[0032] 5. By adopting a power collection device to receive power from the three-phase traction network, a leakage reactance transformer that combines voltage transformation and grid-connected reactance functions, multiple sets of electrically isolated secondary traction windings, and a control method based on current signal regulation of the traction converter, the train's electric drive system structure is more compact. It can effectively suppress negative sequence current and rectify harmonics, optimize power quality, and achieve adaptive and stable regulation under operating conditions, adapting to different power supply scenarios.

[0033] 6. By setting a three-phase Y-connected winding with an output voltage of 400V / 220V on the secondary side of the leakage reactance transformer, the complex process of drawing auxiliary inverters from the DC link of the traction converter to power the train's auxiliary devices is changed. This simplifies the overall structure of the on-board electric drive system, saves the limited installation space of the train, and provides a stable power frequency AC power supply for loads such as on-board lighting, air conditioning, and control auxiliary devices. At the same time, the electromagnetic isolation characteristics of the leakage reactance transformer ensure the electrical safety of the auxiliary power supply circuit.

[0034] 7. By configuring the primary side of the leakage reactance transformer to the national standard voltage level of 3kV and the secondary three-phase traction winding to the voltage level of 0.8kV~1.0kV, the system can directly select mature and standardized power supply and transformation equipment, effectively improving operational reliability and reducing overall costs. At the same time, it can achieve precise adaptation with the existing subway train traction motors, eliminating the need to manufacture new traction motors and effectively reducing costs.

[0035] 8. By setting the equivalent leakage reactance of each three-phase traction winding on the secondary side of the leakage reactance transformer to no less than 20%, the leakage reactance can be directly used as the four-quadrant rectifier grid-connected reactance of the traction converter without the need for additional external smoothing reactors. This optimizes the space utilization of the train's on-board equipment, effectively suppresses harmonic currents generated in the rectifier stage, improves the grid-side power factor, and provides reliable reactance support for the stable operation of the traction converter, ensuring the power quality and operational stability of the entire electric drive system under different operating conditions.

[0036] 9. By adopting a hierarchical control strategy, which dynamically adjusts the slip frequency control coefficient during the zero-speed start-up phase, switches to flux linkage q-axis component closed-loop control during medium-speed operation, and switches to torque current closed-loop control after rated speed, the asynchronous motor obtains sufficient torque to ensure smooth train start-up during the start-up phase, maintains flux linkage stability in the medium-speed range to ensure smooth torque output, and accurately matches traction and braking requirements during rated speed operation to improve operating efficiency, thus comprehensively optimizing the traction performance of the train under all operating conditions. Attached Figure Description

[0037] Fig. 1 The overall structural block diagram of the train electric drive system of the present invention.

[0038] Fig. 2 A schematic diagram of a Δ / Y wiring system for the leakage reactance transformer in an embodiment of the present invention.

[0039] Fig. 3 A schematic diagram of a delta / delta wiring system for the leakage reactance transformer in this embodiment of the invention. Detailed Implementation

[0040] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0041] like Figs. 1-3 As shown, this specification provides a train three-phase electric drive system and its optimized operation control method through multiple embodiments, including a traction network, a current collector, a leakage reactance transformer (TRIN), a traction converter (TCV), a traction motor (M), and a traction controller (CTL).

[0042] The traction network includes a first power supply rail, a second power supply rail, and steel rails. The traction network supplies three-phase power to the leakage reactance transformer TRIN through the current collection device.

[0043] The current collection device includes a first current collector shoe P1, a second current collector shoe P2, and a rail connector P3. One end of the first current collector shoe P1 and the second current collector shoe P2 respectively contact the first power supply rail and the second power supply rail to receive power. The other end of the first current collector shoe P1 is connected to the first terminal of the primary side of the leakage reactance transformer TRIN via a first cable and a first current transformer C1. The other end of the second current collector shoe P2 is connected to the second terminal of the primary side of the leakage reactance transformer TRIN via a second cable and a second current transformer C2. One end of the rail connector P3 contacts the rail to receive power, and the other end is connected to the third terminal of the primary side of the leakage reactance transformer TRIN via a third cable.

[0044] The leakage reactance transformer TRIN secondary side includes multiple three-phase traction windings; the multiple three-phase traction windings are electrically isolated from each other; and the three terminals of each three-phase traction winding are not grounded.

[0045] The equivalent leakage reactance of each traction winding of the leakage reactance transformer TRIN is used as the four-quadrant rectifier grid-connected reactance of the traction converter TCV.

[0046] The inverter terminal of the traction converter TCV is connected to the input terminal of the traction motor M;

[0047] The multiple three-phase traction windings of the secondary side of the leakage reactance transformer TRIN are respectively connected to the three-phase rectifier terminals of multiple traction converters TCV; the inverter terminal of the traction converter TCV is connected to the traction motor M.

[0048] The input terminal of the traction controller CTL is connected to the output terminals of the first current transformer C1 and the second current transformer C2, and the output terminal of the traction controller CTL is connected to the control terminal of the traction converter TCV, which is used to control the operating condition of the traction converter TCV according to the current signal.

[0049] A leakage reactance transformer (TRIN) is a type of transformer with a primary side connected to the traction network and multiple electrically isolated three-phase traction windings on the secondary side. The equivalent leakage reactance of each traction winding can be directly used as the four-quadrant rectifier grid-connected reactance of the traction converter (TCV). The four-quadrant rectifier grid-connected reactance refers to the reactive element used in the four-quadrant rectification stage of the traction converter (TCV) to achieve grid-connected current regulation, harmonic suppression, and reactive power adjustment. The operating conditions of the traction converter (TCV) refer to its rectification, inversion, and shutdown states. When the train is running, it is powered by the first power supply rail. The traction network, consisting of the second power supply rail and the steel rail, provides three-phase power. The first collector shoe P1 contacts the first power supply rail to receive power, and transmits the power to the first terminal of the primary side of the leakage reactance transformer TRIN via the first cable and the first current transformer C1. The second collector shoe P2 contacts the second power supply rail to receive power, and transmits the power to the second terminal of the primary side of the leakage reactance transformer TRIN via the second cable and the second current transformer C2. The rail connector P3 contacts the steel rail to receive power, and transmits the power to the third terminal of the primary side of the leakage reactance transformer TRIN via the third cable, thus completing the receiving and transmission of three-phase power.

[0050] After receiving the three-phase input from the primary side, the leakage reactance transformer TRIN performs voltage transformation and electromagnetic isolation, converting the grid-side voltage to a level suitable for the traction converter TCV. Simultaneously, its equivalent leakage reactance serves as the grid-connected reactance required for the four-quadrant rectification of the traction converter TCV, suppressing harmonic currents generated during rectification and improving the input power factor. The multiple three-phase traction windings on the secondary side of the leakage reactance transformer TRIN are electrically isolated from each other, each transmitting the adapted three-phase power to the corresponding three-phase rectifier terminal of the traction converter TCV.

[0051] The rectifier terminal of the traction converter TCV performs four-quadrant rectification on the three-phase AC power transmitted from the leakage reactance transformer TRIN, converting it into stable DC power. Then, the inverter terminal inverts the DC power into frequency- and voltage-converted three-phase AC power, which is output to the corresponding traction motor M to drive the traction motor M to operate and provide traction power for the train.

[0052] During this process, the traction controller (CTL) collects the current signals output by the first current transformer (C1) and the second current transformer (C2) in real time. Based on the actual current situation, it outputs control commands to the control terminals of each traction converter (TCV), adjusting the rectification and inversion conditions of the TCV to ensure stable and optimized operation of the entire system. By adopting an architecture that receives power from the three-phase traction network using two collector shoes and one rail connector (P3), a leakage reactance transformer (TRIN) that combines voltage transformation and grid-connected reactance functions, multiple electrically isolated secondary traction windings, and a control method based on current signal regulation of the traction converter (TCV), the train's electric drive system structure is more compact. This effectively suppresses rectified harmonics, optimizes power quality, and enables adaptive and stable control of operating conditions, adapting to different power supply scenarios.

[0053] In some embodiments, the secondary side of the leakage reactance transformer TRIN is further provided with a three-phase Y-connected winding, which outputs a 400V / 220V voltage.

[0054] A three-phase Y-connected winding refers to a star-connected three-phase winding in which one end of each of the three windings is connected to form a common neutral point, and the other end serves as an output terminal. The 400V / 220V voltage refers to the AC voltage output by the three-phase Y-connected winding, which is 400V for the line voltage and 220V for the phase voltage. When the train is running, the traction network composed of the first power supply rail, the second power supply rail, and the rail outputs three-phase electrical energy, which is transmitted to the primary winding of the leakage reactance transformer TRIN through the first collector shoe P1, the second collector shoe P2, the rail connector P3, and the corresponding cables and current transformers. After receiving three-phase power on the primary side, the leakage reactance transformer TRIN transforms the voltage through multiple electrically isolated three-phase traction windings on the secondary side, transmitting the power adapted to the traction converter TCV to the rectifier terminals of each traction converter TCV. After rectification and inversion by the traction converter TCV, the power drives the traction motor M to operate, providing traction power for the train. On the other hand, the three-phase Y-connected windings on the secondary side of the leakage reactance transformer TRIN synchronously obtain power from the primary side and transform the voltage using its own Y-connected winding structure, outputting 400V / 220V AC power frequency voltage to provide a stable power supply for various auxiliary loads on the train, such as lighting equipment, air conditioning systems, and on-board control auxiliary devices. During this process, electromagnetic isolation is achieved between the primary and secondary windings of the leakage reactance transformer TRIN, which not only ensures the independence and operational stability of the traction power supply circuit, but also ensures the power safety of the auxiliary power supply circuit. At the same time, there is no need to set up an additional independent auxiliary power supply transformer, which effectively simplifies the structure of the train's power system and saves installation space inside the train. Meanwhile, the electromagnetic isolation characteristics of the leakage reactance transformer TRIN ensure the power safety of the auxiliary power supply circuit.

[0055] In some embodiments, the primary voltage of the leakage reactance transformer TRIN is 3kV; the secondary three-phase traction winding voltage of the leakage reactance transformer TRIN is 0.8kV~1.0kV.

[0056] The primary voltage of the leakage reactance transformer (TRIN) refers to the line voltage applied to the primary winding of the TRIN, with a rated value of 3kV. The secondary three-phase traction winding voltage of the TRIN refers to the line voltage output by a single three-phase traction winding on the secondary side of the TRIN, with a value range of 0.8kV to 1.0kV. During train operation, the traction network, composed of the first power supply rail, the second power supply rail, and the rails, outputs three-phase electrical energy, which is transmitted to the primary winding of the TRIN via the first collector shoe P1, the second collector shoe P2, the rail connector P3, and corresponding cables and current transformers. The primary winding of the TRIN preferentially uses a 3kV voltage level, which is the national standard voltage, compatible with common three-phase power grid voltages, and facilitates the selection of standardized power supply and transformation equipment. This improves the reliability of system operation and effectively reduces the overall system cost. After receiving 3kV three-phase power on the primary side of the leakage reactance transformer TRIN, it transmits the power to multiple three-phase traction windings on the secondary side through electromagnetic induction. The voltage of the three-phase traction windings on the secondary side is preferentially designed to be 0.8kV~1.0kV. This voltage level precisely matches the maximum applicable voltage of the traction converter TCV in current metro EMUs, allowing for direct input of compatible three-phase power to the rectifier terminal of the traction converter TCV without the need for additional voltage adjustment devices. Subsequently, the compatible three-phase power undergoes a series of controllable transformations by the traction converter TCV, including four-quadrant rectification, DC filtering, and three-phase inversion, outputting frequency- and voltage-variable three-phase AC power to drive the traction motor M, providing stable traction power for the train. During this process, the traction controller CTL collects the current signals from the first and second current transformers C2 in real time and dynamically adjusts the operating conditions of the traction converter TCV according to the current status, ensuring the stability and efficiency of the entire transmission system. Meanwhile, the leakage reactance transformer (TRIN), while performing voltage transformation, also functions as a grid-connected reactor due to its inherent leakage inductance design. This effectively suppresses harmonic currents generated in the rectifier stage, improves the input power factor, and eliminates the need for an external smoothing reactor, further optimizing the train's power system structure and saving limited installation space within the train. By configuring the primary side of the TRIN with a 3kV national standard voltage level and the secondary three-phase traction windings with a 0.8kV~1.0kV voltage level, the system can directly utilize mature, standardized power supply and transformation equipment, effectively improving operational reliability and reducing overall costs. Furthermore, it achieves precise compatibility with existing metro train traction converters (TCVs) without requiring additional voltage adjustment devices, further simplifying the structure of the train's electric drive system.

[0057] In some embodiments, the primary winding and secondary winding of the leakage reactance transformer TRIN are respectively Δ / Y connected, and one terminal of the primary winding of the leakage reactance transformer TRIN is connected to the rail via rail connector P3.

[0058] In this embodiment, the primary side of the leakage reactance transformer TRIN uses a delta connection, with one terminal connected to the rail via rail connector P3. The secondary side uses a Y connection. During operation, the delta connection on the primary side can cancel the third harmonic current, effectively optimizing the input power quality. Simultaneously, through the grounding connection of rail connector P3, it can be well adapted to the grounding system of the traction power supply system, avoiding electrical interference caused by potential differences. The Y connection on the secondary side can output symmetrical three-phase voltage, providing a stable rectified input for the traction converter TCV. Furthermore, the ungrounded design of the secondary winding further enhances the electrical isolation effect. This wiring method not only eliminates the need for additional harmonic suppression equipment by utilizing the harmonic suppression characteristics of the delta connection, but also improves the electrical safety of the system through the grounding design. The symmetrical output of the Y connection also ensures the stable operation of the traction converter TCV, making the entire drive system more reliable and compact.

[0059] In some embodiments, the primary winding and secondary winding of the leakage reactance transformer TRIN are respectively Δ / Δ connected, and one terminal of the primary winding of the leakage reactance transformer TRIN is connected to the rail via rail connector P3.

[0060] In this embodiment, the leakage reactance transformer TRIN adopts a primary-side delta (Δ) and secondary-side delta (Δ) wiring structure. One terminal of the primary-side delta winding is connected to the rail via rail connector P3. During operation, the primary-side delta connection can cancel the third harmonic current, effectively optimizing the input power quality. Simultaneously, through the grounding connection of rail connector P3, it can be well adapted to the grounding system of the traction power supply system, avoiding electrical interference caused by potential differences. The multiple three-phase traction windings of the secondary-side delta connection are electrically isolated from each other, and none of their three terminals are grounded. The equivalent leakage reactance of each traction winding of the leakage reactance transformer TRIN is used as the four-quadrant rectifier grid-connected reactance of the traction converter TCV, providing a stable rectified input for the corresponding connected traction converter TCV. The inverter terminal of the traction converter TCV is connected to the traction motor M, and the traction controller CTL adjusts the converter operating conditions according to the current signal. This wiring method not only utilizes the harmonic suppression characteristics of the delta connection to eliminate the need for additional harmonic mitigation equipment, but also improves the electrical safety of the system through grounding design, ensuring the independent and stable operation of multiple traction converter TCVs, making the entire transmission system more reliable and compact.

[0061] In some embodiments, the primary winding and secondary winding of the leakage reactance transformer TRIN are Y / Y connected respectively, and one terminal of the primary winding of the leakage reactance transformer TRIN is connected to the rail via rail connector P3.

[0062] In this embodiment, the leakage reactance transformer TRIN adopts a primary-side Y-connection and secondary-side Y-connection structure. One terminal of the primary-side Y winding is connected to the rail via rail connector P3. During operation, the primary-side Y connection ensures stable phase voltages of the three-phase input. Combined with the grounding connection of rail connector P3, it can be well adapted to the grounding system of the traction power supply system, avoiding electrical interference caused by potential differences. The multiple three-phase traction windings of the secondary-side Y connection are electrically isolated from each other, and none of their three terminals are grounded. The equivalent leakage reactance of each traction winding of the leakage reactance transformer TRIN is used as the four-quadrant rectifier grid-connected reactance of the traction converter TCV, providing a stable rectified input for the corresponding traction converter TCV. The inverter terminal of the traction converter TCV is connected to the traction motor M, and the traction controller CTL adjusts the converter operating conditions according to the current signal. This connection method optimizes the input power quality by utilizing the voltage stability of the Y connection, improves the electrical safety of the system through grounding design, and the secondary-side isolation winding can also ensure the independent and stable operation of multiple traction converter TCVs, making the entire transmission system simpler and more reliable.

[0063] In some embodiments, the primary winding and secondary winding of the leakage reactance transformer TRIN are Y / Δ connected, and one terminal of the primary winding of the leakage reactance transformer TRIN is connected to the rail via rail connector P3.

[0064] In this embodiment, the leakage reactance transformer TRIN adopts a primary-side Y-shaped and secondary-side Δ-shaped wiring structure. One terminal of the primary-side Y winding is connected to the rail via rail connector P3. During operation, the primary-side Y connection can be well adapted to the three-phase voltage input of the three-phase traction network. With the grounding connection of rail connector P3, it can form a good match with the grounding system of the traction power supply system, avoiding electrical interference caused by potential difference. The multiple three-phase traction windings of the secondary-side Δ connection are electrically isolated from each other, and none of the three terminals are grounded. Its equivalent leakage reactance is directly used as the four-quadrant rectifier grid-connected reactance of the traction converter TCV, without the need for additional external reactance. Each traction winding is connected to the three-phase rectifier terminal of the traction converter TCV, and the inverter terminal of the converter is connected to and drives the traction motor M. The traction controller CTL adjusts the converter operating conditions according to the current signal. The delta-shaped secondary winding enhances overvoltage resistance, the primary grounding design ensures system electrical safety, and the secondary isolation winding ensures independent and stable operation of multiple traction converters (TCVs). The compact structure saves limited space in the train, making the entire transmission system more adaptable and more reliable in operation.

[0065] In some embodiments, the traction converter TCV is a three-level converter.

[0066] The traction converter (TCV) in the three-phase electric drive system of this train adopts a three-level topology. Its rectifier side is a three-phase three-level H-bridge topology, and the three bridge arms can be independently modulated to accurately realize three-phase PWM rectification, converting the three-phase AC power output from the secondary side of the leakage reactance transformer (TRIN) into a stable DC bus voltage. The inverter side outputs three-phase AC power with adjustable amplitude and frequency from the three-level inverter circuit to drive the traction motor (M). This three-level topology can effectively reduce the harmonic content in the rectification process, improve the power quality of the system, and is well adapted to the output voltage level of the leakage reactance transformer (TRIN). When the current collector switches to single-phase current collection mode, it can automatically adjust the operating point to adapt to single-phase conditions, ensuring that the traction or braking performance of the train is not significantly affected. At the same time, the compact topology can save the limited installation space on the train, further improving the overall adaptability and operational reliability of the system.

[0067] In some embodiments, the current collector supports single-phase current collection mode.

[0068] Single-phase current collection mode refers to the working mode in which the current collector obtains single-phase power from two power supply lines through two current collector shoes to provide power to the train's electric drive system. At this time, the traction converter TCV will automatically identify the single-phase input condition and then adjust its own working state: the three-phase three-level H-bridge topology on its rectifier side will change the bridge arm modulation strategy, no longer using the three-phase independent modulation method, but instead adapting to the single-phase input power for rectification operation, converting the single-phase AC power into a stable DC bus voltage; the inverter side will maintain the normal operation of the three-level inverter circuit, continuously outputting three-phase AC power with adjustable amplitude and frequency to drive the traction motor M to operate normally.

[0069] In some embodiments, the equivalent leakage reactance of each three-phase traction winding on the secondary side of the leakage reactance transformer is ≥20%.

[0070] Equivalent leakage reactance refers to the comprehensive reactance value obtained after equivalent conversion between a single three-phase traction winding on the secondary side of the leakage reactance transformer TRIN and the primary winding of the leakage reactance transformer TRIN, as well as between the three-phase traction winding and other three-phase traction windings on the secondary side of the leakage reactance transformer TRIN. This reactance value is used as the four-quadrant rectifier grid-connected reactance of the corresponding traction converter TCV. The per-unit value of equivalent leakage reactance refers to the relative value of equivalent leakage reactance calculated based on the rated impedance of the three-phase traction winding.

[0071] In some embodiments, the traction motor M is an asynchronous motor, an asynchronous motor group, or a synchronous motor.

[0072] In the three-phase electric drive system of this train, the traction motor M can be an asynchronous motor, an asynchronous motor set, or a synchronous motor. When the traction converter TCV outputs three-phase AC power with adjustable amplitude and frequency, the asynchronous motor, with its simple and reliable structure, can quickly respond to changes in the converter's output, stably output traction torque, and has low maintenance costs. The asynchronous motor set can output greater power through multi-motor collaboration, adapting to the power requirements of heavy-load trains. The synchronous motor can flexibly adjust the power factor and cooperate with the system's four-quadrant rectifier stage to further optimize the grid-side power quality. This type of motor selection covers train scenarios with different capacity requirements, adapting to the efficient traction conditions of newly built three-phase lines, and maintaining stable traction and braking performance in the scenario of upgrading existing single-phase lines. Relying on mature motor technology, it reduces system operation and maintenance costs and improves overall operational reliability.

[0073] This specification also provides a method for optimizing the operation and control of a train's three-phase electric drive system, wherein the traction controller CTL controls the operating conditions of each traction converter TCV based on the current of the first current transformer C1 and the second current transformer C2. Specifically, this includes: when the traction controller CTL detects that the current of both the first current transformer C1 and the second current transformer C2 is 0, the traction controller CTL controls the traction converter TCV to stop inverter output; when the traction controller CTL detects that the current of one of the first current transformer C1 and the second current transformer C2 is 0, the traction controller CTL controls the rectified power of the corresponding non-zero phase of the traction converter TCV to be 2 / 3, and the rectified power of the other two phases to be 1 / 3; when the traction controller CTL detects that the current of neither the first current transformer C1 nor the second current transformer C2 is 0, the traction controller CTL controls the three-phase rectified power of the traction converter TCV to be 1 / 3 for each phase. Here, 1 / 3 and 2 / 3 refer to the proportion of each phase to the total power of the traction converter TCV rectifier.

[0074] When the train is not powered or completely de-energized, the traction controller CTL detects zero current through the first and second current transformers C1 and C2. At this time, it sends a command to each traction converter TCV to stop its inverter output, preventing a drop in the DC bus voltage of the traction converter. When the train is running on an existing single-phase converted line, or when a single phase of the three-phase power supply fails, one of the first and second current transformers C1 and C2 will detect zero current. Based on this, the traction controller CTL determines that the current condition is a single-phase current-carrying condition and adjusts the rectification power of the traction converter TCV, controlling the rectification power of the phase with current to 2 / 3 and the rectification power of the other two phases to 1 / 3. This balances the power of the three-phase rectification, maintains the stability of the DC bus voltage of the traction converter, and ensures that the inverter side of the traction converter TCV can normally output electrical energy to drive the traction motor M, guaranteeing the traction or braking performance of the train.

[0075] When the currents detected by the first and second current transformers C1 and C2 are both non-zero, the traction controller CTL determines that the current is in three-phase power supply, and then controls the three-phase rectification power of the traction converter TCV to be 1 / 3 each, making the three-phase rectification power uniform, which not only ensures the stability of the DC bus voltage, but also optimizes the power quality on the grid side, reduces harmonic interference, improves the power factor, and at the same time enables the traction motor M to obtain stable variable-frequency and variable-voltage power, ensuring the smooth and efficient operation of the train.

[0076] Through the precise regulation of current detection under different power receiving conditions and the rectification power of the traction converter TCV, the train can maintain traction and braking performance in single-phase power supply or three-phase single-phase fault or existing renovated line scenarios, and can optimize the power quality on the grid side in the new line scenario of normal three-phase power supply, ensuring reliable and stable operation under all working conditions.

[0077] In some embodiments, when the traction motor M is an asynchronous motor and the inverter side of the traction converter TCV adopts slip frequency control, at zero-speed startup, to increase the motor torque, the slip frequency is controlled to be ω sctl =kω scla ;

[0078] where ω scla is the theoretical calculation value of the slip frequency, ω sctl is the actual control value of the slip frequency, where k = f(ω r ) (0 < k < 1), and k gradually increases from a certain value (such as 0.5) to 1 as ω r varies;

[0079] When k = 1, the slip frequency performs closed-loop control of the magnetic flux q-axis component, ω sctl =ω scla +k p1 Φ q +k i1 ∫Φ q dt;

[0080] where Φ q is the actual value of the magnetic flux q-axis component of the motor, k p1 is the proportional parameter of the closed-loop PI control of the slip frequency magnetic flux q-axis component, k i1 is the integral parameter of the closed-loop PI control of the slip frequency magnetic flux q-axis component;

[0081] When the motor speed reaches the rated speed, the modulation method is switched to square wave modulation, and the slip frequency is switched to torque current control, ω sctl =ω scla +k p2 (I qref -I q )+k i2 ∫(I qref -I q)dt;

[0082] Among them, I qref I is the reference value for motor torque current. q k represents the actual value of the motor torque current. p2 k is the proportional parameter for the slip frequency, torque, and current closed-loop PI control. i2 These are the integral parameters for the slip frequency, torque, and current closed-loop PI control.

[0083] The theoretical slip frequency refers to the theoretical slip frequency value calculated based on the asynchronous motor's speed, rated parameters, etc., used to achieve the target torque output; the actual slip frequency control value refers to the actual slip frequency value output to the traction converter TCV after adjustment by the traction controller CTL in combination with actual operating conditions to control the operation of the asynchronous motor; the actual value of the flux linkage q-axis component refers to the actual component value of the asynchronous motor flux linkage on the q-axis of the rotating coordinate system obtained through detection or observation; the torque current reference value refers to the target value of the asynchronous motor torque current calculated based on the train's traction or braking requirements; the actual torque current value refers to the torque current value of the asynchronous motor during actual operation collected by a current detection device; zero-speed start refers to the starting process when the train is stationary.

[0084] Slip frequency control refers to a control method in asynchronous motor traction control that adjusts the motor torque by regulating the difference between the stator frequency and the rotor frequency; square wave modulation refers to a modulation method used on the inverter side of the traction converter TCV after the motor reaches its rated speed, using a square wave signal output voltage with a fixed duty cycle; torque current control refers to a control method that precisely controls the motor torque by adjusting the torque current component of the asynchronous motor; k p1 It is the proportional parameter of the slip frequency flux linkage q-axis component closed-loop PI control, used to adjust the response speed of the closed-loop control; k i1 These are the integral parameters of the slip frequency flux linkage q-axis component closed-loop PI control, used to eliminate the steady-state error of this closed-loop control; k p2 This is the proportional parameter of the slip frequency torque current closed-loop PI control, used to adjust the response speed of the closed-loop control; k i2 These are the integral parameters of the slip frequency torque current closed-loop PI control, used to eliminate the steady-state error of this closed-loop control. When the traction motor M is an asynchronous motor, the traction converter TCV inverter side adopts a slip frequency control strategy, and the specific operation process is as follows:

[0085] During the train's zero-speed start-up phase, to increase the output torque of the asynchronous motor, the traction controller CTL sets the actual control value of the slip frequency to the theoretically calculated value of the slip frequency multiplied by a coefficient k, where k varies with the motor speed ω. rThe variable being changed can be initially set to around 0.5, and gradually increased to 1 as the motor speed rises. In this way, sufficient torque can be provided to the motor at the initial stage of startup, ensuring that the train starts smoothly from a standstill.

[0086] When the coefficient k increases to 1, the slip frequency control switches to closed-loop control mode for the q-axis component of the flux linkage. At this time, the actual control value of the slip frequency is obtained by adding the theoretically calculated slip frequency value to the correction amount after PI adjustment of the actual value of the q-axis component of the flux linkage, specifically ω. sctl =ω scla +k p1 Φ q +k i1 ∫Φ q dt, where k p1 For the proportional parameter, k i1 As an integral parameter, the traction controller CTL detects and obtains the actual value of the q-axis component of the flux linkage, performs proportional-integral calculations on the deviation between it and the theoretically expected value, and corrects the slip frequency in this way to achieve precise control of the motor flux linkage and ensure the stability of the motor torque output.

[0087] Once the motor speed reaches the rated speed, the modulation mode of the traction converter TCV switches to square wave modulation, and the slip frequency control strategy switches to torque current control mode. At this time, the traction controller CTL calculates the torque current reference value based on the train's traction or braking requirements, then collects the actual torque current value through a current detection device, and adjusts the deviation between the two values ​​via PI control (proportional parameter k). p2 Integral parameter k i2 After that, it is superimposed on the theoretically calculated value of the slip frequency to obtain the actual control value of the slip frequency, i.e., ω. sctl =ω scla +k p2 (I qref -I q )+k i2 ∫(I qref -I q )dt.

[0088] This control method allows the actual control value of the slip frequency to better match the traction and braking requirements of the train, ensuring stable and efficient operation of the motor at rated speed, while optimizing the train's traction and braking performance. Through a layered control strategy—dynamically adjusting the slip frequency control coefficient during zero-speed startup, switching to flux linkage q-axis component closed-loop control during medium-speed operation, and switching to torque and current closed-loop control after rated speed—the asynchronous motor obtains sufficient torque to ensure smooth train startup during startup, maintains flux linkage stability in the medium-speed range to ensure stable torque output, and precisely matches traction and braking requirements during rated speed operation to improve operating efficiency, thus comprehensively optimizing the train's traction performance under all operating conditions.

[0089] The applicant declares that the detailed process flow of this invention is illustrated by the above embodiments, but this invention is not limited to the above detailed process flow, that is, it does not mean that this invention must rely on the above detailed process flow to be implemented. Those skilled in the art should understand that any improvements to this invention, equivalent substitutions of raw materials for the product of this invention, additions of auxiliary components, and selection of specific methods, all fall within the protection and disclosure scope of this invention. The above descriptions are merely preferred embodiments of this invention and are not intended to limit this invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this invention should be included within the protection scope of this invention.

Claims

1. A train three-phase electric drive system characterized by: The traction network, the current collecting device, the leakage reactance transformer, the traction converter, the traction motor and the traction controller are included. The traction network includes a first power supply rail, a second power supply rail and a steel rail, and the traction network supplies three-phase power to the leakage reactance transformer through the current collecting device. The current collecting device includes a first current collecting shoe, a second current collecting shoe and a rail connector, one end of the first current collecting shoe and the second current collecting shoe respectively contacts the first power supply rail and the second power supply rail to receive power, the other end of the first current collecting shoe is connected to a first terminal of a primary side of the leakage reactance transformer through a first cable and a first current transformer, the other end of the second current collecting shoe is connected to a second terminal of the primary side of the leakage reactance transformer through a second cable and a second current transformer, one end of the rail connector contacts the steel rail to receive power, and the other end of the rail connector is connected to a third terminal of the primary side of the leakage reactance transformer through a third cable. The secondary side of the leakage reactance transformer includes a plurality of three-phase traction windings, the plurality of three-phase traction windings are electrically isolated from each other, and three terminals of each three-phase traction winding are not grounded. The plurality of three-phase traction windings of the secondary side of the leakage reactance transformer are respectively connected to three-phase rectification terminals of a plurality of traction converters. Equivalent leakage reactances of the traction windings of the leakage reactance transformer are used as four-quadrant rectification network reactance of the traction converter. The inversion terminals of the traction converter are connected to the traction motor. The input terminals of the traction controller are connected to output terminals of the first current transformer and the second current transformer, the output terminals of the traction controller are connected to control terminals of the traction converter, and the traction controller controls working conditions of the traction converter according to current signals.

2. A three-phase electric drive system for a train according to claim 1, characterized in that: The secondary side of the leakage reactance transformer is further provided with a three-phase Y-connected winding, and the three-phase Y-connected winding outputs 400V / 220V voltage.

3. A three-phase electric drive system for a train as claimed in claim 1, characterized in that: The voltage of the primary side of the leakage reactance transformer is 3kV, and the voltage of the three-phase traction winding of the secondary side of the leakage reactance transformer is 0.8kV-1.0kV.

4. A train three-phase electric drive system as claimed in claim 1, characterized in that: The primary side winding and the secondary side winding of the leakage reactance transformer are respectively connected in a delta / Y mode, and one terminal of the primary side winding of the leakage reactance transformer is connected to the steel rail through the rail connector.

5. A train three-phase electric drive system as claimed in claim 1, characterized in that: The primary side winding and the secondary side winding of the leakage reactance transformer are respectively connected in a delta / delta mode, and one terminal of the primary side winding of the leakage reactance transformer is connected to the steel rail through the rail connector.

6. A train three-phase electric drive system as claimed in claim 1, characterized in that: The primary side winding and the secondary side winding of the leakage reactance transformer are respectively connected in a Y / Y mode, and one terminal of the primary side winding of the leakage reactance transformer is connected to the steel rail through the rail connector.

7. A train three-phase electric drive system as claimed in claim 1, characterized in that: The primary side winding and the secondary side winding of the leakage reactance transformer are respectively connected in a Y / delta mode, and one terminal of the primary side winding of the leakage reactance transformer is connected to the steel rail through the rail connector.

8. A train three-phase electric drive system as claimed in claim 1, characterized in that: The traction converter (TCV1-n) is a three-level converter.

9. A train three-phase electric drive system as claimed in claim 1, characterized in that: The current collecting device supports a single-phase current collecting mode, and when the current collecting device switches to the single-phase current collecting mode, the three-phase traction converter operates in a single-phase working condition.

10. A three-phase electric drive system for a train as claimed in claim 1 or claim 9, characterised in that: The equivalent leakage reactance of each three-phase traction winding of the secondary side of the leakage reactance transformer is greater than or equal to 20%.

11. A train three-phase electric drive system as claimed in claim 1, characterized in that: The traction motor is an asynchronous motor, an asynchronous motor group or a synchronous motor.

12. An optimized operation control method of a train three-phase electric drive system according to any one of claims 1-11, characterized in that: The traction controller controls working conditions of each traction converter according to currents of the first current transformer and the second current transformer, and specifically includes: When the traction controller detects that the currents of the first current transformer and the second current transformer are both 0, the traction controller controls the traction converter to stop inverting output; When the traction controller detects that the current of one of the first current transformer and the second current transformer is 0, the traction controller controls the traction converter to make the rectified power of the corresponding phase be 2 / 3 and the rectified power of the other two phases be 1 / 3; When the traction controller detects that the currents of the first current transformer and the second current transformer are both not 0, the traction controller controls the traction converter to make the rectified power of the three phases be 1 / 3.

13. The optimal operation control method of the train three-phase electric drive system according to claim 12, characterized in that: When the traction motor is an asynchronous motor, the slip frequency control is used in the inverter side of the traction converter, and the slip frequency is controlled as ω sctl =kω scla when the motor is started at zero speed to improve the motor torque. where ω scla is the slip frequency theoretical value, ω sctl is the slip frequency actual control value, where k = f(ω r ) (0 < k < 1), k gradually increases from 0.5 to 1 as ω r increases. When k = 1, the slip frequency carries out the flux q-axis component closed-loop control, ω sctl = ω scla + k p1 Φ q + k i1 ∫Φ q dt Wherein, Φ q is the actual value of the q-axis component of the motor flux, k p1 is the proportional parameter of the closed-loop PI control of the q-axis component of the slip frequency flux, k i1 is the integral parameter of the closed-loop PI control of the q-axis component of the slip frequency flux When the motor speed reaches the rated speed, the modulation mode is switched to square wave modulation, the slip frequency is switched to torque current control, ω sctl =ω scla +k p2 (I qref -I q )+k i2 ∫(I qref -I q )dt; Wherein, I qref is the motor torque current reference value, I q is the motor torque current actual value, k p2 is the slip frequency torque current closed-loop PI control proportional parameter, k i2 is the slip frequency torque current closed-loop PI control integral parameter.

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