Traction system for vehicle having electric traction

Abstract

To provide means for moving a train that is equipped with an auxiliary power supply capable of providing electric energy at a voltage level lower than a voltage level necessary for an AC traction motor for the train without using any external power supply and basically on the basis of reuse of existing components.SOLUTION: A traction system 2 for a vehicle, for example, a train or a locomotive, includes: at least one AC traction motor 4 propelling the vehicle; a DC link 6 configured to supply the AC traction motor 4 with voltage at a first voltage level; and a first power supply 8 configured to supply the DC link 6 with the voltage at the first voltage level from overhead contact lines, for example. Moreover, the traction system 2 includes: a second power supply 10 provided with at least one battery for providing voltage at a second voltage level lower than the first voltage level; a chopper circuit 12 connected to the DC link 6; a braking resistor unit 14 provided with at least one braking resistor; and a control unit 16.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a traction system for rail vehicles with electric traction. [Background technology]

[0002] For vehicles with electric traction, which receive electrical energy via, for example, overhead lines or a third rail, there may be situations where externally generated electrical energy is not available from, for example, the overhead lines or third rail.

[0003] It is believed that the technical problem addressed by the traction system described herein is how to provide a means for moving a train with an auxiliary power source capable of providing electrical energy at voltage levels typically lower than those required by the train's alternating current (AC) traction motors, without using any external power source and based essentially on the reuse of existing components, i.e., with minimal additional components.

[0004] Below, several documents disclosing related art are identified and briefly described. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] European Patent Application Publication No. 3876413 [Patent Document 2] US Patent Application Publication No. 2016288666 [Patent Document 3] International Publication No. 2021 / 161191

[0006] Patent document 1 discloses the versatile use of phase legs in a power supply system for a traction unit, which includes a transformer for providing AC voltage from the electric grid and a battery for providing direct current (DC) voltage. Patent document 1 describes a traction system powered by overhead lines or a battery, and discloses a braking resistor unit with a braking chopper.

[0007] Patent Document 2 describes a system for controlling emergency driving of a fuel cell vehicle. The system includes a cut-off relay for connecting or interrupting the flow of current between a chopper and a supercapacitor. This provides a traction system with a fuel cell and a supercapacitor as a second power source. A braking resistor unit with a braking chopper is also disclosed.

[0008] Patent document 3 discloses a vehicle with electric traction including an energy management system comprising a generator set configured to generate a first supply voltage and mechanically disconnected from the wheels in all operating states, a battery storage assembly configured to generate a second supply voltage, and a control unit external to the vehicle that implements operating states of the vehicle including powering an electric traction chain with the first supply voltage, powering the electric traction chain with the second supply voltage, recharging the storage assembly with network voltage from the catenary, recharging the storage assembly with the first supply voltage, and recharging the storage assembly with recovered voltage generated by the traction chain acting as a generator.

[0009] The present invention focuses on reconfiguring existing circuits in traction systems to allow a boosted voltage from an auxiliary battery to be used to propel the train. The auxiliary battery voltage is usually too low to magnetize and provide sufficient traction power to the traction motors, especially in, for example, 750 or 1500V DC link systems.

[0010] It is believed that the technical problem that the present invention aims to solve is how to provide a means for moving trains with auxiliary power without using any external power source and essentially based on the reuse of existing components, i.e., with the inclusion of only a minimum of additional components.

[0011] It is therefore an object of the present invention to provide a traction system with overhead power supply (or via a third rail) or auxiliary power supply and dynamic braking with a minimum of components. Summary of the Invention [Problem to be solved by the invention]

[0012] The above-mentioned object is achieved by the present invention according to the independent claims. Preferred embodiments are set out in the dependent claims.

[0013] According to the present invention, the above-mentioned object is achieved by reconfiguring the chopper circuit to have not only braking chopper functionality but also step-up chopper functionality, thereby boosting the voltage available from the auxiliary battery (typically 110V, but also e.g. 24V, 36V, 54V, 72V, etc.) to the voltage required on the DC link, i.e. a voltage level high enough for train movement. The power and voltage limitations are suitable for shunting and emergency operations, for example to move trains over short distances, up to several kilometers depending on the track gradient, without the use of overhead power.

[0014] If more power (or different functionality) is required, a traction battery solution can be applied, but this adds cost, weight and complexity to the system.

[0015] By implementing the present invention, dual use of the chopper circuit connected to the braking resistor unit is achieved, whereby the chopper connected to the braking resistor unit is used as a step-up chopper for the auxiliary battery to adapt its voltage level to that of the DC link, or as a braking chopper for braking functions.

[0016] This is advantageous as it reduces parts count compared to currently employed solutions that use separate chopper circuits.

[0017] Accordingly, the present disclosure relates to a traction system with means for magnetizing the traction motors and achieving simple, cost-effective battery powered traction for shunting and emergency operations using auxiliary batteries having voltage output levels that are too low to provide traction power to the traction motors over distances greater than 2000 meters, including gradients.

[0018] A battery operation propulsion (BOP) unit as defined herein is applied as an add-on / option feature to the standard architecture of the traction system.

[0019] The primary vehicle application is rail-operated vehicles such as subways and commuter rail cars, but the traction system may have general application to all electric vehicles.

[0020] The BOP unit includes an inductor unit configured to smooth out voltage ripple from a boost chopper used to convert a predetermined second voltage (typically 110V) from the DC link to a voltage (typically 300V) that can be used to power the traction motors.

[0021] A braking resistor unit is provided having at least one braking resistor, whereby the braking resistor unit is connected to the chopper when the chopper circuit is controlled to function as a braking chopper for dynamic control by the control unit.

[0022] By implementing the traction system according to the present invention, it is possible to power, for example, a 1500V based train traction system from a 110V battery. Previous solutions had significant limitations regarding operating conditions (i.e. speed and load). [Brief explanation of the drawings]

[0023] [Figure 1] 1 is a block diagram illustrating a schematic diagram of a traction system according to the present invention; [Figure 2] FIG. 2 is a block diagram illustrating a battery-operated propulsion unit of the traction system according to the present invention. [Figure 3] 1 is a schematic diagram of a traction system according to an embodiment of the present invention; [Figure 4] FIG. 1 is a schematic diagram of a traction system according to an embodiment of the present invention having a chopper circuit operating as a braking chopper. [Figure 5] FIG. 1 is a schematic diagram of a traction system according to an embodiment of the present invention having a chopper circuit operating as a boost chopper. DETAILED DESCRIPTION OF THE INVENTION

[0024] The traction system will now be described in detail with reference to the accompanying drawings. Identical or similar items will have the same reference numerals throughout the drawings. Further, the items and drawings are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the invention.

[0025] FIG. 1 shows, in a block diagram, a schematic representation of a traction system 2 for a vehicle (particularly a train or locomotive) with electric traction. FIG. 3 shows a schematic representation of a traction system such as that shown in FIG. 1, and reference is now made to both figures. A vehicle with electric traction comprises at least one AC traction motor 4 for propelling the vehicle. The electric traction includes at least one DC / AC inverter, particularly a three-phase inverter, for converting DC power to three-phase AC power for the at least one AC traction motor 4, which is powered by AC power provided by the inverter, and a braking resistor unit 14, the power level of which is regulated by a DC / DC converter (not shown) (also known as a "braking chopper") designed to dissipate braking energy in the form of heat when the energy cannot be delivered to the DC link 6 and / or stored. The at least one AC traction motor 4 is designed to provide propulsion to the vehicle's wheels, thereby generating drive torque for the vehicle itself.

[0026] A mains power line 6 (hereinafter referred to as the "DC link") is provided and is configured to transmit a DC supply voltage having a predetermined first voltage level to the vehicle, in particular to power at least one AC traction motor of the vehicle and any loads or auxiliary services (not shown).

[0027] The first power source 8 is arranged to supply the DC link 6, for example from an overhead line or from a third rail supply, i.e. from a high voltage external power supply line, to draw DC electrical energy from such line and to make DC electrical energy available to the vehicle by supplying it towards the DC link even when the vehicle is moving.

[0028] The traction system 2 further comprises a plurality of switches (not shown in FIG. 1 ), in particular bidirectional switches, realized for example in the form of contactors, triacs (TRIACs), electromechanical devices designed to withstand currents under high power conditions and not manually operated, or solid-state devices. Alternatively, the switches can be made in semiconductor technology, for example, metal-oxide-semiconductor field-effect transistors (MOSFETs) or insulated-gate bipolar transistors (IGBTs). In general, the term "switch" refers to an electrical or electronic or electromechanical element capable of interrupting or establishing a current path through it.

[0029] In particular, one switch is electrically coupled between the output of the AC / DC electronic converter and the DC link 6 and is operable to connect or disconnect the electronic converter AC / DC to or from the DC link. Another switch is provided and is electrically coupled between the high voltage external power line and the DC link 6 and is operable to connect or disconnect the external power line to or from the DC link.

[0030] A further switch is electrically coupled between the AC traction motor(s) and the DC link 6 and is operable to connect or disconnect the traction motor(s) to or from the DC link 6.

[0031] The traction system 2 further comprises a second power source 10 comprising at least one battery providing a second predetermined voltage level lower than the first predetermined voltage level. The second power source 10 is also referred to herein as an auxiliary power source. The second power source 10 preferably comprises a rechargeable battery pack including one or more battery modules or cells (e.g., of any available technology, such as lithium, lead, NiCd, NiMH, ZEBRA, etc.) connected in series and / or parallel with each other and configured to store energy and provide power useful for various internal service systems of the train and also useful for traction of the cars over a given distance (e.g., several hundred meters or kilometers in length).

[0032] Furthermore, the traction system 2 comprises a chopper circuit connected to the DC link 6, a braking resistor unit 14 comprising at least one braking resistor, and a control unit. Figure 3 also shows a battery charger module 34 comprising the necessary circuitry for charging the second power source 10. Furthermore, a current return and earth brush arrangement 36 is also shown.

[0033] The traction system 2 further comprises a battery operated propulsion (BOP) unit 18 configured to connect the second power source 10 to the DC link 6 .

[0034] 2, the BOP unit 18 includes a battery isolation switch 20 configured to connect the chopper circuit 12 to the braking resistor unit 14 or the second power source 10, an inductor unit 22, and a braking chopper switch 21. The BOP unit 18 further includes at least one power flow prevention component 24, preferably at least one diode unit, and at least one chopper circuit connecting member 26 configured to prevent direct power flow from the first power source 8 to the second power source 10.

[0035] The control unit 16 controls the chopper circuit 12 by determining a control signal 28 with control instructions and applying the control signal 28 to the BOP unit. a) to act as a step-up chopper to adapt a predetermined second voltage level to a predetermined first voltage level so that the DC link 6 is powered from a second power source 10, or b) To act as a braking chopper for dynamic / rheostatic braking; It is configured to control the BOP unit 18.

[0036] Software for generating the control signals and thereby controlling the BOP unit is advantageously provided in the control unit 16 .

[0037] The battery isolation switch works in conjunction with a High-Speed ​​Circuit Breaker (HSCB) to prevent high voltage on the second power source 10, such as a battery, and an additional layer of safety is at least one power flow prevention component 24, such as a diode. A high-speed circuit breaker refers to a circuit breaker that has the ability to limit fault current before it reaches its predicted value and before it reaches a level that is dangerous to the equipment protected by the high-speed circuit breaker.

[0038] The inductor unit 22 of the BOP unit is provided to smooth out any voltage ripple from the chopper circuit when it functions as a step-up chopper used to change the voltage from a predetermined second voltage level (typically 110V) from the DC link to a predetermined first voltage level (typically 300V) used to power at least one AC traction motor 4.

[0039] 2, the BOP unit 18 includes a first connection line 30 having a first end (left in the figure) connectable to a first connection point of the second power source 10 and a second end (right in the figure) connectable to the braking resistor unit 14. One side of the battery isolation switch 20, an inductor unit 22, a power flow prevention component 24 (e.g., a diode), and a braking chopper switch 21 are arranged in series along the first connection line 30 between the first and second ends. The BOP unit 18 also includes a second connection line 32 having a first end (left in the figure) connectable to a second connection point of the second power source 10 and a second end (right in the figure) that is a chopper circuit connection member 26 connectable to the chopper circuit 12, and the other side of the battery isolation switch 20 is provided on the second connection line 32.

[0040] 4 and 5 show simplified circuit diagrams illustrating the functionality of a traction system according to an embodiment of the present invention.

[0041] In particular, Figure 4 shows the traction system when the chopper circuit is controlled to function as a braking chopper. Accordingly, the control commands include a control command to open the battery isolation switch 20 and to close the braking chopper switch 21. In the figure, the bold lines indicate the current flow.

[0042] In particular, Figure 5 shows the traction system when the chopper circuit is controlled to function as a boost chopper. Accordingly, the control commands include a control command to close the battery isolation switch 20 and to open the braking chopper switch 21. In the figure, the bold lines indicate the current flow.

[0043] Dynamic braking is the use of an electric traction motor as a generator to slow the vehicle: it is called "rheostatic" if the generated power is dissipated as heat in a braking resistor unit, or "regenerative" if the power is returned to the supply line.

[0044] Dynamic braking requires two components: a braking chopper and an external braking resistor unit. The braking chopper typically consists of an IGBT assembly and logic functions. The chopper controls the DC link voltage by connecting a braking resistor across the link when the voltage reaches a predetermined level, dissipating excess energy in the braking resistor unit.

[0045] The present invention is not limited to the preferred embodiments described above. Various alternatives and modifications may be employed. Therefore, the above embodiments should not be construed as limiting the scope of the present invention, which is defined by the appended claims.

Claims

1. A traction system (2) for a vehicle, for example a train or locomotive, comprising: at least one AC traction motor (4) for propelling said vehicle; a DC link (6) configured to supply a voltage having a predetermined first voltage level to the at least one AC traction motor (4); a first power supply (8) configured to supply the DC link (6) with a voltage at the predetermined first voltage level, for example from an overhead line or from a third rail supply; a second power source (10) comprising at least one battery providing a second predetermined voltage level lower than said first predetermined voltage level; a chopper circuit (12) connected to the DC link (6); a braking resistor unit (14) comprising at least one braking resistor; a control unit (16); Equipped with the traction system (2) comprises a battery operation propulsion (BOP) unit (18) configured to connect the second power source (10) to the DC link (6); The BOP unit (18) comprises: a battery isolation switch (20) configured to connect the chopper circuit (12) to the braking resistor unit (14) or the second power source (10); an inductor unit (22); at least one power flow prevention component (24), preferably at least one diode unit, configured to prevent direct power flow from the first power source (8) to the second power source (10); A braking chopper switch (21); at least one chopper circuit connection member (26); Equipped with The control unit (16) controls the chopper circuit (12) by determining a control signal (28) with a control command and applying the control signal (28) to the BOP unit, a) the DC link (6) is supplied by the second power supply (10) and acts as a step-up chopper to adapt the second predetermined voltage level to the first predetermined voltage level, or b) To act as a braking chopper for dynamic / rheostatic braking; configured to control the BOP unit (18); Traction system (2).

2. The BOP unit 18 includes: a first connection line (30) having a first end connectable to a first connection point of the second power source (10) and a second end connectable to the braking resistor unit (14), wherein one of the battery isolation switches (20), the inductor unit (22), the power flow prevention component (24), and the braking chopper switch (21) are arranged in series along the first connection line (30) between the first end and the second end; a second connection line (32) having a first end connectable to a second connection point of the second power source (10) and a second end being the chopper circuit connection member (26) connectable to the chopper circuit, the second connection line (32) being provided with the other end of the battery isolation switch (20); Equipped with The traction system of claim 1 .

3. When the chopper circuit is controlled to function as a boost chopper, the control commands include control commands to close the battery isolation switch (20) and to open the braking chopper switch (21).

3. A traction system according to claim 1 or 2.

4. When the chopper circuit is controlled to function as a braking chopper, the control instructions include control instructions for opening the battery isolation switch (20) and for closing the braking chopper switch (21). A traction system according to any one of claims 1 to 3.

5. when the chopper circuit is controlled to function as a boost chopper, the inductor unit is configured to smooth a voltage ripple in an output voltage from the chopper circuit when changing the voltage from the second predetermined voltage level to the first predetermined voltage level. A traction system according to any one of claims 1 to 4.

6. said predetermined first voltage level is at least 250V, typically 300V; the predetermined second voltage level is below 250V, typically 110V; A traction system according to any one of claims 1 to 5.

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