GB2611341A

GB2611341A - Drive system for a railway vehicle

Info

Publication number: GB2611341A
Application number: GB2114080.1A
Authority: GB
Inventors: ROSENGREN Jonas
Original assignee: Hitachi Rail Ltd
Current assignee: Hitachi Rail Ltd
Priority date: 2021-10-01
Filing date: 2021-10-01
Publication date: 2023-04-05
Also published as: GB2616878A; GB2616876A; GB202204081D0; GB202114080D0; GB202204079D0

Abstract

A railway vehicle for travelling on routes with, and without, an external power supply infrastructure has a drive system with one or more external current collectors 13, one or more on-board generator units (GUs) 11 and one or more on-board energy storage systems (OBESSs) 12. The external current collectors obtain electrical power from the external power supply infrastructure. The GUs generate electrical power from combustion or oxidation of a fuel. The OBESSs store and output electrical energy. Traction motors 14a, 14b drive the railway vehicle using electrical power from the external current collector(s), the GU(s) and the OBESS(s), while a control system selectively controls the provision of power to the traction motors according to different driving modes. In a first driving mode, the power is provided from the external power supply infrastructure via the external current collector(s). In a second driving mode, the power is provided from the GU(s) assisted by the OBESS(s). In a third driving mode, the power is provided from just the OBESS(s). The drive system may include converter-inverter devices comprising converter circuits 21a, 21b that convert AC power into DC power, which is conducted via a DC link to an inverter circuit 25a, 25b which converts the DC power into AC power to drive respective traction motors.

Description

DRIVE SYSTEM FOR A RAILWAY VEHICLE

Field of the Invention

The present invention relates to a drive system for a railway vehicle comprising one or more external current collectors, one or more on-board generator units and one or more on-board energy storage systems.

Background

Figure 1 shows schematically a control system for a conventional bi-mode train. Bi-mode trains are configured to operate two different drive modes in which the train propulsion systems receive electrical power from two different configurations of power sources. The first, externally powered, drive mode 101 is provided on electrified railway lines which have an external power supply infrastructure. The second, self-powered, drive mode 102 is provided on non-electrified railway lines. The bi-mode trains can cross to and from electrified and non-electrified sections of the railways lines by changing between their two available drive modes.

In the externally powered drive mode 101, the bi-mode trains receive electrical power from the external power supply infrastructure via external current collectors for example pantographs which connect to overhead lines (OHL) 110 or shoe gear which connect to live rails on the railway tracks.

In the self-powered drive mode 102, bi-mode trains receive electrical power from on-board power sources. Conventionally, bi-mode trains comprise on-board generator units (GUs) 111, such as diesel engine-powered electricity generators, which generate the electrical power.

When a bi-mode train changes between its externally powered drive mode 101 and its self-powered drive mode 102 the control system manages the handover of the propulsion systems according to Automatic Power Change Over (APCO) routines A' and B'. EP 2689983 A proposes an APCO for a bi-mode train transifioning from an externally powered drive mode, which uses OHLs, to a self-powered drive mode which uses GUs.

Other trains have a hybrid self-powered drive system comprising GUs assisted by on-board energy storage systems (OBESSs), such as batteries. On conventional hybrid trains, GUs are used as the main source of motive power. The GUs are typically assisted by the OBESSs when the train is accelerating. The OBESSs contribute to overall improvements in energy consumption by enabling regenerative braking in which kinetic energy of the train is converted into regenerated electrical power for subsequent re-use.

However, conventional hybrid trains require that the GUs remain active at all times to provide motive power for the train and to power auxiliary systems. This contributes to greenhouse gas emissions and noise pollution, despite receiving assistance from the OBESSs 112 in acceleration phases.

Summary of the Invention

In general terms, a tri-mode train according to the present disclosure is provided with three drive modes. In particular, an externally powered first drive mode is provided for sections of railway lines which have an external power supply infrastructure, a hybrid self-powered second drive mode is provided whereby electrical power for traction is provided by GUs assisted by OBESSs, and a third drive mode is provided whereby electrical power for traction is provided by OBESSs alone. Thus there are two self-powered drive modes which may be operated on non-electrified sections of railway lines. Such a tri-mode train can result in reduced fuel consumption and carbon dioxide emissions on non-electrified sections.

Accordingly, the present disclosure provides a railway vehicle for travelling on routes with external power supply infrastructure and on routes without external power supply infrastructure, the vehicle having a drive system comprising: one or more external current collectors for obtaining electrical power from the external power supply infrastructure; one or more on-board generator units for generating electrical power from combustion or oxidation of a fuel; one or more on-board electrical storage systems for storing and outputting electrical energy; traction motors configured to drive the railway vehicle using electrical power from the external power supply infrastructure via the one or more external current collectors, the one or more generator units and the one or more on-board electrical storage systems; and a control system configured to selectively control the provision of electrical power to the traction motors from the one or more external current collectors, the one or more generator units and the one or more on-board electrical storage systems, and thereby provide: a first driving mode wherein electrical power is provided to the traction motors from the external power supply infrastructure via the one or more external current collectors; a second driving mode wherein electrical power is provided to the traction motors from the one or more generator units assisted by the one or more on-board electrical storage systems; and a third driving mode wherein electrical power is provided to the traction motors from just the one or more on-board electrical storage systems.

Thus, the system can result in overall improvements in energy-consumption performance and reductions in carbon dioxide emissions over the course of a journey, and provide high operational performance.

The following optional features are applicable singly or in any combination with the railway vehicle.

Conveniently, the generator units may be positioned on one or more cars of the railway vehicle, and the on-board electrical storage systems may be positioned on one or more different cars of the railway vehicle. However, this does not exclude other arrangements, e.g. whereby individual cars have both a generator unit and an on-board electrical storage system.

The traction motors may comprise first traction motors and second traction motors, and the control system may be configured such that: in the first driving mode, both the first and second traction motors drive the railway vehicle using electrical power from the external power supply infrastructure via the one or more external current collectors, in the second driving mode the first traction motors drive the railway vehicle using electrical power from the one or more generator units and the second traction motors drive the railway vehicle using electrical power from the one or more on-board electrical storage systems, and in the third driving mode both the first and second traction motors drive the railway vehicle using electrical power from the one or more on-board electrical storage systems. This enables the train to increase the available drive power by using all of the available traction motors in the three drive modes. However, this does not exclude arrangements in which the control system disables the first traction motors in the third driving mode such that the train receives motive power from the second traction motors only in that driving mode.

When the generator units and the on-board electrical storage systems are positioned on different cars of the railway vehicle, the first tractions motors, powered by the generator units in the second driving mode, may then be positioned on cars having generator units, and the second tractions motors, powered by the on-board electrical storage systems in the second driving mode, may be positioned on the cars having on-board electrical storage systems.

The drive system may further comprise first and second converter-inverter devices. Each first converter-inverter device may comprise: first converter circuits to convert AC electrical power into DC electrical power, a first DC link conducting the DC electrical power, and first inverter circuits to convert the DC electrical power conducted by the first DC link into AC electrical power to drive respective first traction motors. Each second converter-inverter device may comprise: a second converter circuit to convert AC electrical power into DC electrical power, a second DC link conducting the DC electrical power, and a second inverter circuit to convert the DC electrical power conducted by the second DC link into AC electrical power to drive respective second traction motors. In the first driving mode the first and second converter circuits receive AC electrical power from the one or more external current collectors, and the first and second DC links are maintained at a first DC voltage. In the second driving mode the first converter circuits receive AC electrical power from respective generator units, the second DC links receive DC electrical power from respective on-board energy storage systems, and the first DC links are maintained at the first DC voltage and the second DC links are maintained at a different second DC voltage. In the third driving mode the first and second DC links receive DC electrical power from respective on-board electrical storage systems, and the first and second DC links are maintained at the second DC voltage. By this arrangement the first and second traction motors may receive power from the external current collectors, the generator units or the on-board electrical storage systems, even when the on-board electrical storage systems provide a different voltage to the external current collectors and the generator units. Therefore, increased drive power may be achieved, even in the third drive mode, since the on-board electrical storage systems may provide power to both sets of traction motors.

The drive system may further comprise: one or more first soft-charging circuits between the one or more external current collectors and the first and second converter-inverter devices, and one or more second soft-charging circuits between the one or more on-board electrical storage systems and the DC links of the second converter-inverter devices; wherein the control system is configured to: connect the one or more external current collectors to the first and second converter-inverter devices via the first soft-charging circuit as part of changing over to the first driving mode from each of the second and third driving modes, and connect the one or more on-board electrical storage systems to the second converter-inverter devices via the second soft-charging circuits as part of changing over to each of the second and third driving modes from the first driving mode. In this way, in-rush currents can be limited to prevent system damage when the voltage level of the DC links is changed between the first and second DC voltages.

The control system may be further configured to discharge the first DC links as part of changing over to the third driving mode from each of the first and second driving modes. Particularly when the first DC voltage is significantly higher than the second DC voltage, discharging the first DC links as part of changing to the third driving mode may help to prevent system damage.

The control system may be further configured to connect the one or more on-board electrical storage systems to the first converter-inverter devices via the second soft-charging circuits (and typically after the first DC links have been discharged) as part of changing over to the third driving mode from each of the first and second driving modes. Conveniently, using the second soft-charging circuits in this way to charge the first DC links avoids the need for additional soft-charging circuits to be fitted to the drive system.

The drive system may further comprise one or more auxiliary power supply units (typically positioned on respective cars of the vehicle) for powering auxiliary systems of the vehicle using electrical power from: the external power supply infrastructure via the one or more external current collectors in the first driving mode, the one or more generator units assisted by the one or more on-board electrical storage systems in the second driving mode, and just the one or more on-board electrical storage systems in the third driving mode. Auxiliary systems, such as air conditioning, can thus remain powered in all three drive modes on non-electrified and non-electrified sections of the track alike.

The one or more auxiliary power supply units may comprise first auxiliary power supply units powered by respective generator units in the second driving mode and second auxiliary power supply units powered by respective on-board electrical storage systems in the second driving mode; and the drive system may further comprise auxiliary power supply contactors which are operable to electrically connect each first auxiliary power supply unit with a respective on-board electrical storage system. The control system may then be further configured to: open the auxiliary power supply contactors in the first and second driving modes to electrically isolate each first auxiliary power supply unit from the respective on-board electrical storage system, and close the auxiliary power supply contactors in the third driving mode to electrically connect each first auxiliary power supply unit with the respective on-board electrical storage system. The first auxiliary power supply units can thus continue to provide power to auxiliary systems in the third driving mode. However, in addition, the closure of the auxiliary power supply contactors in the third driving mode may form circuits between the first traction motors and the one or more on-board electrical storage systems such that the first traction motors drive the railway vehicle using electrical power received from the one or more on-board electrical storage systems. This arrangement enables the on-board electrical storage systems to provide power to the first traction motors by routing power through the first auxiliary power supply units. Advantageously, this approach can avoid a need for additional drive system infrastructure to be installed between the on-board electrical storage systems and the first traction motors.

The control system may be further configured to provide a changeover from the second driving mode to the third driving mode by: disconnecting the first converter circuits from the one or more respective generator units, disabling the first inverter circuits and the first auxiliary power supply units, discharging the first and second DC links, closing the auxiliary power supply contactors, charging the first and second DC links to the second DC voltage via the second soft-charging circuits, and re-enabling the first inverter circuits and the first auxiliary power supply units. The generator units may be stopped after they are disconnected from the first converter circuits.

The control system may be further configured to provide a changeover from the third driving mode to the second driving mode by: starting the one or more generator units, opening the auxiliary power supply contactors, and connecting the first converter-inverter devices to the respective generator units.

The railway vehicle may further comprise: main transformers, between the one or more external current collectors and the first and second converter circuits, for converting AC electrical power from the one or more external current collectors to a lower AC voltage, and DC/DC choppers between the second DC links and the respective on-board electrical storage systems for stepping down voltage such that the one or more on-board electrical storage systems can increase their state of charge using electrical power from the one or more external current collectors. The control system may then be further configured to provide a changeover from the first driving mode to the third driving mode by: disabling the first and second converter circuits, disabling the DC/DC choppers, disconnecting the main transformers from the first and second converter circuits, discharging the first and second DC-links, closing the auxiliary power supply contactors, and charging the first and second DC-links to the second DC voltage using the second soft-charging circuits. This changeover may further include (e.g. after disconnecting the main transformers from the first and second converter circuits): disconnecting the one or more external current collectors from the main transformers, and/or disconnecting the one or more external current collectors from the external power supply infrastructure. In addition, the control system may be further configured to provide a changeover from the third driving mode to the first driving mode by: opening the auxiliary power supply contactors, disconnecting the one or more on-board electrical storage systems, connecting the first and second converter circuits to the main transformers via the first soft charging circuits, enabling the first and second converter circuits, and enabling the DC/DC choppers. This changeover may further include (e.g. after disconnecting the one or more on-board electrical storage systems): connecting the one or more external current collectors to the main transformers, and/or connecting the one or more external current collectors to the external power supply infrastructure.

The above change-over routines enable the railway vehicle to change between each of the three driving modes and the available power sources in a fast and efficient manner that can avoid damage to systems and reduce downtime of the auxiliary power supply units.

The drive system and the control system may be configured such that in the second and third driving modes regenerative braking is performable to increase a state of charge of the on-board electrical storage systems by generator operation of the second traction motors. In generator operation, energy flow through the traction motors is reversed. In this way, kinetic energy of the train can be converted into regenerated electrical power which is stored in the on-board electrical storage systems. This enables the on-board electrical storage systems to increase their state of charge during operation, increasing the amount of power they can provide and thereby increasing the power available to operate the third driving mode or to assist the generator units in the second driving mode. Consequently, improvements can be made to fuel-consumption performance and carbon dioxide emissions can be reduced. Similarly, the drive system and the control system may be configured such that in the first driving mode regenerative braking is performable to return electrical energy to the external power supply infrastructure (or the on-board electrical storage systems) by generator operation of the first and second traction motors. Preferably, the drive system and the control system are configured such that in the second driving mode and the third driving mode, the first traction motors are also operable as generators to contribute to the regenerative braking which increases the state of charge of the on-board electrical storage systems.

The control system may be further configured to change between the first to third driving modes based on any one or more of: a location of the railway vehicle, a state of charge of the one or more on-board electrical storage systems, and an external communication signal received by the railway vehicle. The railway vehicle may further comprise an override mechanism operable by a driver of the railway vehicle to compel the control system to change between the first to third driving modes. Thus the driving modes may be automatically changed by the control system or manually selected by a driver as required.

The invention includes the combination of the aspects and preferred features described except where such a combination is clearly impermissible or expressly avoided.

Summary of the Figures

Embodiments and experiments illustrating the principles of the invention will now be discussed with reference to the accompanying figures in which: Figure 1 shows schematically a control system for a bi-mode train with three power sources and two drive modes; Figure 2 shows schematically a control system for a tri-mode train with three power sources and three drive modes; Figure 3 shows a schematic of a drive system for the tri-mode train; Figure 4 shows a schematic of the drive system of Figure 3 when electrical power is provided to traction motors from an external power supply infrastructure via an external current collector; Figure 5 shows a schematic of the drive system of Figure 3 when electrical power is provided to traction motors from GUs assisted by OBESSs; Figure 6 shows a schematic of the drive system of Figure 3 when electrical power is provided to traction motors from only the OBESSs; and Figure 7 shows a circuit diagram of an OBESS connected to the drive system via a soft-charging circuit.

Detailed Description of the Invention

Aspects and embodiments of the present invention will now be discussed with reference to the accompanying figures. Further aspects and embodiments will be apparent to those skilled in the art. All documents mentioned in this text are incorporated herein by reference.

Figure 2 shows schematically a control system for a tri-mode train having a drive system with three power sources and operable in three drive modes. The first drive mode 1, used on electrified sections of a railway line, is an externally powered drive mode where motive power for the train is provided using electrical power obtained from an external power supply infrastructure using external current collectors (for instance overhead-lines OHL 10). On non-electrified sections of a railway line, where external power supply infrastructure is not present, the train must use a self-powered drive mode. The second drive mode 2 is a hybrid self-powered drive mode where motive power for the train is provided using electrical power generated by on-board GUs 11 assisted by OBESSs 12. The third drive mode 3 is an OBESS-only self-powered drive mode 3 where the GUs are disabled and motive power for the train is obtained using electrical power outputted from just the OBESSs.

The control system manages the drive system of the train and determines which of the three available drive modes is in operation. The control system also manages transitions between the three drive modes according to Automatic Power Change-Over routines (APC05). In particular, the APCO routines define the steps taken to switch between drive modes. Thus six APCO routines (described below), A to F, are required to define the transitions, in both directions, between each of the three drive modes.

Figure 3 shows a schematic of the drive system for the tri-mode train. The train is driven by traction motors 14a and 14b using electrical power provided by the external power supply infrastructure, or by the GUs 11 and the OBESSs 12, or by the OBESSs alone according to the drive mode being provided by the control system.

External current collectors 13 are provided to connect to the external power supply infrastructure on electrified sections of the railway line. Typically, the external current collectors are roof-mounted pantographs, which are raised by the control system to connect to overhead lines (OHL) (not shown).

However, they may be shoe gear provided beneath the train for connecting to live rails along the tracks.

Main voltage transformers 15 are provided to adjust the voltage level between the external power supply infrastructure and the on-board systems. Vacuum circuit breakers (VCBs) 16, or similar, are provided to disconnect the pantographs from the main voltage transformers when they are not in use.

Typically, each GU 11 combines a diesel engine and an electricity generator powered by that engine to produce AC electrical power. However, other arrangements are possible. For example, the GUs could be fuel cells in which a fuel, such as hydrogen, is oxidised to generate DC electrical power. Each OBESS 12 is typically a battery system having an associated state of charge (SoC).

The train may comprise a series of coupled cars 20 in which, as shown in Figure 3, some cars contain respective GUs 11 and first traction motors 14a, and other cars contain respective OBESSs 12 and second traction motors 14b. Alternatively, the GUs and OBESSs may be housed in the same cars, along with their respective first and second traction motors.

Other cars are shown in Figure 3 which do not contain GUs or OBESSs, such as for example the lead and tail cars which typically carry the external current collectors 13 and house the main voltage transformers 15. Auxiliary power supply (APS) units 22a, 22b provided to power the train's auxiliary systems (i.e. power outlets, lights, doors, and air-conditioning systems etc.) may conveniently be located in cars without GUs and OBESSs.

First converter-inverter devices are provided on the cars with the GUs 11 and second converter-inverter devices are provided on the cars with the OBESSs 12. Each first converter-inverter device comprises a first converter circuit 21a and a first inverter circuit 25a joined to its converter circuit by a first DC link, the device providing three phase AC power from the first inverter circuit to drive respective first traction motors 14a. Similarly each second converter-inverter device comprises a second converter circuit 21b and a second inverter circuit 25b joined to its converter circuit by a second DC link, the device providing three phase AC power from the second inverter circuit to drive respective second traction motors 14b. The first and second converter circuits contain AC/DC converters to convert AC electrical power from the external current collectors 13 to DC electrical power. Moreover, in the case of the first converter circuits, these AC/DC converters can also convert AC electrical power from the GUs to DC electrical power. In the case of the second converter-inverter devices, the second DC-links can receive DC electrical power from the OBESSs.

Capacitors (not shown) help the first and second DC links to maintain constant DC voltages. When the DC links receive electrical power from the external current collectors 13 or the GUs 11 they are maintained at a first DC voltage and when DC links receive electrical power from the OBESSs 12 they are typically maintained at a second, different, DC voltage.

The control system manages the first 21a and second 21b converter circuits, and the first 14a and second 14b traction motors. Generally, the control system has a speed controller operable (e.g. by a driver) to select a target vehicle velocity which is converted into target torques for the traction motors. The control system adjusts the amount of electrical power supplied to the first and second traction motors to achieve the target vehicle velocity.

The APS units 22a, 22b receive DC electrical power from the first and second DC links, with the DC electrical power being conducted to neighbouring cars though inter-car DC electrical connectors 24. The control system can close such DC electrical connectors 24along connecting lines joining APS units as needed to enable sharing of DC electrical power between selected APS units, as discussed in more detail below. However, the control system can also open the DC electrical connectors 24to electrically isolate the APS units from each other.

Figure 4 shows a schematic of the drive system for the tri-mode train of Figure 3 when the control system is providing the externally powered (first) drive mode. In this case, electrical power is provided to the first 14a and second 14b traction motors from OHLs via the pantographs 13. Active drive system components are indicated in grey and active connecting lines are indicated in bold.

High voltage, single phase AC electrical power is obtained from the OHLs through the pantographs 13 and applied, via the closed VCBs 16, to the main voltage transformers 15. The resulting reduced voltage AC electrical power is supplied to the first 21a and second 21b converter circuits. The AC electrical power is conducted to neighbouring cars though inter-car AC electrical connectors 23. The AC electrical power is converted to DC electrical power in the first 21a and second 21b converter circuits. The DC electrical power is then conducted by the first and second DC links to the first 25a and second 25b inverter circuits which provide the three phase AC power required by the first 14a and second 14b traction motors. In this way the first and second traction motors can provide torque contributions using electrical power from the external power supply infrastructure. During this operation, the first and second DC links are maintained at the first DC voltage.

The OBESSs 12 may be fitted with DC choppers (described below in relation to Figure 7) to step down the first DC voltage in order to enable charging of the OBESSs using electrical power from the OHLs. In this way the OBESSs can increase their SoC on electrified sections of the railway line.

Furthermore, when the train is actively braking, the control system may operate the first 14a and second 14b traction motors as generators to produce a negative torque contribution. The traction motors thus act as generators to convert kinetic energy of the train into regenerated electrical power. The regenerated electrical power can be fed back to the external power supply infrastructure via the inverter circuits 25a, 25b, the converter circuits 21a, 21b, the transformers 15 and the pantographs 13. This two-way flow of electrical power between the OHL and the traction motors is indicated on Figure 4 by the large grey arrows. However, another option is for the regenerated electrical power from the second traction motors, and optionally the first traction motors, to be stored in the OBESSs 12 to increase their SoC. Yet another option is for the regenerated electrical power from the first traction motors, and optionally the second traction motors, to be dissipated as heat in brake grid resistors (not shown).

When electrical power is applied to the DC links, step changes in voltage and capacitive loads can induce high in-rush currents. To avoid system damage by these high currents, first soft-charging circuits (not shown) can be provided between the main voltage transformers 15 and the converter circuits 21a, 21b to limit the current while the first and second DC links are being charged to achieve the first DC voltage. In particular, the control system can be configured to connect the main voltage transformers to the converter circuits using the first soft-charging circuits when switching from either of the self-powered drive modes to the externally powered drive mode, or when bringing the DC links to the first DC voltage at the beginning of train operation.

Figure 5 shows a schematic of the drive system for the tri-mode train when the control system is providing the hybrid, self-powered (second) drive mode in which electrical power is provided to the first traction motors 14a from the GUs 11. During acceleration phases electrical power is also provided to the second traction motors 14b from the OBESSs 12. Again, in Figure 5 active drive system components are indicated in grey, active connecting lines are indicated in bold, and flow of electrical power is indicated by the large grey arrows.

The main voltage transformers 15 are disconnected from the first 21a and second 21b converter circuits and the external current collectors are disconnected from the external power supply infrastructure, for example by lowering the pantographs 13. The VCBs 16 are also opened.

Three-phase AC electrical power generated by the GUs 11 is supplied to the first converter circuits 21a and converted to DC electrical power which is conducted in the first DC links. These are maintained at the first DC voltage. The first inverter circuits 25a invert the DC electrical power to three phase AC power to drive the train using the first traction motors 14a.

DC electrical power outputted by the OBESSs 12 is supplied to the second DC links, which are maintained at the second DC voltage. The DC electrical power is inverted by the second inverter circuits 25b to provide the three phase AC power required by the second traction motors14b.

Second soft-charging circuits (described below in relation to Figure 7) may be provided between the OBESSs 12 and their second DC links to limit in-rush current when bringing the DC links to the second DC voltage. For example, the control system can connect the OBESSs to their DC links using the second soft-charging circuits when first charging the DC links to the second DC voltage at the beginning of train operation, or when switching from the externally powered drive mode to either of the self-powered drive modes.

DC electrical power can be provided to neighbouring cars that do not have GUs 11 or OBESSs 12 through the inter-car DC electrical connectors 24. The APSs 22a, 22b have their own inverters and transformers enabling them to receive power at either the first or second DC voltage. In particular, first APS units 22a connected to the first converter-inverter devices receive power at the first DC voltage, and are isolated from second APS units 22b connected to the second converter-inverter devices which receive power at the second DC voltage. Therefore, in the hybrid self-powered drive mode the first APS units 22a and the second APS units 22b receive power at different voltages. However, the transformers within the APS units allow the first and second APS units to provide the same voltage to the auxiliary systems regardless of their input power source.

In the hybrid self-powered drive mode, the control system adjusts the amount of electrical power generated by the GUs 11 and outputted by the OBESSs 12 to achieve target torques for the first 14a and second 14b traction motors. Typically the control system is configured to prioritise the generation of power from the GUs, with torque being mainly provided by the first traction motors. When the GUs and first traction motors are unable to achieve the target torques, the control system demands power from the OBESSs to provide additional torques from the second traction motors. This is most likely to happen during the acceleration phase of a journey when the GUs operate at full power. When the railway vehicle reaches the target velocity, the target torques are reduced and the control system reduces the power demanded from the OBESSs and then the GUs, and the vehicle enters a "cruising" state. If the target torques reduce further to zero (and there is no active braking of the vehicle), "cruising" becomes "coasting".

When active braking of the train is required, one braking option in the hybrid self-powered mode is for the control system to perform regenerative braking. In this case the second traction motors 14b operate as generators to produce a negative torque contribution. The second traction motors thus operate as generators, and kinetic energy of the railway vehicle is converted into regenerated electrical power which is used to charge the OBESSs 12. In this way, the OBESSs can improve fuel consumption by using the regenerated power to provide support to the GUs 11 during acceleration.

However, the diesel engines of GUs 11 of trains operating in the hybrid self-powered drive mode still consume fuel and generate carbon dioxide emissions because the GUs are always running in this mode.

In particular, combustion engines consume fuel and produce emissions even when idling. However, the third OBESS-only drive mode enables the GUs to be disabled, reducing overall fuel consumption and emissions for a journey.

Moreover, in the hybrid self-powered drive mode the first DC links and second DC links are operated at the first and second DC voltages and are thus electrically isolated from each other. Therefore, only regenerative power from generator operation of the second traction motors 14b and inverter circuits 25b can be used to charge the OBESSs. Regenerated power from generator operation of the second traction motors 14a and inverter circuits 25a associated with the GUs can be dissipated in brake grid resistors.

Figure 6 shows a schematic of the drive system for a hi-mode train when the control system is providing the OBESS-only, self-powered (third) drive mode in which the control system disables the GUs 11 and electrical power is provided to the first 14a and second 14b traction motors from the OBESSs 12 alone.

Thus, the combustion engines can be powered off, saving fuel and reducing emissions. Again, in Figure 6 active drive system components are indicated in grey, and active connecting lines are indicated in bold, and flow of electrical power is indicated by the large grey arrows.

DC electrical power outputted by the OBESSs 12 is supplied to the second DC links. These links are therefore maintained at the second DC voltage. The control system brings the second DC links to the second DC voltage using the second soft-charging circuits as part of switching from the externally powered drive mode to the OBESS-only drive mode. The second inverter circuits 25b invert the DC electrical power to three phase AC power to drive the train using the second traction motors 14b.

The control system can perform regenerative braking in which the second traction motors 14b operate as generators to produce a negative torque contribution. The second traction motors thus operate as generators, and kinetic energy of the railway vehicle is converted into regenerated electrical power which is used to charge the OBESSs 12. Similarly, the first traction motors 14a may be operated as generators to perform regenerative braking and increase the state of charge of the OBESSs.

In addition, the control system is configured to close inter-car DC electrical connectors 24along the connecting lines joining the first 22a and second 22b APS units. Thus DC electrical power outputted by a given OBESSs 12 can be shared across more than one APS unit. Accordingly, all the APS units connected in this way are configured to power the auxiliary systems using DC electrical power provided at the second DC voltage. Advantageously, this arrangement allows the GUs 11 to be shut down completely while still ensuring power is provided to all the APS units and essential systems.

Furthermore, the drive system is configured such that electrical power outputted by the OBESSs 12 can be used to drive the first traction motors 14a. Advantageously, this allows the same motive power to be achieved in the OBESS-only drive mode as in the externally powered and hybrid self-powered drive modes. Moreover, the connection of the OBESSs to the first traction motors allows generator operation of the first traction motors and the first inverter circuits 25a to be used to charge the OBESSs during regenerative braking. This arrangement enables more kinetic energy of the train to be recovered during braking and reused by the OBESSs.

For example, in one arrangement, the control system is configured so that the second DC links provide DC electrical power to the first DC links via closure of internal APS contactors (not shown in Figure 6) of the first APS units 22a. A similar function, however, can be achieved by closure of the DC electrical connectors 24 on the connecting lines between the first APS units 22a and their respective first DC links.

In this case, any intemal APS contactors of the first 22a and second 22b APS units are kept closed allowing these DC electrical connectors 24 to act as APS contactors managing connecting/disconnecting of the first and second DC-links. Whether the APS contactors are of the internal type or are of external type formed by the DC electrical connectors 24, DC electrical power flows from the second converter-inverter devices associated with the OBESSs 12 to the first converter-inverter devices in the opposite direction to its direction of flow in the other drive modes. Thus the first DC links are maintained at the second DC voltage in the third drive mode, and this DC electrical power is then inverted to three phase AC power by the first inverter circuits 25a to drive the first traction motors 14a. This arrangement allows the OBESSs to provide power to the both the first and second traction motors with little or no additional drive system infrastructure.

However, alternative arrangements may also be possible. For example, the first traction motors 14a may be disabled in the OBESS-only drive mode, or additional inverter circuits may be provided to invert DC electrical power from the OBESSs to AC electrical power in order to directly drive the first traction motors 14a without using the first DC links.

Figure 7 shows a circuit diagram of an OBESS 12 connected to its second DC link 32 via a second soft charging circuit 33 comprising an impedance part 33a and a switch 33b. The second DC link may be operating at the first or second DC voltage according to the driving mode. The dashed line represents the part of the circuit which is active during the first driving mode. Here the DC/DC chopper 35 is operated as a filter to remove ripple emerging over the DC-link if a terminal voltage of the OBESS is close to the voltage of its currently connected DC link. If the terminal voltage of the OBESS is lower than the currently connected DC link voltage, the chopper also operates as a voltage adjustment device to step-down the DC link voltage. The dotted line represents the part of the circuit which is active when the control system is providing the second and third driving modes.

The control system also manages the transition between each of the three drive modes, including determining when to transition between the drive modes. Switching between the externally powered drive mode and the self-powered drives modes is primarily determined by the presence or absence of an external power supply infrastructure. In some arrangements, wayside infrastructure may comprise a transmitter capable of communicating with the train. On the approach to a section of railway line with an external power supply infrastructure, such as an OHL, the control system receives a communication from the wayside infrastructure and recognises that the train is near a boundary between electrified and non-electrified sections. The control system begins the transition from the current self-powered drive mode to the externally powered drive mode according to the pre-defined APCO routines. A similar process may be performed in reverse when moving from electrified to non-electrified sections. Therefore, the trkmode train can travel across electrified and non-electrified sections using the same external infrastructure as existing bi-mode trains.

Alternatively or additionally, the control system may comprise a GPS system, or other means for determining location, and change between the self-powered and externally powered drive modes based on known information about the route. In other arrangements, for instance when there is no wayside infrastructure present to communicate with the train or a GPS system to determine location, the transition between the self-powered and externally powered drive modes may be triggered manually by the driver.

The control system monitors the SoC of the OBESSs. On approach to non-electrified sections of a route the control system may decide which of the two available self-powered drive modes to change to based on the current SoC. If the SoC is larger than a known threshold or if there is sufficient charge to power the train for the non-electrified section, the control system can provide the OBESS-only self-powered drive mode. However, if the OBESSs do not have sufficient charge, the control system can start the GUs and provide the hybrid self-powered drive mode. Since change-over between the two self-powered drive modes does not depend on wayside infrastructure, the control system can continue to monitor the SoC throughout a journey and may change between the self-powered modes several times throughout a non-electrified section of the route.

However, the control system may change between the two self-powered drive modes based on train location and a predefined plan based on the upcoming topography and target velocities. In particular, the control system may switch from the hybrid self-powered drive mode to the OBESS-only drive mode at predetermined locations that a train operator can set arbitrarily.

An override mechanism may be provided, for example in the driver cab, allowing the driver to command a specific drive mode.

The control system manages the hand-over of the drive systems when changing between the three drive modes by performing events as defined in the APCO routines. The events and the order of events defined by the APCO routines help to prevent system damage and ensure smooth transitions. The APCO routines shown in Figure 2 define the transitions between the three drive modes as described below.

APCO A -first drive mode to second drive mode The control system is configured to change from the externally-powered drive mode to the hybrid self-powered drive mode by performing the following events, generally in the following order: * Detection of an upcoming system change-over (according to location, communication from the wayside infrastructure etc.) * Prepare GUs (for example start-up diesel engines) * Stop operation of the converter circuits (ideally the inverter circuits on cars with GUs remain active and the DC-links remain energised to allow the APS units to operate continuously) * Stop operation of DC/DC choppers and make necessary disconnections to cease charging of the OBESSs * Disconnect the main transformers from the first and second converter-inverter devices * Trip (open) the VCBs and drop the pantographs (or raise the shoe gear) * Connect the OBESSs to the second DC-links via the second soft charging circuits. The second DC-link voltages will fall to the OBESS battery voltage level * Connect GU altemators to the converter circuits * Magnetise the GU alternators * Operate the GUs, OBESSs and converter-inverter devices as defined by the hybrid self-powered drive mode APCO B -second drive mode to first drive mode The control system is configured to change from the hybrid self-powered drive mode to the externally-powered drive mode by performing the following events, generally in the following order: * Detection of an upcoming system change-over (according to location, communication from the wayside infrastructure, SoC etc.) * Stop operation of the converter circuits (ideally the inverter circuits on cars with GUs remain active and the DC-links remain energised to allow the APS units to operate continuously) * Disconnect the GUs from the first converter-inverter devices (and optionally stop diesel engines) * Disconnect the OBESSs from the second DC links and connect the DC/DC choppers * Raise the pantographs (or lower the shoe gear) and close the VCBs * Connect the main voltage transformers to the first and second converter-inverter devices via the first soft-charging circuits * Enable operation of the converter circuits APCO C -first drive mode to third drive mode To avoid the need for a second soft-charging circuit on the cars with GUs, the control system may be configured to discharge the first and second DC links as an intermediate step prior to closing the APS contactors (which, as discussed above, can be internal contactors of the first APS units 22a, or external contactors formed by the electrical connectors 24 on the connecting lines between the first APS units 22a and their respective first DC links). Therefore, these DC links can be soft-charged to the second DC voltage using the second soft-charging circuits associated with the OBESSs. The control system is configured to change from the externally-powered drive mode to the OBESS-only drive mode by performing the following events, generally in the following order: * Detection of an upcoming system change-over (according to location, communication from the wayside infrastructure, SoC etc.) * Stop operation of the converter circuits * Stop operation of DC/DC choppers and make necessary disconnections to cease charging of the OBESSs * Trip the VCBs and drop the pantographs (or raise the shoe gear) * Disconnect the main transformers from the first and second converter-inverter devices * Discharge the first and second DC-links * Disconnect the main transformers from the first and second converter-inverter devices * Trip the VCBs and drop the pantographs (or raise the contact shoes) * Close the APS contactors to connect the first APS units to the second DC links, thereby connecting the first DC links to the OBESSs * Charge the first and second DC-links to the second DC voltage using the second soft-charging circuits APCO D -third drive mode to first drive mode The control system is configured to change from the OBESS-only drive mode to the externally-powered drive mode by performing the following events, generally in the following order: * Detection of an upcoming system change-over (according to location, communication from the wayside infrastructure, SoC etc.) * Open the APS contactors to disconnect the first DC links from the OBESSs.

* Disconnect the OBESSs * Raise the pantographs (or lower the shoe gear) and close the VCBs * Connect the first and second converter-inverter devices to the main transformers via the first soft charging circuits.

* Start operation of the converter circuits APCO E -second drive mode to third drive mode The control system is configured to change from the hybrid self-powered drive mode to the OBESS-only drive mode by performing the following events, generally in the following order: * Detection of an upcoming system change-over (according to location, communication from the wayside infrastructure, SoC, driver input etc.) * Disconnect the first converter circuits from the GUs or cease operation of the first converter circuits (and optionally stop diesel engines) * Disable the inverters and APS units * Discharge the first and second DC-links * Close the APS contactors to connect the first DC-links to the OBESSs * Charge the first and second DC links to the second DC voltage using the second soft-charging circuits * Enable the inverters and APS units APCO F -third drive mode to second drive mode The control system is configured to change from the OBESS-only drive mode to the hybrid self-powered drive mode by performing the following events, generally in the following order: * Detection of an upcoming system change-over (according to location, communication from the wayside infrastructure, SoC, driver input etc.) * Prepare GUs (for example start-up diesel engines) * Open the APS contactors to disconnect the first DC links from the OBESSs * Connect the GUs to the first converter circuits if they were disconnected and/or restart operation of the first converter circuits * Enable the inverters The features disclosed in the foregoing description, or in the following claims, or in the accompanying drawings, expressed in their specific forms or in terms of a means for performing the disclosed function, or a method or process for obtaining the disclosed results, as appropriate, may, separately, or in any combination of such features, be utilised for realising the invention in diverse forms thereof While the invention has been described in conjunction with the exemplary embodiments described above, many equivalent modifications and variations will be apparent to those skilled in the art when given this disclosure. Accordingly, the exemplary embodiments of the invention set forth above are considered to be illustrative and not limiting. Various changes to the described embodiments may be made without departing from the spirit and scope of the invention.

For the avoidance of any doubt, any theoretical explanations provided herein are provided for the purposes of improving the understanding of a reader. The inventors do not wish to be bound by any of these theoretical explanations.

Any section headings used herein are for organizational purposes only and are not to be construed as limiting the subject matter described.

Throughout this specification, including the claims which follow, unless the context requires otherwise, the word "comprise" and "include", and variations such as "comprises", "comprising", and "including" will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps.

It must be noted that, as used in the specification and the appended claims, the singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise. Ranges may be expressed herein as from "about" one particular value, and/or to "about" another particular value. When such a range is expressed, another embodiment includes from the one particular value and/or to the other particular value. Similarly, when values are expressed as approximations, by the use of the antecedent "about," it will be understood that the particular value forms another embodiment. The term "about" in relation to a numerical value is optional and means for example +/-10%.

Claims

Claims: 1. A railway vehicle for travelling on routes with external power supply infrastructure and on routes without external power supply infrastructure, the vehicle having a drive system comprising: one or more external current collectors (13) for obtaining electrical power from the external power supply infrastructure; one or more on-board generator units (11) for generating electrical power from combustion or oxidation of a fuel; one or more on-board electrical storage systems (12) for storing and outputting electrical energy; traction motors (14a, 14b) configured to drive the railway vehicle using electrical power from the external power supply infrastructure via the one or more external current collectors (13), the one or more generator units (11) and the one or more on-board electrical storage systems (12); and a control system configured to selectively control the provision of electrical power to the traction motors (14a, 14b) from the one or more external current collectors (13), the one or more generator units (11) and the one or more on-board electrical storage systems (12), and thereby provide: a first driving mode wherein electrical power is provided to the traction motors (14a, 14b) from the external power supply infrastructure via the one or more external current collectors (13); a second driving mode wherein electrical power is provided to the traction motors (14a, 14b) from the one or more generator units (11) assisted by the one or more on-board electrical storage systems (12); and a third driving mode wherein electrical power is provided to the traction motors (14a, 14b) from just the one or more on-board electrical storage systems (12).
2. The railway vehicle of claim 1 wherein the one or more generator units (11) are positioned on one or more cars (20) of the railway vehicle, and the one or more on-board electrical storage systems (12) are positioned on one or more different cars of the railway vehicle.
3. The railway vehicle of claim 1 or 2 wherein the traction motors comprise first traction motors (14a) and second traction motors (14b), and wherein the control system is configured such that: in the first driving mode both the first (14a) and second (14b) traction motors drive the railway vehicle using electrical power from the external power supply infrastructure via the one or more external current collectors (13), in the second driving mode the first traction motors (14a) drive the railway vehicle using electrical power from the one or more generator units (11) and the second traction motors (14b) drive the railway vehicle using electrical power from the one or more on-board electrical storage systems (12), and in the third driving mode both the first (14a) and second (14b) traction motors drive the railway vehicle using electrical power from the one or more on-board electrical storage systems (12).
4. The railway vehicle of claim 3 wherein the drive system further comprises first and second converter-inverter devices, each first converter-inverter device comprising: a first converter circuit (21a) to convert AC electrical power into DC electrical power, a first DC link conducting the DC electrical power, and a first inverter circuit (25a) to convert the DC electrical power conducted by the first DC link into AC electrical power to drive respective first traction motors (14a); and each second converter-inverter device comprising: a second converter circuit (25b) to convert AC electrical power into DC electrical power, a second DC link conducting the DC electrical power, and a second inverter circuit to convert the DC electrical power conducted by the second DC link into AC electrical power to drive respective second traction motors (14b); wherein: in the first driving mode the first (21a) and second (21b) converter circuits receive AC electrical power from the one or more external current collectors (13), and the first and second DC links are maintained at a first DC voltage; in the second driving mode the first converter circuits (21a) receive AC electrical power from respective generator units (11), the second DC links receive DC electrical power from respective onboard energy storage systems, and the first DC links are maintained at the first DC voltage and the second DC links are maintained at a different second DC voltage; and in the third driving mode the first and second DC links receive DC electrical power from respective on-board electrical storage systems, and the first and second DC links are maintained at the second DC voltage.
5. The railway vehicle of claim 4 wherein the drive system further comprises: one or more first soft-charging circuits between the one or more external current collectors (13) and the first and second converter-inverter devices, and one or more second soft-charging circuits between the one or more on-board electrical storage systems (12) and the DC links of the second converter-inverter devices; wherein the control system is configured to: connect the one or more external current collectors (13) to the first and second converter-inverter devices via the first soft-charging circuit as part of changing over to the first driving mode from each of the second and third driving modes, and connect the one or more on-board electrical storage systems (12) to the second converter-inverter devices via the second soft-charging circuits as part of changing over to each of the second and third driving modes from the first driving mode.
6. The railway vehicle of claim 4 or 5 wherein the control system is further configured to discharge the first DC links as part of changing over to the third driving mode from each of the first and second driving modes.
7. The railway vehicle of any of the preceding claims wherein the drive system further comprises one or more auxiliary power supply units (22a, 22b) for powering auxiliary systems of the vehicle using electrical power from: the external power supply infrastructure via the one or more external current collectors (13) in the first driving mode, the one or more generator units (11) assisted by the one or more on-board electrical storage systems in the second driving mode, and just the one or more on-board electrical storage systems (12) in the third driving mode.
8. The railway vehicle of claim 7 wherein: the one or more auxiliary power supply units comprise first auxiliary power supply units (22a) powered by respective generator units (11) in the second driving mode and second auxiliary power supply units (22b) powered by respective on-board electrical storage systems (12) in the second driving mode; the drive system further comprises auxiliary power supply contactors which are operable to electrically connect each first auxiliary power supply unit (22a) with a respective on-board electrical storage system (12); and the control system is further configured to: open the auxiliary power supply contactors in the first and second driving modes to electrically isolate each first auxiliary power supply unit (22a) from the respective on-board electrical storage system (12), and close the auxiliary power supply contactors in the third driving mode to electrically connect each first auxiliary power supply unit (22a) with the respective on-board electrical storage system (12).
9. The railway vehicle of claim 8 as dependent on claim 3 wherein the closures of the auxiliary power supply contactors in the third driving mode form circuits between the first traction motors (14a) and the one or more on-board electrical storage systems (12) such that the first traction motors drive the railway vehicle using electrical power received from the one or more on-board electrical storage systems.
10. The railway vehicle of claim 9 as dependent on claim 4 wherein the control system is further configured to provide a changeover from the second driving mode to the third driving mode by: disconnecting the first converter circuits (21a) from the respective generator units (11), disabling the first inverter circuits (25a) and the first auxiliary power supply units (22a), discharging the first and second DC links, closing the auxiliary power supply contactors, charging the first and second DC links to the second DC voltage via the second soft-charging circuits, and re-enabling the first inverter circuits (25a) and the first auxiliary power supply units (22a).
11. The railway vehicle of claim 9 or 10 as dependent on claim 4 wherein the control system is further configured to provide a changeover from the third driving mode to the second driving mode by: starting the one or more generator units (11), opening the auxiliary power supply contactors, and connecting the first converter-inverter devices to the respective generator units (11).
12. The railway vehicle of any one of claims 9 to 11 as dependent on claim 4 further comprising: main transformers (15), between the one or more external current collectors (13) and the first (21a) and second (21b) converter circuits, for converting AC electrical power from the one or more external current collectors to a lower AC voltage, and DC/DC choppers between the second DC links and the respective on-board electrical storage systems (11) for stepping down voltage such that the one or more on-board electrical storage systems (12) can increase their state of charge using electrical power from the one or more external current collectors (13); wherein the control system is further configured to provide a changeover from the first driving mode to the third driving mode by: disabling the first (21a) and second (21b) converter circuits, disabling the DC/DC choppers, disconnecting the main transformers (15) from the first (21a) and second (22b) converter circuits, discharging the first and second DC-links, closing the auxiliary power supply contactors, and charging the first and second DC-links to the second voltage using the second soft-charging circuits.
13. The railway vehicle of claim 12 wherein the control system is further configured to provide a changeover from the third driving mode to the first driving mode by: opening the auxiliary power supply contactors, disconnecting the one or more on-board electrical storage systems (12), connecting the first (21a) and second (21b) converter circuits to the main transformers (15) via the first soft charging circuits, enabling the first (21a) and second (21b) converter circuits, and enabling the DC/DC choppers.
14. The railway vehicle of any of the preceding claims wherein the drive system and the control system are configured such that in the second and third driving modes regenerative braking is performable to increase a state of charge of the one or more on-board electrical energy storage systems (12) by generator operation of the second traction motors (14b).
15. The railway vehicle of any of the preceding claims wherein the control system is further configured to change between the first to third driving modes based on any one or more of: a location of the railway vehicle, a state of charge of the one or more on-board electrical storage systems, and an external communication signal received by the railway vehicle.