VEHICLE WITH POWER PURGE

Description

[0001] The invention relates to a vehicle according to the preamble of patent claim 1.

[0002] In a vehicle with a purely electric traction drive or with a hybrid-electric traction drive, in which an electric motor can be coupled, for example, to an internal combustion engine or a fuel cell, the traction drive is carried by an unearthed vehicle frame. If the vehicle includes a pantograph that can be connected to the traction drive and brought into galvanic contact with a two-pole overhead line of an earthed overhead line system to feed in traction energy, the vehicle must be equipped with an electrical protection system to prevent dangerous contact voltages on the vehicle frame or on a vehicle part that is conductively connected to it. The protection system must electrically separate the vehicle frame and, for example, the vehicle body from the traction drive and pantograph that are in galvanic contact with the overhead line.If the protective system fails, dangerous contact voltages can occur on the vehicle frame or body, which, if touched by a person connected to earth, can lead to dangerous body currents resulting in injury or even death.

[0003] This applies to both hybrid-electric trucks, such as those used in open-cast mining, which are only partially galvanically connected to a catenary system, and vehicles such as electric trolleybuses, which are permanently galvanically connected to a catenary system. Unlike rail-bound vehicles, whose rail wheels form a conductive connection between the vehicle frame and the grounded rails, the vehicle frames of trucks and trolleybuses are not grounded due to their rubber-tired wheels.

[0004] A vehicle of the type mentioned above is known from patent EP 3 036 127 B1. This comprises a protection system for preventing dangerous contact voltages on the vehicle frame. It has a first protection level, formed by a simple electrically insulated mounting of at least the traction drive on the vehicle frame, and a second protection level with higher safety, which is additionally formed by a galvanically isolating DC-DC converter connected between the pantograph and the traction drive. By means of a switching element, the protection system can be switched between the first and second protection levels by selectively connecting or bypassing the DC-DC converter. The protection system meets different safety requirements in different operating states of the vehicle, which are characterized by different possible interactions between people and the vehicle.In a first operating state—for example, when the vehicle is stationary—it is possible for a driver or a third party to touch the vehicle frame or body from the outside without simultaneously risking injuries due to mechanical force; the risk of injury from body currents outweighs the risk in this operating state. In a second operating state—for example, when the vehicle is traveling at high speed—it is almost impossible for a third party to touch the vehicle frame or body from the outside without risking injuries from a collision with the vehicle.

[0005] EP 2 340 957 A1 discloses a drive control device for a rail vehicle, including an inverter, an energy storage element, and a DC-DC converter connected to the energy storage element. A circuit selection unit selects a power supply either from an external power supply via an overhead line system or from the energy storage element and supplies it to the inverter. Switching from overhead line operation to energy storage operation occurs in an emergency in the event of a defective overhead line or a defective pantograph of the rail vehicle.

[0006] US 2016 / 152129 A1 discloses a hybrid energy system in a vehicle comprising an autonomous power supply and connectable to an external power supply infrastructure along the vehicle's route. The vehicle is configured to operate in an autonomous power supply mode and / or in an external power supply mode. The system comprises a first high-voltage circuit including a first traction motor for propelling the vehicle, which is connected to an energy storage system through a first power converter. It comprises a second high-voltage circuit including a second traction motor for propelling the vehicle, which can be connected to an external power supply through a second power converter. The first high-voltage circuit and the second high-voltage circuit can be connected by a third, galvanically non-isolating power converter between the first and second power converters.

[0007] The invention is based on the object of providing a vehicle of the type mentioned above which enables improved power transmission while maintaining the known protection system.

[0008] The object is achieved according to the invention by a generic vehicle with the features specified in the characterizing part of patent claim 1. The vehicle comprises a pantograph for feeding traction energy from a two-pole overhead line system. It further comprises an electric or hybrid-electric traction drive supported by an ungrounded vehicle frame. Furthermore, the vehicle comprises an electrical energy storage device for temporarily storing fed-in traction energy. The traction drive can be connected to the pantograph via a first line branch. The traction drive and the energy storage device can be connected to the pantograph via a second line branch, wherein a galvanically isolating DC-DC converter of the vehicle is interposed in the second line branch. A first switching element for opening and closing the first line branch is connected upstream of the traction drive.

[0009] According to the invention, the traction drive and the energy storage unit can additionally be connected to the pantograph via a third line branch, into which a non-galvanically isolating DC-DC converter of the vehicle is interposed. This makes it possible to charge the energy storage unit via the non-galvanically isolating DC-DC converter during journeys with a lower protection level, i.e., at higher travel speeds. The DC-DC converter without galvanic isolation can be made smaller and lighter to transmit high charging power than a corresponding DC-DC converter with galvanic isolation and is also more cost-effective to purchase. The galvanically isolating DC-DC converter serves to supply traction and charge the energy storage unit during journeys at low travel speeds, where a higher level of protection against contact voltages is required.The traction drive can be supplied with traction energy from the overhead line system in both protection levels.

[0010] According to the invention, a second switching element for opening and closing the second and third line branches is connected upstream of the traction drive, and a third switching element for opening and closing the third line branch is connected upstream of the non-galvanically isolating DC-DC converter. The arrangement of the switching elements allows the energy flow via the various line branches to be enabled or interrupted—manually via a driver control element, as explained in more detail in the specific embodiment, or automatically controlled depending on the required protection level. At a higher protection level, the first switching element and the third switching element are open, while the second switching element is closed. This allows traction energy to flow from the pantograph through the second line branch via the DC-DC converter with galvanic isolation into the energy storage unit and the traction drive.At a lower protection level, the first switching element is closed and the second switching element is open, allowing traction energy from the pantograph to be fed directly to the traction drive via the first line branch. At this lower protection level, traction energy can continue to flow into the energy storage system via the DC-DC converter with galvanic isolation.

[0011] According to the invention, the vehicle further comprises a speed measuring device for detecting the vehicle speed, a control device which is designed to control the first switching element, the second switching element and the third switching element as a function of the measured vehicle speed in such a way that below a predeterminable threshold value of the vehicle speed, the first switching element and the third switching element open and the second switching element closes, and that above the threshold value, the first switching element closes and the second switching element opens.

[0012] For example, a threshold value of 30 km / h can be specified for the driving speed. If the vehicle is stationary or moving at a speed below the threshold value, the protection system switches to the higher protection level with increased electrical safety, since the consequences of an electric shock are more serious than those of a collision injury. If the threshold value is exceeded, the protection system switches to the lower protection level, since even a collision accident in this operating state would likely result in significant personal injury. Instead of or in addition to the speedometer, the vehicle can also incorporate other sensor devices for detecting the vehicle's operating state, with the state variables detected by these devices being assigned corresponding threshold values ​​for switching between the protection levels.For example, a current measuring device can be provided to detect the current intensity of a traction current generated when power is fed in from the overhead line, whereby a threshold value for the drawn traction current or the fed-in traction power can be determined. A door closure sensor can also be provided to detect the closed state of a vehicle door and / or a seat occupancy sensor to detect the occupancy of a vehicle seat and / or a belt closure sensor to detect the closed state of a vehicle seat's seat belt. The protection level can be switched when the vehicle door is closed from the inside and / or when a vehicle seat is occupied and / or when the seat belt is fastened.

[0013] In a preferred embodiment of the vehicle according to the invention, the traction drive and the energy storage device, as well as the first line branch extending from each of them to the first switching element, the second line branch extending from each of them to the galvanically isolating DC-DC converter, and the third line branch including the non-galvanically isolating DC-DC converter up to the third switching element, are mounted against the vehicle frame with a single electrical insulation layer. Furthermore, the current collector, as well as the first line branch extending from each of them to the first switching element, the second line branch extending from each of them to the galvanically isolating DC-DC converter, and the third line branch extending from each of them to the third switching element, are mounted against the vehicle frame with an electrically double insulation layer.As a result, vehicle components that are galvanically connected to the high voltage level of the overhead line system at a high protection level are electrically doubly insulated to prevent dangerous contact voltages on the vehicle frame or on a vehicle part that is conductively connected to it. For the remaining vehicle components, simple electrical insulation is sufficient. In a further preferred embodiment of the vehicle according to the invention, the control device is further configured so that the third switching element also closes above the threshold value. This allows the charging power for the energy storage device to be increased at a lower protection level by allowing energy to flow from the pantograph via the parallel, third line branch with the DC-DC converter interposed without galvanic isolation.

[0014] In a further preferred embodiment, the vehicle according to the invention further comprises a monitoring device for detecting and signaling insulation faults in the single insulation layer and / or in the double insulation layer. To further increase the operational reliability of vehicles according to the invention, the single or double insulation is monitored for faults. If an insulation fault is detected and indicated to the driver, measures can be initiated immediately; for example, the driver can be instructed to take the vehicle to a workshop.

[0015] Further features and advantages of the invention will become apparent from the following description of an embodiment with reference to the drawing, in whose single figure a circuit diagram of a vehicle according to the invention with a protection system is illustrated.

[0016] According to the figure, parts known per se, such as a vehicle frame carrying wheel axles with rubber-tired wheels, a driver's cab with vehicle doors, vehicle seats and seat belts, and a vehicle body for transporting goods, are not shown in the figure. The vehicle frame further carries a traction drive 2, which can be purely electric or hybrid-electric and whose torque is transmitted to wheels via a transmission (likewise not shown). For track sections with a two-pole overhead line system 3, of which two contact wires suspended above the roadway and designed as forward and return conductors are represented by a common line in the figure, the vehicle 1 comprises a pantograph 4 for the external supply of traction energy.The pantograph 4 has a frame that can be raised and lowered and supports two rockers with contact strips. The contact strips establish a galvanic contact between the pantograph 4 and the overhead line system 3 in order to feed traction energy into the vehicle 1 or to feed back braking energy. If the galvanic contact between the pantograph 4 and the overhead line system 3 is interrupted, or on track sections without an overhead line system 3, the hybrid-electric traction drive 2 can be supplied with traction energy, for example, via a diesel generator or from an energy storage device 5 of the vehicle 1, for example, electrical double-layer capacitors and / or batteries, such as nickel-metal hydride batteries. The energy storage device 5 has a capacity of, for example, between 15 kWh and 80 kWh.

[0017] The vehicle features an electrical protection system to prevent dangerous contact voltages on the vehicle frame or on electrically connected vehicle parts, such as a driver's cab or a vehicle body for transporting goods. Due to the insulated contact of vehicle 1 with earth via rubber-tired wheels, the vehicle frame is not earthed. To prevent dangerous contact voltages from occurring on the vehicle frame when galvanic contact is established between the single-pole earthed overhead line system 3 and the pantograph 4 and thus the traction drive 2, the protection system provides electrical separation or insulation between the vehicle parts that can be conductively connected to the pantograph 4 and traction drive 2 and the vehicle parts that are conductively connected to the vehicle frame.If the protection system fails, a short circuit to the vehicle frame caused by a person standing on ground and touching the vehicle 1 from the outside can result in life-threatening body currents. The protection system has a lower protection level and a higher protection level. The latter provides greater electrical safety against dangerous contact voltages than the lower protection level.

[0018] The lower protection level is formed by a single-insulation electrical installation of the traction drive 2 on the vehicle frame. The area with a single-insulation layer 6 includes the traction drive 2, the energy storage unit 5, and an inverter 7 connected upstream of the traction drive 2 for converting direct current to alternating current. The higher protection level is formed, in addition to the single-insulation layer 6, by a galvanically isolating DC-DC converter 8 connected between the current collector 4 and the traction drive 2. The current collector 4 and the galvanically isolating DC-DC converter 8 belong to an area with a double-insulation layer 9.

[0019] At the higher protection level, all vehicle parts electrically connected to the overhead line system 3 are doubly insulated from the vehicle frame, either by a double-insulated assembly or by galvanic isolation. The double insulation is continuously monitored by a suitable monitoring device 10. At the lower protection level, some or all vehicle parts electrically connected to the overhead line system 3 are single-insulated from the vehicle frame. This insulation can also be monitored by monitoring devices 10.

[0020] The traction drive 2 is connectable to the current collector 4 via a first line branch 11, with a first switching element 12 for opening and closing the first line branch 11 being connected upstream of the traction drive 2. The traction drive 2 and the energy storage device 6 are connectable to the current collector 4 via a second line branch 13, into which the galvanically isolating DC-DC converter 8 is interposed. The traction drive 2 and the energy storage device 5 are connectable to the current collector 4 in parallel via a third line branch 14, into which a galvanically non-isolating DC-DC converter 15 is interposed. A second switching element 16 for opening and closing the second line branch 13 and the third line branch 14 is connected upstream of the traction drive 2. A third switching element 17 for opening and closing the third line branch 14 is connected upstream of the galvanically non-isolating DC-DC converter 15.The switching between the lower and higher protection level is accomplished by actuating the first switching element 12 and the second switching element 16 - depending on whether a currently measured driving speed is above or below a predeterminable threshold value of, for example, 30 km / h.

[0021] When vehicle 1 is stationary or at speeds up to the threshold, it is possible for the driver or an external third party to touch vehicle 1 from the outside without simultaneously risking other hazards with a high degree of damage. At speeds above the threshold, it is impossible or almost impossible for external third parties to touch vehicle 1 from the outside without simultaneously causing, or with a high probability of, serious mechanical damage or an accident with personal injury. Further distinctions between operating states of vehicle 1 and associated protection levels can be implemented analogously.

[0022] The galvanically isolating DC-DC converter 8 installed in vehicle 1 is used to supply the traction drive 2 at low travel speeds. Opening the first switching element 12 and closing the second switching element 16 engages the higher protection level, which is used for starting and traveling at low travel speeds. This allows the use of a galvanically isolating DC-DC converter 8 with a comparatively low rated power of, for example, 30 kW. At higher travel speeds, opening the second switching element 16 and closing the first switching element 12 engages the lower protection level, whereby the galvanically isolating DC-DC converter 8 is bypassed by the first line branch 11 and the traction energy is taken directly from the overhead line system 3.The vehicle parts with a single insulation layer 6 are no longer separated by galvanic isolation from the area with a double insulation layer 9 and the external overhead line system 3.

[0023] At low speeds, the energy storage unit 5 is charged from the pantograph 4 via the DC-DC converter 8 with galvanic isolation in the second line branch 13. The DC-DC converter 8 is also used for driving at low speeds. Traction energy from the energy storage unit 5 or a diesel generator of the vehicle 1 can also be used. Even at speeds above the threshold in the lower protection level, where traction energy is primarily drawn directly from the overhead line system 3 via the first line branch 11, the energy present in the energy storage unit 5 is available as traction energy. The DC-DC converter 8 stabilizes the energy feed to the energy storage unit 5 in both protection levels.To be able to charge the energy storage device 5 with a higher charging power, the third switching element 17 is closed, allowing traction energy to flow from the pantograph 4 into the energy storage device 5 via the non-galvanically isolating DC-DC converter 15 in the third line branch 14. A DC-DC converter 15 without galvanic isolation can transmit a rated power of, for example, 150 kW while maintaining a low overall volume and weight.

[0024] Switching between the protection levels can be done automatically or manually. The driver can operate the switch via a vehicle-mounted control element, regardless of driving speed, when leaving the public driving area and entering a non-public driving area where, through training or other technical measures, contact with the vehicle from the outside is prevented. Switching by third parties, for example, when driving in defined areas, across different overhead line systems, or in the event of an accident, is also possible via a remote control device.

[0025] When the pantograph 4 is lowered, both the first switching element 12 and the second switching element 16 can be opened to detect insulation faults on the drive system side. This switching position also serves to adjust the voltage level on the drive system side to that of the overhead line system 3, preventing a voltage jump when switching between the protection stages.

Claims

1. Vehicle (1) comprising - a current collector (4) for feeding traction energy from a two-pole overhead contact line system (3), - an electric or hybrid-electric traction drive (2), which is carried by a non-earthed vehicle frame, - an electrical energy storage device (5) for intermediate storage of traction energy that is fed in, - a first line branch (11) that can connect the traction drive (2) to the current collector (4), - a second line branch (13) which can connect the traction drive (2) and the energy storage device (5) to the current collector (4) and a galvanically isolating DC converter (8) is interposed in said second line branch, - wherein a first switching element (12) for opening and closing the first line branch (11) is connected upstream of the traction drive (2), characterised by - a third line branch (14) which can connect the traction drive (2) and the energy storage device (5) to the current collector (4) with a galvanically non-isolating DC converter (15) is interposed in said third line branch, wherein a second switching element (16) for opening and closing the second and third line branch (13, 14) is connected upstream of the traction drive (2), wherein a third switching element (17) of opening and closing the third line branch (14) is connected upstream of the galvanically non-isolating DC converter (15) and wherein the first, second, and third line branches (11, 13, 14) can be connected in parallel, - a speed measuring device for detecting the vehicle speed and - a control facility that is configured so as to control the first switching element (12), the second switching element (16) and the third switching element (17) in dependence upon the measured vehicle speed in such a manner - that below a predeterminable threshold value for the vehicle speed, the first switching element (12) and the third switching element (17) open and the second switching element (16) closes, and - that above the threshold value the first switching element (12) closes and the second switching element (16) opens and.

2. Vehicle (1) according to claim 1, - wherein the traction drive (2) and the energy storage device (5) and, leading respectively therefrom, the first line branch (11) up to the first switching element (12), the second line branch (13) up to the galvanically isolating DC converter (8), and the third line branch (14) including the galvanically non-isolating DC converter (15) up to the third switching element (17) are mounted against the vehicle frame with an electrically simple isolation layer (6), and - wherein the current collector (4) and, leading respectively therefrom, the first line branch (11) up to the first switching element (12), the second line branch (13) up to and including the galvanically isolating DC converter (8), and the third line branch (14) up to the third switching element (17) are mounted against the vehicle frame with an electrically double isolation layer (9).

3. Vehicle (1) according to claim 1 or 2, - wherein the control facility is moreover configured so that the third switching element (17) also closes above the threshold value.

4. Vehicle (1) according to one of claims 1 to 3, comprising - a monitoring facility (10) for detecting and signalling insulation faults in the single isolation layer (6) and / or in the double isolation layer (9).