FR2830801A1 - Series hybrid electric vehicle e.g. electric bus or railway train, has motor supplied with current simultaneously by alternator and convertor connected to battery - Google Patents

Abstract

The electric drive vehicle has a motor (14) supplied with power from a feed circuit (11) itself supplied by an alternator (12). The drive motor has a power converter (18). The motor is simultaneously supplied with power by the alternator and the converter. The drive motor can be an asynchronously wound motor.

Description

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ELECTRICALLY DRIVEN VEHICLE
TECHNICAL FIELD DESCRIPTION
The technical field of the present invention is that of hybrid vehicles with electric traction which have a power source producing electric energy capable of supplying the traction and the easements of the vehicle. In particular, the invention relates in particular to public transport vehicles such as trains, metro, trams and buses.

STATE OF THE PRIOR ART
Several projects have already been proposed in this area.

 With reference to FIG. 1 representing the electric chain of a vehicle according to the prior art, a vehicle is known which uses a heat engine 1 connected to an alternator 2. This alternator 2 supplies both a service converter 3 and a motor electric 4 via a converter 5. The electric motor 4 is then connected to a driving axle 6, a speed reducer 7 can be interposed between the two elements mentioned above.

 If we focus on the fuel efficiency of such a vehicle characteristic of the prior art,

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 we can see that it is quite low. Indeed, by way of example, let us assume that the maximum mechanical power required for a wheel of the driving axle 6 is 170 kW, this power corresponding to the power required for a 20-ton vehicle capable of ensuring a acceleration equal to 1 g, and the power required to provide the service converter is 30 kW. In such a case, assuming that the efficiency of each of the elements of the electric chain is 95%, the power consumed by the converter 5 which supplies the electric motor 4 is 198 kW. Consequently, at the output of alternator 2, 198 kW must be available, to which must be added the 32 kW that it is necessary to supply to the service converter 3. The alternator 2 must therefore supply a power of 230 kW, which requires on the part of the heat engine 1, on a drive shaft of the alternator 2, to provide a power of 242 kW.

 The energy efficiency of a vehicle whose elements are located as described above is therefore low, in particular due to the operation of the heat engine 1, which can be assimilated to a generator, the operation being at continuously variable power. In addition, the energy efficiency is further reduced due to the use of a converter for all of the power delivered. In fact, the power at the output of the heat engine 1 passes either through the converter 5 or through the service converter 3, these two elements

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 having a performance such that they hamper the overall performance of the vehicle.

 This drawback relating to the energy efficiency of the vehicle is all the more important since taking into account environmental criteria leads to a significant reduction in the energy consumption on such vehicles, as well as the production of CO2.

STATEMENT OF THE INVENTION
The object of the present invention is therefore to remedy the drawbacks mentioned above, by proposing an electric traction vehicle having an energy efficiency higher than that of vehicles of the prior art, the design of this vehicle also causing a reduction in the atmospheric pollution.

 To do this, the invention relates to an electric traction vehicle comprising: - at least one driving axle, - an electric traction motor, at least one supply system supplying via an alternator, the electric traction motor as well as a converter system, the electric traction motor being simultaneously supplied by the alternator directly, as well as by said converter system.

 Advantageously, the vehicle according to the invention makes it possible to improve the overall energy efficiency of the system. Indeed, the electric traction motor is at least partially supplied directly from the alternator, without the presence of a converter being necessary between these two

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 elements. This is equivalent to saying that part of the energy leaving the power system does not pass through a converter, which is directly felt on the overall performance of the vehicle. These modifications made by the invention to vehicles of the prior art therefore make it possible to reduce the power to be administered, which is also synonymous with reducing the costs generated by the delivery of such power.

 In addition, the absence of a converter between the alternator and the electric traction motor makes it possible to deduce considerably the requirements for power electronics, these elements being often expensive, fragile and difficult to cool. Another advantage linked to that of the reduction in the need for power electronics is the reduction in the volume formed by the various components constituting the vehicle, its cooling thus being simplified and its reliability improved. Finally, the removal of a converter through which a high power flow passed is in line with a policy of compliance with the legislation on electromagnetic compatibility.

 Preferably, the electric traction motor which can be used by the invention is an asynchronous motor with a wound rotor. This type of motor is particularly advantageous in the sense that they are easily capable of being partially supplied at almost constant frequency. In our case, they can therefore be directly supplied by the alternator.

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 The alternator is capable of supplying a stator of the electric traction motor and the converter system is capable of supplying a rotor of this electric traction motor.

In addition, the power supplied to the stator is about 80 to 95% of the total power supplied to the electric traction motor, and the power supplied to said rotor is about 5 to 20% of the total power supplied. to electric traction motor
This particular characteristic has the advantage of having a solution where a maximum of the power going to the traction motor comes directly from the alternator, without going through a converter. This results in an additional increase in the overall performance of the vehicle.

 According to a first particular embodiment of the invention, the converter system is a primary service converter. This arrangement makes it possible to produce a vehicle where the power supply to the electric traction motor by the converter system is effected by means of a simple servitude converter, already existing in the embodiments of the prior art, which is administered a power greater than that required by the easements, in order to power the rotor of the electric traction motor.

 According to a second particular embodiment of the invention, the converter system comprises a four quadrant converter connected to a

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 energy storage and destocking device capable of supplying at least one secondary service converter.

 Advantageously, this particular embodiment makes it possible to favorably increase the overall efficiency of the system, part of the power supplied to the electric traction motor coming from the energy storage and destocking device via a secondary servitude converter, this part of the power then no longer to be supplied by the supply system.

 In addition, the energy storage and destocking system makes it possible to ensure the starting of the supply system via the alternator.

 According to an alternative of the second embodiment of the invention, at least part of the supply to be supplied to the stator of the electric traction motor comes from the energy storage and storage device.

 Once again, this particular arrangement increases the overall energy efficiency of the system. In this case, the aim is to produce part of the power to be supplied to the stator of the electric traction motor, by means of the storage and destocking device.

 Preferably, at least part of the energy storage of the energy storage and destocking device is carried out during vehicle braking operations. This use allows the device to operate

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 relatively simple, the energy storage being carried out by recovering energy coming from the braking phases of the vehicle, relatively frequent in urban public transport vehicles.

 In addition, at least part of the energy recovered during vehicle braking operations is directly returned by the energy storage and storage device, for the benefit of easements and without being stored.

 Advantageously, this energy storage and destocking device can be controlled so as not to store the energy, but to redistribute it directly. Storage or direct redistribution then depends on the specific needs of the vehicle, at a given time. the vehicle can in particular be an electric vehicle powered by at least one of the power sources taken from the group consisting of the following elements: {catenary, poles, rubbers}.

 Other characteristics and advantages will appear in the detailed, non-limiting description, below.

BRIEF DESCRIPTION OF THE DRAWINGS
This description will be made with reference to the appended drawings, among which: - Figure 1 already described, illustrates a vehicle according to the prior art, - Figure 2 shows the electric chain of a first particular embodiment of a vehicle according to the invention,

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 FIG. 3 represents the electric chain of a second particular embodiment of a vehicle according to the invention, FIG. 4 represents the electric chain of a third particular embodiment of a vehicle according to the invention.

DETAILED PRESENTATION OF PARTICULAR EMBODIMENTS
Referring to Figure 2, we see an electric traction vehicle according to the invention, comprising a power system 11 and an alternator 12 being mechanically connected to it, this assembly formed by these two elements being comparable to a generator. The alternator 12 is connected to a converter system 18 on the one hand, and to an electric traction motor 14 on the other hand. The connection between the alternator 12 and the electric traction motor 14 has the particularity of being direct; in other words, there is no element between them, and especially no converter. The electric traction motor 14 is therefore partly and directly supplied by the alternator 12, but also by the converter system 18. This supply takes place simultaneously. The electric traction motor 14 is then connected to at least one driving axle 16, preferably via a speed reducer 17.

 To take advantage of such a connection, it is possible to have an asynchronous motor with a wound rotor acting as an electric traction motor 14. A stator of this motor is then directly supplied at almost constant frequency by the alternator 12. This

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 arrangement thus makes it possible to be exempt from the presence of a converter between these two elements. In addition, it is the difference in frequency between the power supply current of the rotor and the power supply current of the stator which defines the speed of rotation at the output of the asynchronous motor with wound rotor, the slip and the current in the rotor and stator determining the torque. Consequently, it is the converter system which supplies the rotor of this motor, hence the presence of the electrical connection between these elements.

 In such an asynchronous motor with a wound rotor, the power is distributed so that 80 to 95% of this power is supplied to the stator, while 5 to 20% of this power is intended to pass through the converter system 18 to be administered. to the rotor.

 According to a first particular embodiment of the invention, the converter system 18 is a primary service converter 13.

 This arrangement allows a significant increase in overall energy efficiency, in particular due to the absence of the converter between the alternator 12 and the stator of the electric traction motor 14.

 As an example, let us assume that the maximum mechanical power required for a wheel of the driving axle 16 is 170 kW, this power corresponding to the power required for a 20-ton vehicle capable of ensuring an acceleration equal to lg, and that the necessary power

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 to be supplied to the service converter is 30 kW.

In such a case, assuming that the efficiency of each of the elements of the electric chain is 95%, the power consumed by the electric traction motor 14 is 188 kW. These 188 kW can be divided into 171 kW directly supplied by the alternator 12 and 17 kW supplied by the primary service converter 13. The power consumed by the primary service converter, which supplies, among other things, the rotor of the electric traction motor 14 , is therefore 17 kW to which must be added the 30 kW that it is necessary to provide for the various easements. Still taking into account an efficiency of 95%, the power actually consumed by the primary service converter 13 is 50 kW. Alternator 2 must therefore supply a simultaneous power of 171 and 50 kW, or 220 kW. This requires from the supply system 11, on a drive shaft of the alternator 12, to supply a power of 232 kW.

 Having taken the same starting hypotheses as those adopted for the calculations relating to the vehicle according to the prior art, it can be seen that the power to be supplied by the supply system goes from 242 to 232 kW, which corresponds to a 4.5% increase in overall energy efficiency or 5% more power.

 In addition, this arrangement has led to a reduction in the power of the converters used, which directly results in a reduction in the mass and cost of the vehicle.

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 Referring to Figure 3, we can see a second particular embodiment of the invention. The vehicle has the same characteristics described above in the first particular embodiment of the invention, unlike the converter system 28.

 Indeed, the vehicle includes a power supply system 21 mechanically connected to an alternator 22, this set of two elements being comparable to a generator. The alternator 22 is connected to a converter system 28 on the one hand, and to an electric traction motor 24 on the other hand. The connection between the alternator 22 and the electric traction motor 24 has the particularity of being direct; in other words, there is no element interposed between them, and especially no converter. The electric traction motor 24 is therefore partly and directly supplied by the alternator 22, but also by the converter system 28. This supply takes place simultaneously. The electric traction motor 24 is then connected to at least one driving axle 26, preferably via a speed reducer 27.

 The converter system 28 comprises a four-quadrant converter 25 connected to an energy storage and storage device 29, this device 29 preferably being comparable to a battery, a supercapacitor, a flywheel or even to a compressor d 'air. This energy storage and destocking device 29 is capable of supplying at least one secondary converter of

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 easement 23a, 23b. In this embodiment, the energy storage and storage device 29 feeds a secondary converter 23b, which itself is connected to the rotor of the electric traction motor 24.

 By way of example and still taking the same starting hypotheses, let us assume that the maximum mechanical power necessary for a wheel of the driving axle 26 is 170 kW and that the power necessary to supply the servitude converter is 30 kW.

In such a case, assuming that the efficiency of each of the elements of the electric chain is 95%, the power consumed by the electric traction motor 24 is 188 kW. These 188 kW can be divided into 171 kW directly supplied by the alternator 22 and 17 kW supplied by the secondary service converter 23b.

 In addition, the power consumed by this secondary servitude converter 23b, which supplies the rotor of the electric traction motor 24, is supplied by the energy storage and destocking device 29, namely the battery.

 Taking into account a 95% efficiency for each converter and an 80% return efficiency for the battery, the four-quadrant converter 25 must be able to supply 41 kW.

 At the output of the alternator, it is therefore necessary to have a simultaneous power of 171 and 41 kW, or 212 kW. This requires from the supply system 21, on a drive shaft of the alternator 22, to provide a power of 223 kW.

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 The power to be supplied by the power system therefore goes from 242 to 223 kW, which corresponds to an increase in overall energy efficiency of 8%, or to a surplus of power of 8.5%.

 In addition, this arrangement has led to a reduction in the power of the converters used, which results directly in a further reduction in the mass and cost of the vehicle, compared with the first particular embodiment of the invention.

 According to another version of the second particular embodiment of the invention, still with reference to FIG. 3, at least part of the energy to be supplied to the stator of the electric traction motor 24 comes from the storage and destocking device d energy 29. The change made compared to the second particular embodiment of the invention therefore lies in the supply of power to the stator. This supply no longer comes exclusively from the alternator directly, but partially comes from the battery. Once again, this has the effect of reducing power losses and increasing the overall fuel efficiency of the vehicle.

 Still using the same initial assumptions, the power consumed by the electric traction motor 24 is 171 kW for the stator and 17 kW for the rotor.

 In such a case, we will then assume that of the 171 kW to be supplied to the stator, 107 kW are directly supplied by the alternator 22 and 64 kW

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 come from the battery through the four quadrant converter 25.

 The power consumed by the battery is therefore 17 kW to be supplied to the secondary service converter 23b supplying the rotor, 30 kW to be supplied to the secondary service converter 23a to supply the rest of the services, and 64 kW to be supplied to the stator of the engine. electric traction 24.

 Given a conversion efficiency of 95%, the power to be supplied by the battery is therefore 116 kW.

 At the output of the alternator 22, it is therefore necessary to have a power of 107 kW. This requires from the supply system 21, on a drive shaft of the alternator 22, to provide a power of 122 kW.

 The power to be supplied by the power system therefore goes from 242 to 122 kW, which corresponds to a considerable increase in energy efficiency.

 In addition, this arrangement has further led to a reduction in the power of the converters used, which directly results in a further reduction in the mass and cost of the vehicle, compared with the first particular embodiment of the invention. The generator then operates at almost constant power and speed. In this case, the easements can thus be directly supplied by the alternator 22 and no longer use the converter to supply the auxiliaries, which

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 further improves overall system performance.

 During the second particular embodiment of the invention, an energy storage and storage device 29 similar to a battery is used.

 Preferably, at least part of the energy storage is carried out during vehicle braking operations using the four-quadrant converter 25. This battery can therefore be recharged with each braking, which is very particularly suitable for a vehicle in permanent accelerations and decelerations.

 In addition, the energy recovered by the battery may not be stored and be used only during braking operations. Likewise, this battery can be controlled to alternately operate in total energy restitution, in total energy storage, or in a mixed regime of storage and partial restitution of this energy.

 The energy stored in the battery can then allow the use of the alternator 22 to start the generator.

 Note also that the vehicle can be powered by a constant frequency electric group. In this case, at least some of the easements can directly use an electrical output from this electrical group. The electric group can then use any kind of primary source such as a gas turbine, a heat engine or even a converter electric group.

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 Referring to Figure 4, there is a third particular embodiment of the invention. The vehicle is an electric vehicle powered by a power source of the catenary, pole or float type.

 An application of this particular embodiment of the invention can thus relate to vehicles such as trains, metros or trams having two driving axles 36a, 36b intended to drive the vehicle in opposite directions.

 Each of these driving axles 36a, 36b are connected to an electric traction motor 34a, 34b, itself connected to a converter system 38a, 38b. These converter systems 38a, 38b are equivalent to those described above, a pole 39 being connected with the thermal traction motors 38a, 38b on the one hand, and the converter systems 38a, 38b on the other hand.

 With such arrangements, we are then able to reduce the power necessary to supply vehicles of the public transport type, the required power being able to be divided by a factor of 2.

 Of course, various modifications can be made by those skilled in the art to the vehicle which has just been described, only by way of nonlimiting example.

Claims (14)

1. electric traction vehicle comprising:

 - at least one driving axle (16, 26), - an electric traction motor (14, 24), at least one supply system (11,21) supplying the traction motor via an alternator (12,22) electric (14,24) as well as a converter system (18,28), characterized in that said electric traction motor (14,24) is simultaneously supplied by said alternator (12,22) directly and by said converter (18,28).  2. Vehicle according to claim 1, characterized in that the electric traction motor (14,24) is an asynchronous motor with a wound rotor.  3. Vehicle according to claim 1 or claim 2, characterized in that said alternator (12,22) is capable of supplying a stator of the electric traction motor (14,24), and in that said converter system (18 , 28) is capable of supplying a rotor of this electric traction motor (14,24).  4. Vehicle according to claim 3, characterized in that the power supplied to said stator is about 80 to 95% of the total power supplied to the electric traction motor (14,24), and in that the power supplied to said rotor is about 5 to 20% of the total power supplied to the electric traction motor (14,24). <Desc / Clms Page number 18>  5. Vehicle according to any one of the preceding claims, characterized in that said converter system (18) is a primary service converter (13).  6. Vehicle according to claim 3 or claim 4, characterized in that said converter system (28) comprises a four quadrant converter (25) connected to an energy storage and storage device (29) capable of supplying the minus a secondary easement converter (23a, 23b).  7. Vehicle according to claim 6, characterized in that at least part of the power supply to the stator of the electric traction motor (24) comes from the energy storage and destocking device (29).  8. Vehicle according to claim 6 or claim 7, characterized in that said energy storage and destocking device (29) comprises at least one element taken from a battery, a supercapacitor, a flywheel and a compressor air.  9. Vehicle according to any one of claims 6 to 8, characterized in that at least part of the energy storage of said energy storage and storage device (29) is carried out during braking operations of the vehicle.  10. Vehicle according to any one of claims 6 to 9, characterized in that at least part of the energy recovered during vehicle braking operations is directly restored by the <Desc / Clms Page number 19>  energy storage and destocking device (29), without being stored.  11. Vehicle according to any one of the preceding claims, characterized in that the supply system (11,21) and the alternator (12,22) form a generator.  12. Vehicle according to any one of the preceding claims, characterized in that the vehicle is an electric vehicle powered by at least one of the power sources taken from the group consisting of the following elements: {catenary, poles, rubbers} .  13. Vehicle according to any one of the preceding claims, characterized in that the vehicle is supplied by an electric group at constant frequency, at least part of the easements directly using an electric output of said electric group.  14. Vehicle according to claim 13, characterized in that the electric group comprises at least one element taken from a gas turbine, a heat engine and a converter electric group.