Hybrid vehicle

Abstract

A hybrid energy system is provided in a vehicle including an autonomous power supply and being connectable to an external power supply infrastructure along the route of the vehicle, and which vehicle is arranged to operate in an autonomous power supply mode and/or in an external power supply mode. The system includes a first high voltage circuit including a first traction motor connected to an energy storage system by a first power converter for propelling the vehicle; a second high voltage circuit including a second traction motor connectable to an external power supply by a second power converter for propelling the vehicle; and where the first high voltage circuit and the second high voltage circuit are connectable by a third power converter between the first and the second power converters. A method for operating the hybrid energy system is also provided.

Claims

1. Hybrid energy system in a vehicle comprising an autonomous power supply and being connectable to an external power supply infrastructure along the route of the vehicle, and which vehicle is arranged to operate in an autonomous power supply mode and/or in an external power supply mode, wherein the system comprises a first high voltage circuit comprising a first traction motor connected to an energy storage system by a first power converter for propelling the vehicle; a second high voltage circuit comprising a second traction motor connectable to an external power supply by a second power converter for propelling the vehicle; and where the first high voltage circuit and the second high voltage circuit are connectable by a third power converter between the first and the second power converters, wherein a controllable switch is connected in parallel with the third power converter, and that the switch is arranged to by-pass the third power converter when closed.

2. Hybrid energy system according to claim 1, wherein the first and the second power converters are DC/AC power converters.

3. Hybrid energy system according to claim 1, wherein the third power converter is a DC/DC power converter.

4. Hybrid energy system according to claim 1, wherein the energy storage system is a high voltage battery.

5. Hybrid energy system according to claim 1, wherein the autonomous power supply comprises an internal combustion engine connected to the first traction motor.

6. Hybrid energy system according to claim 1, wherein the second high voltage circuit is connectable to an external power supply in the form of overhead wires or a rail.

7. Hybrid energy system according to claim 1, wherein the first traction motor and the second traction motor are connected to individual driven axles.

8. Hybrid energy system according to claim 1, wherein the first traction motor and the second traction motor are connected to one driven axle.

9. Method for operating hybrid energy system in a vehicle comprising; an autonomous power supply and being connectable to an external power supply infrastructure along the route of the vehicle; a first high voltage circuit comprising a first traction motor for propelling the vehicle connected to an energy storage system by a first power converter (207; 307); a second high voltage circuit comprising a second traction motor for propelling the vehicle connectable to an external power supply by a second power converter; and where the first high voltage circuit and the second high voltage circuit are connectable by a third power converter and by a parallel controllable switch between the first and the second power converters, the method comprising operating the hybrid energy system in alternative modes, comprising at least: an autonomous power supply mode involves operating the first traction motor using the energy storage system; an external power supply mode involves connecting the third power converter and operating one or both of the first and second traction motors using the external power supply; and a combined autonomous and external power supply mode involves operating the first traction motor using the energy storage system and the second traction motor using the external power supply.

10. Method according to claim 9, comprising operating the hybrid energy system in an alternative autonomous power supply mode involving bypassing the third power converter and operating both of the first and second traction motors using the energy storage system.

11. Method according to claim 9, comprising operating the hybrid energy system in an alternative external power supply mode by bypassing the third power converter, disconnecting the energy storage system and operating both the first and second traction motors using the external power supply.

12. Method according to claim 9, comprising operating the hybrid energy system in a regenerative mode where the second traction motor is driven using the external power supply to drive a ground engaging element, and driving the first traction motor using a further ground engaging element for charging the energy storage system.

13. Method according to claim 9, comprising operating the hybrid energy system in a regenerative mode where power is supplied to the external power supply by bypassing the third power converter and operating one or both of the first and second traction motors using ground engaging elements.

14. Method according to claim 9, comprising operating the hybrid energy system in a regenerative mode where power is supplied to the energy storage system by disconnecting the external power supply and bypassing the third power converter and operating one or both of the first and second traction motors using ground engaging elements.

15. Method according to claim 9, comprising operating the hybrid energy system in an external power supply mode by connecting the first and second traction motors and disconnecting them from the vehicle driveline, and driving the first traction motor using the second traction motor to charge the energy storage system.

16. Vehicle Wherein the vehicle is a commercial vehicle comprising a hybrid energy system according to claim 1.

17. A computer comprising program code for performing all the steps of claim 9 when the program is run on the computer.

18. A computer program product comprising program code stored on a computer readable medium for performing all steps of claim 9 when the program product is run on a computer.

19. A non-transitory storage medium for use in a computing environment co comprising a computer readable program code to perform the method of claim 9.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) In the following text, the invention will be described in detail with reference to the attached drawings. These schematic drawings are used for illustration purposes only and do not in any way limit the scope of the invention. In the drawings:

(2) FIG. 1A shows a side view of a hybrid vehicle with a power collector according to one embodiment of the invention;

(3) FIG. 1B shows a side view of a hybrid vehicle according to an alternative embodiment of the invention;

(4) FIG. 2A shows a schematic diagram of an energy system according to a first example;

(5) FIG. 2B shows a schematic diagram of an energy system according to a second example;

(6) FIG. 3A shows a schematic diagram of an energy system according to a third example;

(7) FIG. 3B shows a schematic diagram of an energy system according to a fourth example;

(8) FIG. 3C shows a schematic diagram of an energy system according to a fifth example;

(9) FIG. 4 shows a schematic diagram of a conventional hybrid energy system; and

(10) FIG. 5 shows the invention applied on a computer arrangement.

DETAILED DESCRIPTION

(11) FIG. 1A is a side view showing a hybrid vehicle with a power collector according to the present embodiment, and FIG. 1B is a side view showing an alternative hybrid vehicle. As shown in FIGS. 1A-1B, the hybrid vehicle with the power collector is applied to a heavy truck referred to as a vehicle in the subsequent text.

(12) FIG. 1A shows a vehicle 101 in the form of a truck with a front axle 102 and two driven first and second rear axles 103, 104. The vehicle 101 is provided with an autonomous power supply comprising an internal combustion engine (ICE) 105 connected to a first electric motor-generator (EM1) 106 and a transmission 107, such as an automated manual transmission (AMT), for transmitting torque to the first rear axle 103 via a first drive shaft 108. A first electric motor-generator (EM) 106, hereafter referred to as the first motor, can be provided with electrical power from an on-board energy storage system, such as a battery, or an external power supply, such as overhead wires. This will be described in further detail below. The engine 105, the first motor 106, the transmission 107 and first drive shaft 108 constitute a first driving force transmission system that transmits rotational driving force of the engine 105 and/or the first motor 106 to the first rear axle 103.

(13) Although the figures describe an example using overhead wires, the inventive concept is also applicable to alternative conductive arrangements, such as roadside rails or tracks, or inductive arrangements located in the road surface.

(14) A second electric motor-generator (EM2) 110 is provided below adjacent the second rear axle 104 and is connected to said axle via a second drive shaft 111. The second motor 106 and the second drive shaft 111 constitute a second driving force transmission system that transmits rotational driving force of the second motor 106 to the second rear axle 104. The second electric motor-generator 110, hereafter referred to as the second motor, can be provided with electrical power from an external power supply, such as overhead wires, and/or an on-board energy storage system, such as a battery (not shown).

(15) To supply electrical power to the first and/or the second motors 106, 110, pantographs 112 (one shown) are provided as power recovery units of a power collector 113 in an upper pan of the vehicle 101. The pantographs 112 can be mounted to the upper part of the vehicle 101 behind a cab 109, as shown in FIG. 1A, or on the cab itself, as shown in FIG. 1B. Electrical power is supplied via the pantographs 112 to the first and/or the second motors 106, 110 from overhead wires 114 disposed above a road. The overhead wires 114 are comprised of a pair of overhead wires (one shown), and the pantographs 112 are also comprised of a pair of pantographs. The pantographs 112 are connected to the overhead wires 114, respectively. Here, it is assumed that direct current (DC) is supplied to the overhead wires 114, and one of the two overhead wires is a power supply line to which direct current is supplied, and the other one acts as an electricity return line. The power collector 113 comprises the pantographs 112 and an actuator 115 for raising and lowering the pantographs 112, as indicated by arrow A. The pantographs 112 are adapted to be driven between an operating position at which they receive electrical power from the overhead wires 114, as indicated by solid lines in FIG. 1A, and a retracted position at which they receive no electrical power as indicated by dash-dotted lines in FIG. 1A.

(16) An engine electronic control unit (not shown) is provided as an internal combustion engine control means for controlling the engine 105, and the transmission 107. A motor electronic control unit (not shown) is provided as a motor control means for controlling the first and the second motors 106, 110, and a power collector electronic control unit (not shown) is provided as a power collector control means for controlling the power collector 113. For overall control, an electronic control unit (ECU; not shown) is provided as an integrated control means for carrying out integrated control of the engine electronic control unit, the engine electronic control unit and the power collector electronic control unit. The electronic control unit is part of an electrical supply system 120 in the vehicle, which system controls and supplies electrical power to and from the first and the second motors 106, 110 and the energy storage system, such as a battery. The electrical supply system 120 is an integral part of the vehicle hybrid energy system and comprises the requisite power electronics for connecting the power collector 113, the first and second motors 106, 110 and the energy storage system. The electrical supply system 120 will be described in further detail below. The engine 105 is preferably a diesel engine, and its fuel injection quantity is electronically controlled by the engine electronic control unit in response to an output request. The transmission 107 is adapted to be an automated manual transmission that is activated by a gear shift actuator (not shown), to select a shift gear to be used. A clutch (not shown) is adapted to be engaged and disengaged by a clutch actuator (not shown). These actuators are electronically controlled by the engine electronic control unit in response to a gear shift request, so that the clutch is engaged and disengaged, and shift gears are changed. The arrangement and operation of a transmission of this type in a hybrid vehicle is well known and will not be described in further detail.

(17) The first and the second motors 106, 110 are preferably three-phase alternating current (AC) motors, and their rotational state is electronically controlled by the motor electronic control unit in response to an output request. It should be noted that the first and second motors 106, 110 can carry out both regenerative operation, as generators, and normal powering operation, as traction motors. The motor electronic control unit has a function (a regeneration control means) for carrying out regenerative control of the motors 106, 110 so that regenerative energy is stored as electric energy in a battery (or other power storage means), for instance during braking or during downhill travel. Electrical power stored in a battery or similar can be used for operation of at least the first motor 106, for example, when the power collector 13 is not operated for collecting power. Different operating modes will be described in detail below.

(18) The ECU, as the integrated control means, can set a vehicle driving mode and carries out integrated control of the engine electronic control unit, the motor electronic control unit, and the power collector electronic control unit based on information from roads, GPS information, and so on received via a transmitting and receiving unit, output requests (including braking requests) from an accelerator pedal and a brake pedal, not shown, and selection information from a selection switch (a driving mode selection means; not shown) that allows selection of a driving mode. The main vehicle driving modes are an external power supply mode in which the vehicle is driven by only rotational driving force from at least one motor, and an autonomous power supply mode in which the vehicle is driven by the rotational driving force from the engine and/or at least one motor using the power storage means. The selection switch allows a driver to select either of these driving modes, and also allows selection of an automatic selection mode in which a driving mode is automatically selected by the ECU.

(19) When the automatic selection mode is selected using the selection switch, the ECU can act as a driving mode selection means. In a situation where the road is equipped with overhead wires 114, and the vehicle 101 is running in a driving lane equipped with overhead wires 114 and can collect power from the overhead wires 114, the external power supply mode is primarily selected. In a case where electrical power is especially needed in a situation where electrical power can be collected from the overhead wires 114, a combined driving mode is automatically selected. In a situation where electrical power cannot be collected from the overhead wires 114, the autonomous power supply mode is primarily selected. The ECU can also select a combined driving mode in which the vehicle is driven by a combination of rotational driving force from at least one motor and rotational driving force from the engines.

(20) Whether or not electrical power is collectable from the overhead wires 114 can be determined using a sensor, such as a camera, which is disposed in the vicinity of the pantographs 112 and detects the presence of the overhead wires 114. When detection information is obtained from the sensor, it is determined that electrical power can be collected from the overhead wires 114, and when detection information is not obtained from the sensor, it is determined that electrical power cannot be collected from the overhead wires 114. The ECU can be provided with a vehicle position determination means for determining whether or not the pantographs 112 are in a position where they can receive electrical power from the overhead wires 114. The ECU also has an overhead wire determination means for determining whether or not the overhead wires 114 are disposed in the lane in which the vehicle 101 is running based on information from roads and GPS information inputted to the ECU. When the overhead wire determination means determines that the overhead wires 114 are discontinued in the lane in which the vehicle 101 is currently running in the external power supply mode using at least one motor (the external power supply mode or the combined driving mode), the ECU automatically switches to the autonomous power supply mode irrespective of which driving mode is selected by the selection switch before the vehicle 101 enters the area where the overhead wires 114 are not provided. When the vehicle position determination means determines that the pantographs 2 are at positions where they can receive electrical power from the overhead wires 114, the above procedure is carried out in reverse. In a case where an internal combustion engine driving mode, not using the motors, is selected, the engine is started if the engine is at a standstill, and the actuator 115 is controlled to set the pantographs 112 in the retracted position so as to inhibit them from collecting electrical power.

(21) FIG. 1B shows a vehicle 131 in the form of a truck with a front axle 132 and one driven rear axle 133. As in FIG. 1A, the vehicle 131 is provided with an autonomous power supply comprising an internal combustion engine (ICE) 135 connected to a first electric motor-generator (E1) 136 and a transmission 137, such as an automated manual transmission (AMT), for transmitting torque to the rear axle 133 via a drive shaft 138. The first electric motor-generator (EM) 136, hereafter referred to as the motor, can be provided with electrical power from an on-board energy storage system, such as a battery, or an external power supply, such as overhead wires. This will be described in further detail below. The engine 135, the motor 136, the transmission 137 and drive shaft 138 constitute a first driving force transmission system that transmits rotational driving force of the engine 135 and/or the first motor 136 to the rear axle 133. A second electric motor-generator (EM2) 140 is provided for driving the drive shaft 138 after the transmission 137.

(22) Alternatively, the second motor can be arranged below adjacent the rear axle 133 and be connected to said axle via a second drive shaft, similar to the solution shown in FIG. 1A. The second electric motor-generator 136 constitutes a second driving force transmission system that transmits rotational driving force of the second electric motor-generator 136 to the rear axle 133. The second electric motor-generator 140, hereafter referred to as the second motor, can be provided with electrical power from an external power supply, such as overhead wires, and/or an on-board energy storage system, such as a battery (not shown). To supply electrical power to the first and/or the second motors 136, 140, pantographs 142 (one shown) are provided as power recovery units of a power collector 43 in an upper part of the vehicle 131. The pantographs 142 can be mounted to the upper part of the vehicle 131 behind a cab 139, as shown in FIG. 1A, or on the cab itself, as shown in FIG. 1B. Electrical power is supplied via the pantographs 142 to the first and/or the second motors 136, 140 from overhead wires 144 disposed above a road. The overhead wires 144 are comprised of a pair of overhead wires (one shown), and the pantographs 142 are also comprised of a pair of pantographs. The pantographs 142 are connected to the overhead wires 144, respectively. It is assumed that direct current (DC) is supplied to the overhead wires 144, and one of the two overhead wires is a power supply line to which direct current is supplied, and the other one acts as an electricity return line. The power collector 143 comprises the pantographs 142 and an actuator 145 for raising and lowering the pantographs 142. The pantographs 142 are adapted to be driven between an operating position at which they receive electrical power from the overhead wires 144, as indicated by solid lines in FIG. 1B, and a retracted position at which they receive no electrical power as indicated by dash-dotted lines in FIG. 1B.

(23) The vehicle 31 in FIG. 1B is provided with an engine electronic control unit (not shown) as an internal combustion engine control means for controlling the engine 135, and the transmission 137. A motor electronic control unit (not shown) is provided as a motor control means for controlling the first and the second motors 136, 140, and a power collector electronic control unit (not shown) is provided as a power collector control means for controlling the power collector 143. For overall control, an electronic control unit (ECU; not shown) is provided as an integrated control means for carrying out integrated control of the engine electronic control unit, the engine electronic control unit and the power collector electronic control unit. The electronic control unit is part of an electrical supply system 150 in the vehicle, which system controls and supplies electrical power to and from the first and the second motors 136, 140 and the energy storage system, such as a battery. The electrical supply system 150 is an integral part of the vehicle hybrid energy system and comprises the requisite power electronics for connecting the power collector 143, the first and second motors 136, 140 and the energy storage system. Operation of the hybrid energy system is carried out in the same way as for the system described for FIG. 1A above, with the difference that both motors are arranged to drive the same rear axle 133.

(24) FIG. 2A shows a schematic diagram of a vehicle 201 with a hybrid energy system according to a first example. In this example, the hybrid energy system comprises an autonomous power supply and is connectable to an external power supply infrastructure or grid along the route of said vehicle. The vehicle 201 is arranged to operate in an autonomous power supply mode using an on-board energy storage system 202, in an external power supply mode using electrical power from overhead wires 203, or in a combined autonomous and external power supply mode using electrical power from both sources. The electrical energy storage system in this hybrid vehicle comprises batteries, but any suitable technology can be used, such as super-capacitors, fuel cells and flywheels.

(25) The hybrid energy system in FIG. 2A comprises a high voltage propulsion system split into two parts or high voltage circuits 204, 205 inside the vehicle 201. The first high voltage circuit 204 comprises a first traction motor 206 connected to an energy storage system by a first power converter 207 for propelling the vehicle. In this case, the energy storage system is a battery 202 which is connected to the first high voltage system by conventional relays and contactors 208, allowing the battery 202 to be connected and disconnected from the system. The second high voltage circuit 205 comprises a second traction motor 210 connectable to the external source of electrical power 203 by a power collector 211 which is directly connected to a second power converter 212 for propelling the vehicle. The power collector 211 is connected to the second high voltage circuit 205 by conventional relays and contactors 213, allowing the power collector 211 to be connected and disconnected from the system. The first and second power converters 207, 212 are DC/AC converters for converting the DC high voltage in the respective high voltage circuit 204, 205 to an AC voltage for driving the first and second AC motor. The first and second traction motors are three-phase AC motors. The first and the second traction motor 206, 210 can be operated as motors, for propelling the vehicle, or as generators, for regeneration of energy. When the motors are operated in generator mode, the respective first and second power converter is operated as a rectifier.

(26) The first and the second traction motor 206, 210 are each mechanically connected to individual first and second driven axles 215, 216, each provided with a pair of wheels 217, 218. The first traction motor 206 is indirectly connected to the first driven axle 215 via a driveline including an automated manual transmission 219, a first drive shaft 220 and a differential 221. The second traction motor 210 is directly connected to the second driven axle 216 via a second drive shaft 222 and a differential 223. This driveline layout is schematically shown in FIG. 1A. Alternatively, the second axle can be provided with a pair of wheel motors.

(27) The first high voltage circuit 204 and the second high voltage circuit 205 are operated at the same or at similar voltages and are connectable by a third power converter 214 which is located as a bridge between the first and the second high voltage circuits 204, 205 and the first and second DC/AC converters 207, 212. The third power converter 214 is a DC/DC power converter. In this context, the term high voltage refers to a voltage in a preferred range of 500-800 V. For instance, the first high voltage circuit can be operated at 500-700 V and the second high voltage circuit can be operated at 550-800 V.

(28) An advantage is that not all the power from the external power supply needs to pass through the bridge. Instead the main part of the electric power can be directly utilized by the vehicle in the second high voltage circuit. By using the energy storage system in the hybrid system, it will be possible to reduce the required size of the DC/DC converter. Another advantage is that by splitting the high voltage system, the third converter, or DC/DC converter, does not need to be at full power range of the propulsion system of the hybrid vehicle. This further reduces the size and cost of the third converter. For example, in a system according to the invention the continuous rating of the DC/DC converter can be 50-100 kW, as compared to a conventional system. In a conventional system with a DC/DC converter handling all electrical power from an external power supply the continuous rating of can be 150-300 kW depending on the system layout. The positioning of the DC/DC power converter also allows for a very flexible use and a number of alternative operating modes, each allowing for a more energy efficient operation and reduced energy losses. Examples of such operating modes are given in the text below.

(29) The autonomous power supply further comprises an internal combustion engine 224 connected to the first traction motor 206 via a clutch (not shown). The engine 224 can be used for driving the first driven axle via the driveline or for charging the energy storage system 202 by operating the first traction motor 206 as a generator, using the first power converter 207 as a rectifier.

(30) The second high voltage circuit 205 is connectable to the external power supply 203, in this case in the form of overhead wires 225, 226. The overhead wires 225, 226 can be accessed through a conventional pantograph, mounted at a suitable location on the vehicle (see FIGS. 1A and 1B). Direct current (DC) is supplied to the overhead wires 225, 226, and one of the two overhead wires is a power supply line to which direct current is supplied, and the other one acts as an electricity return line. Alternatively, a roadside rail adjacent the route followed by the vehicle, or a recessed rail in the road surface can be used.

(31) FIG. 2B shows a schematic diagram of a vehicle with a hybrid energy system according to a second example. The system shown in FIG. 2B is basically identical to that of FIG. 2A, wherein the same reference numerals have been used for identical components. The system in FIG. 2B differs in that a controllable switch 230 is connected in parallel with the third power converter 214. The switch 230 is arranged to by-pass the third power converter 214 when closed, allowing additional operating modes to be used. The by-pass creates a direct connection between the first and second high voltage circuits 204, 205, whereby losses in the DC/DC converter can be avoided. Operation of the controllable switch 230 is determined by the operating mode selected, which modes will be described below.

(32) FIG. 3A shows a schematic diagram of a vehicle 301 with a hybrid energy system according to a third example. In this example, the hybrid energy system comprises an autonomous power supply and is connectable to an external power supply infrastructure or grid along the route of said vehicle. The vehicle 301 is arranged to operate in an autonomous power supply mode using an on-board energy storage system 302, in an external power supply mode using electrical power from overhead wires 303, or in a combined autonomous and external power supply mode using electrical power from both sources. The electrical energy storage system in this hybrid vehicle comprises batteries, but any suitable technology can be used, such as super-capacitors, fuel cells and flywheels.

(33) The hybrid energy system in FIG. 3A comprises a high voltage propulsion system split into two parts or high voltage circuits 304, 305 inside the vehicle 301. The first high voltage circuit 304 comprises a first traction motor 306 connected to an energy storage system by a first power converter 307 for propelling the vehicle. In this case, the energy storage system is a battery 302 which is connected to the first high voltage system by conventional relays and contactors 308, allowing the battery 302 to be connected and disconnected from the system. The second high voltage circuit 305 comprises a second traction motor 310 connectable to the external source of electrical power 303 by a power collector 311 which is directly connected to a second power converter 312 for propelling the vehicle. The power collector 311 is connected to the second high voltage circuit 305 by conventional relays and contactors 313, allowing the power collector 311 to be connected and disconnected from the system. The first and second power converters 307, 312 are DC/AC converters for converting the DC high voltage in the respective high voltage circuit 304, 305 to an AC voltage for driving the first and second AC motor. The first and second traction motors are three-phase AC motors. The first and the second traction motor 306, 310 can be operated as motors, for propelling the vehicle, or as generators, for regeneration of energy. When the motors are operated in generator mode, the respective first and second power converter is operated as a rectifier.

(34) The first and the second traction motor 306, 310 are each mechanically connected to a common first driven axle 315, provided with a pair of wheels 317. The first traction motor 306 is indirectly connected to the first driven axle 315 via a driveline including an automated manual transmission 319, a first drive shaft 320 and a differential 321. The second traction motor 310 is directly connected to the first driven axle 315 via a second drive shaft 328 and the common differential 321. This driveline layout is schematically shown in FIG. 1B.

(35) The first high voltage circuit 304 and the second high voltage circuit 305 are operated at the same or at similar voltages and are connectable by a third power converter 314 which is located as a bridge between the first and the second high voltage circuits 304, 305 and the first and second DC/AC converters 307, 312. The third power converter 314 is a DC/DC power converter. In this context, the term high voltage refers to a voltage in a preferred range of 500-800 V. For instance, the first high voltage circuit can be operated at 500-700 V and the second high voltage circuit can be operated at 550-800 V.

(36) As indicated above, it is an advantage is that not all the power from the external power supply needs to pass through the bridge. Instead the main part of the electric power can be directly utilized by the vehicle in the second high voltage circuit. By using the energy storage system in the hybrid system, it will be possible to reduce the required size of the DC/DC converter. Another advantage is that by splitting the high voltage system, the third converter, or DC/DC converter, does not need to be at full power range of the propulsion system of the hybrid vehicle. This further reduces the size and cost of the third converter. For example, in a system according to the invention the continuous rating of the DC/DC converter can be 50-100 kW, as compared to a conventional system. In a conventional system with a DC/DC converter handling all electrical power from an external power supply the continuous rating of can be 100-300 kW depending on the system layout. The positioning of the DC/DC power converter also allows for a very flexible use and a number of alternative operating modes, each allowing for a more energy efficient operation and reduced energy losses. Examples of such operating modes are given in the text below.

(37) The autonomous power supply further comprises an internal combustion engine 324 connected to the first traction motor 306 via a clutch (not shown). The engine 324 can be used for driving the first driven axle 315 via the driveline or for charging the energy storage system 302 by operating the first traction motor 306 as a generator, using the first power converter 307 as a rectifier.

(38) The second high voltage circuit 305 is connectable to the external power supply 303, in this case in the form of overhead wires 325, 326. The overhead wires 325, 326 can be accessed through a conventional pantograph, mounted at a suitable location on the vehicle (see FIGS. 1A and 1B). Direct current (DC) is supplied to the overhead wires 325, 326, and one of the two overhead wires is a power supply line to which direct current is supplied, and the other one acts as an electricity return line. Alternatively, a roadside rail adjacent the route followed by the vehicle, or a recessed rail in the road surface can be used.

(39) FIG. 3B shows a schematic diagram of a vehicle with a hybrid energy system according to a fourth example. The system shown in FIG. 3B is basically identical to that of FIG. 3A, wherein the same reference numerals have been used for identical components. The system in FIG. 3B differs in that a controllable switch 330 is connected in parallel with the third power converter 314. The switch 330 is arranged to by-pass the third power converter 314 when closed, allowing additional operating modes to be used. The by-pass creates a direct connection between the first and second high voltage circuits 304, 305, whereby losses in the DC/DC converter can be avoided. Operation of the controllable switch 330 is determined by the operating mode selected, which modes will be described below.

(40) FIG. 3C shows a schematic diagram of a vehicle with a hybrid energy system according to a fifth example. The system shown in FIG. 3C is basically identical to that of FIG. 3A, wherein the same reference numerals have been used for identical components. The system in FIG. 3C differs in that a second traction motor 310 is connected directly to the first driven axle 315 by a power take-off transmission 329. In this way the second traction motor is

(41) connected both to the first driven axle 315, via the first drive shaft 320 and the common differential 321, and to the first traction motor 306, via the transmission 319.

(42) The arrangement in FIG. 3C can be used for charging the energy storage system 302 by operating the first traction motor 306 as a generator when the vehicle is standing still. The second traction motor 310 is then operated using the external power supply 303. In this mode, the second traction motor 310 drives the first traction motor 306 via the first drive shaft 320, the transmission 319 through a suitable gear set. The power take-off transmission 329 also allows the second traction motor 310 to assist the first traction motor 306 and/or the internal combustion engine 324, if required.

(43) The above hybrid energy systems are provided with an autonomous power supply and can be connected to an external power supply infrastructure along the route of a vehicle 201, 301. As indicated in FIGS. 1A-1B and 2A-2B, the hybrid energy systems comprise a first high voltage circuit 204, 304 comprising a first traction motor 206, 306 for propelling the vehicle connected to an energy storage system 202, 302 by a first DC/AC converter 207, 307, and a second high voltage circuit 212, 312 comprising a second traction motor 210, 310 for propelling the vehicle connectable to an external source of electrical power 203, 303 by a second DC/AC converter 212, 312. The first high voltage circuit and the second high voltage circuit 204, 304; 205, 305 are connectable by a DC/DC converter 214, 314. Optionally a parallel controllable switch 230, 330 is provided between the first and the second DC/AC converters 207, 307; 212, 312, by-passing the DC/DC converter 214, 314.

(44) The invention involves operating the hybrid energy system in any one of a number of alternative modes, which operating modes include at least: an autonomous power supply mode involving operating the first traction motor 207 using the energy storage system 202; an external power supply mode involving connecting the DC/DC converter 214, 314 and operating one or both of the first and second traction motors 206, 306; 210, 310 using the external source of electrical power 203, 303; and a combined autonomous and external power supply mode involving operating the first traction motor 206, 306 using the energy storage system 202, 302 and the second traction motor using 210, 310 the external source of electrical power 203, 303.

(45) In the autonomous power supply mode the energy storage system 202, 302 is used for electric operation of the vehicle, when the external power supply 203, 303 is disconnected. The energy storage system 202, 302 can be used for operating the first traction motor 206, 306 only, using the energy storage system 202, 302 directly via the first DC/AC converter 207, 307.

(46) In the external power supply mode the second traction motor 210, 310 can be connected directly to the external power supply 203, 303 via the second DC/AC converter 212, 312, without losses being incurred in the DC/DC converter 214, 314. In addition, the external power supply 203, 303 can also be connected to the first traction motor 206, 306, via the DC/DC 214, 314 converter and the first DC/AC converter 207, 307, order to operate both the first and second traction motors 206, 306; 210, 310. The energy storage system 202, 302 can be charged from the external power supply 203, 303 during the latter operating mode.

(47) In the combined autonomous and external power supply mode the first traction motor 206, 306 can be operated using the energy storage system 202, 302 via the first DC/AC converter 207, 307, and the second traction motor 210, 310 can be operated using the external power supply 203, 303, via the first DC/AC converter 207, 307. In this case, the second traction motor 210, 310 can be driven directly by the external power supply 203, 303, without losses being incurred in the DC/DC converter 214, 314.

(48) As indicated above, the invention allows for a flexible hybrid energy system that can be operated in multiple alternative modes, while minimizing the use of the DC/DC converter 214, 314. The three basic modes described above can be carried out by any one of the examples shown in FIGS. 1A-B and 2A-2B. This flexibility is made possible by the location of the DC/DC converter 214, 314. The reduced power requirement for the DC/DC converter allows it to be dimensioned for a relatively small power rating. This in turn allows for a DC/DC converter of smaller size and lower weight, having very high efficiency and reduced heat generation.

(49) According to an additional example, the hybrid energy system can be operated in an alternative autonomous power supply mode involving bypassing the DC/DC converter 214, 314 and operating both of the first and second traction motors 206, 306; 210, 310 using the energy storage system 202, 302. In this example the energy storage system 202, 302 can be used for operating both the first and second traction motor by controlling a switch 230, 330 connected in parallel to bypass the DC/DC converter 214, 314. The energy storage system 202, 302 can also be used for operating the second traction motor 210, 310, using the energy storage system 202, 302 directly via the second DC/AC converter 212, 312. In the latter case, the second traction motor 210, 310 can be driven directly by the energy storage system 202, 302, without losses being incurred in the DC/DC converter 214, 314. Depending on the design of the vehicle driveline, the first and second traction motors 206, 306; 210, 310 can be used for driving independent first and second driven axles 215, 216; 315, 316, respectively (FIG. 2B), or for driving a common driven axle 315 (FIG. 3B).

(50) According to a further additional example, the hybrid energy system can be operated in an alternative external power supply mode by bypassing the DC/IC converter 214, 314. This example involves disconnecting the energy storage system 202, 302, using existing contactors 208, 308 connecting the energy storage system 202, 302 to the first high voltage circuit, and operating both the first and second traction motors 206, 306; 210, 310 using the external power supply 203, 303 via their respective power converter 207, 212; 307, 312. As in the previous example, the first and second traction motors 206, 306; 210, 310 can be used for driving independent first and second driven axles 215, 216; 315, 316, respectively (FIG. 2B), or for driving a common driven axle 35 (FIG. 3B).

(51) Both these alternative operating modes contribute to increased flexibility for the hybrid energy system, by allowing power to be supplied directly to the first and the second traction motor 206, 306; 210, 310 from the on-board energy storage system 202, 302 or the external power supply 203, 303 without incurring losses in the DC/DC converter 214, 314. The alternative modes described above can be carried out by any one of the examples shown in FIGS. 2B and 3B, where a controllable switch 230, 330 is provided for by-passing the DC/DC converter.

(52) The inventive hybrid energy system can also be operated in a number of alternative regenerative operating modes, adding to the flexibility of the system.

(53) According to a further example, the hybrid energy system can be operated in a first alternative regenerative operating mode. In the first alternative regenerative mode the second traction motor 210, 310 is driven using the external power supply 203, 303 to drive a ground engaging element. As described above, the first and the second traction motor 206, 306; 210, 310 can each be mechanically connected to an individual or a common ground engaging element, such as a driven axle 215, 216 provided with a pair of wheels 217, 218.

(54) Accordingly, when the first and the second traction motor 206, 306; 210, 310 are mechanically connected to individual ground engaging elements, the second traction motor 210, 310 can drive the first traction motor 206, 306 indirectly via the ground engaging elements. The second traction motor 210, 310 drives one ground engaging element, whereby a further ground engaging element drives the first traction motor 206, 306 for charging the energy storage system 202, 302. The first DC/AC converter 207, 307 can be used as a rectifier for this purpose.

(55) The first alternative regenerative mode can be used for charging the energy storage system 202, 302 when the DC/DC converter 214, 314 cannot supply sufficient power for this purpose. This first regenerative mode described above can be carried out by any one of the examples shown in FIGS. 2A and 2B, where two individual axles 215, 216 are provided. According to a further example, the hybrid energy system can be operated in a second alternative regenerative operating mode. In the second alternative regenerative mode power is supplied to the external power supply 203, 303 by using a controllable switch 230, 330 mounted in parallel to bypass the DC/DC converter 214, 314 and operating one or both of the first and second traction motors 206, 306; 210, 310 as generators using ground engaging elements. As described above, the first and the second traction motor 206, 306; 210, 310 can each be mechanically connected to an individual or a common ground engaging element, such as a driven axle 215, 216; 315 provided with a pair of wheels 217, 218; 317. The second alternative regenerative mode can be used for braking the vehicle without using the service brakes or when travelling downhill instead of using compression braking. Kinetic energy is converted to electrical energy by one or both traction motors 206, 210; 306, 310 and is supplied to directly to the external power supply 203, 303 via the respective first and/or second power converters.

(56) The second alternative regenerative mode allows regenerated electrical power to be returned to the grid without using the DC/DC converter 214, 314. This second alternative regenerative mode can be carried out by any one of the examples shown in FIGS. 2B and 3B, where a controllable switch 230, 330 is provided for by-passing the DC/DC converter 214, 314.

(57) According to a further example, the hybrid energy system can be operated in a third alternative regenerative operating mode. In the third alternative regenerative mode power is supplied to the energy storage system 202, 302 by using a controllable switch 230, 330 mounted in parallel to bypass the DC/DC converter 214, 314 and operating one or both of the first and second traction motors 206, 306; 210, 310 as generators using ground engaging elements. As described above, the first and the second traction motor 206, 306; 210, 310 can each be mechanically connected to an individual or a common ground engaging element, such as a driven axle 215, 216; 315 provided with a pair of wheels 217, 218; 317. The second alternative regenerative mode can be used for braking the vehicle without using the service brakes or when travelling downhill instead of using compression braking. Kinetic energy is converted to electrical energy by one or both traction motors 206, 210; 306, 310 and is supplied to directly to the energy storage system 202, 302 via the respective first and/or second power converters. During this operation, the external power supply 203, 303 must be disconnected.

(58) The third alternative regenerative mode allows regenerated electrical power to be returned to the energy storage system 202, 302 without using the DC/DC converter 214, 314. This second alternative regenerative mode can be carried out by any one of the examples shown in FIGS. 2B and 3B, where a controllable switch 230, 330 is provided for by-passing the DC/DC converter 214, 314.

(59) According to a further example, the hybrid energy system can be operated in a fourth alternative regenerative operating mode. In the fourth alternative regenerative operating mode the second traction motor 210, 310 is driven using the external power supply 203, 303. When the first and the second traction motor 206, 306; 210, 310 are mechanically connected to a common ground engaging element, the second traction motor 210, 310 can drive the first traction motor 206, 306 directly via a mechanical connection in the transmission for charging the energy storage system 202, 302. This involves disconnecting both traction motors from the part of the vehicle transmission connecting them to the ground engaging elements. The first traction motor 206, 306 is then driven using the second traction motor to charge the energy storage system 202, 302.

(60) The fourth alternative regenerative mode can be used for charging the energy storage system 202, 302 when the vehicle is standing still, without using the DC/DC converter 214, 314. This fourth regenerative mode described above can be carried out by any one of the examples shown in FIGS. 3A and 3B, where a common axle 315 is provided.

(61) The fifth alternative regenerative mode is also used for charging the energy storage system 202, 302 when the vehicle is standing still, without using the DC/DC converter 214, 314. This fifth regenerative mode described above can be carried out by the example shown in FIG. 3C, where both traction motors 306, 310 are connected to the first drive shaft. This arrangement is advantageous under urban operating conditions where the vehicle frequently stopped at bus stops, traffic lights or in queues.

(62) FIG. 4 shows a schematic diagram of a vehicle 401 comprising a conventional hybrid energy system. The vehicle 401 has a hybrid driveline with an autonomous power supply comprising an internal combustion engine 402, a first traction motor 403, a transmission 404 and a drive shaft 405 for driving a first driven axle 406. An external power supply 407 provides electrical power from overhead wires 408, 409 connectable to a power collector 411 connected to a high voltage circuit 412 by conventional relays and contactors 413 and a DC/DC converter 414. The first traction motor 403 can be driven by the high voltage circuit 412 by a battery 45 or the external power supply 407 connected to the motor 403 via a first DC/AC converter 416. A second traction motor 417 can be driven by the high voltage circuit 412 by the battery 415 or the external power supply 407 connected to the motor 417 via a second DC/AC converter 418.

(63) For a hybrid vehicle of this type, provided with a storage battery, the power converter must be dimensioned for a continuous rating equal to the average power requirement of the propulsion system. For a commercial vehicle such as a truck, similar to those shown in FIGS. 1A-1B, the continuous rating would be at least 100-150 kW. Such an arrangement would be used for a vehicle mainly operated using the power-collecting system, where the engine can be used for charging the storage battery. For a similar arrangement not provided with a storage battery, the DC/DC converter must be dimensioned for a continuous rating equal to the peak power requirement of the propulsion system, that is, at least 200-300 kW. In a high voltage circuit 412 connected directly to the high voltage power-collecting system 407, as shown in FIG. 4, all power from the external power supply 407 must pass through the DC/DC converter 414. This incurs conversion losses and generates heat that requires cooling, which reduces the overall system efficiency and increases the demand on the vehicle cooling system. A power converter of this type would also be relatively large and expensive.

(64) The present invention also relates to a computer program, computer program product and a storage medium for a computer all to be used with a computer for executing the method as described in any one of the above examples.

(65) FIG. 5 shows an apparatus 500 according to one embodiment of the invention, comprising a nonvolatile memory 520, a processor 510 and a read and write memory 560. The memory 520 has a first memory part 530, in which a computer program for controlling the apparatus 500 is stored. The computer program in the memory part 530 for controlling the apparatus 500 can be an operating system.

(66) The apparatus 500 can be enclosed in, for example, a control unit, such as the control unit 45. The data-processing unit 510 can comprise, for example, a microcomputer.

(67) The memory 520 also has a second memory part 540, in which a program for controlling the target gear selection function according to the invention is stored. In an alternative embodiment, the program for controlling the transmission is stored in a separate nonvolatile storage medium 550 for data, such as, for example, a CD or an exchangeable semiconductor memory. The program can be stored in an executable form or in a compressed state.

(68) When it is stated below that the data-processing unit 510 runs a specific function, it should be clear that the data-processing unit 510 is running a specific part of the program stored in the memory 540 or a specific part of the program stored in the nonvolatile storage medium 550.

(69) The data-processing unit 510 is tailored for communication with the storage memory 550 through a data bus 514. The data-processing unit 510 is also tailored for communication with the memory 520 through a data bus 512. In addition, the data-processing unit 510 is tailored for communication with the memory 560 through a data bus 511. The data-processing unit 510 is also tailored for communication with a data port 590 by the use of a data bus 515. The method according to the present invention can be executed by the data-processing unit 510, by the data-processing unit 510 running the program stored in the memory 540 or the program stored in the nonvolatile storage medium 550.

(70) The invention as described solves the above problems and has several advantages over conventional hybrid electric vehicle systems, for instance: i. The average power required to power the vehicle can be drawn from the external power supply and applied directly, without a DC-DC converter loss by the machine or machines connected directly to the external power supply. ii. Recuperated braking energy may be stored in, or drawn from the energy layer directly, without the DC-DC converter efficiency loss, by the machine or machines connected to the vehicle electrical circuits. iii. With the energy layer dimensioned with respect to both power and energy requirement over a mission, the power required to be transferred from the external power supply to the vehicle electrical circuits is a minimum of the losses incurred in the cycling of brake energy plus the auxiliary loads. This level of power could be transferred from the external power supply to the vehicle electrical circuits by either a much smaller DC-DC converter than in conventional systems or in an extreme case, by increasing the power rating of the machines directly connected to the external power supply, and recuperating the power by the other electrical machines. In this way galvanically isolated power transfer can occur from the external power supply to the vehicle electrical circuits via the road without the addition of a DC-DC converter, albeit at a small penalty in efficiency. iv. An additional benefit of adding a separate electrical propulsion instead of utilizing a larger electrical motor in a conventional hybrid drivetrain, is that vehicle manufacturer can use same platform of this part of the original hybrid system, for applications that are designed for an external power supply or not. For an external power supply such as an ERS (Electric Road System) it will be required with an electrical separation of the high voltage components and its surrounding, and traditionally also an impedance monitor will be added to the external power supply voltage system, in order to verify that external power supply components are properly isolated from the vehicle chassis. It is much less complicated, and of less cost, to add (and monitor) such an isolation, to the few extra components for the external power supply application requires, instead of adding isolation costs of the hybrid system, which would be the base of the 1st high voltage circuit. As external power supply application(s) will initially be of smaller volumes, it is better and more efficient to add extra isolation costs to the external power supply components, instead of adding cost to a platform design, which is traditionally used in many other products.

(71) The invention should not be deemed to be limited to the embodiments described above, but rather a number of further variants and modifications are conceivable within the scope of the following patent claims.