WO2016068785A1

WO2016068785A1 - Method and system for pre-charging an electrical component

Info

Publication number: WO2016068785A1
Application number: PCT/SE2015/051143
Authority: WO
Inventors: Michael WAERN
Original assignee: Scania CV AB
Current assignee: Scania CV AB
Priority date: 2014-10-30
Filing date: 2015-10-29
Publication date: 2016-05-06
Anticipated expiration: 2017-04-30
Also published as: SE543145C2; DE112015004205T5; SE1451300A1

Abstract

The present invention relates to a method for pre-charging a first rechargeable component (C1) in a vehicle (100), said first rechargeable component (C1) being pre-charged by applying a voltage to said first rechargeable component (C1), said vehicle (100) comprising at least one electrical machine (110) being arranged to be connected to a first power supply path, said first rechargeable component (C1) being subjected to a voltage (V_DC) of said first power supply path. The method includes, when said first rechargeable component (C1) is to be pre-charged: - charging said first rechargeable component (C1) by applying a voltage over said first rechargeable component (C1) by means of said electrical machine (110).

Description

METHOD AND SYSTEM FOR PRE-CHARGING AN ELECTRICAL COMPONENT Field of the invention

The present invention relates to vehicles, and in particular to a method and system for pre-charging rechargeable

components in an electrical system of the vehicle. The present invention also relates to a vehicle, as well as a computer program and a computer program product that implement the method according to the invention.

Background of the invention With regard to vehicles in general, and at least to some extent heavy/commercial vehicles such as trucks, buses and the like, there is constantly ongoing research and development with regard to increasing fuel efficiency and reducing exhaust emissions . This is often at least partly due to growing governmental concern in pollution and air quality, e.g. in urban areas, which has also led to the adoption of various emission

standards and rules in many jurisdictions.

Apart from governmental concern, one of the main expenses associated with vehicle operation is consumption of fuel for propulsion of the vehicle. The degree of utilization of heavy vehicles is often high, and with its associated fuel

consumption, the cost of fuel can affect the profitability of the owner of the vehicle to a great extent. In view of this, and in view of the fact that transport of goods on roads is expected to continuously increase,

alternatives to conventional combustion engine technology are increasingly being considered.

For example, electric vehicles and hybrid-electrical vehicles are undergoing extensive research and development. These vehicles often include an electrical machine, where the electrical machine is controlled by means of an inverter drive. The inverter drive comprises switching means, e.g. in the form of transistors, to, by means of suitable switching, generate an AC voltage from a DC link/bus voltage to be supplied to the electrical machine. This allows e.g. amplitude and frequency of the terminal voltage of the stator phase windings to be controlled and thereby also the work produced by and rotational speed of the electrical machine. Solutions of this kind often include one or more capacitors, e.g. for stabilising the DC link voltage.

These capacitors, and other components as the case may be, are often directly connected to a power source, such as e.g. an energy storage, where pre-charging of the component is required when the component is connected to the power source from an uncharged state to reduce the risk of component damage .

Summary of the invention

It is an object of the present invention to provide a method and system that allows for pre-charging of rechargeable components in a manner that reduces need for pre-charging circuitry. This object is achieved by a method according to claim 1.

According to the present invention, it is provided a method for pre-charging a first rechargeable component in a vehicle, said first rechargeable component being pre-charged by

applying a voltage to said first rechargeable component, said vehicle comprising at least one electrical machine being arranged to be connected to a first power supply path, said first rechargeable component being subjected to a voltage of said first power supply path. The method includes, when said first rechargeable component is to be pre-charged:

- charging said first rechargeable component by applying a voltage over said first rechargeable component by means of said electrical machine.

As was mentioned above, electrical components may require a pre-charge when starting up a system to avoid component damage. This can, for example, be the case in power

electronics systems where high power supply voltages are used. For example, if an uncharged capacitor connected in parallel to a power source is subjected to voltage of the power source, the resulting current may damage the component. For this reason, pre-charging circuits are often used, where, e.g., sensitive components such as capacitors are pre-charged by limiting the charging current when a high voltage is applied. This can, for example, be accomplished by the use of pre- charging circuits of a kind where the power source is

connected to the component to be charged via a resistor limiting the current. When the component being charged has been charged to some suitable extent, e.g. when the voltage over a capacitor has reached the power supply voltage or some other suitable voltage where the risk of damaging the

component is limited, the pre-charging circuit can be bypassed and the capacitor be connected in parallel to the power source.

Pre-charging circuits of this kind consequently have the advantage that the initial current that electrical components are subjected to when a voltage is applied can be limited to a desired extent. This, however, is obtained at the expense of additional components, such as, e.g., additional contactors, resistors, additional wiring etc. The present invention provides an alternative solution for providing pre-charging of components where high initial currents can be harmful. The invention relates to vehicles, and in particular to systems in which an electrical machine is connectable to a power source via a first power supply path, and where one or more

components requiring a pre-charge when being subjected to the power supply and/or voltage of the power supply path are present .

According to the invention, this is accomplished by a solution where pre-charging is performed by means of the electrical machine. In general, when a rotor of an electrical machine is rotated, a voltage is induced in the stator windings, the induced voltage being substantially proportional to the rotational speed of the rotor. According to the invention, the induced voltage is used to pre-charge the one or more

components for which pre-charging is required, and since the voltage is proportional to the rotational speed of the rotor, the voltage can be e.g. successively increased by increasing the rotational speed of the rotor. In this way capacitors, for example, can be charged from a substantially uncharged state, i.e. a state where the voltage over the uncharged component is zero or close to zero. The rechargeable components can be charged to a partially charged state, e.g. to a voltage of 10% or more of a nominal, or normal, operating voltage, such as a normal operating voltage of the first power supply path which e.g. can be in the order of 300-1000V. The inductance of the stator winding will further "resist" transient current

changes, and hence the "infinite"/high/harmful initial

charging current will never occur. The electrical machine can, for example, consist of a permanent magnet machine, such as a permanent magnet synchronous three-phase machine.

Pre-charging said first rechargeable component by means of said electrical machine can be arranged to be performed at least when the voltage over said first rechargeable component is less than 10% of a normal operating voltage of said first power supply path, and hence when charging is most vulnerable.

The pre-charging of said first rechargeable component using the electrical machine can advantageously be performed when the first rechargeable component is in an uncharged state, since inductance of the stator winding will "resist" transient current changes.

Pre-charging can thus advantageously be performed using the invention also when the system has been disconnected for a period of time and the rechargeable component has completely discharged. Hence, pre-charging can advantageously be

performed using the invention also when the voltage over said first rechargeable component is zero. The rotation of the electrical machine can, for example, be accomplished by any suitable means of rotation of the rotor. For example, the electrical machine can be connectable to an output shaft of a combustion engine, in which case the

rotation can be accomplished by the aid of the combustion engine. Alternatively, the electrical machine can be arranged to be rotated by means of drive wheels of the vehicle, so that rotation can be accomplished at least when the vehicle is in motion. According to one embodiment a starter motor/alternator can be used to rotate the electrical machine. The present invention, consequently, provides a solution that allows for charging of e.g. capacitors in a manner that prohibits harmful initial currents. Furthermore, electrical machines, at least with regard to vehicle propulsion, are often arranged to be controlled by a drive system, such as an inverter drive system, in order to provide for rotational speed and torque control by controlling frequency and/or voltage and/or phase of the stator winding voltage, the electrical machine e.g. being a three phase machine. Such drives commonly include a switching arrangement for

controlling frequency and/or phase and/or amplitude of a stator terminal voltage of said electrical machine, and thereby also torque produced by said electrical machine.

According to one embodiment these switching means are used to controlling the amplitude of the voltage being applied to said first rechargeable component.

However, such inverter drives require at least a minimum voltage in order to make it possible to commence switching. For example, a voltage of e.g. 10% or more of the DC link voltage, e.g. the voltage of said first power supply path, in normal operation may be required to start switching. According to the invention, pre-charging by means of the electrical machine can be used to charge the rechargeable component to a partially charged state in order to increase the voltage over the rechargeable component, and thereby a DC link voltage of the inverter drive, to this voltage in order to allow

activation of the switching means, where further increase of the DC link voltage can be accomplished by suitable switching of the switching means, e.g. to the nominal DC link voltage or suitable fraction thereof prior to connecting a power source to the electrical machine. According to one embodiment, the vehicle is a parallel hybrid vehicle. According to one embodiment the vehicle is an

electric vehicle.

Further characteristics of the present invention and

advantages thereof are indicated in the detailed description of exemplary embodiments set out below and the attached drawings . Brief description of the drawings

Fig. 1A illustrates a power train of an exemplary hybrid electric vehicle;

Fig. IB illustrates an example of a control unit in a vehicle control system;

Fig. 2 illustrates the hybrid portion of the hybrid electric vehicle of fig. 1A more in detail;

Fig. 3A-B illustrates a prior art pre-charging arrangement;

Fig. 4 illustrates an exemplary method according to the present invention.

Detailed description of exemplary embodiments

The present invention will be exemplified in the following for a parallel hybrid vehicle. The invention, however, is

applicable for any hybrid electrical vehicle. For example, the invention is applicable for parallel hybrid vehicles and series hybrid vehicles. Further, for example, the invention is applicable for hybrid vehicles having a plurality of

electrical machines, where these, e.g. can be interconnected, directly and/or by means of transmission elements, such as e.g. planetary gears. The invention is applicable for any electric hybrid vehicle having one or more planetary gears, and also for power-split hybrid vehicles and series-parallel hybrid vehicles. The invention is also applicable for electric vehicles .

Fig. 1A schematically depicts a power train of an exemplary hybrid electric vehicle 100. The vehicle 100 in fig. 1A is a parallel hybrid vehicle 100. The power train of the parallel hybrid vehicle in Fig. 1A comprises a combustion engine 101 which, in a conventional manner, is connected, via an output shaft of the engine 101, to a gearbox 103 via a clutch 106. The engine 101 is controlled by the vehicle's control system via a control unit 115. The clutch 106, which, for example, can be an automatically operated clutch, and the gearbox 103 are also controlled by the vehicle's control system by means of a control unit 116.

The vehicle also includes a hybrid portion with an electrical machine 110, which is connected to the input shaft 109 of the gearbox 103, downstream of the clutch 106, so that the gearbox input shaft 109 can be driven by the electrical machine 110 also when the clutch 106 is open. Thereby, the parallel hybrid vehicle 100 can provide force to drive wheels 113, 114 from two separate power sources simultaneously, i.e. both from the combustion engine 101 and from the electrical machine 110. Alternatively, the vehicle may be propelled by one power source at a time, i.e. either by the combustion engine 101 or the electrical machine 110. The combustion engine 101 can also be arranged to apply a power to the electrical machine 110.

The hybrid portion also comprises further components. Fig. 1A depicts part of these components, and shows the electrical machine 110, an inverter drive 119 for controlling the

electrical machine 110, a power source, such as an energy storage, e.g. consisting of one or more batteries 111 and a hybrid control unit 112 which controls functions of the hybrid portion . As indicated above, the functions of a vehicle are, in

general, controlled by a number of control units, and control systems in vehicles of the disclosed kind generally comprise a communication bus system consisting of one or more

communication buses for connecting a number of electronic control units (ECUs), or controllers, to various components on board the vehicle. Such a control system may comprise a large number of control units, and the control of a specific

function may be divided between two or more of them.

For the sake of simplicity, Fig. 1A depicts only control units 112, 115-116 but vehicles 100 of the illustrated kind are often provided with significantly more control units, as one skilled in the art will appreciate. Control units 112, 115-116 can communicate with one another via said communication bus system, partly indicated by interconnecting lines in fig. 1A.

The present invention can be implemented in any suitable control unit, and in the illustrated example the invention is implemented in control unit 112 for controlling the hybrid drive portion of the vehicle. The invention may, however, also be implemented in any other suitable control unit. Pre- charging according to the present invention will usually depend on signals being received from other control units and/or vehicle components, and it is generally the case that control units of the disclosed type are normally adapted to receive sensor signals from various parts of the vehicle 100. Control units of the illustrated type are also usually adapted to deliver control signals to various parts and components of the vehicle. The control unit 112 will, for example, apart from other control of the hybrid drive system provide control signals for controlling one or more switches for

connecting/disconnecting the power source 111 to the

electrical machine/inverter drive.

Control of this kind is often accomplished by programmed instructions. The programmed instructions typically consist of a computer program which, when it is executed in a computer or control unit, causes the computer/control unit to exercise the desired control, such as method steps according to the present invention. The computer program usually constitutes a part of a computer program product, wherein said computer program product comprises a suitable storage medium 121 (see Fig. IB) with the computer program 126 stored on said storage medium

121. The computer program can be stored in a non-volatile manner on said storage medium. The digital storage medium 121 can, for example, consist of any of the group comprising: ROM (Read-Only Memory) , PROM (Programmable Read-Only Memory) , EPROM (Erasable PROM) , Flash memory, EEPROM (Electrically Erasable PROM) , a hard disk unit etc, and be arranged in or in connection with the control unit, whereupon the computer program is executed by the control unit. The behaviour of the vehicle in a specific situation can thus be adapted by

modifying the instructions of the computer program.

An exemplary control unit (the control unit 112) is shown schematically in Fig. IB, wherein the control unit can

comprise a processing unit 120, which can consist of, for example, any suitable type of processor or microcomputer, such as a circuit for digital signal processing (Digital Signal Processor, DSP) or a circuit with a predetermined specific function (Application Specific Integrated Circuit, ASIC) . The processing unit 120 is connected to a memory unit 121, which provides the processing unit 120, with e.g. the stored program code 126 and/or the stored data that the processing unit 120 requires to be able to perform calculations. The processing unit 120 is also arranged so as to store partial or final results of calculations in the memory unit 121.

Furthermore, the control unit 112 is equipped with devices

122, 123, 124, 125 for receiving and transmitting input and output signals, respectively. These input and output signals can comprise waveforms, pulses or other attributes that the devices 122, 125 for receiving input signals can detect as information for processing by the processing unit 120. The devices 123, 124 for transmitting output signals are arranged so as to convert calculation results from the processing unit 120 into output signals for transfer to other parts of the vehicle control system and/or the component (s) for which the signals are intended. Each and every one of the connections to the devices for receiving and transmitting respective input and output signals can consist of one or more of a cable; a data bus, such as a CAN bus (Controller Area Network bus), a MOST bus (Media Oriented Systems Transport) or any other bus configuration, or of a wireless connection. Fig. 2 discloses the power electronics portion of fig. 1A more in detail. In the current example, and as is generally the case, the power source for providing power to the electrical machine is a direct current power supply of relatively high voltage, e.g. in the order of 300-1000 V. The power source 111, such as a battery pack or other suitable power source, is arranged to be selectively connectable to the electrical machine 110 by means of a pair of switches 205. The circuitry connecting the power source 111 and electrical machine 110 forms a power supply path, and the power source 111 is

connected to the electrical machine 110 via an inverter drive 119.

Electrical machines 110 of the disclosed kind are often arranged to be torque and/or speed controlled by means of an inverter drive system where inverter drives in general allow for rotational speed and torque control of the electrical machine by varying frequency and/or voltage and/or phase of the voltage being fed to the stator winding terminals.

According to the disclosed example, the electrical machine 110 is a three phase machine, hence having three phase windings, each phase voltage being controlled by associated switching means of the inverter drive 119. This is explained below. There exist various examples of inverter drives, and the present invention is suitable for use with any inverter drive solution providing a power path from the electrical machine in a direction towards the inverter drive. The electrical machine 110 of the present example is a permanent magnet synchronous three-phase machine. However, any suitable electrical machine can be used, as long as a voltage is induced when rotating the rotor of the electrical machine. Where required any suitable associated inverter drives can be used, where various kinds of inverter drives often exist for a particular kind of machine.

Inverter drives, in general, use a DC link voltage, also known as DC bus voltage, from which AC voltages of suitable

frequency and amplitude are formed. One or more capacitors are often used to smoothen the DC link voltage and/or enhance voltage stiffness of the DC link voltage. The DC link voltage is affected both by power drawn by the electrical machine and also by a rectified voltage resulting from the electrical machine, where this rectified voltage results in a voltage ripple, as is known per se. The above functionality is at least in part provided by capacitor CI in fig. 2. When a system of the kind shown in fig. 2 is to be started in a situation where the capacitor CI is essentially uncharged, the power source 111 cannot be directly connected to the capacitor CI by closing the switch pair 205. As is known, an uncharged capacitor acts as a short-circuit at the instant a voltage is applied which by definition, in theory, would result in an infinite initial current, and in practice a current that, likely damages or destroys the capacitor CI. For this reason, pre-charging circuits are usually used. Prior art pre-charging is disclosed in fig. 3A-B.

Fig. 3A-B shows a system similar to the system of fig. 2, with the difference that the switch pair 205 in fig. 2 is replaced by pre-charging circuitry 305 (shown more in detail in fig. 3B) . When the power source 311 is to be connected to inverter 319 in a situation where capacitor C is uncharged, switches 306, 307 are first closed, thereby allowing a current to flow from power source 311 to capacitor C via resistors Rl, R2.

The function of the pre-charging circuitry is to reduce or minimize the peak current from the power source at the moment of connection by reducing dV/dT over the capacitor CI. The use of resistors Rl, R2 ensure that the capacitor voltage will rise slowly and controllably with a maximum initial current that is not harmful. The resistors Rl, R2 thus ensures that the capacitor C is charged by means of a limited and suitable charging current. When the capacitor C has been charged to a suitable extent, e.g. when the voltage over the capacitor C has reached some suitable voltage, such as some suitable percentage of the voltage of the power source 311, e.g. 80- 100% of this voltage, the switches 308, 309 are closed so that capacitor C is connected directly in parallel to the power source 111. Systems of the kind disclosed in fig. 3A-B, consequently, require dedicated circuitry to protect components when

starting up the system. According to the present invention, as is shown in fig. 2, such additional circuitry can be omitted while still ensuring proper precaution with regard to charging currents when pre-charging capacitor CI.

An exemplary method 400 according to the invention is shown in fig. 4, which exemplifies a method for connecting the power source 111 to the inverter drive 119.

In step 401 it is determined whether the power supply path for connecting the power source 111 to the electrical machine 110 is to be closed. The method remains in step 401 for as long as this is not the case. When it is determined that the power supply path is to be closed, e.g. when the vehicle 100 is started and the power source 111 is to be used to power the electrical machine 110, or when the power source 111 is to be charged e.g. by regenerative braking using the electrical machine 110, the method continues to step 402, where it is determined whether pre-charging of the system is required.

According to one embodiment, pre-charging is performed when the DC link voltage V_DC is below a first voltage limit V_mi_n, which e.g. can be a voltage at which it is determined that no harmful currents occur upon closing of the switch 205. If the voltage is above the limit V_mi_n, the method continues to step

403 where switch 205 is closed, the power source 110 thereby being connected to the electrical machine 111. When the voltage is below said limit Vii_m, the method continues to step

404 for pre-charging the capacitor CI. According to the present invention, this is performed by inducing a voltage by means of the electrical machine 110. As was explained above, a rotation of the rotor of the electrical machine 110 will induce a voltage in the stator winding (a three-phase voltage will be induced by the phase windings in a three-phase

machine) which will be proportional to the rotational speed of the electrical machine 110.

Inverter drives of the kind disclosed in fig. 2, and inverter drives in general and with regard to hybrid vehicles in particular, allows power to flow in both directions through the inverter. This is made possible by diodes 231-236 being arranged anti-parallel to transistors 221-226. The diodes 231- 236 will rectify the voltage induced by the stator winding, and provide a rectified voltage exhibiting some ripple on the DC link, the rectified voltage, when transistors 221-226 are turned off, having an amplitude being proportional to the rotational speed of the electrical machine 110.

According to one embodiment, the (rotor of the) electrical machine 110 is rotated in step 404 to induce a voltage on the DC link via the rectifying diodes 231-236, which thereby will charge the capacitor CI to a capacitor voltage in the order of the induced voltage, where the current will be limited to the current induced in the stator windings. When the rotor is rotated such that substantially no torque is produced the induced current will be small, and hence the capacitor will not be subjected to harmful currents. The voltage can be controlled by speed of rotation of the electrical machine, which in turn can be controlled e.g. by controlling the rotational speed of the combustion engine 101. In step 405 it is determined whether the DC link voltage has reached desired level Vii_m, e.g. a voltage in the order of 80- 100% of the voltage of the power source 111, and rotation of the electrical machine continues for as long as this is not the case. When the DC link voltage equals or exceeds the desired level Vn_m the method continues to step 406 where the switch 205 is closed without the risk for damaging components. The method is then ended in step 407.

As mentioned, rotation of the electrical machine can be accomplished e.g. by means of the combustion engine 101, for example if the vehicle 100 is standing still. Alternatively, the electrical machine can be rotated by means of the vehicle drive wheels, where, in the present example, a suitable rotation speed can be obtained e.g. by controlling the gear ratio of the gearbox 103. Furthermore, when the DC link voltage has reached some voltage level, it will be possible to activate switching of the transistors, and according to one embodiment the DC link voltage can be further controlled to desired level by suitable switching of the induced voltage using the transistors 221-226.

With regard to the inverter drive exemplified in fig. 2, a plurality of transistors 221-226, such as e.g. IGBT (Insulated Gate Bipolar Transistor) transistors, are used to generate a supply voltage at the stator terminals of the electrical machine 110 my means of appropriate switching of the

transistors. According to the disclosed example, three pairs of transistors, 221-222; 223-224; and 225-226, respectively, each provide a phase voltage of the three-phase voltage, each phase-voltage having a controllable and variable frequency, voltage and phase by means of appropriate switching.

Inverter drives of the disclosed kind often uses Pulse Width Modulation (PWM) in order to accomplish the desired voltage and frequency, which means that the DC link voltage is switched on and off at high frequency (e.g. 1-10 kHz switching frequency) by means of the transistors 221-226, the PWM pattern forming a pulse train mimicking a sine wave of desired frequency and amplitude, as is well known to the person skilled in the art. These transistors, consequently, can also be used to control the DC link voltage using the induced voltage. So far, the invention has been described for pre- charging of capacitor CI, but there may be further and/or other rechargeable components that require pre-charging . For example, vehicles usually comprise a plurality of direct current DC applications and the DC power for powering the electric motor can be used also for powering such other components. For example, the voltage used for powering the electric motor can be converted to, e.g., 24V, (12 V or 48V) for conventional 24 V (12V, 48V) applications, such as cooling fans or conventional vehicle electronics in general. This is illustrated in fig. 2 by AUX power electronics 202- 204, where these often are provided with capacitors as well, which capacitors often are connected in parallel to the power supply path and consequently also can require and be pre- charged using the present invention.

Consequently, the present invention provides for a method for pre-charging sensitive components without the need for pre- charging circuitry.

Further, hitherto the invention has been described for a situation where the power source is to be connected from a disconnected state. The present invention, however can be used also in other situations, e.g. if the electrical machine is to be used for regenerative braking.

The electrical machine 111 can, in general, be used to apply braking powers, which can be used for charging e.g. the power source 111, but occasionally the power source can be fully charged, or charging otherwise be undesired. Still it can be desired to perform regenerative braking, e.g. in order to power auxiliary equipment or simply to dissipate the

regenerated power in a high-power resistor. Also, the power will be transported using the power supply path and hence subject capacitors to high voltages. In order to do this it must be possible to control the electrical machine, and hence the inverter must be in operation. This however, is only possible if the DC link voltage is high enough to allow operation of the transistors, and the present invention can be used also in such situations to pre-charge the capacitor CI, and other capacitors being connected to the DC link, first by the induced voltage alone and the also using switching of the transistors, thereby avoiding the need for connecting the power source 111 altogether in situations where e.g. power is to be dissipated using e.g. a power resistor. Finally, the technology disclosed above can be also be used to control the voltage when switching between different power supply paths for powering an electrical machine, where the power supply paths have different power supply voltages. This is further disclosed in the parallel Swedish patent

application no. 145xxxx-x, with the title "METHOD AND SYSTEM FOR SWITCHING FROM A FIRST POWER SUPPLY PATH TO A SECOND POWER SUPPLY PATH". This application relates to a method for

switching power supply path of at least one electrical

machine, where the electrical machine is arranged to be selectively power supplied by a first power supply path and a second power supply path, respectively, by alternately opening and closing said power supply paths. The power supply paths are arranged to connect a power supply source to a first connection terminal means of the electrical machine. The disclosed method includes, when switching from the first power supply path to the second power supply path:

- opening the first power supply path;

- by means of said electrical machine, controlling a terminal voltage of said first connection terminal means to

substantially a power supply voltage of the second power supply path, and;

- closing said second power supply path.

Finally, it should be understood that the present invention is not limited to the embodiments described above, but relates to and incorporates all embodiments within the scope of the appended independent claims.

Claims

Method for pre-charging a first rechargeable component (CI) in a vehicle (100), said first rechargeable

component (CI) being pre-charged by applying a voltage to said first rechargeable component (CI), said vehicle (100) comprising at least one electrical machine (110) being arranged to be connected to a first power supply path, said first rechargeable component (CI) being subjected to a voltage (V_DC) of said first power supply path, characterised in that said method includes, when said first rechargeable component (CI) is to be pre- charged :

- charging said first rechargeable component (CI) by applying a voltage over said first rechargeable component (CI) by means of said electrical machine (110) .

Method according to claim 1, said electrical machine (110) being arranged to be connected to a first power source (111) by means of said first power supply path, the method further including:

- pre-charging said first rechargeable component (CI) when said first power source (111) is disconnected from said first rechargeable component (CI) .

Method according to claim 1 or 2, further including:

- pre-charging said first rechargeable component (CI) by means of said electrical machine (110) when said first rechargeable component (CI) is in an essentially

uncharged state.

Method according to any one of claims 1-3, further including :

- pre-charging said first rechargeable component (CI) by means of said electrical machine (110) when the voltage over said first rechargeable component (CI) is

essentially zero.

5. Method according to any one of claims 1-4, further

including :

- pre-charging said first rechargeable component (CI) by means of said electrical machine (110) at least when the voltage over said first rechargeable component (CI) is less than 10% of a nominal, or normal operating, voltage of said first power supply path. 6. Method according to any one of claims 1-5, wherein said electrical machine (110) is controllable by means of power electronic switching means, further including:

- pre-charging said first rechargeable component (CI) by means of said electrical machine (110) to a voltage allowing activation of said power electronics switching means .

7. Method according to any one of the claims 1-6, further including :

- pre-charging said first rechargeable component (CI) by means of a voltage being induced by rotation of a rotor of said electrical machine (110) .

8. Method according to claim 7, further including:

- said induced voltage being induced in a stator winding of said electrical machine (110) by rotation of said rotor of said electrical machine (110) .

9. Method according to any of the claims 1-8, further

including, when pre-charging said first rechargeable component :

- controlling rotation of a rotor of said electrical machine (110) .

10. Method according to claim 9, said vehicle (100) including means for rotating said rotor of said electrical machine (110), further including:

- controlling rotation of a rotor of said electrical machine (110) using said means for rotating said rotor of said electrical machine.

11. Method according to claim 10, said means for rotating said rotor of said electrical machine (110) being a combustion engine. 12. Method according to any one of the preceding claims,

further including, during pre-charging of said first rechargeable component (CI) :

- successively increasing the voltage applied over said first rechargeable component (CI) . 13. Method according to any one of the preceding claims,

- increasing the voltage applied over said first

rechargeable component (CI) by increasing the rotational speed of the rotor of said electrical machine (110) .

14. Method according to any one of the claims 1-13, said

vehicle further including an inverter drive (119) for controlling frequency and/or phase and/or amplitude of a stator terminal voltage of said electrical machine (110), said inverter drive further including means (231-236) for rectifying an AC voltage induced by said electrical machine (110), said method further including:

- pre-charging said first electrical component (CI) using said rectified AC voltage. 15. Method according to claim 14, said inverter drive (119) further including switching means (221-226) for varying frequency and/or voltage of an AC voltage for controlling said electrical machine, further including:

- controlling the amplitude of the voltage being applied to said first rechargeable component (CI) using said switching means (221-226) .

16. Method according to any one of the preceding claims, said first rechargeable component being a capacitor (CI) .

17. Method according to claim 14 or 15, said first

rechargeable component being a DC link capacitor for stabilising the DC link voltage of said inverter drive

(119) .

18. Method according to any one of the preceding claims,

further including, when pre-charging said first

rechargeable component :

- controlling the current said first electrical component

(CI) being subjected to by controlling the power

delivered by said electrical machine (110) .

19. Method according to any one of the preceding claims, said method further including, when said electrical machine (110) is to be connected to a first power source (111) for providing electrical power to said electrical machine (110) :

- controlling the voltage of said first component (CI) to at least 80% of the voltage of said first power source (111) prior to connecting said first power source (111) .

20. Method according to any one of the preceding claims, said electrical machine being arranged to provide a propelling torque and or a brake torque to at least one drive wheel of said vehicle.

21. Method according to any one of the preceding claims, said electrical machine consisting of a permanent magnet machine .

22. Computer program comprising program code that, when said program code is executed in a computer, causes said computer to carry out the method according to any of claims 1-21.

23. Computer program product comprising a computer-readable medium and a computer program according to claim 22, wherein said computer program is contained in said computer-readable medium.

24. System for pre-charging a first rechargeable component (CI) in a vehicle (100), said first rechargeable

component (CI) being pre-charged by applying a voltage to said first rechargeable component (CI), said vehicle

(100) comprising at least one electrical machine (110) being arranged to be connected to a first power supply path, said first rechargeable component (CI) being subjected to a voltage (V_DC) of said first power supply path, characterised in that said system includes, when said first rechargeable component (CI) is to be pre- charged :

- means for charging said first rechargeable component (CI) by applying a voltage over said first rechargeable component (CI) by means of said electrical machine (110) .

25. Vehicle, characterised in that it comprises a system

according to claim 24.