WO2011089563A2

WO2011089563A2 - A switching device

Info

Publication number: WO2011089563A2
Application number: PCT/IB2011/050261
Authority: WO
Inventors: Christopher Lewis
Original assignee: Protean Electric Limited
Priority date: 2010-01-22
Filing date: 2011-01-20
Publication date: 2011-07-28
Also published as: GB201001044D0; GB2477128A; GB2477128B; WO2011089563A3

Abstract

A switching device for a vehicle having a DC power source and an electric motor arranged to drive the vehicle, the switching device comprises a plurality of switches and a controller, wherein the controller is arranged to configure the plurality of switches to operate in one of three modes of operation, wherein in the first mode of operation the plurality of switches are arranged to convert a DC voltage generated by the DC power source into a first AC voltage for powering the electric motor, in the second mode of operation the plurality of switches are arranged to convert the DC voltage generated by the DC power source into a second AC voltage for use external to the vehicle, and in the third mode of operation the plurality of switches are arranged to convert an AC voltage generated by a source external to the vehicle into a DC voltage for charging the DC power source.

Description

A SWITCHING DEVICE

The present invention relates to a switching device, and in particular a switching device for a vehicle having a DC power source with an electric motor arranged to drive the vehicle .

With increased interest being placed in environmentally friendly vehicles there has, perhaps unsurprisingly, been a corresponding increase in interest in the use of electric vehicles, where an electric vehicle will typically include one or more electric motors and a power source, for example a battery.

To allow the operation of an electric vehicle, electric vehicles will typically include a number of different electric circuits. For example, for a vehicle having an induction motor or a permanent magnet synchronous electric motor an inverter is typically used to convert a DC voltage provided by the vehicles battery into an AC voltage for driving the one or more electric motors. Further, a charging circuit may be used to convert an external AC power source into a DC power source suitable for charging the vehicles battery .

Additionally, there have been suggestions of the possibility of providing charge stored in an electric vehicles battery to the national grid, thereby potentially reducing the burden upon other electric sources, which inevitably would require further circuitry within the vehicle .

However, with the continuing drive to maximise usable occupancy space within vehicles this inevitably places greater space restraints on mechanical and electrical components within vehicles. In accordance with an aspect of the present invention there is provided a switching device according to the accompanying claims. By having a switching arrangement that includes a plurality of switches, where the plurality of switches are arranged to perform a number of different function, this minimises the circuitry requirements for a vehicle and consequently minimises the space required within a vehicle for components.

The present invention will now be described, by way of example, with reference to the accompanying drawings, in which :

Figure 1 illustrates a vehicle according to an

embodiment of the present invention;

Figure 2 illustrates an exploded view of an electric motor as used in an embodiment of the present invention;

Figure 3 illustrates an exploded view of the electric motor shown in figure 2 from an alternative angle; Figure 4 schematically shows an example for a three phase motor used in an embodiment of the present invention;

Figure 5 illustrates an H-bridge inverter circuit; Figure 6 illustrates a switching arrangement according to a first embodiment of the present invention;

Figure 7 illustrates a switching arrangement according to a second embodiment of the present invention.

Figure 1 illustrates a vehicle 100, for example a car or lorry, having four wheels 101, where two wheels are located in the vehicles forward position in a near side and off side position respectively. Similarly, two additional wheels are located in the vehicles aft position in near side and off side positions respectively, as is typical for a conventional car configuration. However, as would be

appreciated by a person skilled in the art, the vehicle may have any number of wheels.

Incorporated within each wheel 101 is an in-wheel electric motor, as described in detail below. Although the current embodiment describes a vehicle having an in-wheel electric motor associated with each wheel 101, as would be appreciated by a person skilled in the art a central

electric motor or motors may be used in place of the in- wheel electric motors or only a subset of the wheels 101 may have an associated in-wheel electric motor. For example, for a four wheeled vehicle only the front two wheels may have associated in-wheel motors or alternately only the rear two wheels may have associated in-wheel motors.

Coupled to each in-wheel electric motor is a master controller 102 for controlling the operation of the in-wheel electric motors. Additionally, the vehicle includes a battery 120 for providing a power source for the in-wheel electric motors and an interface port 110 for allowing the battery 120 to be charged from a power source external to the vehicle or for providing charge from the battery 120 for use external to the vehicle, as described in detail below.

For the purpose of illustration the in-wheel electric motor is of the type having a set of coils being part of the stator for attachment to the vehicle, radially surrounded by a rotor carrying a set of magnets for attachment to a wheel. However, as would be appreciated by a person skilled in the art, the present invention is applicable to other types of electric motors.

As illustrated in figure 2, the in-wheel electric motor 40 includes a stator 252 comprising a rear portion 230 forming a first part of the housing of the assembly, and a heat sink and drive arrangement 231 comprising multiple coils and electronics to drive the coils. The coil drive arrangement 231 is fixed to the rear portion 230 to form the stator 252 which may then be fixed to a vehicle and does not rotate during use. The coils themselves are formed on tooth laminations which together with the drive arrangement 231 and rear portion 230 form the stator 252. A rotor 240 comprises a front portion 220 and a

cylindrical portion 221 forming a cover, which substantially surrounds the stator 252. The rotor includes a plurality of magnets 242 arranged around the inside of the cylindrical portion 221. The magnets are thus in close proximity to the coils on the assembly 231 so that magnetic fields generated by the coils in the assembly 231 cooperate with the magnets 242 arranged around the inside of the cylindrical portion 221 of the rotor 240 to cause the rotor 240 to rotate. The rotor 240 is attached to the stator 252 by a bearing block 223. The bearing block 223 can be a standard bearing block as would be used in a vehicle to which this motor assembly is to be fitted. The bearing block comprises two parts, a first part fixed to the stator and a second part fixed to the rotor. The bearing block is fixed to a central portion 233 of the wall 230 of the stator 252 and also to a central portion 225 of the housing wall 220 of the rotor 240. The rotor 240 is thus rotationally fixed to the vehicle with which it is to be used via the bearing block 223 at the central portion 225 of the rotor 240. This has an advantage in that a wheel rim and tyre can then be fixed to the rotor 240 at the central portion 225 using the normal wheel bolts to fix the wheel rim to the central portion of the rotor and consequently firmly onto the rotatable side of the bearing block 223. The wheel bolts may be fitted through the central portion 225 of the rotor through into the bearing block itself. With both the rotor 240 and the wheel being mounted to the bearing block 223 there is a one to one correspondence between the angle of rotation of the rotor and the wheel. Figure 3 shows an exploded view of the same assembly as

Figure 2 from the opposite side showing the stator 252 comprising the rear stator wall 230 and coil and electronics assembly 231. The rotor 240 comprises the outer rotor wall 220 and circumferential wall 221 within which magnets 242 are circumferentially arranged. As previously described, the stator 252 is connected to the rotor 240 via the bearing block at the central portions of the rotor and stator walls.

Additionally shown in Figure 2 are circuit boards 80 carrying control electronics, otherwise known as motor drive controllers .

A V shaped seal 350 is provided between the

circumferential wall 221 of the rotor and the outer edge of the stator housing 230.

The rotor also includes a focussing ring and magnets 227 for position sensing, which in conjunction with sensors mounted on the stator allows for an accurate position determination of the rotor relative to the stator to be made .

The electric motor 40 shown in Figures 2 and 3 is a three phase motor having three coil sets. In this

embodiment, each coil set includes eight coil sub-sets.

However, as would be appreciated by a person skilled in the art, the electric motor could have any number of coil sets and coil sub-sets. The coil sub-sets of each coil set are labelled 44, 46 and 48, respectively in Figure 4.

Accordingly, the electric motor illustrated in Figure 4 has a total of twenty four coil sub-sets (i.e. eight coil sub- sets per coil set) .

By way of example, in Figure 4 some of the coil sub^¬ sets are highlighted with a '*'. If these coil sub-sets were to be powered down, the motor would still be able to operate, albeit with reduced performance. In this way, the power output of the motor can be adjusted in accordance with the requirements of a given application. In one example, where the motor is used in a vehicle such as a car, powering down of some of the coil sub-sets can be used to adjust the performance of the car. In the example shown in Figure 4, if each of the coil sub-sets indicated with an ' * ' were powered down the motor would have three coil sets with each coil set having two active coil subsets. A motor drive controller 80 is arranged to drive a group of three coil subsets under control from the master controller 102. For example, a motor drive controller can be associated with the first three coil subsets 44, 46, 48 located at the top of Figure 4. Another motor drive

controller 80 is associated with the next three coil subsets, and so on. Accordingly, the in-wheel electric motor includes eight motor drive controllers 80 arranged to drive the respective coil subsets to form a distributed internal motor architecture that uses multiple motor drive

controllers 80 for controlling the torque generated by the in-wheel electric motor.

The distributed motor drive controller configuration, where each motor drive controller 80 drives a group of three coil sub-sets with a three phase voltage, can be regarded as a group of logical sub motors. Each logical sub-motor can be driven independently of the other sub motors within the in- wheel electric motor under the control of the associated motor control unit, with each logical sub-motor being driven as a three phase motor.

Although the in-wheel electric motor described in the present embodiment includes a plurality of logical sub- motor, as person skilled in the art would appreciate the electric motor may be of a conventional design without the use of logical sub-motors.

The motor drive controller 80, which acts as an

inverter for the associated logical sub-motor, includes a number of switches which may typically comprise one or more semiconductor devices.

In this embodiment, each motor drive controller 80 is substantially wedge-shaped. This shape allows multiple motor drive controllers 80 to be located adjacent each other within the motor, forming a fan-like arrangement.

The motor drive controller 80 switches can include semiconductor devices such as MOSFETs or IGBTs. In the present example, the switches comprise IGBTs. However, any suitable known switching circuit can be employed for controlling the current. One well known example of such a switching circuit is the H-bridge circuit having six

switches configured to drive a three phase electric motor. The six switches are configured as three parallel sets of two switches, where each pair of switches is placed in series and from a leg of the H-bridge circuit. Figure 5 illustrates an example of an H-bridge circuit 400 coupled to three coil subsets.

As illustrated in Figure 6, a plurality of switches are coupled to the motor drive controller inverter switches 400 to form a switch arrangement that can be configured by the master controller 102 to operate in one of three modes. Although, Figure 6 illustrates the plurality of switches being coupled to a single inverter 400, a similar switch configuration could optionally be coupled to other inverter switches associated with other electric motors or to other inverters within the same in-wheel electric motor.

The inverter switches 400 of a motor drive controller associated with a logical sub-motor are coupled to four sets of switches.

The first, third and fifth inverter H bridge switches 401, 403, 405 are coupled to a positive power line. The second, fourth and sixth inverter H bridge switches 402, 404, 406 are coupled to a negative power line.

The inverter has three output lines 461, 462, 463, where each output line is derived from the mid-point between each pair of switches placed in series, as is well known to a person skilled in the art.

Each of the three inverter output lines 461, 462, 463 are coupled to a first set of switches 410, where the first set of switches 410 can be configured to couple or isolate the three inverter output lines 461, 462, 463 to the

respective coil subsets of a logical sub-motor electric motor 40.

Additionally, two of the inverter output lines 461, 462 are coupled to a second set of switches 420 that allow the two output lines 461, 462 to be coupled to separate

terminals on the interface port 110. The third inverter output line 463 is coupled to a third switch 430 that is configured to couple or isolate the third output line 461 to the positive terminal of the battery 120 (i.e. the traction battery) . The positive power line is coupled to a fourth switch 440 for coupling the positive power line to the positive terminal of the battery 120. Preferably, the positive power line is also coupled to a main contact 450, for example an ignition switch, which also allows the positive power line to be coupled to the positive terminal of the battery 120.

The operation of the switch arrangement (i.e. the first, second, third, fourth set of switches 410, 420, 430, 440 and the inverter switches 400) and the main contact 450 are controlled via the master controller 102. However, the control function of the switch arrangement can be

distributed between different control modules, for example between the master controller 102 and a motor drive

controller 80.

Typically a fuse 470 is placed between the switch arrangement and the battery 120 with preferably a further fuse being placed in line between the fuse 470 and the fourth switch 440.

By selective operation of the switches that form the switch arrangement, the embodiment illustrated in Figure 6 can be configured to operate in one of the following modes.

In a first mode of operation the main contact 450 and the first set of switches 410 are closed, thereby allowing the inverter switches 400 to control the voltage supply to the in-wheel electric motor, or logical sub motor. The second set of switches 420 and the third and fourth switches 430, 440 are placed in an open position.

In this mode of operation the controller 102 is arranged to operate the inverter switches 400 in accordance with a pulse width modulation scheme for controlling the torque of the in-wheel electric sub motor, as is well known to a person skilled in the art. In a second mode of operation, the first, second, third and fourth set of switches 410, 420, 430, 440 and the inverter 400 are configured to provide charge to the battery 120.

In this mode of operation, the fourth switch 440, the main contact 450 and the first set of switches 410 are opened and the third switch 430 and second set of switches 420 are closed and an external single phase power supply is coupled to the interface port 110, thereby providing a single phase voltage across two legs of the inverter 400. If a domestic single phase voltage supply is coupled to the interface port 110 the voltage at the interface port will typically be between 120V and 240V. If the battery voltage needs to be charged at a higher voltage a transformer (not shown) may also be used with the external power supply to step the voltage up as required, this has the additional advantage of providing galvanic isolation of the vehicle from the external voltage supply.

The controller 102 is arranged to operate four inverter switches 410, 402, 403, 404, which form the two legs of the inverter across which the single phase voltage is provided across, to rectify the single phase voltage. The controller 102 is arranged to operate the two inverter switches 405,406 on the third leg of the inverter 400 to provide a pulse width modulated DC voltage that is provided to the battery 120 to allow charging of the battery 120. The DC voltage is pulse width modulated to control the voltage/current profile provided to the battery 120 to ensure optimum charging of the battery 120.

In a third mode of operation the switch arrangement is configured to allow battery charge to be used externally to the vehicle, for example for providing charge back to the national grid or for domestic use within a residence. In this mode of operation, the first set of switches 410 and the third switch 403 are opened and the fourth switch 440 and second set of switches 402 are closed. As the positive power line is coupled to the battery 120 via the fourth switch 440 the main contactor 450 can either be opened or closed. However, as the main contractor 450 is likely to be under key switch control the main contactor 450 is likely to remain open during stationary activities.

The controller 102 is arranged to operate four inverter switches 401, 402, 403, 404, which form the two legs of the inverter 400 that are coupled to the interface port 110, to generate an ac phase voltage that is synthesised by PWM control from the DC voltage supply provided by the battery 120.

When providing charge to the national grid, preferably the second set of switches 420 should be closed only when the synthesised ac waveform is substantially equal in frequency, phase and amplitude to the national grids voltage waveform. For this to be achievable the battery terminal voltage must be greater than the peak-to-peak national grids voltage. Alternatively, if a transformer is placed in line between the switching arrangement and the national grid, the battery terminal voltage only needs to be a percentage of the peak-to-peak national grids voltage, as determined by the winding ratio of the transformer. Once the second set of switches 420 are closed the inverter switches 401, 402, 403, 404 can be controlled so that the synthesised waveform amplitude is increased to enable current flow into the national grid.

If the peak to peak voltage supply of the national grid becomes greater than the battery terminal voltage, or a percentage of the peak-to-peak national grids voltage based upon the winding ratio of a transformer placed in line between the switch arrangement and the national grid, the fourth switch 440 may be opened and the second switch 420 closed to allow the battery to be charged. Thus a

bidirectional charger/provider function is possible.

Figure 7 illustrates a second embodiment, where the switch arrangement includes two three phase inverters 400 for providing three modes of operation.

The use of two three phase inverters 400 provides the advantage of allowing the switch arrangement to generate a three phase voltage supply, which can be made available at the interface port, and to allow charging of the battery 120 from an external three phase voltage supply.

The first, third and fifth inverter H bridge switches 401, 403, 405, 407, 409, 411 on the first and second

inverters 400 are coupled to a positive power line. The second, fourth and sixth inverter H bridge switches 402, 404, 406, 408, 410, 412 on the first and second inverters 400 are coupled to a negative power line.

The first and second inverters 400 have three output lines respectively, where each output line is derived from the mid-point between each pair of switches placed in series, as is well known to a person skilled in the art.

Each of the three inverter output lines on the first and second inverters 400 are coupled to a first set of switches 410 respectively, where the first set of switches 410 can be configured to couple or isolate the three

inverter output lines on each inverter to the respective coil subsets of a respective logical sub-motor electric motor 40.

Additionally, the three inverter output lines on the first inverter 400 are coupled to a second set of switches 420 that allow the three output lines to be coupled to the interface port 110.

The three inverter output lines on the second inverter 400 are coupled to a third set of switches 403 that are configured to couple or isolate the three output lines to the positive terminal of the battery 120 (i.e. the traction battery) . Although, Figure 7 illustrates that each of the inverter output lines on the second inverter 400 are be coupled, via the third set of switches 430, to the positive terminal of the battery 120, only one output line is required .

The positive power line is coupled to a fourth switch 440 for coupling the positive power line to the positive terminal of the battery 120. Preferably, the positive power line is also coupled to a main contact 450, for example via an ignition switch, which also allows the positive power line to be coupled to the positive terminal of the battery 120.

controller 80.

By selective operation of the switches that form the switch arrangement, the embodiment illustrated in Figure 7 can be configured to operate in one of the following modes. In a first mode of operation the main contact 450 and the first set of switches 410 are closed, thereby allowing the inverter switches on the first and second inverters 400 to control the voltage supply to a respective in-wheel electric motor, or logical sub motor. The second set of switches and the third and fourth switches 430 are placed in an open position.

In this mode of operation the controller 102 is arranged to operate the inverter switches in accordance with a pulse width modulation scheme for controlling the torque of the in-wheel electric motors, as is well known to a person skilled in the art.

In a second mode of operation, the first, second, third and fourth set of switches and the inverter 410, 420, 430, 440, 400 are configured to provide charge to the battery

In this mode of operation, the fourth switch 440, the main contact 450 and the first set of switches 410 are opened and the third set of switches 430 and second set of switches 420 are closed and an external single phase power supply is coupled to respective terminals of the interface port 110, thereby providing a three phase voltage across the three legs of the first inverter 400. If the battery needs to be charged at a higher voltage than that being provided to the first inverter 400, a transformer (not shown) may also be used with the external power supply to step the voltage up as required, this has the additional advantage of providing galvanic isolation of the vehicle.

The controller 102 is arranged to operate the six inverter switches 401, 402, 403, 404, 405, 406, which form the three legs of the first inverter 400 across which the three phase voltage is provided, to rectify the three phase voltage. The controller 102 is arranged to operate the inverter switches on the second inverter 400 to provide a pulse width modulated DC voltage that is provided to the battery 120 to allow charging of the battery 120. The DC voltage is pulse width modulated to control the voltage/current profile provided to the battery 120 to ensure optimum charging of the battery.

In a third mode of operation the switch arrangement is configured to allow battery charge to be used externally to the vehicle in the form of a three phase voltage supply, for example for providing charge back to the national grid.

In this mode of operation, the first set of switches 410 and the third set of switches are opened and the fourth switch 440 and second set of switches 420 are closed. As the positive power line is coupled to the battery 120 via the fourth switch 440 the main contact 450 can either be opened or closed. However, as the main contractor 450 is likely to be under key switch control the main contactor 450 is likely to remain open during stationary activities.

The controller 102 is arranged to operate the six inverter switches that form the first inverter 400 to generate a three phase ac voltage that is synthesised by PWM control from the DC voltage supply provided by the battery 120.

When providing charge to the national grid, preferably the second set of switches 420 should be closed only when the synthesised ac waveform is substantially equal in frequency, phase and amplitude to the national grids voltage waveform. For this to be achievable the battery terminal voltage must be greater than the peak-to-peak national grids voltage. Alternatively, if a transformer is placed in line between the switching arrangement and the national grid, the battery terminal voltage only needs to be a percentage of the peak-to-peak national grids voltage, as determined by the winding ratio of the transformer. Once the second set of switches 420 are closed the inverter switches can be controlled so that the synthesised waveform amplitude is increased to enable current flow into the national grid.

If the peak to peak voltage supply of the national grid becomes greater than the battery terminal volt, or a percentage of the peak-to-peak national grids voltage based upon the winding ratio of a transformer placed in line between the switch arrangement and the national grid, the fourth switch 440 may be opened and the second set of switches 420 closed to allow the battery 120 to be charged. Thus a bidirectional charger/provider function is possible.

Claims

1. A switching arrangement for a vehicle having a DC power source and an electric motor arranged to drive the vehicle, the switching device comprises a plurality of switches and a controller, wherein the controller is arranged to configure the plurality of switches to operate in one of three modes of operation, wherein in the first mode of operation the plurality of switches are arranged to convert a DC voltage generated by the DC power source into a first AC voltage for powering the electric motor, in the second mode of operation the plurality of switches are arranged to convert the DC voltage generated by the DC power source into a second AC voltage for use external to the vehicle, and in the third mode of operation the plurality of switches is arranged to convert an AC voltage generated by a source external to the vehicle into a DC voltage for

charging the DC power source.

2. A switching arrangement according to claim 1, wherein the plurality of switches include a first set of switches, a second set of switches and a third set of switches that are configured by the controller to provide the three modes of operation.

3. A switching arrangement according to claim 2, wherein in the first mode of operation the first set of switches are configured as an inverter circuit for

converting a DC voltage generated by the power source into the first AC voltage for powering the electric motor, and the second set of switches are arranged to couple the first AC voltage to the electric motor.

4. A switching arrangement according to claim 2, wherein in the second mode of operation the first set of switches are configured as an inverter circuit arranged to convert the DC voltage generated by the DC power source into the second AC voltage for use external to the vehicle, the second set of switches are arranged to electrically isolate the first set of switches from the electric motor, and the third set of switches are arranged to couple at least a subset of the first set of switches to an interface to allow access to the second AC voltage.

5. A switching arrangement according to claim 4, wherein in the third mode of operation the third set of switches are arranged to couple at least a subset of the first set of switches to the interface to allow an external AC voltage source to be provided to the first set of

switches, wherein the first set of switches are arranged to convert the external AC voltage source into a DC voltage with one or more switches configured to couple the first set of switches to the DC power source for charging the DC power source .

6. A switching arrangement according to any one of claims 3 to 5, wherein the first set of switches are

arranged to control the voltage of the first AC voltage and the second AC voltage using pulse width modulation.

7. A switching arrangement according to claims 3 to 6, wherein the first set of switches are configured as a three phase inverter when in the first mode of operation and a single phase inverter when in the second mode of

operation .

8. A switching arrangement according to claims 3 to

6, wherein the first set of switches are configured as a three phase inverter when in the first mode of operation and a three phase inverter when in the second mode of operation.

9. A switching arrangement according to claims 3 to

6, wherein the first set of switches are configured as a plurality of inverters associated with a respective

plurality of electric motors.

10. A vehicle comprising a DC power source, and electric motor arranged to drive the vehicle and a switching arrangement according to any one of the preceding claims.

11. A vehicle according to claim 10, wherein the electric motor is an in-wheel electric motor.

12. A vehicle according to claim 11 when claim 10 is dependent on any one of claims 2 to 9, wherein the first set of switches are mounted to the in-wheel electric motor.