CN114829188A

CN114829188A - Electric vehicle powertrain bus management

Info

Publication number: CN114829188A
Application number: CN202080088694.2A
Authority: CN
Inventors: S.格雷瑟姆
Original assignee: Dyson Technology Ltd
Current assignee: Dyson Technology Ltd
Priority date: 2019-12-19
Filing date: 2020-11-16
Publication date: 2022-07-29
Also published as: GB201918794D0; WO2021123723A1; GB2590458A

Abstract

An electric vehicle comprises a battery pack (1) for powering a first vehicle system (9) and a second vehicle system (9 a). The battery pack includes a first subgroup, a second subgroup, a first auxiliary bus bar (8) connected to the first subgroup, and a second auxiliary bus bar (8a) connected to the second subgroup. The first vehicle system (9) is connected to a first auxiliary bus (8), the second vehicle system (9a) is connected to a second auxiliary bus (8a), and the first and second vehicle systems each perform the same vehicle function.

Description

Electric vehicle powertrain bus management

Technical Field

The present invention relates to an electric vehicle powertrain and related method of bus management in an electric vehicle.

Background

Electric vehicles, as considered herein, include both vehicles powered solely by a battery pack and vehicles in which the battery pack is one of a plurality of alternative power sources (e.g., hybrid vehicles), including battery packs that need to provide sufficient power to drive the vehicle. In the case of a pure electric vehicle, the current from the battery drives the motor through an inverter. The battery of an electric vehicle will also typically power a number of subsystems within the vehicle.

While some subsystems will be driven by the main high voltage bus and inverter, while others are low power DC systems typically driven by a 12V DC bus, the power being obtained by a separate battery or by step-down conversion using a DC-DC converter, there are others (e.g., HVAC system compressors) that are most efficiently driven by higher power DC systems, which have lower voltages than those used for the inverter. The higher power DC system may be, for example, a 400V auxiliary bus. This may be used to operate components of the vehicle, such as an air conditioning system compressor.

Disclosure of Invention

Accordingly, in a first aspect, the present invention provides an electric vehicle comprising a battery pack, a first vehicle system powered by the battery pack and a second vehicle system powered by the battery pack, wherein: the battery pack includes a first sub-group, a second sub-group, a first auxiliary bus bar connected to the first sub-group, and a second auxiliary bus bar connected to the second sub-group; the first vehicle system is connected to the first auxiliary bus; the second vehicle system is connected to the second auxiliary bus; and the first and second vehicle systems each perform the same vehicle function.

This arrangement may allow equipment required for vehicle functions to be operated from the auxiliary bus even if there is a significant fault. In an embodiment, the battery pack is configured such that in case of a failure of the first vehicle system or the first sub-group, the vehicle function continues to be provided by the second vehicle system and the second sub-group. This may allow the vehicle systems most suitably located on the auxiliary bus to be located there without losing the necessary functionality in the event of a related failure of the auxiliary bus or sub-group.

Such an electric vehicle may comprise a motor unit for providing a power drive, wherein the battery pack comprises a main bus on which the first and second subsets are connected in series and the motor unit is connected to the main bus in a normal operation mode. A first voltage may be provided on the main bus and a second, lower voltage may be provided on each of the first and second auxiliary buses. In case of a failure of the first subgroup, the second lower voltage may then continue to be provided on the second auxiliary bus. A second, lower voltage may then also be provided on the main bus.

In an embodiment, the battery pack further comprises a diagnostic circuit for diagnosing a fault condition of one or more contactors of the battery system.

In the case where the motor unit is driven by the main bus bar as described above, the battery pack may be configured between a first configuration in which two sub-groups are connected in series on the main bus bar and a second configuration in which the sub-groups are connected in parallel. This may be beneficial because it may enable proper configuration of the subgroups for charging (e.g. in series) and discharging (e.g. in parallel).

The battery pack may then comprise a first path across the main bus bar comprising the first subgroup and a second path across the main bus bar comprising the second subgroup, wherein the battery pack further comprises a central path connecting the first path to the second path, the central path being provided with a central switch for switching the battery pack between the first configuration and the second configuration. Each of the first path and the second path may then comprise a high voltage side and a low voltage side on both sides of its connection to the central path, wherein the first subset is arranged on the high voltage side of the first path and the second subset is arranged on the low voltage side of the second path, wherein the first branch switch is arranged on the low voltage side of the first path and the second branch switch is arranged on the high voltage side of the second path. There may also be a switch bank for disabling or enabling the current of the subset in series with each of the first and second subsets and on the same voltage side as the subset. Each such switch bank may include a main switch in parallel with a series combination of a pre-charge resistor and a pre-charge switch.

In such an arrangement, the motor unit may be coupled to the main bus and operate at a first electrical power when the subset is in the first configuration and at a second, lower electrical power when the subset is in the second configuration. The electric vehicle may be in a limp home mode with the motor unit operating at the second electric power.

For each auxiliary bus, the connection of the battery system to the auxiliary bus may include a respective auxiliary bus switch. The first vehicle system may be an air conditioning compressor, although various other vehicle systems may be provided in this manner. The second vehicle system may include an air conditioning compressor.

In a second aspect, the present invention provides a method of operating an electric vehicle as described in the first aspect above, comprising: a failure of the first vehicle system or the first sub-battery pack is detected, and the vehicle functions previously provided by the first vehicle system continue to be provided by the second vehicle system and the second battery module.

The failure of the first sub-group may comprise a failure of the battery pack preventing effective use of the first sub-group. The battery pack may comprise a diagnostic circuit for diagnosing a fault status of one or more switches of the battery pack, wherein detecting a fault may then comprise the diagnostic circuit diagnosing a fault of or associated with the first sub-group. Such an electric vehicle may comprise a motor unit for providing a power drive, the battery pack comprising a main bus to which a first subset and a second subset are connected in series in a normal operation mode and to which the motor unit is connected, wherein the main bus is connected across the second subset in case of a failure of the first subset. In this state, the electric vehicle may be operated in the limp home mode.

Drawings

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

fig. 1 is a first schematic diagram illustrating the arrangement of a battery pack suitable for use in a vehicle employing an embodiment of the invention;

fig. 2 is a schematic view of the internal structure of the battery pack shown in fig. 1;

fig. 3 illustrates an exemplary configuration circuit of a battery pack according to an embodiment of the present invention;

FIG. 4 illustrates a state machine of an embodiment of a high voltage system for an electric vehicle, wherein the battery is reconfigurable between 400V and 800V operation;

FIG. 5 shows further details of the diagnostic state of FIG. 4;

FIG. 6 shows a control channel state for use with the configuration circuit of FIG. 4 and an associated contactor configuration;

FIG. 7 depicts the transition of the state machine of FIG. 4 from a fully disconnected state to an 800V ready state;

FIG. 8 depicts the transition of the state machine of FIG. 4 from the 800V ready state to the motoring state;

FIGS. 9 and 10 depict the transition of the state machine of FIG. 4 from the motoring state to the 800V ready state and from the 800V ready state to the fully off state;

FIG. 11 depicts the transition of the state machine of FIG. 4 to a subgroup limp home state;

FIG. 12 depicts the disconnection of the state machine of FIG. 4 from a subgroup limp-home state to a fully disconnected state;

FIGS. 13 and 14 depict the transition from the fully off state to the 800V charged state and back again, respectively;

FIG. 15 depicts the transition of the state machine of FIG. 4 from a fully disconnected state to a 400V ready state;

FIG. 16 depicts the transition of the state machine of FIG. 4 from the 400V ready state to the 400V charged state;

FIGS. 17 and 18 depict the transition of the state machine of FIG. 4 from a fully disconnected state to a subgroup 400V ready state and back again;

FIG. 19 depicts the transition of the state machine of FIG. 4 from the 400V ready state to the fully disconnected state; and

fig. 20 depicts the state machine of fig. 4 transitioning from the subgroup 400V ready state to the fully disconnected state.

Detailed Description

Fig. 1 shows the arrangement of a battery pack 1, and an embodiment of the present invention may be used in an electric vehicle 10. Those skilled in the art will recognize that although described herein as a single unit, such a battery pack 1 may include components in separate housings and/or at separate locations within the vehicle, and thus the battery pack may also be considered a battery system.

The battery pack 1 is connected to the front motor unit 2 and the rear motor unit 3. These motor units include an inverter and a motor, and provide power drive for the vehicle. The battery 1 also provides power to the high voltage bus (or buses) of the vehicle. The high voltage bus provides power to high power systems (e.g., air conditioning systems) within the vehicle. The high voltage bus is connected to a DC-DC converter that provides a low power bus (again, there may be multiple low power buses) that typically operates at 12V.

The embodiment shown herein relates to an electric vehicle 10 in which a rechargeable cellular battery operates as the sole power source to power the vehicle, but embodiments of the invention may be used in other vehicle types in which battery power is used to power the vehicle for some or all of the time. For example, embodiments may be applied to hybrid vehicles, where the electric machine may be powered by another power source (e.g., an internal combustion engine) and a battery, or to other forms of electric vehicles where energy is provided by another power source (e.g., a fuel cell), but the battery is an intermediary between the power source and the electric motor.

In this case, the battery pack 1 may be configured to provide 800V or 400V-which allows charging at 800V or 400V in particular, but also 800V and 400V output (with 800V output, the 400V output may be provided by tapping the output at an intermediate voltage). The high voltage bus can then provide 800V or 400V output, while the lower power bus typically provides 12V output to drive electronics and other low power vehicle systems. As will be described in more detail below, in embodiments of the invention, the bus bar system may be more complex in structure than a monolithic high voltage bus bar providing a single supply voltage-for example, the high voltage bus bar may be associated with a lower (but still high) voltage auxiliary bus bar, such as may be used in drive systems, such as air conditioning compressors, that require a significant drive voltage, but less than the optimum voltage for driving a vehicle motor. Although general reference is made below to use of reconfiguring between 800V and 400V states, in other embodiments different specific voltage values may be used — for example, the higher voltage may be 1000V and the lower voltage may be 500V.

In order to provide the configurable properties of the battery pack 1, the battery pack 1 comprises a first subgroup 101 and a second subgroup 102 (which may also be referred to as half-pack in this embodiment). Each sub-pack 102, 102 may include one or more battery modules. The connections of these subgroups 101,102 may be changed according to various requirements using the configuration circuit 26, as shown in fig. 3. The configuration circuit 26 is controlled by a battery management system (not shown), which may be located at the battery pack 1, or at a location remote from the battery pack 1.

The configuration circuit 26 includes two

battery sub-packs

101 and 102. Configuring the circuit 26 allows them to be connected in series (to provide 800V) or in parallel (to provide 400V) or only a subset (again, to provide 400V). The output includes, either individually (when the two subgroups are connected in series) or in parallel (when the two subgroups are connected in parallel), a main bus 110 that typically receives 800V, a rear inverter 111 that typically will also receive 800V to drive the vehicle, and first and second

auxiliary buses

113 and 112 that typically receive 400V individually. When the subgroups are connected in series, the first auxiliary bus bar is connected across the first subgroup and the second auxiliary bus bar is connected across the second subgroup. Also shown here is a dc charging circuit 114.

In series with each subgroup is a set of

contacts

121, 122 comprising contacts in one parallel branch and contacts and resistors in the other parallel branch. Although described herein as contactors, it will be appreciated that relays may be used if appropriate, and thus the contact bank may be more generally considered a switch bank. The same applies to all contactors mentioned herein. Only the branch with the contactor is the main circuit arrangement in normal operation, while the other branch is the pre-charge circuit, so the voltage level in the circuit is correct before full operation. For the first subset 101, the first main contactor 135 is connected in parallel with the series combination of the first pre-charge contactor 138 and the first pre-charge resistor 171. For the second sub-group 102, the second main contactor 131 is connected in parallel with the series combination of the second pre-charge resistor 172 and the second pre-charge contactor 139.

A set of three contactors-a bridge contactor 133 and branch contactors 132 and 134-control the basic configuration circuit 26. The circuit as a whole is an H-structure, with

subgroups

101 and 102 each located on diagonally opposite branches of the H-structure. And branch contactors are respectively arranged on the other two branches. To provide a series connection, the bridging contactor 133 is closed and the

branch contactors

132, 134 are driven open. In this arrangement, the voltage of the entire battery pack is 800V. Alternatively, to provide a parallel connection, the bridging contactor is driven open while the branch contactors remain closed. As will be discussed below, different contactor arrangements may be provided if a contactor failure is identified.

There are also two pairs of contactors associated with the configuration circuit 26, the first and second auxiliary bus contactors 137, 136 forming one pair, and the DC charging

circuit contactors

190, 191 forming the other pair. These contactors may be used to isolate the associated circuitry if desired.

The configuration circuit 26 includes sensors for measuring voltage and current to determine if the circuit is operating properly and if remedial action needs to be taken to isolate the fault or allow operation in a limited function mode. For efficiency and cost, it is desirable to use a limited number of sensors designed to disrupt the normal operation of the configuration circuit 26 as little as possible. The high voltage sensors are disposed at various points within the circuit. For the bus, the first voltage sensor 151 is disposed on the positive rail of the main bus, and the fourth voltage sensor 154 is disposed on the negative rail of the main bus. The second voltage sensor 152 is provided on the negative rail of the second auxiliary bus (the positive rail of the bus is the positive rail of the main bus), and the third voltage sensor 153 is provided on the positive rail of the first auxiliary bus (the negative rail of the bus is the negative rail of the main bus). Sixth and seventh voltage sensors 156, 157 are disposed on both sides of the bridging contactor 133. Within the first subgroup of circuits, an eighth voltage sensor 158 is arranged between the first subgroup 101 itself and the first set of contacts 121, and a fifth voltage sensor 155 is similarly arranged within the second subgroup of circuits. A ninth voltage sensor 159a and a tenth voltage sensor 159b are provided within the DC charging circuit.

For the measurement strategy described below, the current is sensed at some point in the circuit to supplement the voltage measurement described above. The

current sensors

141, 142 are thus arranged in each subgroup 101,102, but they themselves comprise two components.

The fuses are placed at relevant points in the system. Each sub-bank contains a

sub-bank fuse

161, 162 and a

fuse

163, 164 is also provided to isolate the auxiliary load from each sub-bank. The rear inverter fuse 165 isolates the rear inverter from the positive rail.

As will be described in more detail below, the

auxiliary buses

112, 113 and associated contactors 136, 137 are arranged to allow at least one auxiliary bus to operate in the presence of an operating subset, even if another subset is not operating.

The state machine of the configuration circuit 26 will now be described with reference to fig. 5. The state machine reverts to the "off" state in which all high voltage contactors are open 600. It can be seen that this is the reset state of the system-typically involving specific steps during transition to the fully operational state 640, but in an emergency (a major crash or an identified safety hazard event), any state can be restored directly to the HV open state 600 with all contactors turned off.

The normal transition into and out of the HV disconnected state 600 is to check the operation of the HV system in the diagnostic state 610. This diagnostic process will be discussed in more detail below. The output of the diagnostic process is a determination of whether both subgroups are available, or whether only one (or neither) is available. If the HV system is not available, the system will revert to the HV disconnected state 600-otherwise, it will transition 620 to an available system state. If normally both subgroups are available, the HV system will transition to the full system available state 621-however, if only the first subgroup is available, then the first subgroup only state 622 is entered, and if only the second subgroup is available, then the second subgroup state 623 is entered-as shown in fig. 5, possibly after a transition through the HV disconnect state 600.

The system then needs to transition to a precharge state 630 appropriate for its associated bus configuration. For a normally functioning system, there are two possibilities at this stage — the subgroups can be connected in series for 800V operation (motoring or 800V charging), in which case it will use the 800V precharge state 631, or in parallel for 400V charging, in which case it will use the 400V precharge state 632. The subgroup state has only one option, since only 400V operation (for 400V charging or limp driving) is available, so the 400V subgroup precharge states 633, 634 can only be entered.

The operational mode 640 may be entered when the associated bus configuration has been entered and precharged. This may be a charging mode, low voltage (400V) charging may be used in both normal operation (low voltage charging mode 641) and sub-group operation (sub-group charging mode 642), and high voltage (800V) charging may also be used in normal operation (high voltage charging mode 643). The normal mode entered when the HV system is operating normally is motoring mode 644, in which the high voltage bus and the rear inverter bus provide a full 800V to the inverter of the motor system. Alternatively, if only one subgroup is operating, the system may enter the subgroup limp home mode 645, in which case 400V is provided to the inverter and unnecessary systems are managed, thereby safely and efficiently using power.

The implementation of these states using the configuration circuit of fig. 3 will now be described in more detail, with particular reference to the control of the contactors and the measurement, diagnosis and management of fault conditions.

The symmetry of the design allows a limited number of control channels (not shown in fig. 3) to be used to control the contactor-seven channels may be used to control the different contactor states desired.

Channels

1 and 2 may be used to enable the first and second subsets, respectively, and channel 3 (providing a common drive signal to the first and second main contactors 135, 131) is used to control the use of the subset mode. Channel 4 controls the 400V mode (providing a common drive signal to the branch contactors 132, 134) and channel 5 controls the 800V mode, driving the bridge contactor 133. Auxiliary bus control is effected via channel 6 to provide a common drive signal to the first and second auxiliary bus contactors 137, 136.

Precharge contactors

138 and 139 are controlled by channel 7. The contactor configuration associated with these control channel conditions is shown in figure 6.

Before discussing other state transitions, the use of fault detection and diagnostic states will be discussed with reference to FIG. 4 and Table 1 below. Fig. 4 shows the arrangement of contactors in the system, while table 1 shows the safety detection of each individual contactor fault condition and the system response available when an individual contactor fault condition is detected. For purposes of this discussion, a single contactor fault condition refers to a condition where the battery system suffers a sustained fault of a single contactor. There are two possible single contactor fault conditions for each contactor-the contactor is open and not closed, and the contactor is closed and not open.

TABLE 1 Single contactor Fault status-measurement and consequences

As can be seen from table 1 above, circuit symmetry means that the fault detection and consequences of a particular contactor pair are substantially similar (although consequences associate one subset with one consequence and another subset with another) — these pairs are as follows: first and second

main contactors

135, 131;

branch contactors

132, 134; first and second auxiliary bus contactors 137, 136; and

precharge contactors

138 and 139. The only unmated contact is the bridging contact 133. The fault conditions are summarized in table 1, although some fault conditions have more complex consequences, as discussed in the following paragraphs.

This also charges the associated 400V dc bus capacitor immediately upon closure of the associated auxiliary bus contactor if the main contactor is shorted, and halves the pre-charge resistance to charge the 800V dc bus capacitor after the pre-charge contactor is closed. If the main contactor is open, a significant voltage drop will occur across the associated pre-charge resistor under load.

If a branch contactor is shorted, there is a risk of the relevant subgroup being shorted — the relevant precharge resistor limits the current during the precharge phase, but a short circuit occurs when the relevant main contactor is closed to place the battery pack in run mode. As described above, if the branch contactor is open, the affected subset will open the circuit.

If the bridging contactor 133 is shorted, then if either branch contactor is closed, there is a risk of a short circuit — meaning that not only is 800V operation disabled, but it is also necessary to decide which of the two subsets to program the state accordingly.

If the pre-charge contactor is shorted, there is a risk of pre-charge resistor overload during shutdown-however, this can be addressed by managing the time of the associated main and auxiliary bus contactor transitions. If the precharge contactor is open, it cannot precharge the associated bus-however, operation from another subgroup is still possible, and in embodiments the sequencing may be managed to allow precharging to be achieved using other precharge resistors.

As can be seen from the above, this circuit arrangement allows some form of operation using at least one subset for the majority of single contactor fault conditions. Each single contactor short circuit can be addressed by allowing use of one of the 400V subgroups, allowing the vehicle to operate in a "limp home" mode-although this is not the normal operating mode of the vehicle, it is still a viable operating mode in which the vehicle can be used (as opposed to the HV open state 600, which is not considered herein as an operating mode because the vehicle is not operating as a vehicle in this mode). In this limp home mode, the power source is still able to drive the motor-typically the capacity will be reduced-but vehicle functionality may be limited. The circuit arrangement shown thus allows a limp home mode to be used to reconfigure any shorted single contactor fault in the circuit. It can also be seen from table 1 that many open single contactor failures also allow for limp home mode to be performed.

Reconfiguring the arrangement of voltage and current measurement points in the circuit allows each individual contactor fault condition to be determined efficiently with limited expense and complexity. The arrangement of the voltage measurement points allows the voltage to be measured across each contactor or group of contactors in the measurement circuit. The term "contact set" as used herein refers to a parallel circuit in which a contactor is provided in each parallel path, with measurements being taken between two branch points. This applies to the main contactor and the precharge contactor of each subgroup, which are arranged in a parallel circuit, the main contactor being on one branch and the precharge contactor and the precharge resistor being on the other branch. This voltage measurement is supplemented by a finite current measurement, requiring only the first 141 and second 142 subsets of current sensors to make current measurements for each battery pack.

The embodiment shown in fig. 4 provides two auxiliary buses, each providing a 400V output. These busbar arrangements are such that the first auxiliary busbar output 113 is connected to the configuration circuit 26 between the first subgroup 101 and the central contactor 133 and the second auxiliary busbar output 112 is connected to the configuration circuit 26 between the second subgroup 102 and the central contactor 103. This approach allows connecting at least one auxiliary bus in most fault conditions-for example a fault short circuit condition for all the individual contactors discussed above-thus ensuring that vital systems can continue to operate in a fault situation if they are provided on two auxiliary buses or can be switched between. This can also be used to enable limp home mode by ensuring that the necessary system driven by the 400V bus is also available.

Suitable diagnostic states, including a plurality of sub-states, will be described with reference to fig. 5. This involves a standby state 6101 (which may be equivalent to HV open 600, but is shown here as a separate sub-state) where the diagnostic process begins and the diagnostic state is restored to this state after any detected fault. During the diagnostic process, the central (bridging) contactor 133 is first tested 6102, and upon failure returns to the standby state 6101. The

branch contactors

132, 134 are then tested in turn at 6103, 6104, where any failure results in a return to the standby state 6101. If the tested contactor has not failed, the system may proceed to two subgroup available state 621. If a failure occurs, the HV open state 600 will be returned, but in the case of a single failure, knowledge of the particular failure will allow progress to one of the subgroup

available states

622, 623.

It should be noted that the diagnostic state 610 is not the only time that fault diagnosis occurs. The measurement system is adapted to determine when other contactors are malfunctioning by a specific response to a fault event (see table 1) detectable during a normal start-up sequence. The purpose of the diagnostic state 610 is to ensure that a contactor fault that cannot be directly detected as part of a normal start-up procedure is still detected.

The diagnostic state 610 may be entered at start-up, but another possibility is that it may be performed at shut-down (when response speed is generally less critical). If a contactor failure is not detected at shutdown, it may be reasonable to assume that they will be operational at startup. However, any suitable choice may be made as to when to enter the diagnostic state 610-for example, it may be used for start-up and shut-down, and typically for shut-down due to any system failure.

The transitions between the various states will now be described in more detail below.

The transition between the HV open state 600 and the normal "ready" state 631 before 800V motoring operation will now be discussed with reference to FIG. 7.

In the HV open state 600, all of the contactors described above should be in an open state. If any one of the contactors fails into a short-circuit state, it can be immediately detected because a voltage will be detected between a pair of interconnected voltage sensors due to the contactor failure; for a shorted main or pre-charge contactor, the relevant sub-group voltage will be seen on the voltage sensors connected to either end of the sub-group; for a branch contactor, the associated sub-pack voltage will be seen between the voltage sensor located between the sub-pack battery cell and the pre-charge contactor pack and the opposite power rail (i.e., the power rail that is not adjacent to the other side of the pre-charge contactor pack); for the center contactor 133, a first sub-pack voltage will be seen between the second sub-pack side of the sixth voltage sensor 156 to the center contactor and the other side of the eighth voltage sensor to the first sub-pack battery cell; for an auxiliary bus contactor, the relevant sub-pack voltage will be seen between the voltage sensor on the demand side of the relevant auxiliary bus and the voltage sensor between the contact set and the sub-pack battery cell of the relevant sub-pack. As described above, some single contactor faults will allow transition to the 400V state, but these will typically not allow progression to the normal 800V motoring state, so detecting any of these faults in the HV open state will determine a possible transition from the diagnostic state 610, and will not follow the path indicated in fig. 7, as this will result in an unacceptable state (e.g. a direct short of a sub-group).

In preparation for the 800V mode, the center contactor 133 is switched to a closed circuit. An open fault in the center contactor 133 may be detected at this time because the first sub-pack voltage should now be seen between the sixth voltage sensor 156 to the second sub-pack side of the center contactor and the eighth voltage sensor to the other side of the first sub-pack battery cells, if not, an open fault condition exists.

After this, the auxiliary bus contactor is also closed-again meaning that the relevant sub-pack voltage should be seen between the voltage sensor on the demand side of the relevant auxiliary bus and the voltage sensor between the contact set and the sub-battery cell of the relevant sub-pack, and if not, an open fault condition exists.

The battery pack is not in a loaded state at this time, but it is in two sub-pack available states 621, ready. To accomplish this, a precharge process is used to activate the bus. The closing of the pre-charge contactor will indicate other open circuit fault conditions. If the center contactor 133 is open, the precharge circuit is incomplete and no precharge current is detected in either current sensor — if either precharge contactor is open, no precharge current is detected.

When the bus bar has been activated, the pre-charge circuit is bypassed by closing the respective main contactor of each subgroup. If any of the main contactors experiences an open circuit fault, this can be detected because the pre-charge resistor will still be subjected to a significant load, and therefore a high voltage drop across the load (e.g., by the associated current sensor) for that subset can be easily detected. The pre-charge contactor is then opened to put the battery pack into a ready state.

Fig. 8 shows the transition from the 800V start-up and ready state 631 to the normal motoring state 644. The battery pack configuration between these two states does not change, but now the inverter can be driven, typically using Pulse Width Modulation (PWM) control signals, to power the vehicle.

Fig. 9 and 10 show the transition from the normal motoring state 644 back to the HV disconnect state 600. The transition to the 800V start and ready state 631 does not change the contactor state as shown in fig. 9-the two states are different only in that no drive signal can be given in the start and ready states. The transition from the start-up and ready state 631 back to the HV open state 600 is somewhat simpler than the opposite transition, since no precharge step is required, only for discharging. Each subgroup is opened by opening its main contactor, then the auxiliary bus contactor is also opened and the discharge path is opened. The center contactor 133 is then opened to keep the subgroup fully open-discharge path in the circuit to ensure that this is a fully safe open state.

If only one subset is available, as is the case with most of the single contactor fault conditions described above, the system transitions to the limp home condition 645 instead. The transition to this state is shown in fig. 11. In this case, it has been determined during the diagnostic state 610 or the start-up sequence that only the first subset 101 is available for use, and therefore the second subset 102 is disabled by commanding the second main contactor 131, the second pre-charge contactor 139, the branch contactor 132 and the second auxiliary bus contactor 136 to open. Since the battery pack is operating in a 400V configuration, the center contactor 133 is also always in an open state. The system enters the subgroup start-up and ready state by closing the other branch contactor, then the other auxiliary bus contactor, and enters precharge by closing the first subgroup precharge contactor 138. Upon completion of the precharge, the first subset main contactor 135 is closed, and the precharge circuit is opened by opening the first subset precharge circuit contactor, thereby bringing the system into the 400V first subset only enable state 633. This can now transition to the limp home state 645 without changing the contactor arrangement and can provide a drive signal to power the at least one inverter.

In the case where only one subset is used, typically only one auxiliary bus bar is available. There may be some vehicle systems that most efficiently cut off power to the auxiliary bus and may need to ensure that this function can be used even in limp home operating conditions of the vehicle. This can be done by ensuring that such functionality is available from either auxiliary bus. This may involve duplicating some system between the first and second auxiliary buses to ensure that if either auxiliary bus is available, the vehicle function will be available. One such load that is typically operated by an auxiliary bus is an air conditioning (HVAC) compressor. Systems that can be run from the auxiliary bus in different vehicle types include generators, water pumps, cooling fans, air compressors, oil pumps and power steering pumps-in some prior art vehicles such systems can be run from the main bus to ensure that if the vehicle is running they will run, whereas in the arrangement described herein they can be run from the auxiliary bus but still ensure functional continuity. This approach also allows managing faults in the relevant systems by simply using other auxiliary buses-in this way, faults in the battery system that prevent the use of an auxiliary bus or any system on an auxiliary bus can be managed by switching to another auxiliary bus.

Fig. 12 shows the disconnection from the limp home mode. Again, this shows the arrangement with the second subset inactive, so the same set of contactors associated with the second subset and the central contactor 133 are always open. The return process is again similar in that no pre-charging is required, so the system ends in the high voltage disconnect state 600 with the discharge path still connected, before the relevant sub-group is disconnected by the relevant main contactor opening, starting to disconnect the relevant auxiliary bus by the relevant auxiliary bus contactor opening and discharging.

The transition into and out of the 800V state of charge is shown with reference to fig. 13 and 14. As shown in fig. 13, the master battery pack contactor is configured identically in the 800V start and ready state 631 and the 800V charge state 643. These differences are that the originally open terminal block contactor becomes a closed circuit when the state is switched, so that the charging voltage of the entire battery pack can be seen. Before this, the inverter will be disabled using an appropriate command (LV ENABLE) from the Vehicle Control Unit (VCU). The transition from the 800V state of charge to the normal motoring state 644 can be simple because the battery pack contactor configuration is the same. DC charging will be disabled (this is typically controlled with AC charging circuitry) and the inverter enabled by an appropriate command (e.g., LV ENABLE) when removal of the DC charging voltage has been confirmed. To turn off from 800V charging, the system reverts to HV open state by opening the terminal block contactor into 800V start and ready state 631, exactly as described previously with respect to the transition from 800V motoring state 644 to HV open state 600.

The 400V state of charge and associated transitions will now be described with reference to fig. 15 to 20.

Fig. 15 shows the transition from the HV disconnect state 600 to the 400V start-up and ready state 632 of a fully charged battery, where two sub-packs are used-in this case there is little imbalance between the two sub-packs and therefore it is simple to charge the two sub-packs together. Since the battery pack is in 400V mode, the first step is to close the

branch contactors

132, 134, with the center contactor 133 remaining open at all times-this establishes the two sub-groups as operating in parallel. The same sequence as the previous transition to the ready state-the auxiliary contactor is closed, the pre-charge contactor is closed, when the battery pack sees a load, the main contactor is closed, the pre-charge contactor is bypassed, and the pre-charge contactor is opened. In each case, the contacts of each subgroup are switched together with their equivalent contacts from the other subgroup. The transition to the charging state is effected by closing the relevant terminal block contacts as before (see fig. 16).

Fig. 17 shows how the method of fig. 15 can be modified if there is a severe imbalance between the two subgroups-in this case the first subgroup is significantly under-voltage. It is decided to charge only the first subset and disable the second subset by forcing the relevant contactors (main, pre-charge, branch and auxiliary bus) open. The contactors associated with the first subgroup transition in the manner shown in fig. 15 and reach a first subgroup 400V enable state 633. This transitions to the first subset 400V charge state 642 by disabling the inverter and closing the junction box contactors as before (as shown in fig. 18). This transition can be made smoother by using the precharge circuit of the isolated ion group when the undervoltage subgroup (here the first subgroup) approaches the voltage of the isolated ion group.

Fig. 19 shows the shutdown process from the full battery 400V start-up and ready state 632 and the first sub-stack start-up and ready state 633 of fig. 20. They differ only in that the contactors associated with the second subgroup are always open during the transition from the active and standby state of the first subgroup, since the second subgroup is disabled. The same process of opening the operational subgroup by opening the associated main contactor, opening the auxiliary bus by opening the associated auxiliary bus contactor and starting the discharge is performed in each case and finally reaches the HV open state 600 and discharges into place.

Additional conversions may be required. For example, a battery pack may be configured for 800V charging, but it is determined that 400V charging is preferred (e.g., if there is a fast charger output available but the voltage is below 800V). In this case, the system should transition back to the HV disconnected state 600, then proceed again to the full battery HV Start and prepare state 632, then proceed again to the full battery 400V Charge state 643.

It may also be necessary to switch from 400V charging to 800V charging-which may occur if the sub-battery packs are unbalanced, in which case it may be necessary to charge at 400V to balance the two sub-packs and then switch to 800V charging to charge the battery most efficiently. Again, this is achieved by transitioning from the 400V state of charge back to the HV off state, and then proceeding to the 800V state of charge.

Inverter fault determination is not within the scope of the discussion herein, but it should be noted that inverter faults may be slight, in which case the inverter does not affect other system components and can be restored, or severe, in which case it cannot be used. For major faults, the inverter is completely out of circuit-the line fuse opens. If the fault is slight, the configuration of the battery pack contactor is not affected, the inverter is connected with the battery pack, but the PWM control signal of the inverter is closed, so that the inverter cannot be driven to provide power. If the fault is resolved, the PWM signal can simply be turned on by the VCU.

Embodiments of the present invention have been described above by way of example. Those skilled in the art will understand that the present invention is not limited to these embodiments, and that other embodiments falling within the scope of the claims may be developed without the features of, or with alternatives to, the features of the above-described embodiments. As described above, embodiments of the present invention are not particularly limited to electric vehicles, all of which are powered by rechargeable cellular batteries, while no other power source is provided in the vehicle.

Claims

1. An electric vehicle comprising a battery pack, a first vehicle system powered by the battery pack, and a second vehicle system powered by the battery pack, wherein:

the battery pack includes a first sub-group, a second sub-group, a first auxiliary bus bar connected to the first sub-group, and a second auxiliary bus bar connected to the second sub-group;

the first vehicle system is connected to the first auxiliary bus;

the second vehicle system is connected to the second auxiliary bus; and is

The first and second vehicle systems each perform the same vehicle function.

2. The electric vehicle of claim 1, wherein the battery pack is configured such that in the event of a failure of the first vehicle system or first subset, vehicle functions continue to be provided by the second vehicle system and second subset.

3. The electric vehicle according to claim 1 or 2, wherein the electric vehicle includes a motor unit for providing power drive, the battery pack includes a main bus on which the first and second subsets are connected in series and the motor unit is connected to the main bus in a normal operation mode.

4. The electric vehicle of claim 3, wherein a first voltage is provided on the main bus and a second, lower voltage is provided on the first and second auxiliary buses.

5. The electric vehicle of claim 4, wherein in the event of a failure of the first subset, a second lower voltage continues to be provided on a second auxiliary bus.

6. The electric vehicle of claim 5, wherein in the event of the fault, a second lower voltage is also provided on the main bus.

7. An electric vehicle as claimed in any preceding claim, wherein the battery pack comprises a diagnostic circuit for diagnosing a fault condition of one or more switches of the battery pack.

8. An electric vehicle according to any preceding claim, wherein the battery pack is configurable between a first configuration in which two sub-groups are connected in series on the main busbar and a second configuration in which the sub-groups are connected in parallel.

9. The electric vehicle of claim 8, wherein the battery pack includes a first path across a main bus including a first subset and a second path across a main bus including a second subset, wherein the battery pack further includes a central path connecting the first path to the second path, the central path having a central switch disposed thereon for switching the battery pack between a first configuration and a second configuration.

10. The electric vehicle according to claim 9, wherein each of the first and second paths includes a high-voltage side and a low-voltage side to both sides of a connection thereof with a center path, wherein the first subset is provided on the high-voltage side of the first path, and the second subset is provided on the low-voltage side of the second path, wherein a first branch switch is provided on the low-voltage side of the first path, and a second branch switch is provided on the high-voltage side of the second path.

11. The electric vehicle of claim 10, wherein the first subset is connected in series with and on a same voltage side as a first switch set for inhibiting or enabling current flow of the first subset, and the second subset is connected in series with and on a same voltage side as a second switch set for inhibiting or enabling current flow of the second subset.

12. The electric vehicle of claim 11, wherein each of the switch banks includes a main switch in parallel with a series combination of a pre-charge resistor and a pre-charge switch.

13. The electric vehicle according to any one of claims 8-12 as dependent on claim 3, wherein the electric machine unit is coupled to the main bus and operates at a first electrical power when the subset is in the first configuration and at a second, lower electrical power when the subset is in the second configuration.

14. The electric vehicle of any of the preceding claims, wherein, for each auxiliary bus, the connection of the battery system to the auxiliary bus comprises a respective auxiliary bus switch.

15. The electric vehicle of any of the preceding claims, wherein the first vehicle system is an air conditioning compressor and the second vehicle system is an air conditioning compressor.

16. A method for operating an electric vehicle according to claim 1, the method comprising:

detecting a failure of the first vehicle system or the first subgroup, an

The vehicle functions previously provided by the first vehicle system continue to be provided by the second vehicle system and the second subset.

17. The method of claim 16, wherein the failure of the first sub-group comprises a failure of a battery pack that prevents effective use of the first sub-group.

18. The method of claim 17, wherein the battery pack includes a diagnostic circuit for diagnosing a fault condition of one or more switches of the battery pack, wherein detecting the fault includes the diagnostic circuit diagnosing a fault of or associated with the first sub-group.

19. A method according to claim 17 or 18, wherein the electric vehicle comprises a motor unit for providing a power drive, the battery pack comprises a main bus on which the first and second subsets are connected in series in a normal operating mode and to which the motor unit is connected, wherein the main bus is connected across the second subset in case of a failure of the first subset.