WO2018166900A1

WO2018166900A1 - Drive system for a vehicle, method for operating a drive system, and use of the drive system

Info

Publication number: WO2018166900A1
Application number: PCT/EP2018/055854
Authority: WO
Inventors: Ahmet Kilic; Tunan Shen
Original assignee: Robert Bosch Gmbh
Priority date: 2017-03-13
Filing date: 2018-03-09
Publication date: 2018-09-20
Also published as: CN110382287B; CN110382287A; EP3595925A1; DE102017204065A1

Abstract

The invention relates to a drive system (10) for a vehicle, comprising a battery (14) for storing electric energy, said battery having a plurality of battery banks (12) connected in parallel, each battery bank (12) being separately switchable on and off. The battery banks (12) connected in parallel are connected to a common switch unit (40) which has multiple switches for separately switching the connected battery banks (12) on and off and multiple current sensors for separately measuring battery currents (IB) flowing in the connected battery banks (12). The invention relates to a method for operating a drive system (10) according to the invention, wherein the battery currents (IB) flowing in the connected battery banks (12) are measured separately and each of which is compared with a threshold assigned to the battery bank (12), and the battery bank (12) is separately switched off if the battery current (IB) flowing in the battery bank (12) exceeds the assigned threshold.

Description

DRIVE SYSTEM FOR A VEHICLE AND METHOD FOR OPERATING A DRIVE SYSTEM AND USE OF THE DRIVE SYSTEM

The invention relates to a drive system for a vehicle, which comprises a battery for storing electrical energy, wherein the battery has a plurality of battery strings connected in parallel, and wherein each of the battery strings is separately switchable and disconnectable. The invention also relates to a method for operating a device according to the invention

Drive system.

State of the art

It seems that in the future, especially in vehicles like

Electric vehicles (EV), hybrid vehicles (HEV) and plug-in hybrid vehicles (PHEV) are increasingly being used in electrical and electronic systems that combine new energy storage technologies with electric drive technology. Such vehicles have drive systems for controlling an electric drive motor, which serves to drive the vehicle.

Known drive systems for vehicles include, among others

Battery Management System. The battery management system is used for

Monitoring the battery by means of several sensors, for example

Temperature sensors, current sensors and voltage sensors. The

Battery management system also serves to control the battery. In particular, the battery management system is used to shut down the battery in case of failure.

A generic drive system includes, for example, a

rechargeable battery for storing electrical energy comprising a plurality of battery strings connected in parallel. Every battery string includes, for example, a plurality of serially connected battery cells. Each battery string is assigned its own switch, by means of which the respective battery string can be switched on and off. The battery string is switched off in particular when an error, for example a short circuit, is detected therein.

From US 2013/0088201 Al a battery system for a vehicle is known, which has a plurality of battery strings connected in parallel. Everyone

Battery string can be switched on and off by means of a separate switch. A control circuit is used to measure voltages of the individual battery strings connected in parallel and to control the switches assigned to the battery strings. In this case, a backup battery string is provided, which is switched on when another battery string in case of failure

is switched off.

The US 2012/0091964 AI also discloses a battery system for a

Vehicle. The battery system includes several parallel connected

Battery strings, each battery string can be switched on and off by means of a separate switch. Each battery string comprises a plurality of serially connected battery cells.

Disclosure of the invention

A propulsion system for a vehicle is proposed. The drive system comprises a battery for storing electrical energy, which has a plurality of battery strings connected in parallel. Each battery string can be switched separately as well as switched off. The battery is in particular a high-voltage battery which supplies the energy for driving the vehicle. About a DC-DC converter, the high-voltage battery can also feed a low-voltage electrical system with a rated voltage of 12 V, for example. Each of the battery strings includes several serially connected battery cells.

According to the parallel-connected battery strings are connected to a common switching unit, which has a plurality of switches for separate power on and separate shutdown of the connected battery strings, and which have multiple current sensors for separately measuring flowing in the connected Batteriesträngen

Battery currents has.

Such switching units are known, for example, as "ePDU" (Enclosure Power Distribution Unit). Such switching units are used, for example, to transfer energy from one power source to multiple consumers. The individual consumers can be switched on separately and switched off. The switches of the switching unit are preferably designed as electronic switches, for example MOSFET.

Preferably, the switching unit has a control module, which receives measured values of the current sensors and which drives the switches. In particular, the control module compares the recorded readings of the current sensors to predetermined limits and turns off a battery string when the battery current in that battery string exceeds a threshold. But even with other detected errors, for example, at too high a temperature or failure of a battery cell, the control module of the switching unit one

Switch off the battery string.

According to an advantageous embodiment of the invention, the switching unit communicates via a communication line with a

Battery Management System. The communication line is part of a bus system present in the vehicle. In particular, that can

Battery management system, the limits for the battery currents in the individual Batteriesträngen over the communication line to the switching unit, in particular to the control module transmitted. The battery management system is powered by the low-voltage electrical system with energy.

According to an advantageous embodiment of the invention, the switching unit via a main switch with a consumer and / or with a

DC link capacitor connectable. The main switch is designed, for example, as a contactor, that is, as a controllable electromechanical relay, and can be controlled by the battery management system. Preferably, a precharge resistor and a precharge switch are connected in parallel to the main switch, via which the switching unit with the consumer and / or with the DC link capacitor is connectable. Also the

Vorladeschalter example, as a contactor, so as a controllable electromechanical relay, executed and is of the

Battery management system controlled.

It is also a method for operating an inventive

Propulsion system proposed. In this case, the battery currents flowing in the connected battery strings are measured separately and compared in each case with a limit value associated with the battery string. In this case, a battery string is switched off separately when the current flowing in the battery string battery current exceeds the associated limit. The battery currents flowing in the individual battery strings are determined by the

Current sensors of the switching unit measured and a battery string is switched off by a switch of the switching unit.

According to an advantageous embodiment of the invention is doing each

Battery string assigned a separate limit. The limit value assigned to the battery string can be dependent, for example, on an internal structure or configuration of the battery string.

For example, a connected battery string can have a high energy density but a low power density. Another battery string may have a high power density but a low energy density. In this case, the battery string with the high power density can have a higher

Be assigned limit value. According to an advantageous embodiment of the invention, the

Battery limits assigned by one

Battery management system transmitted to the switching unit. In particular, the assigned limit values are transmitted to the switching unit via a communication line. It is conceivable that each battery string is statically assigned a limit value. However, the limit values assigned to the battery strings are preferably determined dynamically by the battery management system and transmitted to the switching unit. A threshold for a battery string may thus be changed during operation of the propulsion system and the vehicle. Of the

Limit value may be dependent on the temperature and the state of charge of the battery cells of the battery string, for example.

The drive system according to the invention and the method according to the invention find advantageous use in an electric vehicle (EV), in one

Hybrid vehicle (HEV) or in a plug-in hybrid vehicle (PH EV).

Advantages of the invention

An inventive drive system has an increased availability. In the case of a fault, for example a short circuit, in a battery string, this battery string can be switched off separately. With the rest

Batteriesträngen continues to operate the drive system and thus the vehicle with reduced power possible. Likewise, after disconnecting a faulty battery string, a low-voltage electrical system can be fed further, which supplies a battery management system. Thus, the battery management system remains operational.

The switching unit is independent of the type of battery cells in the Batteriesträngen the battery. In particular, a battery may include high energy density battery strings and high power density battery strings. The switching unit can monitor each battery string separately and precisely by specifying different limit values. The switching unit can itself measure the battery currents flowing in the battery strings. Other required data, such as voltage, state of charge and temperature of the

Battery cells in the individual battery strings, the switching unit via the communication line, such as a CAN bus, from the

Battery management system received. The switching unit additionally provides partial redundancy to the

Battery management system. Even in case of failure of the

Battery management system, the switching unit can continue the

Control drive system in an emergency operation. Thus, even in the event of a failure of multiple battery strings and the battery management system, the vehicle can still be operated with reduced power, for example to reach the nearest parking space on a motorway. By the way

existing redundancy drive system of the invention can also meet the requirements for autonomous driving.

Brief description of the drawings

Embodiments of the invention will be explained in more detail with reference to the drawings and the description below.

Show it:

1 shows a schematic representation of a drive system and FIG. 2 shows a schematic representation of a switching unit from FIG. 1.

Embodiments of the invention

In the following description of the embodiments of the invention, the same or similar elements are denoted by the same reference numerals, wherein a repeated description of these elements is dispensed with in individual cases. The figures illustrate the subject matter of the invention only schematically. In FIG. 1, a drive system 10 for a vehicle is shown schematically.

The drive system 10 includes a battery 14 for storage

electrical energy having a plurality of battery strings 12. In the present case, the battery 14 has three battery strings 12, which are connected in parallel. During operation of the drive system 10 flows in each case

Battery current IB through each battery string 12. Each of the parallel-connected battery strings 12 has a plurality of battery cells 2, which are connected in series. There are so many battery cells 2 connected in series that an output voltage of the battery string 12 has a desired value. The battery strings 12 may have similar battery cells 2. But it is also conceivable that one of the connected

Battery strings 12 battery cell 2 having a high energy density but a low power density, and that another of the battery strings 12 battery cells 2 with a high power density but a small

Has energy density.

The drive system 10 also includes a switching unit 40 having a plurality of inputs 38. Each of the battery strings 12 of the battery 14 is connected to a separate input 38 of the switching unit 40. By means of

Switching unit 40, each of the connected battery strings 12 can be switched on separately and switched off. When a battery string 12

is switched on, then the battery string 12 with an output 36 of

Switching unit 40 electrically connected.

The drive system 10 further comprises a load 30 which is, for example, an inverter or an inverter and serves to drive a drive motor, not shown here, of the vehicle. The as

Inverter or inverter configured consumer 30 takes the battery 14 during operation of the vehicle electrical energy and converts a supplied from the battery 14 DC voltage in an AC voltage to

Control of the drive motor to.

The drive system 10 further comprises an intermediate circuit capacitor 16. The intermediate circuit capacitor 16 is connected in parallel with the load 30. During operation of the vehicle drops above the intermediate circuit capacitor 16 a

Capacitor voltage from which supplied by the battery 14

DC voltage corresponds.

The drive system 10 comprises a first main switch 21 which is connected to the output 36 of the switching unit 40 and to the intermediate circuit capacitor 16 and the consumer 30 is connected. Via the first main switch 21, the switching unit 40 is thus connected to the DC link capacitor 16 and the

Consumers 30 connectable. Also, the drive system 10 includes a second main switch 22, which with the battery 14 and with the

DC link capacitor 16 and the load 30 is connected. When the main switches 21, 22 are closed, a drive current IA can flow from the battery 14 to the load 30.

The drive system 10 also includes a precharge switch 20 and a precharge resistor 25. The precharge switch 20 and the precharge resistor 25 are connected in series with each other and are connected in parallel with the first main switch 21. Via the precharge switch 20 and the precharge resistor 25, the switching unit 40 is thus connected to the DC link capacitor 16 and the

Consumers 30 connectable. The precharge switch 20 and the precharge resistor 25 serve to precharge the link capacitor 16 when starting the vehicle. The precharge resistor 25 limits a charging current when precharging the DC link capacitor 16. When the DC link capacitor 16 has a sufficient precharge the first main switch 21 is closed and the precharge switch 20 is opened.

The drive system 10 further includes a battery management system 50. The switching unit 40 is connected via a communication line 52 with the

Battery management system 50 connected. The communication line 52 is part of a bus system present in the vehicle, for example a CAN bus. The switching unit 40 communicates with the battery management system 50 via the communication line 52. The battery management system 50 serves, inter alia, to control the main switches 21, 22 and the

Precharge switch 20.

The battery management system 50 is powered from a vehicle electrical system 54, which is designed as a low-voltage electrical system with a rated voltage of 12 V, for example. The vehicle electrical system 54 is fed by a not shown DC-DC converter from the battery 14, that is supplied with electrical energy. Figure 2 shows a schematic representation of the switching unit 40 of Figure 1. The switching unit 40 is presently designed as "ePDU" (Enclosure Power Distribution Unit). As already mentioned, the switching unit 40 comprises several

Inputs 38 and an output 36. The inputs 38 are each connected by means of a current path 48 to the output 36. The switching unit 40 in this case represents a structural unit.

Each current path 48 has a switch 42, which is designed, for example, as a MOSFET. The switches 42 are independently controllable. The switching unit 40 thus comprises a plurality of switches 42 for separately switching on and for the separate switching off of the battery strings 12 connected to the inputs 38.

Each current path 48 also has a current sensor 44. Each current sensor 44 serves to measure a current flowing in the current path 48. The

Switching unit 40 thus comprises a plurality of current sensors 44 for separately measuring currents flowing in the connected battery strings 12

Battery currents IB.

The switching unit 40 further comprises a control module 46. The control module 46 is connected to the switches 42 and to the current sensors 44 of the individual current paths 48. The switching unit 40 receives measured values of the battery currents IB from the current sensors 44 and drives the switches 42. Also, the switching unit 40 includes a communication interface 32. To the

Communication interface 32 is the communication line 52

connected. The communication interface 32 is also connected to the control module 46.

In the regular operation of the vehicle and the drive system 10, the switches 42 of the switching unit 40 and the two main switches 21, 22

closed. The precharge switch 20 is open. From each battery string 12 of the battery 14, a battery current IB flows into the switching unit 40. The individual battery currents IB can have different values. The drive current IA flows from the switching unit 40 to the load 30. Der DC link capacitor 16 is fully charged. The drive current IA results as the sum of the battery currents IB.

The battery currents IB flowing in the individual battery strings 12 flow through the current paths 48 of the switching unit 40 and are supplied by the

Current sensors 44 of the switching unit 40 is measured separately. The measured values of the current sensors 44 are received by the control module 46. The control module 46 compares the recorded measured values of the current sensors 44 with predetermined limit values.

If in one of the battery strings 12 and thus in one of the current paths 48, a battery current IB flows that exceeds the associated limit, the control module 46 opens the switch 42 in the corresponding current path 48. Thus, the corresponding battery string 12 is turned off. The remaining battery strings 12 whose battery currents IB do not exceed the assigned limit remain switched on.

Each battery string 12 is assigned a separate limit value in the present case, which depends on, among other things, an internal structure or an embodiment of the battery string 12. The battery management system 50 transmits the limit values assigned to the individual battery strings 12 via the communication line 52 and the communication interface 32 to the switching unit 40 and to the control module 46. It is also conceivable that the limit values in the control module 46 are fixed.

It is conceivable that each battery string 12 is statically associated with a limit value. In this case, for example, at the start of the drive system 10 and the vehicle, the limit values become unique from the

Battery management system 50 transmitted to the control module 46. In the present case, the limit values assigned to the battery strings 12 are determined by the

Battery management system 50 dynamically determined and transmitted to the control module 46. The transmission of the limit values can take place cyclically or event-controlled. A threshold for a battery string 12 is thus re-determined by the battery management system 50 during the operation of the drive system 10 and the vehicle under changed conditions. Such conditions that cause a change of a limit value, for example, a temperature or a state of charge of at least one of the battery cells 2 of the relevant

Battery string 12.

The invention is not limited to the embodiments described herein and the aspects highlighted therein. Rather, within the scope given by the claims a variety of modifications are possible, which are within the scope of expert action.

Claims

claims

A drive system (10) for a vehicle, comprising

a battery (14) for storing electrical energy having a plurality of battery strings (12) connected in parallel, wherein

each battery string (12) can be switched separately and switched off, characterized in that

the parallel-connected battery strings (12) are connected to a common switching unit (40),

which has a plurality of switches (42) for separately switching on and for separately switching off the connected battery strings (12) and a plurality of current sensors (44) for separately measuring battery currents (IB) flowing in the connected battery strings (12).

2. Drive system (10) according to claim 1, characterized in that the switching unit (40) has a control module (46),

which receives measurements from the current sensors (44) and

which controls the switches (42).

3. Drive system (10) according to one of the preceding claims,

characterized in that

the switching unit (40) communicates with a battery management system (50) via a communication line (52).

4. Drive system (10) according to one of the preceding claims,

characterized in that

the switching unit (40) via a main switch (21) with a

Consumer (30) and / or with a DC link capacitor (16) is connectable. Drive system (10) according to claim 4, characterized in that parallel to the main switch (21), a pre-charge resistor (25) and a precharge switch (20) are connected,

via which the switching unit (40) with the load (30) and / or with the intermediate circuit capacitor (16) is connectable.

Method for operating a drive system (10) according to one of the preceding claims, wherein

the in the connected Batteriesträngen (12) flowing

Battery currents (IB) are measured separately and each with a battery string (12) associated limit value to be compared, and wherein

a battery string (12) is switched off separately when the current flowing in the battery string (12) battery current (IB) exceeds the associated limit.

The method of claim 6, wherein

Each battery string (12) is assigned a separate limit.

Method according to one of claims 6 to 7, wherein

the battery limits (12) associated limits of one

Battery management system (50) are transmitted to the switching unit (40).

The method of claim 8, wherein

the battery limits (12) associated limit values are determined dynamically by the battery management system (50).

Use of the drive system (10) according to one of claims 1 to 5 and / or the method according to one of claims 6 to 9 in an electric vehicle (EV), in a hybrid vehicle (HEV) or in a plug-in hybrid vehicle ( PHEV).