DE102014011828A1 - Method and device for heating a traction battery in a motor vehicle - Google Patents

Abstract

The invention relates to a method for heating a traction battery (12) in a motor vehicle, wherein a programmable drive converter (14) is coupled to a prime mover (16) and further the traction battery (12) is coupled to the drive converter (14). In this case, the drive machine (16) is operated with a field-oriented control in operating points of the characteristic field, where a torque-forming, rotor-related current component (iq) is controlled such that in the drive machine (16) no torque is built up. As a result, an increase in temperature of the traction battery (12) is brought about by a battery load current (IDC), which occurs during operation of the drive machine (16) between the drive converter (14) and the traction battery (12). In this way, an effective heating of the traction battery (12) is possible. Furthermore, the invention relates to a drive device (10) for carrying out said method and to a motor vehicle having such a drive device (10).

Description

The invention relates to a method for heating a traction battery in a motor vehicle, which is equipped with a programmable drive converter, wherein the drive converter is coupled to a drive machine for driving the motor vehicle and the traction battery.

Motor vehicles, particularly electric vehicles or hybrid vehicles, may include a battery which must cover a wide range of power in varying environmental conditions. Batteries are chemical energy stores that react only very slowly at low temperatures. You can then slowly release and record your stored charge. In addition, rapid charging, especially with the lithium-ion technology used today at low temperatures, is poor for the durability or service life of the battery. Therefore, batteries are charged extremely slowly at temperatures below 0 degrees Celsius for their protection.

Alternatively, you can warm the battery before charging. One way to heat the battery is to load the battery by current pulses. Due to the internal resistance of the battery, this heats up.

In this context, the DE 10 2009 054 461 A1 a battery heater in which the inductance of a motor winding of the electric drive motor is used to be connected via a Polwendeschaltung with the traction battery and thereby approximately to flow an alternating current through the traction battery and to heat them thereby. In this case, the power required for heating the battery in the electric drive motor can be selected such that the engine generates no torque and thus the battery heater can be operated even when the vehicle is stationary.

It is an object of the present invention to provide a method which enables efficient heating of the traction battery using already existing devices in the motor vehicle.

This object is achieved by an operating method having the features of patent claim 1 and by a drive device having the features of patent claim 7. Advantageous developments of the present invention are the subject of the dependent claims.

For the inventive method for heating a traction battery in a motor vehicle, a programmable drive converter is provided, which is coupled to a drive machine for driving the motor vehicle and the traction battery. In this case, the prime mover is operated with a field-oriented control in such operating points of the characteristic field, where a torque-forming, rotor-related current component is controlled such that in the prime mover no torque is built up. As a result, a temperature increase of the traction battery is caused by a battery load current, which occurs during operation of the drive machine between the drive converter and the traction battery. Here, advantageously, by varying a flow-forming, rotor-related current component, the heating power of the battery can be changed, the drive machine is only up and demagnetized without forming a torque. In other words, mainly reactive power is exchanged between the traction battery and the engine. In particular, the traction battery can result in an almost average-free alternating current, as a result of which no appreciable ion exchange takes place in the traction battery, which is why this load has little or no effect on the aging.

In an advantageous development of the method, the drive machine is operated with a field-oriented control in operating points of the characteristic field, where a flow-forming, rotor-related current component is controlled such that periodically between a positive and a negative setpoint for the flow-forming, rotor-related current component is changed. This results in the advantage that a deactivation of the control is not required, thus allowing an application at speeds not equal to zero.

In an alternative embodiment, the drive converter is operated alternately in a field-controlled mode and an unregulated freewheel mode. This results in particular the advantage that in the freewheeling mode, the energy stored in the magnetic circuits of the drive machine is inevitably fed back into the battery via the DC intermediate circuit, which can couple the traction battery and the drive converter.

In an advantageous embodiment of the method, a closed temperature control loop is provided, wherein the battery load current is used as a manipulated variable for setting a predeterminable temperature level (setpoint) within the traction battery.

The method according to the invention can be implemented in a drive device for a motor vehicle, whereby a drive device according to the invention is produced. In this case, the Drive device to a programmable drive converter, which is designed to carry out a field-oriented control. Furthermore, the drive device has a drive machine which is coupled to the drive converter and is designed to be operated with a field-oriented control in operating points of the characteristic field, where a torque-forming, rotor-related current component is controlled so that no torque is built up in the drive machine , Finally, the drive device has a traction battery, which is designed to bring about an internal temperature increase by a battery load current, which occurs during operation of the drive machine between the drive converter and the traction battery.

Preferably, a motor vehicle may have such a drive device, resulting in a motor vehicle according to the invention.

In the following the invention is explained in more detail with reference to the figures. Showing:

1 a simplified schematic representation of a drive device according to the invention,

2 an exemplary representation of a characteristic field with preferred operating points for carrying out the operating method according to the invention, and

3 a simplified schematic representation of a temperature control loop.

A preferred embodiment of a drive device according to the invention 10 is in 1 shown. This includes a traction battery 12 which has a two-pole battery contactor K in addition to the battery cells, which allows the traction battery 12 to de-energize. A voltage arrow indicates the internal battery voltage U _HV , an arrow in the upper power supply line of the traction battery 12 denotes the battery current I _DC , which from the traction battery 12 is removed. With positive battery voltage U _HV and positive battery current I _DC thus results in a positive power, which from the traction battery 12 is removed.

About a DC intermediate circuit whose DC link voltage is identified by U _DC , is the traction battery 12 by means of two connections, marked DC + and DC-, with a drive converter 14 coupled. In this case, the drive converter 14 between the terminals DC + and DC- on a DC link capacitor C _ZK .

Furthermore, the drive converter 14 six semiconductor switches Q1, Q2, Q3, Q4, Q5 and Q6, where Q1 and Q2, Q3 and Q4, and Q5 and Q6 respectively form a branch pair having a common connection point, hereinafter called a branch pair center. The respective branch pair center point is designated U for branch pair Q1 / Q2, V for branch pair Q3 / Q4 and W. for branch pair Q5 / Q6. The three branch pairs Q1 / Q2, Q3 / Q4 and Q5 / Q6 are coupled on the DC side the intermediate circuit capacitor C _ZK . The illustrated embodiment has as a semiconductor switch Q1, Q2, Q3, Q4, Q5 and Q6 IGBT each with antiparallel freewheeling diode, the invention is not limited thereto. In particular, for example, MOSFET can be used.

Three connection points of the drive converter coupled to the three branch pair centers U, V and W. 14 are electrically coupled with a prime mover 16 , Wherein the individual windings of this prime mover are connected in the triangle in the present example. The voltage applied across the windings voltages are labeled U _UV , U _VW and U _WU . Likewise, of course, a star connection is possible. Furthermore, an embodiment according to the invention is not limited to a certain number of phases, as presented here by the example of three phases.

In a first step, the charging of the DC voltage intermediate circuit can take place. Here, the battery contactor K is closed and charged the intermediate circuit capacitor C _{ZK of} the drive converter. The semiconductor switches Q1 to Q6 in the drive converter 14 are in the state "Six Switch Open" (6SO).

In a second step, one in the prime mover 16 existing inductance are magnetized, in other words, it is a predetermined current impressed into the winding. This is a field-oriented control, which in the drive converter 14 can be implemented for application, wherein a reference to a rotor fixed coordinate reference system flow-forming current component i _d and a torque-forming current component i _{q is} specified. In the case of stoppage of the prime mover 16 is the construction of a torque undesirable. To prevent this, is in the prime mover 16 only a flow-forming current component i _d constructed. In contrast, the torque-forming current component i _q must be regulated to zero, since this would lead to a torque build-up. During the magnetization of the prime mover 16 For example, a state may be set where the semiconductor switches Q1 / Q3 / Q5 are in a state 1/0/0 and the semiconductor switches Q2 / Q4 / Q6 are in a state 0/1/1. It indicates a 1 active in the conductive state controlled semiconductor switch, a 0 a blocking semiconductor switch, which in this state current flow through an antiparallel freewheeling diode is possible. As a result, a current I _DC may be greater than zero and one from the branch pair center U to the prime mover 16 flowing current I _U greater than zero, also one from the branch pair center point V to the prime mover 16 flowing current I _V less than zero and one from the branch pair center W to the prime mover 16 flowing current I _W less than zero. In other words, the current I _U concerning the branch pair center U flows toward the prime mover, whereas the currents I _V and I _W concerning the branch pair centers V and W flow from the prime mover to the drive converter.

In a further step can now be the demagnetization of the inductance in the drive machine 16 take place, in other words, the stored magnetic energy is returned to the drive converter 14 fed back. Starting from the previously impressed currents, all the semiconductor switches Q1, Q2, Q3, Q4, Q5 and Q6 are switched to the state 6SO. In this case, the positive current I _U commutated by the semiconductor switch Q1 now in the freewheeling diode of the switch Q2 and the current I _V , which is negative, from the semiconductor switch Q4 in the freewheeling diode of the switch Q3. Furthermore, the negative current I _W commutates from the semiconductor switch Q6 into the free-wheeling diode of the switch Q5.

Thus arises now in the traction battery 12 a current I _DC , which is in the traction battery 12 flows back and thus is negative. In other words, those in the prime mover 16 stored magnetic energy is dissipated and minus the corresponding losses in the traction battery 12 fed back. After the magnetic energy in the prime mover 16 completely removed, the process can be repeated from the second step. As by current drain and - fed back to the internal resistance of the traction battery 12 a power loss occurs, this leads to a heating of the traction battery 12 ,

In a preferred method is permanently between the controlled operation of the drive converter 14 and switched to 6SO mode.

In an advantageous embodiment of the method, the demagnetization of the drive machine 16 achieved by adjusting a new setpoint for the flow-forming current component i _d , which has the opposite sign and preferably the same amount. Two such points are in the characteristic field according to 2 indicated by pointer. During the demagnetization phase, a current I _DC results from the traction battery 12 less than zero, that is, energy is being added to the traction battery at this stage 12 fed back. Once the electricity and thus the magnetic energy in the prime mover 16 When it is depleted, magnetization can take place in the opposite direction, whereby I _DC becomes positive again, in other words, energy is now restored from the traction battery 12 taken. This approach has the advantage that the control can be permanently active and no change between two operating modes is required. It is sufficient to specify the setpoint values for the flow-forming current component i _d alternately positive and negative.

2 shows an example of the characteristic diagram of a permanent magnet synchronous machine. On the horizontal axis, a flux-forming current component i _d in the unit amperes of -300 amps to +300 amperes is shown, on the vertical axis a torque-forming current component i _{q is} also shown in the unit ampere in the range of -300 amps to +300 Amp. The circuit indicates the current limit i _{max of} the maximum operating currents that can be realized with the given machine. A first family of curves drawn with dashed lines indicates operating points of the same torque. In this case, the curve for which a torque of zero results lies on the axis i _q = 0. A second family of curves drawn with dotted lines indicates operating points of the same magnetic flux. For ease of illustration because of slightly offset from the axis with i _q = 0, two pointers are shown starting from the origin of the coordinate system, representing two opposing points of equal magnetization, as they are driven in the aforementioned method.

Using the aforementioned method, a closed temperature control loop 20 being constructed. An exemplary embodiment of such a temperature control loop 20 is below in the 3 described. At this time, a battery temperature setpoint becomes 22 passed to a subtraction point, wherein a battery temperature reading 30 from the battery temperature setpoint 22 is subtracted. A resulting control deviation becomes a subsequent PI controller 24 fed, which is a manipulated variable 26 outputs. This manipulated variable 26 becomes a transmission link below 28 supplied, which in particular the drive converter 14 and the prime mover 16 as well as the traction battery 12 includes. At the output of the transmission link 28 is the battery temperature reading 30 to disposal.

For adjusting the heat output within the traction battery 12 can the manipulated variable 26 For example, act to the drive converter 14 a variable amplitude for the einzuegelnde flow-forming current component i _{d is} given. Alternatively, the specification of a constant amplitude for the flow-forming current component i _{d to be} regulated _is proposed, wherein the heating power is varied by a pulsed operation, for example by means of pulse width modulation (PWM)

The operating method according to the invention is not limited to the use of a three-phase synchronous machine, but, for example, a three-phase asynchronous machine or a reluctance machine can be used. In particular, the switched reluctance machine is suitable for use in such a method because of its higher reactive power requirement.

Preferably, a temperature control according to the described method can also be implemented directly in a drive converter, if this provides a corresponding interface for an external temperature detection. In particular, can be a binary input, for example, when using a bimetallic switch or a corresponding electronic component, which provides a temperature-dependent switching signal, build a very simple way a two-step control for a temperature of the traction battery.

Overall, it is thus shown how, using components already present in the motor vehicle, a method for heating a battery, in particular a traction battery, can be carried out.

LIST OF REFERENCE NUMBERS

10

driving device

12

traction battery

14

Drive Converters

16

prime mover

20

Temperature control loop

22

Battery temperature setpoint

24

PI controller

26

manipulated variable

28

transmission member

30

Battery temperature reading

C _ZK

Link capacitor

DC +, DC

connections

i _d

flow-forming current component

i _max

current limit

i _d

torque-forming current component

I _DC

battery power

I _U , I _V , I _W

electricity

K

battery contactor

Q1, Q2, Q3, Q4, Q5, Q6

Semiconductor switches

AND MANY MORE

Branch Pair center

U _DC

Intermediate circuit voltage

U _HV

battery voltage

_UV , U _VW , U _WU

tension

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 102009054461 A1 [0004]

Claims (7)

Method for heating a traction battery ( 12 ) in a motor vehicle comprising the steps of: - providing a programmable drive converter ( 14 ), which with an engine ( 16 ) for driving the motor vehicle and the traction battery ( 12 ), - operating the prime mover ( 16 ) with a field-oriented control in operating points of a characteristic field, where a torque-forming, rotor-related current component (i _q ) is controlled such that in the prime mover ( 16 ) no torque is built up, and thereby - causing a temperature increase of the traction battery ( 12 ) by a battery load current (I _DC ), which in the operation of the prime mover ( 16 ) between the drive converter ( 14 ) and the traction battery ( 12 ). A method according to claim 1 characterized by the further step: - operating the drive machine ( 16 ) with a field-oriented control in operating points of the characteristic field, where a flow-forming, rotor-related current component (i _d ) is controlled so that periodically between a positive and a negative setpoint for the flow-forming, rotor-related current component (i _d ) is changed. A method according to claim 1 characterized by the further step: - operating the drive machine ( 16 ) at standstill. Method according to claim 3, characterized by the further step: - operating the drive converter ( 14 ) alternately in a field-controlled mode and an uncontrolled free-wheeling mode. Method according to one of the preceding claims, characterized by the further step: - providing a closed temperature control loop ( 20 ) with the battery load current (I _DC ) as a manipulated variable for setting a predeterminable temperature level within the traction battery. Drive device ( 10 ) for a motor vehicle with. - a programmable drive converter ( 14 ), which is designed for carrying out a field-oriented control, - an engine ( 16 ), which are connected to the drive converter ( 14 ) and is adapted to be controlled with a field-oriented control in operating points of the characteristic field, where a torque-forming, rotor-related current component (i _q ) is controlled such that in the prime mover ( 16 ) no torque is built to operate, and - a traction battery ( 12 ), which is adapted to an internal temperature increase by a battery load current (I _DC ), which in the operation of the prime mover ( 16 ) between the drive converter ( 14 ) and the traction battery ( 12 ) to induce. Motor vehicle with a drive device according to claim 6.

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