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EP-4736313-A1 - METHOD FOR HEATING A BATTERY

EP4736313A1EP 4736313 A1EP4736313 A1EP 4736313A1EP-4736313-A1

Abstract

The method relates to a method for heating a battery (1) of a drive arrangement, wherein the drive arrangement has the battery (1), an inverter (3) electrically connected to the battery and an electric machine (2) connected to the inverter (3), said electric machine comprising a rotor and a stator with at least three phase windings. In the method, the inverter is operated such that a multiphase AC current with different current amplitude values flows between the inverter (3) and the at least three phase windings (U, V, W) of the electric machine (2).

Inventors

  • FASSNACHT, JOCHEN

Assignees

  • Robert Bosch GmbH

Dates

Publication Date
20260506
Application Date
20240515

Claims (17)

  1. 1. Method for heating a battery (1) of a drive arrangement, wherein the drive arrangement comprises the battery (1), an inverter (3) electrically connected to the battery and an electrical machine (2) connected to the inverter (3) comprising a rotor and a stator with at least three phase windings, the method comprising: Operating (S110) the inverter (3) such that a multiphase alternating current with different current amplitude values flows between the inverter (3) and the at least three phase windings (II, V, W) of the electrical machine (2).
  2. 2. The method according to claim 1, wherein the electrical machine has exactly three phase windings and the operation (S110) of the inverter (3) is carried out such that a first alternating current ( ) is generated in one of the three phase windings (II, V, W), and a second alternating current (/ 2 ) is generated in each of the other three phase windings (U, V, W), the two second alternating currents (/ 2 ) being in total opposite to the first alternating current (/
  3. 3. Method according to claim 2, wherein the operation of the inverter (3) is carried out such that the first alternating current ( ) and the second alternating current (/ 2 ) have a wave-like, in particular sinusoidal, shape, wherein an amplitude of the second alternating current (/ 2 ) corresponds to half the amplitude of the first alternating current ( ) and the second alternating current (/ 2 ) is phase-shifted by an angle of 180° to the first alternating current ( ).
  4. 4. The method according to any one of claims 2 or 3, wherein operating (S110) the inverter (3) comprises: Specifying (S120) at least one setpoint value which characterizes an amplitude of the first alternating current (/, Determining (S130) a control signal (A) for controlling current switches of the inverter (3) such that the first alternating current (/ in one of the three phase windings (II, V, W) with an amplitude corresponding to the setpoint value, and the second alternating current (/ 2 ) in each of the other three phase windings (II, V, W) with an amplitude corresponding to half the setpoint value and with a phase shifted by 180° to the first alternating current (/, Controlling (S140) the current switches of the inverter (3) using the control signal (A).
  5. 5. Method according to the preceding claim, further comprising: specifying (S120) a target value of a frequency of the first alternating current ( ), wherein the frequency of the first alternating current (/ in particular is at least 50 Hz or at least 100 Hz or at least 150 Hz, and/or at most 150 Hz, or at most 500 Hz or at most 1000 Hz or at most 2000 Hz or at most 2400 Hz.
  6. 6. The method according to the preceding claim, wherein determining (S130) a control signal further comprises the following steps: Determining (S131) a profile of the first alternating current (/ based on at least the target value of the amplitude and the target value of the frequency, determining (S134) the control signal (A) for controlling the current switches of the inverter (3) as a function of the profile of the first alternating current (/ .
  7. 7. The method according to the preceding claim, wherein determining (S131) a profile of the first alternating current (/) further comprises: Determining (S131a) the one phase winding of the at least three phase windings (U, V, W) in which the first alternating current ( ) is to be generated, based on the position of the rotor relative to the stator.
  8. 8. Method according to one of the preceding claims, wherein the method is carried out on a stationary electrical machine (2), wherein in particular the rotor of the electrical machine (2) is braked via a parking brake (7) of a vehicle (4).
  9. 9. Method according to the preceding claim, wherein the rotor of the electric machine (2) is held in a predetermined position, in particular by locking positions of the parking brake (7) of the vehicle (4).
  10. 10. Method according to one of the preceding claims, wherein the electric machine (2) further comprises a rotor cooling system (8) and the heat given off by the rotor to the rotor cooling system is additionally used for heating the battery (1).
  11. 11. A method according to any one of the preceding claims, wherein the method further comprises: Determining (S100) a temperature of the battery (1) and, if the temperature of the battery (1) reaches or exceeds a temperature threshold, charging (S150) the battery (1).
  12. 12. The method according to claim 11, wherein the temperature threshold value, depending on the battery type used, is at least 0°C or at least 10°C or at least 20°C or at least 30°C and/or at most 10°C or at most 20°C or at most 30°C.
  13. 13. Computing unit (6) configured to carry out the method according to one of the preceding claims.
  14. 14. Computing unit (6) according to claim 13, wherein the computing unit (6) comprises a phase modulator (6c), which is in particular a space vector pulse width modulator, which is configured to determine a control signal (A) for current switches of an inverter (3).
  15. 15. Computing unit (6) according to the preceding claim, wherein the computing unit (4) further comprises a phase current regulator (6a) which is adapted to regulate the first alternating current ( ) of the one phase winding.
  16. 16. Computer program which causes a computing unit (6) to carry out all method steps of a method according to one of claims 1 to 12 when it is executed on the computing unit.
  17. 17. Machine-readable storage medium with a computer program stored thereon according to claim 16.

Description

Description title Method for heating a battery The present invention relates to a method for heating a battery as well as a computing unit and a computer program for carrying out the method. Background of the invention If a lithium (Li)-ion battery is very cold, it has a high internal resistance and is therefore not efficient. In particular, the charging performance, but also the discharging performance, is severely limited at low temperatures and charging at these low temperatures is detrimental to the life of the battery. This is especially true when charging with high charging currents. This can be particularly problematic in electric vehicles, as these can get very cold, especially in winter. The battery should therefore be warmed to a minimum temperature before a journey so that the electric vehicle has sufficient performance and recuperation capability. To heat the battery before driving or before (quick) charging, a heating element (eg positive temperature coefficient, PTC) can be used in the battery cooling circuit. This heats the cooling water that is pumped through the battery and thus the battery. However, a heating element is expensive because it is an additional component that has to be connected to the on-board network as well as to the cooling water circuit and the communications network. Heating elements also need a large surface area to the cooling water in order to be able to quickly transfer the heat output to the cooling water. Heating the battery via the cooling water, which is traditionally thermally coupled to the outside of the battery cell, also causes a significant temperature gradient within the battery. This leads to faster aging of the cells because thermal stress occurs due to the temperature gradient. Advantageously, the power loss for heating would be generated in the battery, which would cause the battery to heat up much more evenly. For example, an approach is known from DE10 2010 032 088 A1 in which the generation of a high-frequency battery current pulse heats the battery through the resulting losses. To do this, the battery is divided into two sections that are charged and discharged out of phase in order to achieve a constant battery voltage despite the battery current pulse. A battery current pulse with frequencies above 25 kHz is generated by a load device. disclosure of the invention According to the invention, a method for heating a battery as well as a computing unit and a computer program for carrying it out are proposed with the features of the independent patent claims. Advantageous embodiments are the subject of the subclaims and the following description. The invention is based on a drive arrangement, for example of a vehicle, which has a battery, an inverter or power converter electrically connected to the battery and an electric machine connected to the inverter comprising a rotor and a stator with at least three phase windings. Charging or discharging the battery at low temperatures can sometimes significantly reduce the service life of the battery. The battery, which is in particular a Li-ion battery, is in particular the traction battery, i.e. the battery with which the electric machine that drives the electric vehicle is supplied with energy. It is therefore intended to heat the battery through losses in the battery, e.g. before charging or driving. Within the scope of the invention, the inverter is operated in such a way that a multi-phase alternating current with different current amplitude values flows between the inverter and the at least three phase windings of the electric machine. This advantageously leads to an alternating current flowing between the battery and the inverter, which leads to the internal heating of the battery. The control or control of the inverter is thus used to generate electrical losses in the battery. These losses can be used to heat the battery from the inside. When the battery cells are heated via the internal resistance, the cells heat up much more evenly and thus have a longer service life than if they were heated via externally heated cooling water. Furthermore, the method advantageously makes it possible to generate the greatest possible losses in the battery, while at the same time small losses occur in the electric drive or the on-board network, provided that they are designed accordingly. The method according to the invention is therefore advantageously particularly (energy) efficient. By heating the battery through internal losses, a heating element in the battery cooling circuit is no longer required. Furthermore, the method can be implemented using the normal hardware and large parts of the normal software of a conventional inverter. Only minor adjustments or extensions to the inverter software are necessary, meaning that a conventional drive arrangement can also be used as a generator for current oscillations to heat the battery with minor hardware and software adjustments. This means that existing components