TW202120351A - Battery system for a motor vehicle, method for operating a battery system, and motor vehicle - Google Patents

Abstract

The invention relates to a battery system (10) for a motor vehicle, comprising a battery module (5) which has an internal voltage source (Vi), an internal resistance (Ri), an internal inductance (Li), a positive pole (22) and a negative pole (21), an output capacitor (CA) which has a positive terminal (12) and a negative terminal (11), and a switching unit (60) for electrically connecting the battery module (5) to the output capacitor (CA). The switching unit (60) has a first switching element (61), a second switching element (62) and a third switching element (63), wherein a first connection of the first switching element (61) is connected to a node (25), a second connection of the first switching element (61) is connected to one of the poles (21, 22) of the battery module (5), a first connection of the second switching element (62) is connected to the node (25), a second connection of the second switching element (62) is connected to one of the terminals (11, 12) of the output capacitor (CA), a first connection of the third switching element (63) is connected to the other of the poles (21, 22) of the battery module (5) and is connected to the other of the terminals (11, 12) of the output capacitor (CA), and a second connection of the third switching element (63) is connected to the node (25). The invention relates to a method for operating a battery system (10) according to the invention, wherein the switching unit (60) is controlled in such a manner that an alternating current (I) flows through the battery module (5). The invention also relates to a motor vehicle comprising at least one battery system (10) according to the invention which is operated using a method according to the invention.

Description

Battery system for motor vehicle, method for operating battery system and motor vehicle

The present invention relates to a battery system for a motor vehicle, which includes a battery module with internal voltage source, internal resistance, internal inductance, positive and negative electrodes; an output capacitor with positive and negative terminals; and a battery module The group is electrically connected to the switching unit of the output capacitor. The invention also relates to a method for operating the battery system according to the invention and a motor vehicle with a corresponding battery system.

The conventional motor vehicle has a drive device that usually includes an internal combustion engine. The conventional motor vehicle also includes a battery system for supplying electric energy to the starter motor and other loads of the motor vehicle, and a generator for charging the battery system. Electric vehicles have a battery system for supplying electric energy to traction motors and other loads.

The conventional battery system of the general type of motor vehicles includes a battery module having at least one battery cell, preferably a plurality of battery cells connected in series, for example. Such battery modules have a nominal voltage of, for example, 12 V, 24 V, or 48 V. Under this condition, the output voltage of the battery system of the conventional motor vehicle corresponds to the nominal voltage of the battery module. The battery system of an electric vehicle may include a plurality of battery modules connected in series, and therefore may have a higher output voltage of, for example, 600 V.

The general-purpose battery system also includes an output capacitor for buffering the output voltage of the battery system. This type of output capacitor is electrically connected to the vehicle electrical system of the motor vehicle, and is also called an intermediate circuit capacitor. The general-purpose battery system also includes a switch unit for electrically connecting the battery module to the output capacitor. The switch unit can be used to electrically connect the battery module to the vehicle electrical system and the output capacitor of the motor vehicle and disconnect the battery module from the vehicle electrical system and the output capacitor.

For example, the battery cell of the battery module is a lithium-ion battery cell. For example, when the low operating temperature of the lithium-ion battery cell is less than 0°C, the lithium-ion battery cell has a relatively high internal resistance. The high internal resistance causes severe limitations during the operation of the battery system at low temperatures, especially during the cold start of motor vehicles in winter. The internal resistance of lithium-ion battery cells decreases significantly as the operating temperature increases.

The documents DE 10 2014 202 717 B3 and US 2015/0236616 A1 disclose a drive system for a motor vehicle. The drive system includes an intermediate circuit capacitor that can be supplied with voltage from the motor vehicle battery. The intermediate circuit capacitor is electrically connected to an inverter for controlling the three-phase electric motor. The inverter has a switching unit with a plurality of switching elements.

Documents DE 10 2011 110 906 A1 and CN 102 39 8507 B disclose a hybrid transmission system that includes a high-voltage battery and a DC coupling element coupled to a rectifier/inverter module. The rectifier/inverter module is electrically connected to the two torque machines and includes a switching device, and the switching device includes a pair of power transistors.

Document WO 2017/064820 A1 discloses a system for generating electrical energy, which has a generator and a frequency converter. In this situation, the frequency converter has a switching unit, and the switching unit has a plurality of switching elements.

A battery system for a motor vehicle is proposed. In this situation, the battery system includes: a battery module having an internal voltage source, an internal resistance, an internal inductance, a positive electrode and a negative electrode; an output capacitor having a positive terminal and a negative terminal; And a switch unit for electrically connecting the battery module to the output capacitor.

The battery module includes a plurality of battery cells that can be connected in series and in parallel within the battery module. The battery cell is preferably in the form of a lithium ion battery cell. The battery cell simulates a voltage source with an internal resistance that depends on the temperature. The wires inside the battery module also have resistance and inductance. The voltage source of the battery unit forms the internal voltage source of the battery module. The internal resistance of the battery unit and the resistance of the wires form the internal resistance of the battery module. The inductance of the wire forms the internal inductance of the battery module. Optionally, the battery module may additionally include a coil with additional inductance.

For example, the output capacitor is an intermediate circuit capacitor. The intermediate circuit capacitor can be electrically connected to the vehicle electrical system of the motor vehicle and used to buffer the output voltage of the battery system. As an alternative to or in addition to the intermediate circuit capacitor, the battery module can additionally have further capacitors.

The switch unit can be used to electrically connect the battery module to the vehicle electrical system and the output capacitor of the motor vehicle and disconnect the battery module from the vehicle electrical system and the output capacitor.

According to the present invention, the switch unit has a first switch element, a second switch element, and a third switch element. Each of the switching elements has three connecting pieces, and a switching path that can be controlled by the third connecting piece is formed between the first connecting piece and the second connecting piece.

In this situation, a first connector of the first switching element is connected to a node, and a second connector of the first switching element is connected to one of the positive electrode and the negative electrode of the battery module. A first connector of the second switching element is connected to the node, and a second connector of the second switching element is connected to one of the positive terminal and the negative terminal of the output capacitor. A first connector of the third switching element is connected to the other of the positive electrode and the negative electrode of the battery module and the other of the positive terminal and the negative terminal of the output capacitor, and the third A second connector of the switching element is connected to the node.

For example, the second connector of the first switching element is connected to the positive electrode of the battery module, and the second connector of the second switching element is connected to the positive terminal of the output capacitor. The first connector of the third switching element is then connected to the negative electrode of the battery module and the negative terminal of the output capacitor. Under this condition, the negative electrode of the battery module is permanently connected to the negative terminal of the output capacitor.

The connection of the switching elements of the switching unit according to the present invention realizes a plurality of switching states of the battery system. In the first switching state where the first switching element is closed, the second switching element is open, and the third switching element is closed, current can flow through the internal resistance and internal inductance of the battery module, but cannot flow to the output capacitor and the motor vehicle. Vehicle electrical system. In the second switching state where the first switching element is closed, the second switching element is closed, and the third switching element is open, current can flow through the internal resistance and internal inductance of the battery module and the output capacitor. In the third switching state where the first switching element is off, current cannot flow through the battery module. In the fourth switching state where the second switching element is off and the third switching element is off, the current cannot flow through the battery module as well.

According to a preferred configuration of the present invention, the first switching element, the second switching element, and the third switching element are in the form of field-effect transistors and each has a source connection, a drain connection, and a gate connection. The switching elements are connected in a manner such that in each situation, the first connector is a source connector, the second connector is a drain connector, and the third connector is a gate connector. For example, the switching element is a MOSFET, especially an enhancement type n-channel MOSFET.

A method for operating a battery system according to the present invention is also proposed. In this situation, the switch unit is controlled in a way that allows an alternating current to flow through the battery module.

The alternating current therefore specifically flows through the internal resistance of the battery module. Under this condition, the alternating current crosses the internal resistance of the battery module and therefore generates a voltage drop across the internal resistance of the battery cell. Therefore, electrical energy is converted into heat in the internal resistance of the battery module and therefore at the internal resistance of the battery cell. Therefore, heating of the battery module, especially the battery cells of the battery module, occurs. Therefore, the internal resistance of the battery cell decreases as the operating temperature increases.

Preferably, the switch unit is controlled in a plurality of successive stages. In this situation, the switch unit is controlled in a manner such that during a first phase, electric energy is transferred from the internal voltage source of the battery module to the internal inductance of the battery module, and a second During the phase, electrical energy is transferred from the internal inductance of the battery module to the output capacitor, and during a third phase, electrical energy is transferred from the output capacitor to the internal voltage source of the battery module.

The switching unit is preferably controlled in a manner such that during a first phase, the first switching element is closed, the second switching element is opened, and the third switching element is closed. During the first phase, current flows through the internal voltage source, internal resistance, internal inductance, first switching element, and third switching element.

The switching unit is preferably also controlled in a manner such that during a second phase, the first switching element is closed, the second switching element is closed and the third switching element is open. During the second phase, current flows through the internal voltage source, internal resistance, internal inductance, the first switching element, the second switching element, and the output capacitor.

The switching unit is preferably also controlled in a manner such that during a first intermediate phase between the first phase and the second phase, the second switching element is turned off and the third switching element is turned off . In this situation, the first switching element can remain closed.

The switching unit is preferably also controlled in a manner such that during a third phase, the first switching element is closed, the second switching element is closed and the third switching element is open. During the third phase, current flows through the internal voltage source, internal resistance, internal inductance, the first switching element, the second switching element, and the output capacitor. During the third phase, the current flows in a direction opposite to the direction during the second phase.

The switching unit is preferably also controlled in a manner such that during a second intermediate phase between the third phase and the first phase, the second switching element is turned off and the third switching element is turned off open. In this situation, the first switching element can remain closed.

The switch unit is preferably also controlled in a manner such that the first stage, the second stage and the third stage are repeated cyclically. The first stage, the second stage, and the third stage are preferably repeated at a relatively high frequency of, for example, 20 kHz.

A motor vehicle comprising at least one battery system according to the invention is also proposed, the battery system being operated using the method according to the invention. Advantages of the invention

The method of the present invention makes it possible to heat the battery cells of the battery module to an appropriate operating temperature in a relatively short time in the battery system for a motor vehicle according to the present invention. Therefore, the internal resistance of the battery unit decreases, and the battery system of the motor vehicle is ready for use in a relatively short time. There is no need for a separate heating device for heating the battery cells.

The method of the present invention can be used to operate the battery system according to the present invention in a manner similar to a DC/DC converter or a boost converter. The alternating current flowing under this condition always flows through the internal resistance of the battery module and therefore through the internal resistance of the battery cell. Due to the voltage drop generated during the process, electrical energy is converted into heat at the internal resistance of the battery unit, thereby heating the battery unit. During this operation, electrical energy is transferred between the voltage source, internal inductance, and output capacitor. Therefore, the electric energy is displaced inside the battery system according to the present invention. Except for the conversion of electrical energy into heat at the internal resistance of the battery cell, no other significant losses occur. Therefore, the battery module only discharges insignificantly.

In the following description of the embodiments of the present invention, the same component symbols are used to denote the same or similar components. In this case, repeated descriptions of these components are omitted in individual cases. The drawings only schematically illustrate the subject of the present invention.

Figure 1 shows a schematic illustration of a battery system 10 for a motor vehicle. The battery system 10 includes a battery module 5, an output capacitor CA and a switch unit 60. The switch unit 60 is used to electrically connect the battery module 5 to the output capacitor CA.

The battery module 5 includes a plurality of battery cells that are not described here and can be connected to each other in series and in parallel within the battery module 5. Each of the battery cells simulates a voltage source with an internal resistance that depends on temperature. The voltage source of the battery unit forms the internal voltage source Vi. The internal resistance of the battery cell and the resistance of the wire form the internal resistance Ri. The wire and the inductance of the battery cell 2 form an internal inductance Li. Optionally, a coil with additional inductance can be provided. Under this condition, the inductance of the wire and battery cell 2 together with the inductance of the coil forms an internal inductance Li.

Therefore, the battery module 5 has an internal voltage source Vi, an internal resistance Ri, and an internal inductance Li. The battery module 5 also has a positive electrode 22 and a negative electrode 21. During the idling period, the voltage provided by the internal voltage source Vi is applied between the positive electrode 22 and the negative electrode 21.

The output capacitor CA has a positive terminal 12 and a negative terminal 11. The output capacitor CA is, for example, an intermediate circuit capacitor electrically connected to the vehicle electrical system of the motor vehicle. The battery module 5 may have another capacitor, which then forms the output capacitor CA together with the intermediate circuit capacitor.

The switch unit 60 has a first switch element 61, a second switch element 62, and a third switch element 63. The switching elements 61, 62, and 63 each have three connecting members, and a switching path that can be controlled by the third connecting member is formed between the first connecting member and the second connecting member.

Under the conditions of the present invention, the first switching element 61, the second switching element 62 and the third switching element 63 are in the form of field effect transistors. The switching elements 61, 62, and 63 each have a source connector, a drain connector, and a gate connector. The switching elements 61, 62, and 63 are connected in a manner such that in each situation, the first connection is a source connection, the second connection is a drain connection, and the third connection is a gate connection Pieces.

In the present invention, the switching elements 61, 62, and 63 are enhancement type n-channel MOSFETs. The switching elements 61, 62, and 63 each have a switching path and a reverse diode connected in parallel with the switching path. Reverse diodes (also known as internal diodes) are produced in any MOSFET due to its internal structure and are not an explicit component.

The first connector of the first switching element 61 is connected to the node 25. The second connector of the first switching element 61 is connected to the positive electrode 22 of the battery module 5. The first connector of the second switching element 62 is connected to the node 25. The second connector of the second switching element 62 is connected to the positive terminal 12 of the output capacitor CA. The first connector of the third switching element 63 is connected to the negative electrode 21 of the battery module 5 and the negative terminal 11 of the output capacitor CA. The second connector of the third switching element 63 is connected to the node 25.

Figure 2 shows a schematic illustration of the battery system 10 during the first stage of the method. During the first phase, the first switching element 61 is closed, the second switching element 62 is open, and the third switching element 63 is closed. During the first phase, the current I flows through the internal voltage source Vi, the internal resistance Ri, the internal inductance Li, the first switching element 61 and the third switching element 63.

Under this condition, electric energy is transferred from the internal voltage source Vi to the internal inductor Li. The current I also generates a voltage drop across the internal resistance Ri, whereby electrical energy is converted into heat.

After the end of the first phase, the third switching element 63 is turned off, and the first intermediate phase in which the second switching element 62 and the third switching element 63 are turned off starts. In this situation, the first switching element 61 remains closed. After the end of the first intermediate phase, the second switching element 62 is closed and the second phase starts.

Figure 3 shows a schematic illustration of the battery system 10 during the second stage of the method. During the second phase, the first switching element 61 is closed, the second switching element 62 is closed and the third switching element 63 is open. During the second phase, the current I flows through the internal voltage source Vi, the internal resistance Ri, the internal inductance Li, the first switching element 61, the second switching element 62, and the output capacitor CA.

Under this condition, electric energy is transferred from the internal inductance Li to the output capacitor CA. The internal inductance Li releases its stored energy into the output capacitor CA. The current I also generates a voltage drop across the internal resistance Ri, whereby electrical energy is converted into heat.

Figure 4 shows a schematic illustration of the battery system 10 during the third stage of the method. During the third phase, the first switching element 61 is closed, the second switching element 62 is closed and the third switching element 63 is open. During the third phase, the current I flows through the internal voltage source Vi, the internal resistance Ri, the internal inductance Li, the first switching element 61, the second switching element 62, and the output capacitor CA. However, during the third phase, the current I flows in a direction opposite to the direction during the second phase.

Under this condition, the electric energy is transferred from the output capacitor CA to the internal voltage source Vi. The current I also generates a voltage drop across the internal resistance Ri, whereby electrical energy is converted into heat.

After the third stage ends, the second switching element 62 is turned off, and the second intermediate stage in which the second switching element 62 and the third switching element 63 are turned off starts. In this situation, the first switching element 61 remains closed. After the second intermediate phase ends, the third switching element 63 is closed and another first phase starts.

The present invention is not limited to the exemplary embodiments described herein and the aspects highlighted herein. On the contrary, a large number of amendments within the scope of activities of persons with ordinary knowledge in the field can be associated within the scope stated in the scope of the patent application.

5: Battery module 10: Battery system 11: Negative terminal 12: Positive terminal 21: negative electrode 22: positive 25: Node 60: switch unit 61: The first switching element 62: second switching element 63: third switching element CA: output capacitor I: current Li: Internal inductance Ri: Internal resistance Vi: Internal voltage source

The embodiments of the present invention will be explained in more detail based on the drawings and the following description.

In the schema: [Figure 1] Show a schematic description of the battery system, [Figure 2] Shows a schematic illustration of the battery system during the first stage of the method, [Figure 3] Shows a schematic illustration of the battery system during the second stage of the method, and [Figure 4] Shows a schematic illustration of the battery system during the third phase of the method.

5: Battery module

10: Battery system

11: Negative terminal

12: Positive terminal

21: negative electrode

22: positive

25: Node

60: switch unit

61: The first switching element

62: second switching element

63: third switching element

CA: output capacitor

Li: Internal inductance

Ri: Internal resistance

Vi: Internal voltage source

Claims (11)

A battery system (10) for a motor vehicle, which includes: A battery module (5) having an internal voltage source (Vi), an internal resistance (Ri), an internal inductance (Li), a positive electrode (22) and a negative electrode (21), An output capacitor (CA), which has a positive terminal (12) and a negative terminal (11), and A switch unit (60) for electrically connecting the battery module (5) to the output capacitor (CA), Its characteristics are: The switch unit (60) has a first switch element (61), a second switch element (62) and a third switch element (63), wherein A first connecting piece of the first switching element (61) is connected to a node (25), A second connector of the first switch element (61) is connected to one of the positive electrode and the negative electrode (21, 22) of the battery module (5), A first connector of the second switching element (62) is connected to the node (25), A second connector of the second switching element (62) is connected to one of the positive terminal and the negative terminal (11, 12) of the output capacitor (CA), A first connector of the third switching element (63) is connected to the other of the positive electrode and the negative electrode (21, 22) of the battery module (5) and connected to the output capacitor (CA) The other of the positive terminal and the negative terminal (11, 12), and A second connector of the third switching element (63) is connected to the node (25). Such as the battery system (10) of claim 1, where The first switching element (61), the second switching element (62), and the third switching element (63) are in the form of field-effect transistors, wherein under each condition The first connecting piece is a source connecting piece, The second connecting piece is a drain connecting piece, and A third connecting piece is a gate connecting piece. A method for operating a battery system (10) such as claim 1 or 2, wherein The switch unit (60) is controlled in a way that makes An alternating current (I) flows through the battery module (5). Such as the method of claim 3, where The switch unit (60) is controlled in a way that makes During the first stage, electric energy is transferred from the internal voltage source (Vi) of the battery module (5) to the internal inductance (Li) of the battery module (5), During the second phase, electric energy is transferred from the internal inductance (Li) of the battery module (5) to the output capacitor (CA), and During the third phase, electric energy is transferred from the output capacitor (CA) to the internal voltage source (Vi) of the battery module (5). Such as the method of claim 3 or 4, where The switch unit (60) is controlled in a way that makes During the first phase, the first switching element (61) is closed, the second switching element (62) is opened, and the third switching element (63) is closed. Such as the method of claim 5, where The switch unit (60) is controlled in a way that makes During the second phase, the first switching element (61) is closed, the second switching element (62) is closed and the third switching element (63) is open. Such as the method of claim 6, where The switch unit (60) is controlled in a way that makes During the first intermediate phase between the first phase and the second phase, the second switching element (62) is turned off and the third switching element (63) is turned off. Such as the method of claim 5, where The switch unit (60) is controlled in a way that makes During the third phase, the first switching element (61) is closed, the second switching element (62) is closed and the third switching element (63) is opened. Such as the method of claim 8, where The switch unit (60) is controlled in a way that makes During the second intermediate phase between the third phase and the first phase, the second switching element (62) is turned off and the third switching element (63) is turned off. Such as the method of claim 5, where The switch unit (60) is controlled in a way that makes The first stage, the second stage, and the third stage are repeated cyclically. A motor vehicle comprising at least one battery system (10) as claimed in claim 1 or 2, the battery system being operated using a method as claimed in any one of claims 3 to 10.

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