CN115042673A - A battery self-heating circuit with transformer and vehicle - Google Patents

Abstract

The embodiment of the application provides a take battery self-heating circuit and vehicle of transformer, wherein, the circuit includes: the power supply comprises a half-bridge circuit consisting of a high-voltage end, a low-voltage end, a transformer and a power switch, and a plurality of battery branches; a half-bridge circuit consisting of a plurality of battery branches and power switches is arranged between the high-voltage end and the low-voltage end; each battery branch is formed by connecting a plurality of batteries in series; the plurality of battery branches includes: a first battery branch and a second battery branch; a first end of a first secondary side of the transformer is connected with a series point of any two batteries in the first battery branch; the second end of the first secondary side of the transformer is connected with the series point of any two batteries in the second battery branch circuit; and the primary side of the transformer is connected with the midpoint of a half-bridge circuit formed by the power switches.

Description

A battery self-heating circuit and vehicle with a transformer

technical field

The present application relates to the technical field of new energy vehicles, in particular, to a battery self-heating circuit with a transformer and a vehicle.

Background technique

The low temperature performance of new energy vehicle power batteries is poor, so it is necessary to try to increase the battery temperature at low temperatures. The current technical solutions include: after heating the cold zone liquid by means of PTC, electric drive system heat generation, etc., the battery is heated by the cold zone liquid to realize indirect heating; the motor winding is charged and discharged through the motor controller, thereby generating AC current in the battery , The battery is heated by the internal resistance of the battery, that is, the internal resistance of the battery is directly heated. However, the method of indirect heating has the following disadvantages: a large amount of heat cannot be effectively transferred to the battery, but is dissipated into the environment, resulting in low efficiency; heat needs to be input into the battery through the cold zone liquid, the external structure of the battery, etc., and the battery heats up very slowly. There is a situation of slow heat transfer; the temperature of the battery cells close to the cold zone liquid rises rapidly, resulting in uneven heating of the battery. The problem with the direct heating method is: the frequency of the heating current is low, the frequency of the AC current for direct heating is generally about 2kHz, the human ear is very sensitive, and the noise generated has a great negative impact on the driver or passenger; this kind of method It is not easy to use when the vehicle is running, and it is easy to cause torque jitter or affect the power output of the motor. Therefore, in order to achieve a better heating effect, the above-mentioned battery heating method requires a heating circuit composed of devices with higher specification parameters, and the cost is relatively high.

SUMMARY OF THE INVENTION

In the first aspect, the purpose of the embodiments of the present application is to provide a battery self-heating circuit with a transformer and a vehicle, which can increase the effective heating current and improve the heating effect.

In a first aspect, an embodiment of the present application provides a battery self-heating circuit with a transformer, including:

Half-bridge circuit composed of high-voltage side, low-voltage side, transformer, power switch, and multiple battery branches;

A half-bridge circuit composed of a plurality of battery branches and the power switch is arranged between the high-voltage end and the low-voltage end;

Each of the battery branches is formed by connecting a plurality of batteries in series;

The plurality of battery branches include: a first battery branch and a second battery branch;

The first end of the first secondary side of the transformer is connected to the series point of any two batteries in the first battery branch;

The second end of the first secondary side of the transformer is connected to the series point of any two batteries in the second battery branch;

The primary side of the transformer is connected to the midpoint of the half-bridge circuit formed by the power switch,

A voltage difference is formed between the first end and the second end of the primary side of the transformer.

In the above implementation process, due to the impedance transformation effect of the transformer, the internal resistance of the battery is mapped to the primary side of the transformer according to the ratio of the square of the turns of the primary side and the secondary side, which greatly enhances the resistance of the primary side, improves the system power factor, reduces the The apparent power required by the system during heating is reduced. As the apparent power is reduced, the specifications and parameters of the power switch are also greatly reduced, and the cost is also reduced.

Further, the battery self-heating circuit further includes: a capacitor;

the capacitor and the primary side of the transformer form a series branch;

One end of the series branch is connected to the midpoint of the half-bridge circuit.

In the above implementation process, on the one hand, the capacitor is used to prevent the saturation of the bias magnet of the transformer; on the other hand, it is used to resonate with the leakage inductance of the transformer to improve the power factor and reduce the apparent power. As the apparent power is reduced, the parameter requirements such as the capacitance value of the capacitor are correspondingly greatly reduced, and the cost is also reduced accordingly.

Further, the battery self-heating circuit further includes: a capacitor;

the capacitor and the primary side of the transformer form a series branch;

the first end of the series branch is connected with the midpoint of the half-bridge circuit formed by the power switch;

The second end of the series branch is connected to the midpoint of at least one battery branch of the plurality of battery branches.

Further, the battery self-heating circuit further includes: a capacitor;

the capacitor and the primary side of the transformer form a series branch;

the first end of the series branch is connected with the midpoint of the half-bridge circuit formed by the power switch;

The second end of the series branch is connected to the low voltage end.

Further, the battery self-heating circuit further includes: a capacitor;

the capacitor and the primary side of the transformer form a series branch;

the first end of the series branch is connected with the midpoint of the half-bridge circuit formed by the power switch;

The second end of the series branch is connected to the high voltage end.

Further, the battery self-heating circuit further includes: a capacitor branch;

The capacitor branch and the half-bridge circuit formed by the power switch are connected in parallel;

The primary side of the transformer is connected to the midpoint of the capacitor branch.

Further, two ends of the capacitor are connected to two different ends of the transformer.

In the above implementation process, the primary side current and the secondary side current are superimposed and enhanced, thereby increasing the heating power of one of the one battery branch.

Further, the plurality of battery branches further include: a third battery branch;

The first end of the primary side is connected to the series point of any two batteries of the third battery branch.

In the above implementation process, there are three battery branches. Due to the impedance of the transformer, the resistance of the primary side is increased, the power factor of the circuit is improved, and the apparent power of the circuit is reduced. The half-bridge circuit composed of power switches generates high voltage frequency current to heat the three battery branches.

Further, the leakage inductance of the transformer and the capacitor form a resonant circuit, and the resonant frequency of the resonant circuit is equal to the switching frequency of the half-bridge circuit formed by the power switch.

In the above implementation process, on the one hand, the capacitor is used to prevent the saturation of the bias magnet of the transformer; on the other hand, it is used to resonate with the leakage inductance of the transformer to improve the power factor and reduce the apparent power.

Further, the leakage inductance of the transformer and the capacitor form a resonance circuit, and the resonance frequency of the resonance circuit is lower than the switching frequency of the half-bridge circuit formed by the power switch.

In the above implementation process, the capacitor is used to isolate the DC voltage to avoid the saturation of the transformer bias.

Further, the turns ratio of the primary side of the transformer and the secondary side of the transformer is greater than 1

In the above implementation process, because of the impedance transformation effect of the transformer, it is equivalent to mapping the internal resistance of the battery to the primary side of the transformer according to the ratio of the square of the turns ratio, which greatly enhances the resistance of the primary side, improves the circuit power factor, and reduces the the apparent power of the circuit.

Further, the capacity ratio of the first battery branch and the second battery branch is: (k+1)/k; where k is the turns of the primary side of the transformer and the secondary side of the transformer number ratio.

In the above implementation process, the first battery branch and the second battery branch generate heat evenly.

Other features and advantages disclosed herein will be set forth in the description that follows, or some of the features and advantages may be inferred or unambiguously determined from the description, or may be learned by practicing the above-described techniques disclosed herein.

In order to make the above-mentioned objects, features and advantages of the present application more obvious and easy to understand, the preferred embodiments are exemplified below, and are described in detail as follows in conjunction with the accompanying drawings.

Description of drawings

In order to explain the technical solutions of the embodiments of the present application more clearly, the following briefly introduces the accompanying drawings that need to be used in the embodiments of the present application. It should be understood that the following drawings only show some embodiments of the present application, therefore It should not be regarded as a limitation of the scope. For those of ordinary skill in the art, other related drawings can also be obtained from these drawings without any creative effort.

1 is a schematic structural diagram of a battery self-heating circuit with a transformer provided by an embodiment of the application;

2 is another schematic structural diagram of a battery self-heating circuit with a transformer provided by an embodiment of the application;

3 is another schematic structural diagram of a battery self-heating circuit with a transformer provided by an embodiment of the application;

4 is another schematic structural diagram of a battery self-heating circuit with a transformer provided by an embodiment of the application;

5 is another schematic structural diagram of a battery self-heating circuit with a transformer provided by an embodiment of the application;

6 is another schematic structural diagram of a battery self-heating circuit with a transformer provided by an embodiment of the application;

FIG. 7 is another schematic structural diagram of the battery self-heating circuit with a transformer provided in an embodiment of the present application.

Icon: Tx-transformer; U1-first battery module; U2-second battery module; U3-third battery module; U4-fourth battery module; U5-fifth battery module; U6-sixth battery module; Lp- Primary side; Ls1-first secondary side; Ls2-second secondary side; Ls3-third secondary side; Q1-first power switch; Q2-second power switch; Cr-capacitor; Cr1-first capacitor; Cr2- The second capacitor; Cdc-DC bus capacitor

Detailed ways

The technical solutions in the embodiments of the present application will be described below with reference to the accompanying drawings in the embodiments of the present application.

It should be noted that like numerals and letters refer to like items in the following figures, so once an item is defined in one figure, it does not require further definition and explanation in subsequent figures. Meanwhile, in the description of the present application, the terms "first", "second", etc. are only used to distinguish the description, and cannot be understood as indicating or implying relative importance.

Example 1

Referring to FIG. 1 to FIG. 5, an embodiment of the present application provides a battery self-heating circuit with a transformer Tx, including:

Half-bridge circuit composed of high-voltage side, low-voltage side, transformer Tx, power switch, and multiple battery branches;

There is a half-bridge circuit composed of multiple battery branches and power switches between the high-voltage terminal and the low-voltage terminal;

Exemplarily, the half-bridge circuit is composed of a first power switch Q1 and a second power switch Q2.

Each battery branch is formed by connecting multiple batteries in series;

The plurality of battery branches include: a first battery branch and a second battery branch;

In FIG. 1 , the first battery branch includes: a first battery module U1 and a second battery module U2; the second battery branch includes: a third battery module U3 and a fourth battery module U4.

The first end of the first secondary side Ls1 of the transformer Tx is connected to the series point of any two batteries in the first battery branch;

The second end of the first secondary side Ls1 of the transformer Tx is connected to the series point of any two batteries in the second battery branch;

The primary side Lp of the transformer Tx is connected to the series point of any two batteries of one battery branch of the plurality of battery branches,

A voltage difference is formed between the first end and the second end of the primary side of the transformer.

In the above implementation process, due to the impedance transformation effect of the transformer Tx, the internal resistance of the battery is mapped to the primary side Lp of the transformer Tx according to the ratio of the primary side Lp and the secondary side turns squared, which greatly enhances the primary side Lp resistance and improves the The system power factor is reduced, and the apparent power required by the system during heating is reduced. As the apparent power is reduced, the specifications and parameters of the power switch are also greatly reduced, and the cost is also reduced.

Referring to FIG. 1 , in a possible implementation manner, the battery self-heating circuit further includes: a capacitor Cr;

The capacitor Cr and the primary side Lp of the transformer Tx form a series branch;

the first end of the series branch is connected with the midpoint of the half-bridge circuit formed by the power switch;

The second end of the series branch is connected to the midpoint of at least one battery branch of the plurality of battery branches.

Referring to FIG. 2, in a possible implementation manner, the battery self-heating circuit further includes: a capacitor Cr;

The capacitor Cr and the primary side Lp of the transformer Tx form a series branch;

the first end of the series branch is connected with the midpoint of the half-bridge circuit formed by the power switch;

The second end of the series branch is connected to the low voltage end.

Referring to FIG. 3, in a possible implementation manner, the battery self-heating circuit further includes: a capacitor Cr;

The capacitor Cr and the primary side Lp of the transformer Tx form a series branch;

the first end of the series branch is connected with the midpoint of the half-bridge circuit formed by the power switch;

The second end of the series branch is connected to the high voltage end.

Referring to FIG. 4 , in a possible implementation manner, the battery self-heating circuit further includes: a capacitor branch;

Exemplarily, the capacitor branch includes first capacitors Cr1 and Cr2;

The capacitor branch and the half-bridge circuit formed by the power switch are connected in parallel;

The primary side of the transformer Tx is connected to the midpoint of the capacitor branch.

In the above implementation process, on the one hand, isolation of the primary and secondary sides of the transformer Tx is achieved. On the other hand the initialization transient problem is small.

It should be noted that the capacitor Cr is not necessary. See Figure 5. When there is no capacitor Cr, the circuit has no resonance at this time, and the half-bridge circuit adopts the complementary conduction mode with a small dead time, or a large dead time and a transformer. The non-continuous conduction mode of Tx leakage inductance current can still achieve battery heating, but at this time, there is a risk of transformer Tx bias saturation. This risk can be avoided if the transformer Tx excitation current can be closed-loop controlled at this time, which is also achievable.

Further, the battery pack is connected to the high-voltage bus bar of the vehicle through a relay, and the bus bar is connected with electrical equipment such as a three-phase inverter.

The working condition of the battery self-heating circuit with transformer Tx has nothing to do with the state of the vehicle. Whether the vehicle is parked, connected to a charging pile for charging, or driving normally, the battery self-heating circuit with transformer Tx can work normally.

1-5, in a possible implementation manner, the battery self-heating circuit further includes: a capacitor Cdc; the capacitor Cdc is connected in parallel with a plurality of battery branches.

In the above implementation process, the capacitor Cdc can absorb the pulse current generated during the operation of the half-bridge circuit. Since the apparent power is reduced, the parameter requirements such as the capacitance value of the capacitor Cdc are correspondingly greatly reduced, and the cost is also reduced accordingly.

In a possible implementation manner, the first battery branch is formed by connecting two batteries in series;

The second battery branch is formed by connecting two batteries in series.

1-5 , the first battery branch is formed by connecting a first battery module U1 and a second battery module U2 in series; the second battery branch is formed by connecting a third battery module U3 and a fourth battery module U4 in series.

In the above implementation process, the battery is divided into two parallel parts, and each parallel part is divided into two parts of the same size, high and low, which are equivalent to two half-bridge circuits. The first secondary side Ls1 of the transformer Tx crosses the boundary between two parts. The midpoint of a half-bridge circuit.

Further, both ends of the capacitor Cr are connected to two different ends of the transformer Tx.

In the above implementation process, the two ends of the capacitor Cr are connected to the two opposite ends of the transformer Tx, so that the primary side Lp current and the secondary side current will be superimposed and enhanced, thereby increasing the heating power of one of the half-bridge circuits of the battery.

Referring to Figure 3, it is another connection method of the transformer Tx terminal with the same name.

In a possible implementation manner, the plurality of battery branches further include: a third battery branch;

The first end of the primary side Lp is connected to the series point of any two batteries of the third battery branch.

In a possible implementation manner, the leakage inductance of the transformer Tx and the capacitance Cr form a resonance circuit, and the resonance frequency of the resonance circuit is equal to the switching frequency of the half-bridge circuit formed by the power switch.

It can be understood that, in the actual application process, there may be a certain error between the resonant frequency of the resonant circuit and the switching frequency of the half-bridge circuit composed of the power switches.

For example, for example, the switching frequency of the first power switch Q1 and the second power switch Q2 is 20 kHz, and the resonant frequency of the transformer Tx and the capacitor Cr is 20 kHz.

Preferably, the turns ratio of the primary side Lp of the transformer Tx to the secondary side of the transformer Tx is greater than 1.

Further, in order to make the first battery branch and the second battery branch generate heat evenly, the capacity ratio of the first battery branch and the second battery branch is: (k+1)/k; where k is the capacity of the transformer Tx. The turns ratio of the primary side Lp and the secondary side of the transformer Tx.

As shown in Figure 1, the heating current of the battery half bridge on the left side is the in-phase superposition of the primary side Lp current and the secondary side current, while the right side only has the secondary side current. Assuming k=5, the heating current ratio of the left and right parallel parts is 6: 5, the capacity of the left and right parallel parts should be designed to be 6:5, so that the batteries on both sides will heat up equally. The specific derivation process is as follows:

The internal resistance of the battery branch is inversely proportional to the capacity of the battery branch. Assuming the capacity of the first battery branch: the capacity of the second battery branch=m:1, then the internal resistance of the first battery branch: the second battery branch The internal resistance = 1:m. Since the heating current of the first battery branch: the heating current of the second battery branch=(k+1):k, therefore, if the heating power of the battery per unit capacity is the same, it is required:

After finishing, you can get:

With reference to the battery self-heating circuit with transformer Tx in FIG. 1 , an embodiment of the present application provides a working method of the circuit: when the battery needs to be heated, the first power switch Q1 and the second power switch Q2 operate at a certain switching frequency, With a certain duty cycle, the complementary mode is alternately turned on. At this time, under the excitation of the square wave voltage generated by the half-bridge circuit formed by the first power switch Q1 and the second power switch Q2, the leakage inductance of the transformer Tx will resonate with the capacitor Cr, and a relatively small voltage will be generated on the primary side Lp of the transformer Tx. resonant current. The secondary side current = primary side current*k, which is several times larger than the primary side current, so a high-frequency alternating current is generated between the midpoints of the two "battery half bridges". This high-frequency current will generate a large amount of thermal power through the internal resistance of the battery to rapidly heat the battery.

In the above implementation process, the capacitor Cdc is used to absorb the pulse current.

In a possible implementation manner, the leakage inductance of the transformer Tx and the capacitance Cr form a resonance circuit, and the resonance frequency of the resonance circuit is lower than the switching frequency of the half-bridge circuit formed by the power switch.

In the above implementation process, the capacitor Cr is used to isolate the DC voltage to avoid the bias saturation of the transformer Tx.

Referring to FIG. 6 , in a possible implementation manner, the plurality of battery branches further include: a third battery branch; the first end of the primary side Lp is connected to a series point of any two batteries of the third battery branch.

The third battery branch is formed by connecting the fifth battery module U5 and the sixth battery module U6 in series.

In the above implementation process, there are three battery branches. Due to the impedance transformation effect of the transformer Tx, the resistance of the primary side Lp is increased, the power factor of the circuit is improved, and the apparent power of the circuit is reduced. The circuit generates high-frequency current that heats the three battery branches.

In a possible implementation, the transformer Tx includes: a plurality of secondary sides;

Two ends of each secondary side of the plurality of secondary sides are respectively connected between any two batteries in the two battery branches;

Referring to FIG. 7 , the fourth battery branch and the fifth battery branch include four batteries connected in series; the transformer Tx has a primary side Lp and three secondary sides; The second secondary side Ls2 and the third secondary side Ls3.

Exemplarily, the two battery branches connected to each secondary side have the same structure; the two connection points of each secondary side are at the same position of the battery branch to which it is connected.

Wherein, the second secondary side Ls2 is connected between the first battery and the second battery of the fourth battery branch and the fifth battery branch; the third secondary side Ls3 is connected between the fourth battery branch and the fifth battery branch between the third battery and the fourth battery.

It should be noted that, on the basis of the embodiments of the present application, the battery pack may also adopt a design manner in which a plurality of battery branches are connected in series and in parallel.

The above descriptions are merely examples of the present application, and are not intended to limit the protection scope of the present application. For those skilled in the art, various modifications and changes may be made to the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of this application shall be included within the protection scope of this application. It should be noted that like numerals and letters refer to like items in the following figures, so once an item is defined in one figure, it does not require further definition and explanation in subsequent figures.

The above are only specific embodiments of the present application, but the protection scope of the present application is not limited to this. should be covered within the scope of protection of this application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

It should be noted that, in this document, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any relationship between these entities or operations. any such actual relationship or sequence exists. Moreover, the terms "comprising", "comprising" or any other variation thereof are intended to encompass a non-exclusive inclusion such that a process, method, article or device that includes a list of elements includes not only those elements, but also includes not explicitly listed or other elements inherent to such a process, method, article or apparatus. Without further limitation, an element qualified by the phrase "comprising a..." does not preclude the presence of additional identical elements in a process, method, article or apparatus that includes the element.

Claims (12)

1. A battery self-heating circuit with a transformer, comprising:

the power supply comprises a half-bridge circuit consisting of a high-voltage end, a low-voltage end, a transformer and a power switch, and a plurality of battery branches;

a half-bridge circuit consisting of a plurality of battery branches and power switches is arranged between the high-voltage end and the low-voltage end;

each battery branch is formed by connecting a plurality of batteries in series;

the plurality of battery branches includes: a first battery branch and a second battery branch;

a first end of a first secondary side of the transformer is connected with a series point of any two batteries in the first battery branch;

the second end of the first secondary side of the transformer is connected with the series point of any two batteries in the second battery branch circuit;

the primary side of the transformer is connected with the midpoint of a half-bridge circuit formed by the power switches, and the first end and the second end of the primary side of the transformer form a pressure difference.

2. The transformer-equipped battery self-heating circuit according to claim 1, further comprising: a capacitor;

the capacitor and the primary side of the transformer form a series branch;

the first end of the series branch is connected with the midpoint of a half-bridge circuit formed by the power switches;

the second end of the series branch is connected to a midpoint of at least one of the plurality of battery branches.

3. The transformer-equipped battery self-heating circuit according to claim 1, further comprising: a capacitor;

the capacitor and the primary side of the transformer form a series branch;

the first end of the series branch is connected with the midpoint of a half-bridge circuit formed by the power switches;

the second end of the series branch is connected to the low voltage end.

4. The transformer-equipped battery self-heating circuit according to claim 1, further comprising: a capacitor;

the capacitor and the primary side of the transformer form a series branch;

the first end of the series branch is connected with the midpoint of a half-bridge circuit formed by the power switches;

the second end of the series branch is connected to the high-pressure end.

5. The transformer-equipped battery self-heating circuit according to claim 1, further comprising: a capacitor branch circuit;

the capacitor branch circuit is connected with a half-bridge circuit formed by the power switches in parallel;

and the primary side of the transformer is connected with the midpoint of the capacitor branch.

6. The battery self-heating circuit according to claim 2, wherein two ends of the capacitor are connected to two different name ends of the transformer.

7. The battery self-heating circuit of claim 5,

the plurality of battery branches further includes: a third battery branch;

the first end of the primary side is connected to the series point of any two batteries of the third battery branch.

8. The transformer-equipped battery self-heating circuit according to claim 2, wherein the leakage inductance of the transformer and the capacitor constitute a resonant circuit, and a resonant frequency of the resonant circuit is equal to a switching frequency of a half-bridge circuit constituted by the power switches.

9. The transformer-equipped battery self-heating circuit according to claim 7, wherein the leakage inductance of the transformer and the capacitor constitute a resonant circuit having a resonant frequency lower than a switching frequency of a half-bridge circuit constituted by the power switches.

10. The transformer-equipped battery self-heating circuit according to any one of claims 1 to 8,

the turn ratio of the primary side of the transformer to the secondary side of the transformer is greater than 1.

11. The transformer-equipped battery self-heating circuit according to claim 9, wherein the capacity ratio of the first battery branch and the second battery branch is: (k + 1)/k; and k is the turn ratio of the primary side of the transformer to the secondary side of the transformer.

12. A vehicle characterized by comprising the transformer-equipped battery self-heating circuit according to any one of claims 1 to 10.

Images