Heating method and heating system for a power battery

Abstract

The embodiment of the present application provides a heating method and a heating system of a power battery, the power battery is connected with a switching circuit of a motor, the switching circuit comprises a plurality of bridge arms, the plurality of bridge arms are connected with the power battery in parallel, and the method comprises the following steps: receiving a heating signal sent by a battery management system of the power battery; and according to the heating signal, controlling at least one bridge arm in the plurality of bridge arms to form a short-circuit loop of the power battery, so that the power battery is discharged, and the power battery is heated in the discharging process.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of batteries, in particular to a heating method and a heating system for a power battery. BACKGROUND

[0002] Due to the advantages of high energy density, cyclic chargeability, safety and environmental protection, power batteries are widely used in new energy vehicles, consumer electronics, energy storage systems and other fields.

[0003] However, the use of power batteries in low temperature environments will be limited. Specifically, the discharge capacity of power batteries in low temperature environments will be severely degraded, and power batteries cannot be charged in low temperature environments. Therefore, in order to ensure the normal use of power batteries, it is necessary to heat the power batteries in low temperature environments. How to effectively heat the power batteries has become a problem to be solved. SUMMARY

[0004] The embodiments of the present application provide a heating method and a heating system for a power battery, which can effectively heat the power battery.

[0005] In a first aspect, a heating method for a power battery is provided. The power battery is connected to a switching circuit of a motor, and is configured to provide power to the motor through the switching circuit. The switching circuit includes a plurality of bridge arms, and the plurality of bridge arms are connected in parallel with the power battery. The method includes receiving a heating signal sent by a battery management system of the power battery, and controlling at least one bridge arm in the plurality of bridge arms to form a short circuit loop of the power battery according to the heating signal. The short circuit loop is configured to discharge the power battery and heat the power battery during the discharging process.

[0006] In this embodiment, the short circuit loop of the power battery is formed, so that the power battery discharges through the short circuit loop, thereby achieving the heating of the power battery during the discharging process of the power battery. Since the short circuit loop is formed by using the switching circuit of the motor, no additional heating device needs to be added, and the heating of the power battery can be completed at low cost.

[0007] In a possible implementation, the method further includes obtaining a current passing through the power battery and / or a voltage of the power battery, determining a conduction duty cycle of the short circuit loop according to the current passing through the power battery and / or the voltage of the power battery, and controlling the short circuit loop to be conductive according to the conduction duty cycle, so that the current in the short circuit loop does not exceed the allowable discharge current of the power battery, and / or the voltage of the power battery is not lower than the minimum discharge voltage of the power battery.

[0008] In the embodiment, the current and / or voltage in the short circuit loop is controlled within a safety threshold by controlling the on-duty ratio of the short circuit loop, so that the power battery is prevented from exceeding its allowable discharge current and / or voltage during heating, and the power battery is prevented from being damaged during heating, and the safety of the heating process is ensured.

[0009] In a possible implementation, the acquiring the current in the short circuit loop comprises: detecting the current in the short circuit loop by a current sensor arranged in the short circuit loop; and / or determining the current in the short circuit loop according to the voltage of the power battery and the internal resistance of the power battery.

[0010] In the embodiment, in order to monitor the current in the short circuit loop, a current sensor can be arranged in the short circuit loop to detect the current, which is more intuitive and accurate; or the current in the short circuit loop can be determined according to the voltage of the power battery and the internal resistance of the power battery, so as to reduce the devices in the short circuit loop to reduce the cost and complexity, wherein the internal resistance of the power battery is the internal resistance of the power battery at the current temperature, which can be calculated by the relationship curve between the internal resistance and the temperature.

[0011] In a possible implementation, the controlling the short circuit loop to be turned on according to the on-duty ratio comprises: controlling at least one bridge arm to be turned on according to the on-duty ratio.

[0012] In the embodiment, the on of each bridge arm in the switching circuit of the motor can be controlled according to the on-duty ratio, so as to form the short circuit loop, and no additional devices are needed, avoiding additional cost.

[0013] In a possible implementation, a second switch is arranged between the power battery and the at least one bridge arm, and the controlling the short circuit loop to be turned on according to the on-duty ratio comprises: controlling the second switch to be turned on according to the on-duty ratio.

[0014] In the embodiment, the on of the additional second switch can be controlled according to the on-duty ratio, so as to form the short circuit loop, reducing the complexity of the control process.

[0015] In a possible implementation, the method further comprises: acquiring the internal resistance of the power battery; determining the on frequency of the short circuit loop according to the internal resistance of the power battery, wherein the smaller the internal resistance of the power battery is, the higher the on frequency is; and controlling the short circuit loop to be turned on according to the on frequency.

[0016] In the embodiment, the smaller the internal resistance of the power battery is, the faster the current in the short-circuit loop increases, and thus a higher conduction frequency is required to control the increase of the current, thereby ensuring the safety of the heating process and preventing the power battery from being damaged during the heating process.

[0017] In a possible implementation, the power battery is further connected in parallel with a capacitor branch, the capacitor branch comprising a capacitor and a first switch connected in series, and the method further comprises: controlling the first switch to be turned off before controlling the short-circuit loop to be turned on.

[0018] In the embodiment, the first switch is arranged on the branch where the voltage stabilizing capacitor connected in parallel with the power battery, and the first switch is controlled to be turned off during the heating process, so that the voltage stabilizing capacitor of the power battery can be prevented from affecting the heating process of the power battery, and the heating efficiency is improved.

[0019] In a possible implementation, each of the at least one bridge arm comprises a first switch device and a second switch device connected in series, and a connection point between the first switch device and the second switch device of each of the at least one bridge arm is connected to at least one winding of the motor in one-to-one correspondence.

[0020] In a possible implementation, the method further comprises: receiving a heating stop signal sent by the battery management system; and controlling the short-circuit loop to be turned off to stop heating the power battery according to the heating stop signal.

[0021] In a possible implementation, the power battery is a solid-state battery, and / or the internal resistance of the power battery is greater than a preset value.

[0022] In the embodiment, the smaller the internal resistance of the power battery is, the faster the current in the short-circuit loop increases, and thus a higher conduction frequency is required to control the increase of the current, which has a high requirement for the switch device. Therefore, the method of heating the power battery by using the short-circuit loop is more suitable for solid-state batteries or power batteries with large internal resistance, thereby reducing the requirement for the switch device.

[0023] In a second aspect, a heating system of a power battery is provided, comprising: a power battery; a switching circuit arranged between the power battery and a motor, used to provide power for the motor by the power battery, the switching circuit comprising a plurality of bridge arms connected in parallel with the power battery; and a control circuit used to receive a heating signal sent by a battery management system of the power battery, and control at least one bridge arm of the plurality of bridge arms to form a short-circuit loop of the power battery according to the heating signal, the short-circuit loop being used to discharge the power battery and heat the power battery during the discharging process.

[0024] In a possible implementation, the control circuit is further configured to: acquire a current passing through the power battery and / or a voltage of the power battery; determine a conduction duty cycle of the short-circuit loop according to the current passing through the power battery and / or the voltage of the power battery; and control the short-circuit loop to be conductive according to the conduction duty cycle, so that the current in the short-circuit loop does not exceed the allowable discharge current of the power battery and / or the voltage of the power battery is not lower than the minimum discharge voltage of the power battery.

[0025] In a possible implementation, the control circuit is specifically configured to: detect the current in the short-circuit loop by using a current sensor arranged in the short-circuit loop; and / or determine the current in the short-circuit loop according to the voltage of the power battery and the internal resistance of the power battery.

[0026] In a possible implementation, the control circuit is specifically configured to: control the at least one bridge arm to be conductive according to the conduction duty cycle.

[0027] In a possible implementation, a second switch is arranged between the power battery and the at least one bridge arm, and the control circuit is specifically configured to: control the second switch to be conductive according to the conduction duty cycle.

[0028] In a possible implementation, the control circuit is further configured to: acquire the internal resistance of the power battery.

[0029] determine a conduction frequency of the short-circuit loop according to the internal resistance of the power battery, wherein the smaller the internal resistance of the power battery is, the higher the conduction frequency is; and control the short-circuit loop to be conductive according to the conduction frequency.

[0030] In a possible implementation, the switching circuit further includes a capacitor branch connected in parallel with the power battery, the capacitor branch including a capacitor and a first switch connected in series, and the control circuit is further configured to: control the first switch to be disconnected before controlling the short-circuit loop to be conductive.

[0031] In a possible implementation, each of the at least one bridge arm includes a first switch device and a second switch device connected in series, and a connection point between the first switch device and the second switch device of each of the at least one bridge arm is connected to at least one winding of the motor in one-to-one correspondence.

[0032] In a possible implementation, the control circuit is further configured to: receive a heating stop signal sent by the battery management system; and control the short-circuit loop to be disconnected according to the heating stop signal, so as to stop heating the power battery.

[0033] In a possible implementation, the power battery is a solid-state battery, and / or the internal resistance of the power battery is greater than a preset value.

[0034] Based on the above technical solution, the switching circuit of the motor is used to form a short circuit loop of the power battery, so that the power battery discharges through the short circuit loop, thereby achieving heating of the power battery during discharging of the power battery. Since no additional heating device needs to be added, the heating of the power battery can be completed at low cost. BRIEF DESCRIPTION OF DRAWINGS

[0035] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings needed to be used in the embodiments of the present application will be briefly introduced as follows. Obviously, the drawings described below are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative effort on the basis of the drawings.

[0036] Figure 1 is a schematic block diagram of a battery heating system disclosed by an embodiment of the present application;

[0037] Figure 2 is Figure 1 is a schematic diagram of a circuit structure of the battery heating system shown in

[0038] Figure 3 is a schematic flow chart of a battery heating method disclosed by an embodiment of the present application;

[0039] Figure 4 is a schematic diagram of a conduction duty cycle of the short circuit loop;

[0040] Figure 5 is a schematic diagram of the short circuit loop formed in the method shown in Figure 3

[0041] is a schematic diagram of the short circuit loop formed in the method shown in Figure 6 Figure 3 is a schematic diagram of the short circuit loop formed in the method shown in

[0042] Figure 7 Figure 3 is a schematic diagram of the short circuit loop formed in the method shown in

[0043] Figure 8 is a schematic diagram of the short circuit loop formed in the method shown in Figure 3

[0044] is a schematic diagram of the short circuit loop formed in the method shown in Figure 9 Figure 1 is a schematic diagram of a circuit structure of the battery heating system shown in

[0045] Figure 10 Figure 1 ​​​​A schematic diagram of a circuit structure of the battery heating system shown in FIG. 1 is shown in FIG. 2.

[0046] Figure 11 A schematic diagram of a capacitor branch in a switching circuit according to an embodiment of the present application is shown in FIG. 3.

[0047] Figure 12 is Figure 1 A schematic diagram of another circuit structure of the battery heating system shown in FIG. 1 is shown in FIG. 4.

[0048] Figure 13 is based on Figure 3 A flowchart of a possible implementation of the method shown in FIG. 1 is shown in FIG. 5. DETAILED DESCRIPTION

[0049] The embodiments of the present application will be further described in detail below with reference to the accompanying drawings and embodiments. The detailed description and the accompanying drawings of the following embodiments are used to exemplarily illustrate the principles of the present application, but cannot be used to limit the scope of the present application, i.e., the present application is not limited to the described embodiments.

[0050] In the description of the present application, it should be noted that, unless otherwise specified, the meaning of "a plurality of" is more than two; the orientation or positional relationship indicated by the terms "upper", "lower", "left", "right", "inner", "outer" and the like only serves to facilitate the description of the present application and simplify the description, and does not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application. In addition, the terms "first", "second", "third" and the like are only for descriptive purposes and cannot be understood as indicating or implying relative importance. "Vertical" is not strictly vertical, but within the allowable range of error. "Parallel" is not strictly parallel, but within the allowable range of error.

[0051] The orientation words appearing in the following description are the directions shown in the drawings, and are not a limitation on the specific structure of the present application. In the description of the present application, it should be noted that, unless otherwise specified and limited, the terms "mounting", "connection", "connection" should be understood broadly, for example, it can be fixedly connected, or it can be detachably connected, or integrally connected; it can be directly connected, or indirectly connected through an intermediate medium. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0052] With the development of the times, new energy vehicles have great market prospects and can effectively promote energy saving and emission reduction, which is conducive to the development and progress of society due to their environmental protection, low noise, low use cost and other advantages.

[0053] Due to the electrochemical characteristics of power batteries, their charging and discharging capabilities are significantly limited in low-temperature environments, severely impacting the customer's winter driving experience. Therefore, in order to ensure the normal operation of the power battery, it is necessary to heat it in low-temperature environments.

[0054] Therefore, this application proposes a heating scheme that heats the internal resistance of the power battery by forming a short-circuit loop, thereby rapidly raising the battery temperature. Since this short-circuit loop is formed using the switching circuit of the motor, no additional heating device is required, enabling the heating of the power battery at low cost.

[0055] The power battery in this application embodiment can be a lithium-ion battery, lithium metal battery, lead-acid battery, nickel-metal hydride battery, lithium-sulfur battery, lithium-air battery, or sodium-ion battery, etc., and is not limited thereto. In terms of scale, the power battery in this application embodiment can be a single cell, a battery module, or a battery pack, and is not limited thereto. In terms of application scenarios, this power battery can be used in power devices such as automobiles and ships. For example, it can be used in electric vehicles to power the motor of the electric vehicle, serving as a power source for electric vehicles. This power battery can also power other electrical components in electric vehicles, such as in-vehicle air conditioning and in-vehicle media players.

[0056] For ease of description, the following will use the application of power batteries in new energy vehicles (i.e., electric vehicles, or electric vehicles) as an example to illustrate the solution of this application.

[0057] Figure 1 This is a schematic diagram of a battery heating system 100 according to an embodiment of this application. Figure 1 As shown, the battery heating system 100 includes a power battery 110, a switching circuit 120, and a control circuit 130. The control circuit 130 is connected to the switching circuit 140 and can control the connection state of the switching circuit 140. Furthermore, the control circuit 130 can interact with the power battery 110, specifically with the battery management system (BMS) of the power battery 110. The switching circuit 120 is the switching circuit for the motor 140, or rather, the inverter for the motor 140. The switching circuit 120 is located between the power battery 110 and the motor 140, for example... Figure 1 As shown, the switch circuit 120 is connected between the power battery 110 and the motor 140. The power battery 110 supplies power to the motor 140 through the switch circuit 120 to drive the vehicle.

[0058] The switching circuit 120 may include multiple bridge arms, which are connected in parallel with the power battery 110. For example, as Figure 2As shown, the switching circuit 120 includes bridge arm 121, bridge arm 122 and bridge arm 123, all of which are connected in parallel with the power battery 110.

[0059] In one implementation, in at least one bridge arm used to form a short-circuit loop, each bridge arm includes a first switching device and a second switching device connected in series, and the connection point between the first switching device and the second switching device in each of the at least one bridge arm is connected one-to-one with at least one winding of the motor 140.

[0060] The number of bridge arms in the switching circuit 120 can be the same as the number of windings in the motor 140. Assuming the motor 140 has three windings, the switching circuit 120 includes three bridge arms: bridge arm 121, bridge arm 122, and bridge arm 123. Each of the three bridge arms includes an upper bridge arm and a lower bridge arm, each equipped with an IGBT switch.

[0061] like Figure 2 As shown, the motor 140 may specifically include a winding L1 connected to bridge arm 121, a winding L2 connected to bridge arm 122, and a winding L3 connected to bridge arm 123. One end of winding L1 is connected to the connection point between the upper bridge arm 1211 and the lower bridge arm 1212 of bridge arm 121; one end of winding L2 is connected to the connection point between the upper bridge arm 1221 and the lower bridge arm 1222 of bridge arm 122; and one end of winding L3 is connected to the connection point between the upper bridge arm 1231 and the lower bridge arm 1232 of bridge arm 123. The other ends of windings L1, L2, and L3 are connected together.

[0062] In addition, the motor 140 may include, but is not limited to, three windings, and may also include six windings, etc. Correspondingly, the switch module 120 may include six bridge arms.

[0063] Each bridge arm in the switching circuit 120 can be implemented using various types of switches. As an example, each bridge arm is implemented based on an Insulated Gate Bipolar Transistor (IGBT) switch, such as those described later. Figures 5 to 10 .

[0064] In one implementation, the control circuit 130 is used to perform... Figure 3 Method 200 is shown. (As shown) Figure 3 As shown, method 200 includes some or all of the following steps:

[0065] Step 210: Receive the heating signal sent by the BMS of the power battery 110;

[0066] Step 220: according to the heating signal, control at least one of the plurality of bridge arms to form a short-circuit loop of the power battery 110, the short-circuit loop being used to discharge the power battery 110 and heat the power battery 110 during the discharging process.

[0067] It can be seen that by forming a short-circuit loop of the power battery 110 and discharging the power battery 110 through the short-circuit loop, the heating of the power battery 110 during the discharging process of the power battery 110 can be achieved. Since the short-circuit loop is formed by the switching circuit 120 of the motor 140, no additional heating device needs to be added, and the heating of the power battery 110 can be completed at low cost.

[0068] The BMS can determine whether to send a heating signal to the control circuit 130 according to the state parameters of the power battery 110, such as SOC, voltage U, temperature T, etc. The control circuit 130 can be a controller of the motor 140, which is used to control the operation of the motor 140 to drive a vehicle or the like, and is used to control the heating process of the power battery 110, or the control circuit 130 can also be a control circuit that is independently arranged from the controller of the motor 140, and is used to control the heating process of the power battery 110.

[0069] The short-circuit loop of the power battery 110 refers to the discharging loop of the power battery 110. At this time, the positive and negative electrodes of the power battery 110 are short-circuited. The power battery 110 heats its internal resistance through the discharging loop, thereby heating itself.

[0070] In an implementation manner, the method 200 can include part or all of the following steps:

[0071] Step 230: obtaining the current I passing through the power battery 110 and / or the voltage U of the power battery 110;

[0072] Step 240: determining the conduction duty cycle of the short-circuit loop according to the current I passing through the power battery 110 and / or the voltage U of the power battery 110;

[0073] Step 250: according to the conduction duty cycle, control the short-circuit loop to be turned on, so that the current I in the short-circuit loop does not exceed the allowable discharging current I of the power battery 110 A , and / or the voltage U of the power battery 110 is not lower than the minimum discharging voltage U A of the power battery.

[0074] When the control circuit 130 performs steps 230 to 250, the short circuit loop is turned on according to a certain on-duty ratio, so as to control the current I and the voltage U in the short circuit loop within the safety threshold, thereby preventing the power battery 110 from exceeding its allowable discharge current and / or preventing the voltage of the power battery 110 from exceeding its minimum discharge voltage during the heating process, preventing the power battery 110 from being damaged during the heating process, and ensuring the safety of the heating process.

[0075] Specifically, when the short circuit loop of the power battery 110 is formed, the current I in the short circuit loop, i.e., the discharge current I of the power battery, will rapidly increase, and when it exceeds the allowable discharge current I of the power battery 110 A , the power battery 110 may be damaged, thereby causing a safety problem. Therefore, it is necessary to control the current I in the short circuit loop not to exceed the allowable discharge current I of the power battery 110 A . When the short circuit loop is turned on according to a certain on-duty ratio, the current I in the short circuit loop is turned off before it reaches the allowable discharge current I A , for example, when the current I exceeds a first threshold, and the short circuit loop is turned on again when the current I drops to a certain extent, so that the current I during the battery heating process can be controlled to always not exceed the allowable discharge current I of the power battery 110 A , until the power battery 110 is heated to a predetermined temperature.

[0076] The first threshold is, for example, less than or equal to the allowable discharge current I of the power battery 110 A . Hereinafter, the case where the first threshold is equal to the allowable discharge current I A is described.

[0077] For example Figure 4 , as shown in FIG. 1, in a heating period T, the short circuit loop needs to be turned on to heat the power battery 110 in a T1 period, and the short circuit loop needs to be turned off to prevent the current I in the short circuit loop from exceeding the allowable discharge current I of the power battery 110 A in a T2 period. The on-duty ratio D = T1 / T2. Alternatively, the on-duty ratio D can be determined according to the allowable discharge current I of the power battery 110 A , the voltage U of the power battery 110, the internal resistance R of the power battery 110, etc. For example, the initial on-duty ratio D max may be set as D max = I A / (U / R). The on-duty ratio D max may be a constant value, i.e., remains unchanged during the heating process; or can be adjusted in real time.

[0078] The allowable discharge current I of the power battery 110 Arelated to the characteristics of the power battery, if the allowable discharge current I A is larger, the initial duty ratio D max may be set larger; on the contrary, if the allowable discharge current I A of the power battery 110 is smaller, the initial duty ratio D max may be set smaller.

[0079] During the heating of the power battery 110, the voltage U of the power battery 110 will change because the power battery 110 is discharging. Generally, the voltage U should not be less than the minimum discharge voltage U A of the power battery 110. Therefore, when the voltage U is about to be lower than the minimum discharge voltage U A of the power battery 110, for example, when the voltage is less than a second threshold, the duty ratio D can be appropriately reduced to reduce the effective value of the current I, so as to stabilize the voltage U above the minimum discharge voltage U A .

[0080] The second threshold is greater than or equal to the minimum discharge voltage U A of the power battery 110, for example. Hereinafter, the second threshold is equal to the minimum discharge voltage U A is taken as an example for description.

[0081] In an implementation manner, the step 230 performed by the control circuit 130 can further include: detecting the current I in the short-circuit loop through a current sensor arranged in the short-circuit loop; and / or determining the current I in the short-circuit loop according to the voltage U of the power battery 110 and the internal resistance R of the power battery 110.

[0082] In order to monitor the current in the short-circuit loop, a current sensor can be arranged in the short-circuit loop to detect the current I, which is more intuitive and accurate. For example, a current sensor can be connected in series between the battery and the switching circuit 120.

[0083] Alternatively, the current I in the short-circuit loop can also be determined according to the voltage U of the power battery 110 and the internal resistance R of the power battery, so as to reduce the devices in the short-circuit loop, thereby reducing the cost and complexity. The control circuit 130 can obtain the voltage U, the internal resistance R, the temperature T and other information of the power battery 110 from the BMS of the power battery 110, for example.

[0084] The internal resistance R of the power battery 110 is the internal resistance R of the power battery 110 at the current temperature T, and the internal resistance R can be determined by a relationship curve between the internal resistance R and the temperature T. During the heating process, the temperature change of the power battery 110 will cause the internal resistance R of the power battery 110 to change accordingly. Generally, as the temperature T of the power battery 110 increases, the internal resistance R of the power battery 110 decreases, causing the current I to increase, and the temperature T and the internal resistance R conform to a certain relationship curve. The temperature T of the power battery 110 can be detected by a temperature sensor, and according to the regularity between the temperature T and the internal resistance R, the internal resistance R corresponding to the current temperature T can be determined, and then the current I in the current short circuit loop can be obtained according to I=U / R.

[0085] In an implementation manner, the step 250 performed by the control circuit 130 can further include controlling at least one bridge arm in the switching circuit 120 to be turned on according to the turn-on duty cycle.

[0086] For example, as shown in FIG. 6, the control circuit 130 can control the bridge arm 121 in the switching circuit 120 to be turned on, that is, control the switch V11 and the switch V12 on the bridge arm 121 to be closed, thereby forming a short circuit loop including the power battery 110, the switch V11 and the switch V12. Figure 5

[0087] For example, as shown in FIG. 7, the control circuit 130 can control the bridge arm 122 in the switching circuit 120 to be turned on, that is, control the switch V21 and the switch V22 on the bridge arm 122 to be closed, thereby forming a short circuit loop including the power battery 110, the switch V21 and the switch V22. Figure 6

[0088] For example, as shown in FIG. 8, the control circuit 130 can control the bridge arm 123 in the switching circuit 120 to be turned on, that is, control the switch V31 and the switch V32 on the bridge arm 123 to be closed, thereby forming a short circuit loop including the power battery 110, the switch V31 and the switch V32. Figure 7

[0089] For example, as shown in FIG. 9, the control circuit 130 can control the bridge arm 121, the bridge arm 122 and the bridge arm 123 in the switching circuit 120 to be turned on at the same time, that is, control the switch V11, the switch V12, the switch V21, the switch V22, the switch V31 and the switch V32 to be closed, thereby forming three short circuit loops, respectively, a short circuit loop composed of the power battery 110, the switch V11 and the switch V12; a short circuit loop composed of the power battery 110, the switch V21 and the switch V22; and a short circuit loop composed of the power battery 110, the switch V31 and the switch V32. Figure 8

[0090] ​​​​In one implementation, whether the short-circuit loop includes part or all of the bridge arms of the motor 140, and the number of bridge arms included in the short-circuit loop, can be determined based on the heating requirements of the power battery 110, such as the required increase in temperature and the heating rate. For example, if the current temperature of the power battery 110 is not very low and only needs to be slightly heated to operate normally, then only part of the bridge arms can be controlled to form a short-circuit loop to reduce the power output of the power battery 110 for heating; if the current battery temperature is very low, then all bridge arms need to be controlled to form a short-circuit loop to improve heating efficiency and heat up the power battery 110 as quickly as possible.

[0091] As can be seen, by controlling the on / off state of each bridge arm in the switching circuit 120, the on / off state of the short-circuit loop can be achieved more conveniently without the need to add any other additional components, thus avoiding additional costs.

[0092] In another implementation, a second switch 125 is provided between the power battery 110 and at least one arm of the switching circuit 120. In this case, step 250 executed by the control circuit 130 may further include: controlling the second switch 125 to conduct according to the duty cycle. The second switch 125 may be, for example, a main positive switch or a main negative switch in the vehicle system, connected to the positive or negative terminal of the power battery 110.

[0093] For example, such as Figure 9 As shown, the second switch 125 is the main positive switch or main negative switch in the vehicle system. It is located between the power battery 110 and the switching circuit 120. Assuming three short-circuit loops need to be formed to heat the power battery 110, the control circuit 130 only needs to control the second switch 125 to close. Similarly, when it is necessary to disconnect the three short-circuit loops, the control circuit 130 only needs to control the second switch 125 to open. Therefore, it is not necessary to simultaneously close and open switches V11, V12, V21, V22, V31, and V32 in each bridge arm. Although an additional second switch 125 is added, the control circuit 130 only needs to control the on / off state of the second switch 125 to achieve the on / off state of the short-circuit loops, without needing to control each bridge arm in the switching circuit 120, thus reducing the complexity of the control circuit 130.

[0094] In one implementation, the method 200 executed by the control circuit 130 may further include: obtaining the internal resistance R of the power battery 110; determining the conduction frequency f of the short-circuit loop based on the internal resistance R of the power battery 110; and controlling the short-circuit loop to conduct based on the conduction frequency f.

[0095] Among them, the smaller the internal resistance R of the power battery 110, the higher the conduction frequency f. For example... Figure 4 As shown, f = 1 / T.

[0096] Assume that, at low frequency, the relationship between the current I of the power battery 110 and the voltage U of the power battery 110 is:

[0097]

[0098] At high frequency, the relationship between the current I of the power battery 110 and the voltage U of the power battery 110 is:

[0099]

[0100] where D is the duty ratio, and f is the on-off frequency of the short-circuit loop.

[0101] When I = 0, the above formula can be solved as:

[0102]

[0103] When f becomes larger and larger, the variable t tends to 0, and the above formula can be equivalent to:

[0104]

[0105] where L represents the parasitic capacitance of the switch.

[0106] Thus, in a heating period, the effective value of the current I can be approximately:

[0107]

[0108] where 2fL / D 2 can be defined as the equivalent external resistance when high-frequency heating, that is, the boundary condition of the model of the power battery 110 when high-frequency heating.

[0109] It can be seen that by increasing the frequency f, the current I in the short-circuit loop can be reduced.

[0110] In an implementation mode, as shown in Figure 10 the power battery 110 is also connected in parallel with a capacitor branch 126, the capacitor branch 126 including a capacitor C and a first switch 124 connected in series, and the method further includes: before controlling the short-circuit loop to be turned on, controlling the first switch 124 to be turned off.

[0111] The capacitor C usually functions as a voltage stabilizer for stabilizing the voltage across the power battery 110, and is thus also called a voltage stabilizing capacitor. When the short-circuit loop is formed, the capacitor C can divert a part of the current I, thus reducing the heating efficiency. By providing the first switch 124 on the branch where the capacitor C is located and controlling the first switch 124 to be turned off during the heating process, the influence of the capacitor C on the heating process of the power battery 110 can be prevented, and the heating efficiency can be improved.

[0112] Figure 10The capacitor C and the first switch 124 are connected in series in the above-mentioned circuit. In practical applications, when there are multiple voltage stabilizing capacitors, the multiple capacitors can also be connected with the first switch 124 in other connection manners, for example Figure 11 A to Figure 11 The positions of the first switch 124 in the series connection and the parallel connection of the capacitor C1 and the capacitor C2 are shown in B.

[0113] It should be understood that the smaller the internal resistance R of the power battery 110, the faster the current I in the short-circuit loop increases. For example, for a liquid battery, the current I in the short-circuit loop can rapidly increase to more than 7000 A within 0.5 ms. In order to avoid damage to the power battery 110 caused by the large current, the switching device needs to be switched at a higher frequency to control the on and off time of the short-circuit loop, so as to prevent the power battery 110 from being damaged in the heating process, thereby ensuring the safety of the heating process.

[0114] The embodiments of the present application do not limit the type of the power battery 110, but when the internal resistance R is too small, the current I in the short-circuit loop will rapidly increase to a large value, which puts higher requirements on the tolerance of the switching device. Therefore, in some implementations, the power battery 110 can be a solid-state battery, or a power battery with an internal resistance greater than a preset value. The preset value can be determined according to the tolerance of the switching device, so as to ensure that the switching frequency of the switching device is within its bearing range, and the current I in the short-circuit loop is not too large to cause safety problems.

[0115] The embodiments of the present application also provide a heating mode, that is, a third switch 127 is connected in parallel across the two ends of the power battery 110, as shown in Figure 12 When the power battery 110 is heated, the switch 127 can be closed, thereby forming a short-circuit loop composed of the power battery 110 and the third switch 127.

[0116] In one implementation, the method 200 performed by the control circuit 130 can further include: receiving a heating stop signal sent by the BMS of the power battery 110; and controlling the short-circuit loop to be disconnected according to the heating stop signal, so as to stop heating the power battery 110.

[0117] Figure 13 One possible specific implementation of the above-mentioned method 200 is shown in Figure 13 which specifically includes part or all of the following steps:

[0118] Step 301: receiving a heating signal sent by the BMS;

[0119] Step 302: controlling at least one bridge arm to form a short-circuit loop of the power battery 110 according to the heating signal;

[0120] Step 303: judging whether the current I in the short circuit loop exceeds the allowable discharge current IA of the power battery 110, and / or whether the voltage U is lower than the minimum discharge voltage U A ,

[0121] wherein if I≥I A and / or U≤U A , step 304 is performed, if I A and / or U A , step 305 is performed;

[0122] Step 304: controlling the on-off of the short circuit loop according to the on-duty;

[0123] Step 305: keeping the short circuit loop on;

[0124] Step 306: receiving the heating stop signal sent by the BMS, and disconnecting the short circuit loop according to the heating stop signal.

[0125] It should be understood that step 303 needs to be periodically performed, that is, the relationship between the current I and the current I A , and / or the relationship between the voltage U and the voltage U A needs to be periodically determined to ensure the safety of the heating process.

[0126] Although the present application has been described with reference to the preferred embodiments, various modifications can be made to it without departing from the scope of the present application, and equivalent components can be substituted therefor. In particular, the technical features mentioned in each embodiment can be combined in any manner as long as there is no structural conflict. The present application is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A method of heating a power cell, characterized by, The power battery is connected with a switching circuit of the motor, and is configured to provide power to the motor through the switching circuit, the switching circuit includes a plurality of bridge arms, the plurality of bridge arms are connected with the power battery in parallel, and the method includes: receiving a heating signal sent by a battery management system of the power battery; and According to the heating signal, at least one bridge arm of the plurality of bridge arms is controlled to form a short circuit loop of the power battery, and the short circuit loop is configured to discharge the power battery and heat the power battery during discharging; The method further includes: obtaining the internal resistance of the power battery; According to the internal resistance of the power battery, the on frequency of the short circuit loop is determined, wherein the smaller the internal resistance of the power battery is, the higher the on frequency is; According to the on frequency, the short circuit loop is controlled to be turned on.

2. The heating method according to claim 1, characterized in that, The method further includes: obtaining the current passing through the power battery and / or the voltage of the power battery; According to the current passing through the power battery and / or the voltage of the power battery, the on duty cycle of the short circuit loop is determined; According to the on duty cycle, the short circuit loop is controlled to be turned on, so that the current in the short circuit loop does not exceed the allowable discharge current of the power battery, and / or the voltage of the power battery is not lower than the minimum discharge voltage of the power battery.

3. The heating method according to claim 2, characterized in that, The method further includes: obtaining the current passing through the power battery and / or the voltage of the power battery; According to the voltage of the power battery and the internal resistance of the power battery, the current in the short circuit loop is determined.

4. The heating method of claim 2, wherein, The method further includes: According to the on duty cycle, the at least one bridge arm is controlled to be turned on.

5. The heating method of claim 2, wherein, The second switch is provided between the power battery and the at least one bridge arm, and the method further includes: According to the on duty cycle, the second switch is controlled to be turned on.

6. The heating method of claim 2, wherein, The power battery is further connected with a capacitor branch in parallel, the capacitor branch includes a capacitor and a first switch connected in series, and the method further includes: Before controlling the short circuit loop to be turned on, the first switch is controlled to be turned off.

7. The heating method of claim 1, wherein, Each of the at least one bridge arm includes a first switch device and a second switch device connected in series, and a connection point between the first switch device and the second switch device of each of the at least one bridge arm is connected with at least one winding of the motor one by one.

8. The heating method of claim 1, wherein, The method further includes: receiving a heating stop signal sent by the battery management system; According to the heating stop signal, the short circuit loop is controlled to be turned off to stop heating the power battery.

9. The heating method according to any one of claims 1 to 8, characterized in that, The power battery is a solid-state battery, and / or the internal resistance of the power battery is greater than a preset value.

10. A heating system for a power cell, characterized by The method further includes: a power battery; a switching circuit provided between the power battery and a motor, configured to provide power to the motor by the power battery, the switching circuit includes a plurality of bridge arms, and the plurality of bridge arms are connected with the power battery in parallel; and The control circuit is configured to receive a heating signal sent by a battery management system of the power battery, and control at least one of the plurality of bridge arms to form a short-circuit loop of the power battery according to the heating signal, the short-circuit loop being used to discharge the power battery and heat the power battery during the discharging process. The control circuit is further configured to: obtain an internal resistance of the power battery; determine a conduction frequency of the short-circuit loop according to the internal resistance of the power battery, wherein the smaller the internal resistance of the power battery is, the higher the conduction frequency is; control the short-circuit loop to conduct according to the conduction frequency.

11. The heating system of claim 10, wherein, The control circuit is further configured to: obtain a current passing through the power battery and / or a voltage of the power battery; determine a conduction duty cycle of the short-circuit loop according to the current passing through the power battery and / or the voltage of the power battery; control the short-circuit loop to conduct according to the conduction duty cycle, so that a current in the short-circuit loop does not exceed an allowable discharging current of the power battery, and / or the voltage of the power battery is not lower than a minimum discharging voltage of the power battery.

12. The heating system of claim 11, wherein, The control circuit is specifically configured to: detect the current in the short-circuit loop by a current sensor arranged in the short-circuit loop; and / or determine the current in the short-circuit loop according to the voltage of the power battery and the internal resistance of the power battery.

13. The heating system of claim 11, wherein, The control circuit is specifically configured to: control the at least one bridge arm to conduct according to the conduction duty cycle.

14. The heating system of claim 11, wherein, A second switch is arranged between the power battery and the at least one bridge arm, and the control circuit is specifically configured to: control the second switch to conduct according to the conduction duty cycle.

15. The heating system of claim 11, wherein, The power battery is further connected in parallel with a capacitor branch, the capacitor branch comprising a capacitor and a first switch connected in series, and the control circuit is further configured to: control the first switch to be disconnected before controlling the short-circuit loop to conduct.

16. The heating system of claim 10, wherein, Each of the at least one bridge arm comprises a first switching device and a second switching device connected in series, and a connection point between the first switching device and the second switching device of each of the at least one bridge arm is connected to at least one winding of the motor in one-to-one correspondence.

17. The heating system of claim 10, wherein, The control circuit is further configured to: receive a heating stop signal sent by the battery management system; control the short-circuit loop to be disconnected according to the heating stop signal, so as to stop heating the power battery.

18. The heating system of any one of claims 10 to 17, wherein, The power battery is a solid-state battery, and / or the internal resistance of the power battery is greater than a preset value.

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