Power battery heating method and heating system

Abstract

An embodiment of the present application provides a heating method and heating system for a power battery, the power battery being connected to a switch circuit of a motor and used to provide power to the motor through the switch circuit, the switch circuit including a plurality of bridge arms connected in parallel with the power battery, the method including: receiving a heating signal sent by a battery management system of the power battery; and controlling at least one bridge arm of the plurality of bridge arms based on the heating signal to form a short circuit of the power battery, the short circuit being used to discharge the power battery and heat the power battery during discharging.

Description

Technical Field

[0001] This application relates to the field of battery technology, and particularly to a method and a system for heating a power battery.

Background Art

[0002] Due to advantages such as high energy density, rechargeability, safety, and environmental friendliness, power batteries are widely applied in fields such as new energy vehicles, consumer electronics, and energy storage systems.

[0003] However, the use of power batteries in a low-temperature environment may be subject to certain limitations. Specifically, the power battery has a significantly reduced discharge capacity in a low-temperature environment, and the power battery cannot be charged in a low-temperature environment. Therefore, in order to ensure the normal use of the power battery, it is necessary to heat the power battery in a low-temperature environment. How to effectively heat the power battery is an urgent problem to be solved.

Summary of the Invention

Means for Solving the Problems

[0004] Embodiments of this application provide a method and a system for heating a power battery that can effectively heat the power battery.

[0005] According to a first aspect, a method for heating a power battery is provided. The power battery is connected to a switch circuit of a motor and is used to provide power to the motor through the switch circuit. The switch circuit includes a plurality of bridge arms connected in parallel with the power battery. The method includes receiving a heating signal transmitted by a battery management system of the power battery, and based on the heating signal, controlling at least one of the plurality of bridge arms to form a short-circuit circuit of the power battery, where the short-circuit circuit is used to discharge the power battery and heat the power battery during discharge.

[0006] In this embodiment, a short - circuit of the power battery is formed, and by discharging the power battery through this short - circuit, heating of the power battery during discharge is realized. Since this short - circuit is formed by using the switch circuit of the motor, the heating of the power battery can be completed at low cost without adding an extra heating device.

[0007] In one possible implementation, the method further includes obtaining the current passing through the power battery and / or the voltage of the power battery, determining the on - duty of the short - circuit based on the current passing through the power battery and / or the voltage of the power battery, and controlling the short - circuit to turn on so that the current in the short - circuit does not exceed the allowable discharge current of the power battery and / or the voltage of the power battery does not fall below the minimum discharge voltage of the power battery based on the on - duty.

[0008] In this embodiment, by controlling the on - duty of the short - circuit, by controlling the current and / or voltage in the short - circuit within a safe threshold, during heating, the power battery Current is prevented from exceeding its allowable discharge current and / or the voltage of the power battery is prevented from falling below its minimum discharge voltage, preventing damage to the power battery during heating and ensuring safety during heating.

[0009] In one possible implementation, obtaining the current in the short - circuit includes detecting the current in the short - circuit by a current sensor installed in the short - circuit and / or determining the current in the short - circuit based on the voltage of the power battery and the internal resistance of the power battery.

[0010] In this embodiment, in order to monitor the current in the short - circuit circuit, a current sensor may be installed in the short - circuit circuit to detect this current more intuitively and accurately, or the current in the short - circuit circuit may be determined based on the voltage of the power battery and the internal resistance of the power battery, thereby reducing the devices in the short - circuit circuit to reduce costs and complexity. Here, the internal resistance of the power battery is the internal resistance at the current temperature of the power battery, which can be calculated from the relationship curve between the internal resistance and the temperature.

[0011] In one possible implementation, the above - mentioned controlling to turn on the short - circuit circuit based on the duty cycle includes controlling to turn on at least one bridge arm based on the duty cycle.

[0012] In this embodiment, based on the duty cycle, the turning - on of each bridge arm in the switch circuit of the motor may be controlled, thereby forming a short - circuit circuit and avoiding the occurrence of extra costs without adding other extra devices.

[0013] In one possible implementation, a second switch is installed between the power battery and the at least one bridge arm, and the above - mentioned controlling to turn on the short - circuit circuit based on the duty cycle includes controlling to turn on the second switch based on the duty cycle.

[0014] In this embodiment, based on the duty cycle, the turning - on of the extra second switch may be controlled, thereby forming a short - circuit circuit and reducing the complexity of the control process.

[0015] In one possible implementation, the method further includes obtaining the internal resistance of the power battery, determining the on - frequency of the short - circuit circuit based on the internal resistance of the power battery, where the smaller the internal resistance of the power battery, the higher the on - frequency, and controlling to turn on the short - circuit circuit based on the on - frequency.

[0016] In this embodiment, the smaller the internal resistance of the power battery, the faster the increase in current in the short - circuit, so a higher on - frequency is required to control this increase in current, thereby ensuring safety during heating and preventing damage to the power battery during heating.

[0017] In one possible implementation, a capacitance branch circuit including a capacitance connected in series and a first switch is further connected in parallel to the power battery, and the method further includes controlling the first switch to turn off before controlling the short - circuit to turn on.

[0018] In this embodiment, by installing a first switch in the branch where the constant - voltage capacitance connected in parallel with the power battery is located and controlling the first switch to turn off during heating, the influence of the constant - voltage capacitance of the power battery on the heating process of the power battery can be prevented, and the heating efficiency can be improved.

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

[0020] In one possible implementation, the method further includes receiving a heating stop signal transmitted by the battery management system and controlling the short - circuit to turn off to stop heating the power battery based on the heating stop signal.

[0021] In one 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 this embodiment, the smaller the internal resistance of the power battery, the faster the increase in current in the short - circuit, so a higher on - frequency is required to control this increase in current. This places very high requirements on the switch device. Therefore, the method of heating the power battery using a short - circuit is more applicable to solid - state batteries or power batteries with a large internal resistance to reduce the requirements on the switch device.

[0023] According to a second aspect, a heating system for a power battery is provided. This heating system includes a power battery, and a switch circuit installed between the power battery and a motor, where the power battery provides power to the motor. The switch circuit includes a plurality of bridge arms connected in parallel with the power battery, a control circuit that receives a heating signal transmitted by the battery management system of the power battery, and based on the heating signal, controls at least one of the plurality of bridge arms to form a short - circuit of the power battery. The short - circuit is used to discharge the power battery and heat the power battery during discharge.

[0024] In one possible implementation, the control circuit is further used to obtain the current passing through the power battery and / or the voltage of the power battery, determine the on - duty of the short - circuit based on the current passing through the power battery and / or the voltage of the power battery, and control the short - circuit to turn on so that the current in the short - circuit does not exceed the allowable discharge current of the power battery and / or the voltage of the power battery does not fall below the minimum discharge voltage of the power battery.

[0025] In one possible implementation, specifically, the control circuit is used to detect the current in the short - circuit by a current sensor installed in the short - circuit and / or determine the current in the short - circuit based on the voltage of the power battery and the internal resistance of the power battery.

[0026] In one possible implementation, the control circuit is specifically used to control at least one bridge arm to turn on based on the duty cycle.

[0027] In one possible implementation, a second switch is installed between the power battery and the at least one bridge arm, and the control circuit is specifically used to control the second switch to turn on based on the duty cycle.

[0028] In one possible implementation, the control circuit is further configured to obtain the internal resistance of the power battery, determine the on-frequency of the short-circuit circuit based on the internal resistance of the power battery, where the smaller the internal resistance of the power battery, the higher the on-frequency, and control the short-circuit circuit to turn on based on the on-frequency.

[0029] In one possible implementation, the switch circuit further includes a capacitive branch connected in parallel with the power battery, and the capacitive branch includes a capacitor and a first switch connected in series. The control circuit is further used to control the first switch to turn off before controlling the short-circuit circuit to turn on.

[0030] In one possible implementation, each bridge arm of the at least one bridge arm includes a first switch device and a second switch device connected in series, and the connection point between the first switch device and the second switch device of each bridge arm of the at least one bridge arm is connected one-to-one with at least one winding of the motor.

[0031] In one possible implementation, the control circuit is further configured to receive a heating stop signal transmitted by the battery management system, and control the short-circuit circuit to turn off so as to stop heating the power battery based on the heating stop signal.

[0032] In one possible implementation, the power battery is a solid battery, and / or the internal resistance of the power battery is greater than a preset value.

[0033] Based on the above technical solution, by using the switch circuit of the motor to form a short-circuit of the power battery, the power battery is discharged through this short-circuit, thereby realizing the heating of the power battery during the discharge of the power battery. Since there is no need to add an extra heating device, the heating of the power battery can be completed at low cost.

[0034] To more clearly explain the technical solution of the embodiments of the present application, the following briefly introduces the drawings that need to be used in the embodiments of the present application. Obviously, the drawings described below are only some embodiments of the present application. For those skilled in the art, other drawings can also be obtained based on the drawings on the premise of not paying creative labor.

Brief Description of the Drawings

[0035]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Figure 13

Embodiments for Carrying Out the Invention

[0036] Hereinafter, the embodiments of the present application will be described in more detail while combining the drawings and examples. Hereinafter, the detailed description of the examples and the drawings are for exemplarily explaining the principle of the present application, but not for limiting the scope of the present application. That is, the present application is not limited to the described embodiments.

[0037] In the description of the present application, it should be noted that, unless otherwise specified, the meaning of "a plurality of" is two or more. The orientation or positional relationship indicated by terms such as "upper", "lower", "left", "right", "inner", "outer", etc. is only for the convenience of description and simplification of the description of the present application, and does not indicate or imply that the mentioned device or element must have a specific orientation and be configured and operated in a specific orientation. Therefore, it should not be understood as a limitation to the present application. It should be noted that terms such as "first", "second", "third", etc. are only used for the purpose of description and should not be understood as indicating or implying relative importance. "Vertical" is not strictly vertical but within the allowable error range. "Parallel" is not strictly parallel but within the allowable error range.

[0038] The directional terms that appear in the following description are all in the directions shown in the figures and do not limit the specific structure of this application. In the description of this application, it should be further noted that unless otherwise clearly defined and limited, the terms "attachment", "connection", and "connection" should be understood in a broad sense. For example, it may be a fixed connection, a removable connection, or an integral connection. It may be a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of these terms in this application according to the specific situation.

[0039] With the development of the times, new energy vehicles have great market prospects due to their advantages such as environmental protection, low noise, and low usage costs, and can effectively promote energy conservation and reduction of pollutant emissions, which is beneficial to the development and progress of society.

[0040] Due to the electrochemical characteristics of the power battery, in a low-temperature environment, the charge and discharge ability of the power battery is greatly limited, which has a profound impact on the customer's winter vehicle use experience. Therefore, it is necessary to heat the power battery in a low-temperature environment so that the power battery can be used normally.

[0041] Therefore, this application proposes a heating solution to rapidly increase the temperature of the power battery by forming a short-circuit circuit of the power battery to generate heat through the internal resistance of the power battery. To form this short-circuit circuit by using the switch circuit of the motor, the heating of the power battery can be completed at low cost without adding an extra heating device.

[0042] The power battery in the embodiments of this application may be a lithium-ion battery, a lithium metal battery, a lead-acid battery, a nickel-cadmium battery, a nickel-metal hydride battery, a lithium-sulfur battery, a lithium-air battery, a sodium-ion battery, etc., and is not limited herein. From the perspective of scale, the power battery in the embodiments of this application may be a single cell, a battery module or a battery pack, and is not limited herein. From the perspective of application scenarios, this power battery may be applied in power devices such as automobiles and steamships. For example, as the power source of an electric vehicle self to supply power to the motor of the vehicle self it may be used in a vehicle. This power battery may further supply power to other power-consuming devices in the electric vehicle, for example, supply power to the in-vehicle air conditioner, in-vehicle player, etc.

[0043] For the sake of easy description, hereinafter, taking the use of the power battery in a new energy vehicle (i.e., self a vehicle, or what is called an electric vehicle) as an example, the solution of this application will be described.

[0044] FIG. 1 is a schematic diagram of a battery heating system 100 according to an embodiment of this application. As shown in FIG. 1, the battery heating system 100 includes a power battery 110, a switch circuit 120, and a control circuit 130. The control circuit 130 is 120 connected to the switch circuit 120 and can control the connection state of the switch circuit. And the control circuit 130 performs information interaction with the power battery 110. Specifically, it can perform information interaction with the battery management system (Battery Management System, BMS) of the power battery 110. Here, the switch circuit 120 is the switch circuit of the motor 140 or the inverter of the motor 140. The switch circuit 120 is installed between the power battery 110 and the motor 140. For example, as shown in FIG. 1, the switch circuit 120 is connected between the power battery 110 and the motor 140, and the power battery 110 provides power to the motor 140 through the switch circuit 120 to drive the vehicle to run.

[0045] The switch circuit 120 may include a plurality of bridge arms connected in parallel with the power battery 110. For example, as shown in FIG. 2, the switch circuit 120 includes a bridge arm 121, a bridge arm 122, and a bridge arm 123, and the bridge arm 121, the bridge arm 122, and the bridge arm 123 are all connected in parallel with the power battery 110.

[0046] In one embodiment, in at least one bridge arm for forming a short - circuit circuit, each bridge arm includes a first switch device and a second switch device connected in series, and the connection point between the first switch device and the second switch device of each bridge arm among the at least one bridge arm is connected one - to - one with at least one winding of the motor 140.

[0047] The number of bridge arms in the switch circuit 120 may be the same as the number of windings of the motor 140. Assuming that the motor 140 includes three windings, this switch circuit 120 includes three bridge arms, namely, a bridge arm 121, a bridge arm 122, and a bridge arm 123. Here, each of the three bridge arms includes an upper bridge arm and a lower bridge arm, and IGBT switches are installed on the upper bridge arm and the lower bridge arm, respectively.

[0048] As shown in FIG. 2, the motor 140 may specifically include a winding L1 connected to the bridge arm 121, a winding L2 connected to the bridge arm 122, and a winding L3 connected to the bridge arm 123. Here, one end of the winding L1 is connected to the connection point between the upper bridge arm 1211 and the lower bridge arm 1212 of the bridge arm 121, one end of the winding L2 is connected to the connection point between the upper bridge arm 1221 and the lower bridge arm 1222 of the bridge arm 122, and one end of the winding L3 is connected to the connection point between the upper bridge arm 1231 and the lower bridge arm 1232 of the bridge arm 123. The other ends of the winding L1, the winding L2, and the winding L3 are connected.

[0049] Note that the motor 140 includes three windings, but is not limited thereto, and may further include six windings or the like. Correspondingly, the switch circuit 120 may include six bridge arms.

[0050] Each bridge arm in the switch circuit 120 may be realized by various types of switches. As an example, each bridge arm is realized based on an Insulated Gate Bipolar Transistor (IGBT) switch, for example, from FIGS. 5 to 10 below.

[0051] In one embodiment, the control circuit 130 is used to execute the method 200 shown in FIG. 3. As shown in FIG. 3, the method 200 includes some or all of the following steps.

[0052] Step 210: Receive the heating signal transmitted by the BMS of the power battery 110, Step 220: Based on this heating signal, control at least one of the plurality of bridge arms to form a short-circuit circuit of the power battery 110, and this short-circuit circuit is used to discharge the power battery 110 and heat the power battery 110 during discharge.

[0053] As can be seen, by forming a short-circuit circuit of the power battery 110 and discharging the power battery 110 through this short-circuit circuit, heating of the power battery 110 can be realized during discharge of the power battery 110. Since this short-circuit circuit is formed using the switch circuit 120 of the motor 140, heating of the power battery 110 can be completed at low cost without adding an extra heating device.

[0054] Based on the state parameters of the power battery 110, such as information on SOC, voltage U, temperature T, etc., the BMS can determine whether to send a heating signal to the control circuit 130. The control circuit 130 is used to control the operation of the motor 140 to drive a vehicle or the like, and may also be a controller of the motor 140 for controlling the heating process of the power battery 110. Alternatively, the control circuit 130 may be a control circuit installed relatively independently of the controller of the motor 140 for controlling the heating process of the power battery 110.

[0055] The short - circuit circuit of the power battery 110 refers to the discharge circuit 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 itself by generating heat due to its internal resistance through the discharge circuit.

[0056] In one embodiment, the method 200 may include some or all of the following steps.

[0057] Step 230: Obtain the current I passing through the power battery 110 and / or the voltage U of the power battery 110. Step 240: Determine the on - duty of the short - circuit circuit based on the current I passing through the power battery 110 and / or the voltage U of the power battery 110. Step 250: Based on this on - duty, control the short - circuit circuit to turn on so that the current I in this short - circuit circuit does not exceed the allowable discharge current I A of the power battery 110, and / or the voltage U of the power battery 110 does not fall below the minimum discharge voltage U A of the power battery.

[0058] When the control circuit 130 executes steps 230 to 250, the short - circuit circuit is turned on with a certain on - duty, and by controlling the current I and voltage U in the short - circuit circuit within a safe threshold, during heating, it is prevented that the power battery 110 exceeds its allowable discharge current, and / or the power battery 110Prevented the voltage from exceeding its minimum discharge voltage, prevented the power battery 110 from being damaged during heating, and ensured safety during heating.

[0059] Specifically, when forming the short - circuit circuit of the power battery 110, the current I in the short - circuit circuit, that is, the discharge current I of the power battery, increases rapidly. When the discharge current I of the power battery 110 A exceeds the allowable discharge current I A of the power battery 110, there may be safety problems due to damage to the power battery 110. Therefore, it is necessary to control the current I in the short - circuit circuit so that it does not exceed the allowable discharge current I A of the power battery 110. When controlling to turn on the short - circuit circuit with a certain duty, before the current I in the short - circuit circuit reaches the allowable discharge current I A turn off the short - circuit circuit. For example, when the current I exceeds the first threshold, turn off the short - circuit circuit, and when the current I drops to a certain extent, turn on this short - circuit circuit again. In this way, until the power battery 110 is heated to a predetermined temperature, the current I during battery heating can always be controlled so that it does not exceed the allowable discharge current I A of the power battery 110.

[0060] This first threshold is, for example, below the allowable discharge current I A of the power battery 110. Hereinafter, the case where this first threshold is equal to the allowable discharge current I A will be described as an example.

[0061] For example, as shown in FIG. 4, in one heating cycle T, in the time period T1, it is necessary to turn on the short - circuit circuit to heat the power battery 110. In the time period T2, it is necessary to turn off the short - circuit circuit to prevent the current I in the short - circuit circuit from exceeding the allowable discharge current I A of the power battery 110. Here, the duty D = T1 / T2. Optionally, the duty D may be determined based on the allowable discharge current I A of the power battery 110, the voltage U of the power battery 110, the internal resistance R of the power battery 110, etc. For example, the initial duty D max is D max =I A / (U / R) may be set. Duty D max is a constant value, that is, it may be maintained without changing during heating, or may be adjusted in real time.

[0062] The allowable discharge current I of the power battery 110 A is related to the characteristics of the power battery, and the allowable discharge current I of the power battery 110 A When it is relatively large, the initial duty D max may be set relatively large. Conversely, when the allowable discharge current I of the power battery 110 A is relatively small, the initial duty D max may be set relatively small.

[0063] In the process of heating the power battery 110, since the power battery 110 is discharging, the voltage U of the power battery 110 changes. Generally, the voltage U should not be lower than the minimum discharge voltage U A of the power battery 110. Therefore, when the voltage U is likely to be lower than the minimum discharge voltage U A of the power battery 110, for example, when the voltage is smaller than the second threshold, the duty D may be appropriately reduced to reduce the effective value of the current I, thereby stabilizing the voltage U to be higher than the minimum discharge voltage U A of the power battery 110.

[0064] This second threshold is, for example, not less than the minimum discharge voltage U A of the power battery 110. Hereinafter, the case where this second threshold is equal to the minimum discharge voltage U A will be taken as an example for explanation.

[0065] In one embodiment, step 230 executed by the control circuit 130 may further include detecting the current I in the short - circuit circuit by a current sensor installed in the short - circuit circuit, and / or determining the current I in the short - circuit circuit based on the voltage U and the internal resistance R of the power battery 110.

[0066] To monitor the current in the short - circuit circuit, a current sensor may be installed in the short - circuit circuit to detect this current I more intuitively and accurately. For example, one current sensor may be connected in series between the battery and the switch circuit 120.

[0067] Alternatively, based on the voltage U of the power battery 110 and the internal resistance R of the power battery, the current in the short - circuit circuit may be determined as I, thereby reducing the devices in the short - circuit circuit and reducing the cost and complexity. The control circuit 130 may obtain information such as the voltage U, internal resistance R, and temperature T of the power battery 110 from, for example, the BMS of the power battery 110.

[0068] Here, the internal resistance R of the power battery 110 is the internal resistance R at the current temperature T of the power battery 110, and the internal resistance R can be determined from the relationship curve between the internal resistance R and the temperature T. During heating, when the temperature of the power battery 110 changes, the internal resistance R of the power battery 110 changes accordingly. Generally, as the temperature T of the power battery 110 increases, the internal resistance R of the power battery 110 decreases, the current I increases, and there is a certain relationship curve between the temperature T and the internal resistance R. The temperature of the power battery 110 can be detected by a temperature sensor, and based on the rule 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 circuit can be obtained based on I = U / R.

[0069] In one embodiment, step 250 executed by the control circuit 130 may further include controlling at least one bridge arm of the switch circuit 120 to turn on based on the on - duty.

[0070] For example, as shown in FIG. 5, the control circuit 130 can control the bridge arm 121 in the switch circuit 120 to turn on, that is, control the switches V11 and V12 on the bridge arm 121 to close, thereby forming a short - circuit circuit including the power battery 110, the switch V11, and the switch V12.

[0071] Also, for example, as shown in FIG. 6, the control circuit 130 controls to turn on the bridge arm 122 in the switch circuit 120, that is, it can control to close the switch V21 and the switch V22 on the bridge arm 122, thereby forming a short - circuit circuit including the power battery 110, the switch V21, and the switch V22.

[0072] Also, for example, as shown in FIG. 7, the control circuit 130 controls to turn on the bridge arm 123 in the switch circuit 120, that is, it can control to close the switch V31 and the switch V32 on the bridge arm 123, thereby forming a short - circuit circuit including the power battery 110, the switch V31, and the switch V32.

[0073] Also, for example, as shown in FIG. 8, the control circuit 130 controls to turn on the bridge arm 121, the bridge arm 122, and the bridge arm 123 in the switch circuit 120 simultaneously, that is, it can control to close the switch V11, the switch V12, the switch V21, the switch V22, the switch V31, and the switch V32, thereby forming three short - circuit circuits, namely, a short - circuit circuit composed of the power battery 110, the switch V11, and the switch V12, a short - circuit circuit composed of the power battery 110, the switch V21, and the switch V22, and a short - circuit circuit composed of the power battery 110, the switch V31, and the switch V32.

[0074] In one embodiment, whether the short - circuit circuit includes some or all of the bridge arms of the motor 140, and the number of bridge arms included in the short - circuit circuit, are determined according to the heating demand of the power battery 110, for example, determined according to demands such as the temperature that needs to be increased, the heating rate, etc. For example, when the current temperature of the power battery 110 is not very low and only a slight temperature increase is required for normal operation, in order to reduce the amount of electric power output by the power battery 110 for heating, only some of the bridge arms may be controlled to form a short - circuit circuit. When the current temperature of the battery is very low, in order to increase the temperature of the power battery 110 as quickly as possible, all the bridge arms need to be controlled to form a short - circuit circuit to improve the heating efficiency.

[0075] As can be seen, by controlling the on - off of each bridge arm in the switch circuit 120, the on - off of the short - circuit circuit can be more easily realized, and without adding other extra devices, the occurrence of extra costs can be avoided.

[0076] In another implementation form, a second switch 125 is installed between at least one bridge arm of the power battery 110 and the switch circuit 120. At this time, step 250 executed by the control circuit 130 may further include controlling the second switch 125 to turn on based on the on - duty. The second switch 125 may be, for example, the main positive switch or the main negative switch in the complete vehicle system connected to one end of the positive electrode or one end of the negative electrode of the power battery 110.

[0077] For example, as shown in FIG. 9, the second switch 125 is the main positive switch or the main negative switch in the completed vehicle system, which is located between the power battery 110 and the switch circuit 120. If it is necessary to form three short - circuit circuits to heat the power battery 110, the control circuit 130 may control to close only the second switch 125. Similarly, when it is necessary to turn off the three short - circuit circuits, the control circuit 130 may control to turn off only the second switch 125. Therefore, it is not necessary to simultaneously turn on and off the switch V11, switch V12, switch V21, switch V22, switch V31, and switch V32 in each bridge arm. Although an extra second switch 125 is added, the control circuit 130 can realize the on - off of the short - circuit circuit only by controlling the on - off of the second switch 125, without controlling each bridge arm in the switch circuit 120, thus reducing the complexity of the control circuit 130.

[0078] In one embodiment, the method 200 executed by the control circuit 130 may further include obtaining the internal resistance R of the power battery 110, determining the on - frequency f of the short - circuit circuit based on the internal resistance R of the power battery 110, and controlling to turn on the short - circuit circuit based on the on - frequency f.

[0079] Here, the smaller the internal resistance R of the power battery 110, the higher the on - frequency f. As shown in FIG. 4, f = 1 / T.

[0080] At low frequencies, the relationship between the current I of the power battery 110 and the voltage U of the power battery 110 is

Equation

[0081] At high frequencies, the relationship between the current I of the power battery 110 and the voltage U of the power battery 110 is

Equation

[0082] When I = 0, the above equation can be solved as [Equation number] to obtain.

[0083] As f increases and the variable t approaches 0, the above equation can be [Equation number] equivalent to, where L represents the parasitic capacitance of the switch.

[0084] Thus, within one heating cycle, the effective value of the current I can be [Equation number] of the order of, where 2fL / D 2 may be defined as the equivalent external resistance during high - frequency heating, i.e., the boundary condition of the model during high - frequency heating of the power battery 110.

[0085] It can be seen that by increasing the frequency f, the current I in the short - circuit can be decreased.

[0086] In one embodiment, as shown in FIG. 10, a capacitance shunt 126 is further connected in parallel to the power battery 110. The capacitance shunt 126 includes a capacitor C and a first switch 124 connected in series. This method further includes controlling the first switch 124 to be turned off before controlling the short - circuit to be turned on.

[0087] The capacity C is generally also called the constant voltage capacity to perform a constant voltage function for stabilizing the voltage across the power battery 110. When a short - circuit is formed, since the capacity C divides a part of the current I, the heating efficiency is reduced. On the other hand, by installing the first switch 124 in the branch path where the capacity C exists and controlling the first switch 124 to be turned off during heating, the influence of the capacity C on the heating process of the power battery 110 can be prevented, and the heating efficiency can be improved.

[0088] Between the capacity C and the first switch 124 in FIG. 10, they are connected in series. In actual applications, when there are multiple constant voltage capacities, the multiple capacities and the first switch 124 may be connected by other connection relationships. For example, it may be the position of the first switch 124 when the capacity C1 and the capacity C2 shown in FIGS. 11A to 11B are connected in series and in parallel.

[0089] 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 increases. For example, for a liquid battery, the current I in the short - circuit can rapidly increase to more than 7000 A within 0.5 ms. In order to avoid damage to the power battery 110 caused by a large current, it is necessary to switch the switch device at a higher frequency, thereby controlling the on - and - off time of the short - circuit and preventing the power battery 110 from being damaged during heating, and ensuring the safety of the heating process.

[0090] The embodiments of the present application are not limited to the type of the power battery 110. However, if the internal resistance R is too small, the current I in the short - circuit will rapidly reach a relatively large value, and higher resistance of the switch device is required. Therefore, in some implementation forms, the power battery 110 may be a solid - state battery or a power battery with an internal resistance greater than a preset value. This preset value may be determined according to the resistance degree of the switch device, thereby ensuring that the switching frequency of the switch device is within its allowable range and ensuring that the current I in the short - circuit is not relatively large enough to cause safety problems.

[0091] The embodiments of the present application further provide a heating method, that is, a third switch 127 is connected in parallel to both ends of the power battery 110. As shown in FIG. 12, when heating the power battery 110, the switch 127 may be closed, thereby forming a short - circuit loop composed of the power battery 110 and the third switch 127.

[0092] In one embodiment, the method 200 executed by the control circuit 130 may further include receiving a heating stop signal transmitted by the BMS of the power battery 110, and based on this heating stop signal, controlling to turn off the short - circuit loop so as to stop heating the power battery 110.

[0093] FIG. 13 shows a possible specific implementation form of the above - mentioned method 200. As shown in FIG. 13, it specifically includes some or all of the following steps.

[0094] Step 301: Receive a heating signal transmitted by the BMS. Step 302: Based on the heating signal, control at least one bridge arm to form a short - circuit loop of the power battery 110. Step 303: Determine whether the current I in the short - circuit loop exceeds the allowable discharge current I A of the power battery 110, and / or whether the voltage U is lower than the minimum discharge voltage U A of the power battery 110. Here, if I≧I A and / or U≦U A , execute step 304; if I<I A and / or U>U A , execute step 305. Step 304: Control the on - off of the short - circuit loop based on the on - duty ratio. Step 305: Keep the short - circuit loop on. Step 306: Receive a heating stop signal transmitted by the BMS, and turn off the short - circuit loop based on the heating stop signal.

[0095] It should be understood that step 303 needs to be executed periodically, that is, in order to ensure the safety of the heating process, the current I and electric current I A the relationship of, and / or the voltage U and voltage U A the relationship of need to be determined periodically.

[0096] Although the present application has been described with reference to preferred embodiments, various improvements can be made thereto without departing from the scope of the present application, and the members thereof can be replaced with equivalents. In particular, as long as there is no structural conflict, each technical feature mentioned in each embodiment may be combined in any manner. The present application is not limited to the specific embodiments disclosed in the text, but includes all technical solutions included within the scope of the claims.

Description of Reference Numerals

[0097] 100 Battery heating system 110 Power battery 120 Switch circuit 121, 122, 123 Bridge arm 1211, 1221, 1231 Upper bridge arm 1212, 1222, 1232 Lower bridge arm 124 First switch 125 Second switch 126 Capacitance branch circuit 127 Third switch 130 Control circuit 140 Motor C, C1, C2 Capacitance L1, L2, L3 Windings V11, V12, V21, V22, V31, V32 Switches

Claims

1. A method for heating a power battery, wherein the power battery is connected to a switch circuit of a motor and is used to provide power to the motor through the switch circuit. The switch circuit includes a plurality of bridge arms connected in parallel with the power battery. The method includes: Receiving a heating signal transmitted by a battery management system of the power battery; Based on the heating signal, controlling at least one of the plurality of bridge arms to form a short-circuit circuit of the power battery, wherein the short-circuit circuit is used to discharge the power battery and heat the power battery during discharge; Obtaining the internal resistance of the power battery; Based on the internal resistance of the power battery, determining the on-frequency of the short-circuit circuit, wherein the smaller the internal resistance of the power battery, the higher the on-frequency; Based on the on-frequency, controlling the short-circuit circuit to be turned on. A heating method characterized by including the above.

2. The method further includes: Obtaining the current passing through the power battery and / or the voltage of the power battery; Based on the current passing through the power battery and / or the voltage of the power battery, determining the on-duty of the short-circuit circuit; Based on the on-duty, controlling the short-circuit circuit to be turned on so that the current in the short-circuit circuit does not exceed the allowable discharge current of the power battery and / or the voltage of the power battery does not fall below the minimum discharge voltage of the power battery. The heating method according to claim 1, characterized by further including the above.

3. Obtaining the current in the short-circuit circuit includes: Detecting the current in the short-circuit circuit by a current sensor installed in the short-circuit circuit and / or Determining the current in the short-circuit circuit based on the voltage of the power battery and the internal resistance of the power battery. The heating method according to claim 2, characterized by including the above.

4. Controlling the short-circuit circuit to be turned on based on the on-duty includes: Based on the on-duty, controlling at least one of the bridge arms to be turned on. The heating method according to claim 2 or 3, characterized by including the above.

5. A second switch is installed between the power battery and the at least one bridge arm. ​ Controlling to turn on the short - circuit circuit based on the on - duty ratio includes Controlling to turn on the second switch based on the on - duty ratio The heating method according to claim 2 or 3, characterized by including this.

6. In the power battery, a capacitance branch path including a capacitance connected in series and a first switch is further connected in parallel, The method is Before controlling to turn on the short - circuit circuit, controlling to turn off the first switch The heating method according to any one of claims 2 to 5, further characterized by including this.

7. Each bridge arm of the at least one bridge arm includes a first switch device and a second switch device connected in series, and the connection point between the first switch device and the second switch device of each bridge arm of the at least one bridge arm is connected one - to - one with at least one winding of the motor. The heating method according to any one of claims 1 to 6, characterized by this.

8. The method is Receiving a heating stop signal transmitted by the battery management system, and Based on the heating stop signal, controlling to turn off the short - circuit circuit so as to stop heating the power battery The heating method according to any one of claims 1 to 7, further characterized by including this.

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

10. A heating system for a power battery, A power battery, A switch circuit installed between the power battery and the motor, which is a switch circuit for the power battery to supply power to the motor. The switch circuit includes a plurality of bridge arms connected in parallel with the power battery, A control circuit that receives a heating signal transmitted by the battery management system of the power battery and controls at least one of the plurality of bridge arms based on the heating signal to form a short - circuit circuit of the power battery. The short - circuit circuit is Used to discharge the power battery and heat the power battery during discharge, Including a control circuit The control circuit further Obtains the internal resistance of the power battery Determining the on-frequency of the short-circuit circuit based on the internal resistance of the power battery, wherein the smaller the internal resistance of the power battery, the higher the on-frequency, and Controlling to turn on the short-circuit circuit based on the on-frequency A heating system characterized by being used for the above.

11. The control circuit further includes Obtaining the current passing through the power battery and / or the voltage of the power battery, and Determining the on-duty of the short-circuit circuit based on the current passing through the power battery and / or the voltage of the power battery, and Controlling to turn on the short-circuit circuit so that the current in the short-circuit circuit does not exceed the allowable discharge current of the power battery and / or the voltage of the power battery does not fall below the minimum discharge voltage of the power battery based on the on-duty A heating system according to claim 10, characterized by being used for the above.

12. Specifically, the control circuit Detecting the current in the short-circuit circuit by a current sensor installed in the short-circuit circuit, and / or Determining the current in the short-circuit circuit based on the voltage of the power battery and the internal resistance of the power battery A heating system according to claim 11, characterized by being used for the above.

13. Specifically, the control circuit Controlling to turn on the at least one bridge arm based on the on-duty A heating system according to claim 11 or 12, characterized by being used for the above.

14. A second switch is installed between the power battery and the at least one bridge arm, and Specifically, the control circuit Controlling to turn on the second switch based on the on-duty, which is used for the heating system according to claim 11 or 12.

15. A capacitance branch including a capacitance connected in series and a first switch is further connected in parallel to the power battery, and The control circuit further includes Controlling to turn off the first switch before controlling to turn on the short-circuit circuit A heating system according to any one of claims 11 to 14, characterized by being used for the above.

16. Each of the at least one bridge arm among 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 bridge arm among the at least one bridge arm is connected one-to-one with at least one winding of the motor. The heating system according to any one of claims 10 to 15, characterized in that.

17. The control circuit further receives a heating stop signal transmitted by the battery management system, and based on the heating stop signal, controls to turn off the short-circuit circuit so as to stop heating the power battery. The heating system according to any one of claims 10 to 16, characterized in that it is used for.

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

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