Heating method and heating system for a power battery
By creating a short-circuit loop for the power battery through the motor switching circuit, the problem of power battery heating in low-temperature environments is solved, achieving low-cost and safe heating.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- CONTEMPORARY AMPEREX TECHNOLOGY CO LTD
- Filing Date
- 2021-10-29
- Publication Date
- 2026-05-29
AI Technical Summary
Power batteries experience capacity degradation and charging difficulties in low-temperature environments, requiring effective heating methods to ensure normal operation.
By creating a short-circuit loop for the power battery through the motor's switching circuit, the battery is discharged and heated, eliminating the need for additional heating devices by utilizing the existing motor circuit.
It achieves effective heating of power batteries at low cost, ensuring the safety and efficiency of the heating process.
Smart Images
Figure CN122118192A_ABST
Abstract
Description
[0001] This application is a divisional application of the invention application filed on October 29, 2021, with Chinese application number 202180055390.0 and titled "Heating Method and Heating System for Power Batteries". Technical Field
[0002] This application relates to the field of battery technology, and in particular to a heating method and heating system for a power battery. Background Technology
[0003] Due to their advantages such as high energy density, rechargeability, safety, and environmental friendliness, power batteries are widely used in new energy vehicles, consumer electronics, energy storage systems, and other fields.
[0004] However, the use of power batteries is limited in low-temperature environments. Specifically, the discharge capacity of power batteries degrades significantly at low temperatures, and they cannot be charged. Therefore, to ensure the normal operation of power batteries, heating is necessary in low-temperature environments. How to effectively heat power batteries has become a pressing issue. Summary of the Invention
[0005] This application provides a heating method and heating system for a power battery, which can effectively heat the power battery.
[0006] In a first aspect, a method for heating a power battery is provided. The power battery is connected to a switching circuit of a motor and is used to provide power to the motor through the switching circuit. The switching circuit includes multiple bridge arms 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, according to the heating signal, controlling at least one of the multiple bridge arms to form a short-circuit loop for the power battery. The short-circuit loop is used to discharge the power battery and heat the power battery during the discharge process.
[0007] In this embodiment, a short-circuit loop is formed in the power battery, allowing the battery to discharge through this loop, thereby heating the power battery during the discharge process. Since the short-circuit loop is formed using the motor's switching circuit, no additional heating device is required, enabling low-cost heating of the power battery.
[0008] In one possible implementation, the method further includes: acquiring the current flowing through the power battery and / or the voltage of the power battery; determining the duty cycle of the short-circuit loop based on the current flowing through the power battery and / or the voltage of the power battery; and controlling the short-circuit loop to be turned on based on the 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.
[0009] In this embodiment, by controlling the duty cycle of the short-circuit circuit, the current and / or voltage in the short-circuit circuit are controlled within a safe threshold, thereby preventing the power battery from exceeding its allowable discharge current and / or preventing the power battery voltage from exceeding its minimum discharge voltage during the heating process, preventing damage to the power battery during the heating process, and ensuring the safety of the heating process.
[0010] In one possible implementation, obtaining the current in the short-circuit loop includes: detecting the current in the short-circuit loop using a current sensor disposed in the short-circuit loop; and / or determining the current in the short-circuit loop based on the voltage of the power battery and the internal resistance of the power battery.
[0011] In this embodiment, in order to monitor the current in the short-circuit loop, a current sensor can be set 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 and internal resistance of the power battery, thereby reducing the number of devices in the short-circuit loop to reduce cost and complexity. The internal resistance of the power battery is the internal resistance of the power battery at the current temperature, which can be calculated from the relationship curve between internal resistance and temperature.
[0012] In one possible implementation, controlling the short-circuit loop to conduct according to the conduction duty cycle includes: controlling the at least one bridge arm to conduct according to the conduction duty cycle.
[0013] In this embodiment, the conduction of each bridge arm in the motor's switching circuit can be controlled according to the duty cycle, thereby forming a short-circuit loop without the need for additional components, thus avoiding additional costs.
[0014] In one possible implementation, a second switch is provided between the power battery and the at least one bridge arm, and controlling the short-circuit circuit to conduct according to the conduction duty cycle includes: controlling the second switch to conduct according to the conduction duty cycle.
[0015] In this embodiment, an additional second switch can be turned on according to the duty cycle, thereby forming a short-circuit loop and reducing the complexity of the control process.
[0016] In one possible implementation, the method further includes: obtaining the internal resistance of the power battery; determining the conduction frequency of the short-circuit circuit based on the internal resistance of the power battery, wherein the lower the internal resistance of the power battery, the higher the conduction frequency; and controlling the short-circuit circuit to conduct based on the conduction frequency.
[0017] In this embodiment, since the smaller the internal resistance of the power battery, the faster the current in the short-circuit circuit increases, a higher conduction frequency is needed to control the increase of this current, thereby ensuring the safety of the heating process and preventing the power battery from being damaged during the heating process.
[0018] In one possible implementation, the power battery is also connected in parallel with a capacitor branch, the capacitor branch including a capacitor connected in series and a first switch, and the method further includes: controlling the first switch to open before controlling the short-circuit circuit to conduct.
[0019] In this embodiment, a first switch is set on the branch where the voltage regulator capacitor connected in parallel with the power battery is located, and the first switch is controlled to open during the heating process. This can prevent the voltage regulator capacitor of the power battery from affecting the heating process of the power battery and improve the heating efficiency.
[0020] In one possible implementation, each of the at least one 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 of each of the at least one bridge arm is connected one-to-one with at least one winding of the motor.
[0021] In one possible implementation, the method further includes: receiving a heating stop signal sent by the battery management system; and controlling the short-circuit circuit to disconnect according to the heating stop signal, so as to stop heating the power battery.
[0022] 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.
[0023] In this embodiment, since the smaller the internal resistance of the power battery, the faster the current in the short-circuit circuit increases, a higher conduction frequency is needed to control the increase of the current. This places high demands on the switching devices. Therefore, the method of heating the power battery using the short-circuit circuit is more suitable for solid-state batteries or power batteries with high internal resistance, thereby reducing the requirements on the switching devices.
[0024] Secondly, a heating system for a power battery is provided, comprising: a power battery; a switching circuit disposed between the power battery and a motor for supplying power from the power battery to the motor, the switching circuit including multiple bridge arms connected in parallel with the power battery; and a control circuit for receiving a heating signal sent by a battery management system of the power battery, and controlling at least one of the multiple bridge arms to form a short-circuit loop for 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 discharge process.
[0025] In one possible implementation, the control circuit is further configured to: acquire the current passing through the power battery and / or the voltage of the power battery; determine the duty cycle of the short-circuit loop based on the current passing through the power battery and / or the voltage of the power battery; and control the short-circuit loop to conduct based on the 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.
[0026] In one possible implementation, the control circuit is specifically used to: detect the current in the short-circuit loop using a current sensor disposed in the short-circuit loop; and / or determine the current in the short-circuit loop based on the voltage of the power battery and the internal resistance of the power battery.
[0027] In one possible implementation, the control circuit is specifically used to: control the at least one bridge arm to conduct according to the conduction duty cycle.
[0028] In one possible implementation, a second switch is provided between the power battery and the at least one bridge arm, and the control circuit is specifically used to control the second switch to be turned on according to the duty cycle.
[0029] In one possible implementation, the control circuit is further configured to: obtain the internal resistance of the power battery; The conduction frequency of the short-circuit circuit is determined based on the internal resistance of the power battery, wherein the lower the internal resistance of the power battery, the higher the conduction frequency; the short-circuit circuit is controlled to conduct based on the conduction frequency.
[0030] In one 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 open before controlling the short-circuit loop to be turned on.
[0031] In one possible implementation, each of the at least one 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 of each of the at least one bridge arm is connected one-to-one with at least one winding of the motor.
[0032] In one possible implementation, the control circuit is further configured to: receive a heating stop signal sent by the battery management system; and, based on the heating stop signal, control the short-circuit circuit to disconnect to stop heating the power battery.
[0033] 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.
[0034] Based on the above technical solution, a short-circuit loop is formed in the motor's switching circuit to allow the power battery to discharge through this loop, thereby heating the power battery during the discharge process. Since no additional heating device is required, heating the power battery can be achieved at a low cost. Attached Figure Description
[0035] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the embodiments of this application will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on the drawings without creative effort.
[0036] Figure 1 This is a schematic block diagram of a battery heating system disclosed in an embodiment of this application; Figure 2 yes Figure 1 A schematic diagram of a circuit structure for a battery heating system is shown. Figure 3 This is a schematic flowchart of a battery heating method disclosed in an embodiment of this application; Figure 4 This is a schematic diagram of the duty cycle of the short-circuit loop; Figure 5 yes Figure 3 A schematic diagram of the short-circuit loop formed in the method shown; Figure 6 yes Figure 3 A schematic diagram of the short-circuit loop formed in the method shown; Figure 7 yes Figure 3 A schematic diagram of the short-circuit loop formed in the method shown; Figure 8 yes Figure 3A schematic diagram of the short-circuit loop formed in the method shown; Figure 9 yes Figure 1 A schematic diagram of the circuit structure of the battery heating system is shown. Figure 10 yes Figure 1 A schematic diagram of the circuit structure of the battery heating system is shown. Figure 11 This is a schematic diagram of the capacitor branch in a switching circuit disclosed in an embodiment of this application; Figure 12 yes Figure 1 A schematic diagram of another circuit structure for the battery heating system shown. Figure 13 Based on Figure 3 The flowchart shows one possible specific implementation of the method shown. Detailed Implementation
[0037] The embodiments of this application will be described in further detail below with reference to the accompanying drawings and examples. The detailed description of the following embodiments and the accompanying drawings are used to illustrate the principles of this application by way of example, but should not be used to limit the scope of this application, that is, this application is not limited to the described embodiments.
[0038] In the description of this application, it should be noted that, unless otherwise stated, "a plurality of" means two or more; the terms "upper," "lower," "left," "right," "inner," and "outer," etc., indicating orientation or positional relationships, are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on this application. Furthermore, the terms "first," "second," and "third," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance. "Vertical" is not vertical in the strict sense, but within the allowable tolerance range. "Parallel" is not parallel in the strict sense, but within the allowable tolerance range.
[0039] The directional terms used in the following description refer to the directions shown in the figures and are not intended to limit the specific structure of this application. It should also be noted in the description of this application that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.
[0040] With the development of the times, new energy vehicles have huge market prospects due to their advantages such as environmental friendliness, low noise, and low operating costs. They can also effectively promote energy conservation and emission reduction, which is beneficial to social development and progress.
[0041] 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.
[0042] 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.
[0043] 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.
[0044] 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.
[0045] 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 1As 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.
[0046] The switching circuit 120 may include multiple bridge arms, which are connected in parallel with the power battery 110. For example, as Figure 2 As 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.
[0047] 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.
[0048] 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.
[0049] 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.
[0050] 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.
[0051] 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 .
[0052] In one implementation, the control circuit 130 is used to perform... Figure 3Method 200 is shown. (As shown) Figure 3 As shown, method 200 includes some or all of the following steps: Step 210: Receive the heating signal sent by the BMS of the power battery 110; Step 220: According to the heating signal, control at least one of the multiple bridge arms to form a short circuit circuit of the power battery 110. The short circuit circuit is used to discharge the power battery 110 and heat the power battery 110 during the discharge process.
[0053] As can be seen, by forming a short-circuit loop in the power battery 110, the power battery 110 can be discharged through this short-circuit loop, thereby heating the power battery 110 during the discharge process. Since the short-circuit loop is formed using the switching circuit 120 of the motor 140, no additional heating device is required, and heating of the power battery 110 can be achieved at low cost.
[0054] The BMS can determine whether to send a heating signal to the control circuit 130 based on the state parameters of the power battery 110, such as SOC, voltage U, and temperature T. The control circuit 130 can be a controller for the motor 140, used to control the operation of the motor 140 to drive the vehicle, and also to control the heating process of the power battery 110. Alternatively, the control circuit 130 can be a control circuit that is relatively independent of the controller for the motor 140, used to control 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. In this case, the positive and negative terminals of the power battery 110 are short-circuited. The power battery 110 heats itself by generating heat through its internal resistance via the discharge circuit.
[0056] In one implementation, method 200 may include some or all of the following steps: Step 230: Obtain the current I and / or voltage U of the power battery 110; Step 240: Determine the duty cycle 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 the duty cycle, control the short-circuit loop to conduct so that the current I in the short-circuit loop does not exceed the allowable discharge current I of the power battery 110. A And / or the voltage U of the power battery 110 is not lower than the minimum discharge voltage U of the power battery. A .
[0057] When the control circuit 130 executes steps 230 to 250, the short-circuit loop is turned on according to a certain duty cycle to control the current I and voltage U in the short-circuit loop within a safe threshold. This prevents the power battery 110 from exceeding its allowable discharge current and / or prevents the voltage of the power battery 10 from exceeding its minimum discharge voltage during the heating process, thus preventing damage to the power battery 110 during the heating process and ensuring the safety of the heating process.
[0058] Specifically, when a short-circuit loop is formed in the power battery 110, the current I in the short-circuit loop, i.e., the discharge current I of the power battery, will increase rapidly. When it exceeds the allowable discharge current I of the power battery 110... A In some cases, the power battery 110 may be damaged, leading to safety issues. Therefore, it is necessary to control the current I in the short-circuit circuit to ensure it does not exceed the allowable discharge current I of the power battery 110. A When the short-circuit loop is controlled to conduct according to a certain duty cycle, the current I in the short-circuit loop reaches the allowable discharge current I0. A Previously, the short-circuit loop was disconnected, for example, when the current I exceeded a first threshold, and then reconnected when the current I dropped to a certain level. This ensures that the current I during the battery heating process will never exceed the allowable discharge current I of the power battery 110. A Until the power battery 110 is heated to the predetermined temperature.
[0059] This first threshold is, for example, less than or equal to the allowable discharge current I of the power battery 110. A Hereinafter, the first threshold is equal to the allowable discharge current I. A Let's take an example to illustrate.
[0060] For example Figure 4 As shown, in a heating cycle T, during period T1, the short-circuit circuit needs to be turned on to heat the power battery 110; during period T2, the short-circuit circuit needs to be turned off to prevent the current I in the short-circuit circuit from exceeding the allowable discharge current I of the power battery 110. A Wherein, the duty cycle D = T1 / T2. Optionally, the duty cycle D can be determined based on the allowable discharge current I of the power battery 110. A The voltage U of the power battery 110 and the internal resistance R of the power battery 110 are determined. For example, the initial duty cycle D... max It can be set to D max =I A / (U / R). Duty cycle D max It can be a constant value, meaning it remains unchanged during the heating process; or it can be adjusted in real time.
[0061] The allowable discharge current I of the power battery 110 ARelated to the characteristics of the power battery, if the allowable discharge current I of the power battery 110... A If the initial duty cycle D is large, then... max It can be set to a larger value; conversely, if the allowable discharge current I of the power battery 110 is... A If the initial duty cycle D is smaller, then... max It can be set to a smaller value.
[0062] During the heating process 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 of the power battery 110. A Therefore, when the voltage U is about to drop below the minimum discharge voltage U of the power battery 110... A When the voltage is below the second threshold, for example, the duty cycle D can be appropriately reduced to decrease the effective value of the current I, thereby stabilizing the voltage U at the minimum discharge voltage U. A Above.
[0063] This second threshold is, for example, greater than or equal to the minimum discharge voltage U of the power battery 110. A Hereinafter, the second threshold is equal to the minimum discharge voltage U. A Let's take an example to illustrate.
[0064] In one implementation, step 230 performed by the control circuit 130 may further include: detecting the current I in the short-circuit loop using a current sensor provided in the short-circuit loop; and / or determining the current I in the short-circuit loop based on the voltage U of the power battery 110 and the internal resistance R of the power battery 110.
[0065] To monitor the current in a short-circuit loop, a current sensor can be installed 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.
[0066] Alternatively, the current I in the short-circuit loop can be determined based on the voltage U and internal resistance R of the power battery 110, thereby reducing the number of components in the short-circuit loop and lowering cost and complexity. The control circuit 130 can, for example, obtain information such as the voltage U, internal resistance R, and temperature T of the power battery 110 from its BMS.
[0067] The internal resistance R of the power battery 110 is the internal resistance R of the power battery 110 at the current temperature T. The internal resistance R can be determined by the 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 a corresponding change in the internal resistance R of the power battery 110. Generally, as the temperature T of the power battery 110 increases, the internal resistance R of the power battery 110 will decrease, resulting in an increase in the current I. The relationship between temperature T and internal resistance R follows a certain curve. The temperature T of the power battery 110 can be detected by a temperature sensor. Based on the relationship between temperature T and internal resistance R, the internal resistance R corresponding to the current temperature T can be determined. Then, the current I in the current short-circuit loop can be obtained according to I=U / R.
[0068] In one implementation, step 250 performed by the control circuit 130 may further include: controlling at least one bridge arm of the switching circuit 120 to conduct according to the conduction duty cycle.
[0069] For example, such as Figure 5 As shown, the control circuit 130 can control the bridge arm 121 in the switch circuit 120 to be turned on, that is, control the switches V11 and V12 on the bridge arm 121 to be closed, thereby forming a short circuit loop including the power battery 110, switch V11 and switch V12.
[0070] For example, such as Figure 6 As shown, the control circuit 130 can control the bridge arm 122 in the switch circuit 120 to be turned on, that is, control the switches V21 and V22 on the bridge arm 122 to be closed, thereby forming a short circuit loop including the power battery 110, switch V21 and switch V22.
[0071] For example, such as Figure 7 As shown, the control circuit 130 can control the bridge arm 123 in the switch circuit 120 to be turned on, that is, control the switches V31 and V32 on the bridge arm 123 to be closed, thereby forming a short circuit loop including the power battery 110, switch V31 and switch V32.
[0072] For example, such as Figure 8 As shown, the control circuit 130 can control the bridge arms 121, 122, and 123 in the switch circuit 120 to be simultaneously turned on, that is, control the switches V11, V12, V21, V22, V31, and V32 to be closed, thereby forming three short-circuit loops: a short-circuit loop consisting of the power battery 110, switch V11, and switch V12; a short-circuit loop consisting of the power battery 110, switch V21, and switch V22; and a short-circuit loop consisting of the power battery 110, switch V31, and switch V32.
[0073] 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.
[0074] 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.
[0075] 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.
[0076] 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.
[0077] In one implementation, the method 200 executed by the control circuit 130 may further include: acquiring the internal resistance R of the power battery 110; and determining the conduction frequency of the short-circuit loop based on the internal resistance R of the power battery 110. f According to the conduction frequency f Control the short-circuit loop to conduct.
[0078] Among them, the smaller the internal resistance R of the power battery 110, the higher the conduction frequency. fThe higher. For example... Figure 4 As shown, f =1 / T.
[0079] Assume that, at low frequencies, the relationship between the current I and the voltage U of the power battery 110 is as follows: .
[0080] At high frequencies, the relationship between the current I and the voltage U of the power battery 110 is as follows: ; Where D is the duty cycle. f This is the conduction frequency of the short-circuit loop.
[0081] When I=0, the above equation can be solved to obtain: .
[0082] when f As the value increases, the variable t approaches 0, and the above expression can be equivalent to: ; Where L represents the parasitic capacitance of the switch.
[0083] Thus, the effective value of the current I within one heating cycle can be approximately: ; Among them, 2 f L / D 2 It can be defined as the equivalent external resistance during high-frequency heating, that is, the boundary condition of the power battery 110 model during high-frequency heating.
[0084] It can be seen that by increasing the frequency f This can reduce the current I in the short-circuit loop.
[0085] In one implementation, such as Figure 10 As shown, the power battery 110 is also connected in parallel with a capacitor branch 126, which includes a capacitor C connected in series and a first switch 124. The method further includes: controlling the first switch 124 to open before the control short-circuit circuit is turned on.
[0086] Capacitor C typically functions as a voltage regulator, stabilizing the voltage across the power battery 110; hence, it is also called a voltage-stabilizing capacitor. When a short-circuit loop is formed, capacitor C can divert a portion of the current I, thus reducing heating efficiency. By installing a first switch 124 on the branch containing capacitor C and controlling the first switch 124 to open during heating, the heating process of the power battery 110 can be prevented from being affected by capacitor C, thereby improving heating efficiency.
[0087] Figure 10The capacitor C and the first switch 124 are connected in series. In practical applications, when multiple voltage-regulating capacitors are present, there can be other connections between these capacitors and the first switch 124, such as... Figure 11 A to Figure 11 The positions of the first switch 124 are shown in Figure B, where capacitors C1 and C2 are connected in series and parallel.
[0088] 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 circuit increases. For example, for a liquid battery, the current I in the short-circuit circuit can rapidly increase to over 7000A within 0.5 ms. In order to avoid damage to the power battery 110 by the large current, the switching devices need to switch at a higher frequency to control the conduction and disconnection time of the short-circuit circuit, prevent the power battery 110 from being damaged during the heating process, and thus ensure the safety of the heating process.
[0089] This application does not limit the type of power battery 110, but when the internal resistance R is too small, the current I in the short-circuit circuit will rapidly increase to a large value, which places higher demands on the tolerance of the switching devices. 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. This preset value can be determined according to the tolerance of the switching devices to ensure that the switching frequency of the switching devices is within its tolerance range and that the current I in the short-circuit circuit is not too large, thus preventing safety issues.
[0090] This application embodiment also provides a heating method, namely, connecting a third switch 127 in parallel across the two ends of the power battery 110, such as... Figure 12 As shown, when the power battery 110 is heated, the switch 127 can be closed, thereby forming a short-circuit loop consisting of the power battery 110 and the third switch 127.
[0091] In one implementation, the method 200 executed by the control circuit 130 may further include: receiving a heating stop signal sent by the BMS of the power battery 110; and controlling the short-circuit loop to disconnect according to the heating stop signal, so as to stop heating the power battery 110.
[0092] Figure 13 This illustrates one possible specific implementation of the above method 200, such as... Figure 13 As shown, it specifically includes some or all of the following steps: Step 301: Receive the heating signal sent by the BMS; Step 302: Based on the heating signal, control at least one bridge arm to form a short-circuit loop for the power battery 110; Step 303: Determine 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 , Where, if I≥I A and / or U≤U A Then proceed to step 304. If I < I A and / or U>U A Then proceed to step 305; Step 304: Control the on / off state of the short-circuit loop according to the duty cycle; Step 305: Keep the short-circuit loop open; Step 306: Receive the heating stop signal sent by the BMS, and disconnect the short circuit loop according to the heating stop signal.
[0093] It should be understood that step 303 needs to be performed periodically, that is, the current I and the flow rate I need to be determined periodically. A The relationship between, and / or voltages U and U A This relationship is crucial to ensure the safety of the heating process.
[0094] Although this application has been described with reference to preferred embodiments, various modifications can be made thereto and components can be replaced with equivalents without departing from the scope of this application. In particular, the technical features mentioned in the various embodiments can be combined in any manner, provided there is no structural conflict. This 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 for heating a power battery, characterized in that, The power battery is connected to the switching circuit of the motor, and is used to provide power to the motor through the switching circuit. The switching circuit includes multiple bridge arms, which are connected in parallel with the power battery. The method includes: Receives a heating signal sent by the battery management system of the power battery; and, According to the heating signal, at least one of the plurality of bridge arms is controlled to form a short-circuit circuit for the power battery. The short-circuit circuit is used to discharge the power battery and heat the power battery during the discharge process. The method further includes: Obtain the current passing through the power battery and / or the voltage of the power battery; The duty cycle of the short-circuit circuit is determined based on the current passing through the power battery and / or the voltage of the power battery. Based on the 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.
2. The heating method according to claim 1, characterized in that, The step of obtaining the current in the short-circuit loop includes: The current in the short-circuit circuit is detected by a current sensor installed in the short-circuit circuit; and / or, The current in the short-circuit loop is determined based on the voltage and internal resistance of the power battery.
3. The heating method according to claim 1 or 2, characterized in that, The step of controlling the short-circuit loop to conduct according to the conduction duty cycle includes: The at least one bridge arm is controlled to conduct according to the conduction duty cycle.
4. The heating method according to claim 1 or 2, characterized in that, A second switch is provided between the power battery and the at least one bridge arm. The step of controlling the short-circuit circuit to conduct according to the duty cycle includes: The second switch is controlled to be turned on according to the duty cycle.
5. The heating method according to any one of claims 1 to 4, characterized in that, The method further includes: Obtain the internal resistance of the power battery; The conduction frequency of the short-circuit circuit is determined based on the internal resistance of the power battery, wherein the lower the internal resistance of the power battery, the higher the conduction frequency. The short-circuit loop is controlled to conduct according to the conduction frequency.
6. The heating method according to any one of claims 1 to 5, characterized in that, The power battery is also connected in parallel with a capacitor branch, which includes a capacitor connected in series and a first switch. The method further includes: Before the short-circuit loop is turned on, the first switch is turned off.
7. The heating method according to any one of claims 1 to 6, characterized in that, Each of the at least one 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 to at least one winding of the motor in a one-to-one correspondence.
8. The heating method according to any one of claims 1 to 7, characterized in that, The method further includes: Receive the heating stop signal sent by the battery management system; Based on the heating stop signal, the short-circuit circuit is disconnected 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 battery, characterized in that, include: Power battery; A switching circuit, disposed between the power battery and the motor, is used for the power battery to supply power to the motor. The switching circuit includes multiple bridge arms connected in parallel with the power battery. A control circuit is used to receive a heating signal sent by the battery management system of the power battery, and according to the heating signal, control at least one of the plurality of bridge arms to form a short circuit loop for the power battery. The short circuit loop is used to discharge the power battery and heat the power battery during the discharge process. The control circuit is also used for: Obtain the current passing through the power battery and / or the voltage of the power battery; The duty cycle of the short-circuit circuit is determined based on the current passing through the power battery and / or the voltage of the power battery. Based on the 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.
11. The heating system according to claim 10, characterized in that, The control circuit is specifically used for: The current in the short-circuit circuit is detected by a current sensor installed in the short-circuit circuit; and / or, The current in the short-circuit loop is determined based on the voltage and internal resistance of the power battery.
12. The heating system according to claim 10 or 11, characterized in that, The control circuit is specifically used for: The at least one bridge arm is controlled to conduct according to the conduction duty cycle.
13. The heating system according to claim 10 or 11, characterized in that, A second switch is provided between the power battery and the at least one bridge arm, and the control circuit is specifically used for: The second switch is controlled to be turned on according to the duty cycle.
14. The heating system according to any one of claims 10 to 13, characterized in that, The control circuit is also used for: Obtain the internal resistance of the power battery; The conduction frequency of the short-circuit circuit is determined based on the internal resistance of the power battery, wherein the lower the internal resistance of the power battery, the higher the conduction frequency. The short-circuit loop is controlled to conduct according to the conduction frequency.
15. The heating system according to any one of claims 10 to 14, characterized in that, The power battery is also connected in parallel with a capacitor branch, which includes a capacitor connected in series and a first switch. The control circuit is also used for: Before the short-circuit loop is turned on, the first switch is turned off.
16. The heating system according to any one of claims 10 to 15, characterized in that, Each of the at least one 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 to at least one winding of the motor in a one-to-one correspondence.
17. The heating system according to any one of claims 10 to 16, characterized in that, The control circuit is also used for: Receive the heating stop signal sent by the battery management system; The short-circuit circuit is disconnected according to the heating stop signal to stop heating the power battery.
18. The heating system according to any one of claims 10 to 17, 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.