A method and system for heating a power battery and a vehicle

Abstract

The application provides a power battery heating method, a system and a car. The method comprises the following steps: when the power battery needs to be heated, performing two-dimensional scanning on the switching frequency of a plurality of switches in a high-frequency excitation loop of the power battery and the phase shift angle between the switches; based on the scanning result, confirming the optimal combination of the switching frequency and the phase shift angle with the optimal heating efficiency as the target; and controlling the plurality of switches in the high-frequency excitation loop based on the optimal combination to heat the power battery. The application expands the heating point into a heating area by the two-dimensional scanning and optimization of the switching frequency and the phase shift angle, systematically finds the global optimal working point, realizes the comprehensive optimization of the heating efficiency, and fundamentally overcomes the low efficiency problem caused by the single parameter adjustment in the prior art.

Description

Technical Field

[0001] This invention relates to the field of new energy vehicles, and in particular to a heating method, system and vehicle for a power battery. Background Technology

[0002] In low-temperature environments, the internal chemical reaction rate of power batteries (such as lithium-ion batteries) decreases significantly, leading to increased internal resistance, reduced charge and discharge capacity, and a sharp decline in usable capacity. This not only affects the driving range of electric vehicles and other devices but also causes charging difficulties, accelerated battery aging, and even safety hazards. Therefore, it is crucial to rapidly and efficiently preheat batteries before use or during operation to raise their operating temperature.

[0003] Currently, heating solutions for power batteries are mainly divided into two categories. One is external heating, such as adding independent PTC heating films or liquid thermal systems. This method requires additional hardware support, increasing the system's cost, weight, and complexity, and suffers from response lag and uneven heat distribution. The other is heating by utilizing the battery's internal resistance to generate Joule heat, i.e., battery self-heating technology. However, many existing self-heating methods often only adjust a single parameter in the excitation circuit (such as switching frequency or duty cycle). This one-dimensional optimization approach is difficult to find a globally optimal solution under complex operating conditions, easily getting trapped in local high-efficiency points, resulting in poor overall heating efficiency, or causing harsh high-frequency noise in pursuit of efficiency, making it difficult to achieve a good balance between heating efficiency and NVH performance.

[0004] In conclusion, there is currently no heating method that can systematically solve these problems. Summary of the Invention

[0005] In order to overcome the above-mentioned technical defects, the purpose of this invention is to provide a heating method, system and automobile for a power battery.

[0006] This invention discloses a heating method for a power battery, comprising: When the power battery needs to be heated, a two-dimensional scan is performed on the switching frequency of multiple switches in the high-frequency excitation circuit of the power battery and the phase shift angle between the switches. Based on the scanning results, with the goal of achieving optimal heating efficiency, the optimal combination of switching frequency and phase shift angle of the power battery was determined. The optimal combination of switching frequency and phase shift angle is used to control multiple switches in the high-frequency excitation circuit to heat the power battery.

[0007] Preferably, the heating efficiency is optimal when the ratio of the battery current of the power battery to the inductor current in the high-frequency excitation circuit is maximized.

[0008] Preferably, the heating method further includes: A Randle equivalent circuit model of the power battery is established. The equivalent circuit model treats the power battery as a component consisting of a first resistor and a capacitor connected in parallel and then connected in series with a second resistor. The effect of the combination of switching frequency and phase shift angle on heating efficiency is determined by using an equivalent circuit model.

[0009] Preferably, the heating method includes: changing the switching frequency to minimize the total impedance in the high-frequency excitation circuit, thereby maximizing the battery current.

[0010] Preferably, the heating method includes changing the ratio of battery current to inductor current by changing the phase shift angle.

[0011] Preferably, when controlling multiple switches, the switching frequency is set to ±1000Hz of the optimal combination of switching frequency and phase shift angle.

[0012] Preferably, the heating method further includes: monitoring the temperature of the power battery during the heating process, and repeatedly performing the step of confirming the optimal combination of switching frequency and phase shift angle according to the temperature change; and heating the power battery based on the new optimal combination of switching frequency and phase shift angle.

[0013] A second aspect of this application provides a heating system for a power battery that operates the power battery heating method as described in any of the foregoing embodiments.

[0014] Preferably, the heating system includes a power battery, a BOOST module, and a motor connected in sequence; the BOOST module and the power battery form a high-frequency excitation circuit; and all three phase arms of the motor are kept off.

[0015] A third aspect of this application provides a vehicle that includes a heating system for a power battery according to any of the foregoing embodiments.

[0016] Compared with existing technologies, the above technical solution has the following advantages: 1. The power battery heating method provided in this application upgrades the control strategy from traditional single-parameter adjustment to a two-dimensional scanning and optimization that coordinates the switching frequency and phase shift angle. This method expands the efficient "heating point" into a broad "heating zone," and through the joint control of multiple parameters, systematically finds the globally optimal operating point, achieving comprehensive optimization of heating efficiency and fundamentally overcoming the inefficiency problem caused by single-parameter adjustment in existing heating methods. 2. First, by establishing an accurate equivalent battery model, the goal is clearly defined as maximizing the ratio of battery current to inductor current. Based on this, by adjusting the switching frequency to maximize the battery current and adjusting the phase shift angle to minimize the effective value of the inductor current, direct and precise control of the core heating parameters is achieved. This ensures that energy is used to the maximum extent for internal battery heating while reducing reactive power losses in the circuit, thus achieving high thermal efficiency. 3. By further expanding the control range, the switching frequency is dispersed while maintaining efficient heating. This expands the selectable frequency range during heating, reduces noise generation, and solves the problems of narrow frequency range and high noise in battery heating. Simultaneously, the introduced dynamic adaptive mechanism can update the optimal control parameters in real time according to changes in battery temperature, ensuring that the system continuously maintains operation near peak efficiency throughout the entire heating process, achieving high efficiency and stability throughout the entire cycle. 4. The aforementioned method is integrated into a heating system. By reusing the BOOST module, it cleverly utilizes the vehicle's existing electronic control hardware, eliminating the need for additional dedicated components and significantly saving cost and space. This reduces overall vehicle cost and optimizes overall vehicle energy consumption performance. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the circuit structure of the three-electric system of the automobile provided in this application; Figure 2 A schematic flowchart of the heating method for the power battery provided in this application; Figure 3 for Figure 1 Simplified equivalent circuit diagram; Figure 4 The equivalent circuit diagram of the power battery provided in this application; Figure 5 for Figure 3 Simplified equivalent circuit diagram; Figure 6 A schematic diagram illustrating the relationship between the phase shift angle and the battery current and the inductor current in the heating method for the power battery provided in this application; Figure 7 A schematic diagram illustrating the relationship between phase shift angle, switching frequency, and heating efficiency in the power battery heating method provided in this application. Detailed Implementation

[0018] The advantages of the present invention will be further illustrated below with reference to the accompanying drawings and specific embodiments.

[0019] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numerals in different drawings denote the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this disclosure. Rather, they are merely examples of apparatuses and methods consistent with some aspects of this disclosure as detailed in the appended claims.

[0020] The terminology used in this disclosure is for the purpose of describing particular embodiments only and is not intended to be limiting of the disclosure. The singular forms “a,” “the,” and “the” as used in this disclosure and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that the term “and / or” as used herein refers to and includes any and all possible combinations of one or more of the associated listed items.

[0021] It should be understood that although the terms first, second, third, etc., may be used in this disclosure to describe various information, such information should not be limited to these terms. These terms are used only to distinguish information of the same type from one another. For example, without departing from the scope of this disclosure, first information may also be referred to as second information, and similarly, second information may also be referred to as first information. Depending on the context, the word "if" as used herein may be interpreted as "when," "when," or "in response to determination."

[0022] In the description of this invention, it should be understood that the terms "longitudinal", "lateral", "up", "down", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention 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. Therefore, they should not be construed as limitations on this invention.

[0023] In the description of this invention, unless otherwise specified and limited, it should be noted that the terms "installation", "connection" and "linking" should be interpreted broadly. For example, they can refer to mechanical or electrical connections, or internal connections between two components. They can be direct connections or indirect connections through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms according to the specific circumstances.

[0024] In the following description, suffixes such as "module," "part," or "unit" used to denote elements are used only for the convenience of the description of the invention and have no specific meaning in themselves. Therefore, "module" and "part" can be used interchangeably.

[0025] Please see Figures 1-2 , Figure 1 This is a schematic diagram of the circuit structure of the three-electric system of the automobile provided in this application. Figure 2 This is a schematic flowchart of the heating method for the power battery provided in this application.

[0026] like Figures 1-2 As shown, this application first provides a heating system for a power battery, which is directly based on the vehicle's three-electric system (battery, motor, and electronic control system) without adding any additional components. For example, such as... Figure 1 As shown, the heating system includes a power battery, a BOOST module, and a motor connected in sequence; the BOOST module and the power battery form a high-frequency excitation circuit; all three phase arms of the motor are kept off. For example, as... Figure 1 As shown, the BOOST module can be an interleaved parallel Boost module.

[0027] Those skilled in the art will understand that the heating system may also include more structures, such as... Figure 1 As shown, it may also include generators, etc. The specific structure of the heating system depends on the vehicle type, and this application does not impose any restrictions here. By keeping all three phase arms of the motor off, the circuit can be further simplified, so as to subsequently screen parameters that affect heating efficiency.

[0028] Please see Figure 3 , Figure 3 for Figure 1 The simplified equivalent circuit diagram.

[0029] like Figure 3 As shown in the simplified diagram, it can be seen that the main factors affecting heating efficiency are the switching frequency and the phase shift angle.

[0030] Therefore, as Figure 2 As shown, and in combination Figure 1 and Figure 3 It is understood that the second aspect of this application also provides a method for heating a power battery. This heating method relies on the aforementioned heating system and includes: When the power battery needs to be heated, a two-dimensional scan is performed on the switching frequency of multiple switches in the high-frequency excitation circuit of the power battery and the phase shift angle between the switches. Based on the scanning results, with the goal of achieving optimal heating efficiency, the optimal combination of switching frequency and phase shift angle of the power battery was determined. The optimal combination of switching frequency and phase shift angle is used to control multiple switches in the high-frequency excitation circuit to heat the power battery.

[0031] The power battery heating method provided in this application upgrades the control strategy from traditional single-parameter adjustment to a two-dimensional scanning and optimization that coordinates the switching frequency and phase shift angle. This method expands the efficient "heating point" into a broad "heating zone," and through the joint control of multiple parameters, systematically finds the globally optimal operating point, achieving comprehensive optimization of heating efficiency and fundamentally overcoming the inefficiency problem caused by the single-parameter adjustment of traditional methods.

[0032] The above is an explanation of the basic concept of this application. The specific implementation methods of this application will be described below in conjunction with the accompanying drawings.

[0033] In one possible implementation, such as Figure 3 As shown, the battery current Ibat = capacitor current Ic + inductor current Il. However, in actual heating, the battery current Ibat is actually the current used to heat the battery, which is directly related to the heating intensity. The inductor current Il does no work, so the heating efficiency can be considered highest when the ratio of battery current Ibat to inductor current Il is at its maximum.

[0034] By setting the "maximization of the battery current to inductor current ratio" as a clear optimization objective, a precise and quantifiable evaluation standard is provided for efficient heating. This indicator directly reflects the system's efficiency in converting the reactive power circulating in the loop into effective heat dissipation within the battery, guiding the control system to always operate within its most efficient operating range. This fundamentally avoids unnecessary energy loss in components such as inductors and achieves precise control of energy flow.

[0035] Please see Figures 4-5 , Figure 4 The equivalent circuit diagram of the power battery provided in this application; Figure 5 for Figure 3 The simplified equivalent circuit diagram.

[0036] like Figures 4-5 As shown, the heating method also includes: A Randle equivalent circuit model of the power battery is established. The equivalent circuit model treats the power battery as a component consisting of a first resistor and a capacitor connected in parallel and then connected in series with a second resistor. The effect of the combination of switching frequency and phase shift angle on heating efficiency is determined by using an equivalent circuit model.

[0037] By establishing a Randle equivalent circuit model of the power battery, a more accurate circuit structure can be further simplified. This simplification allows for further reduction of the circuit structure and parameters, enabling the determination of how the switching frequency and phase shift angle affect the ratio of battery current Ibat to inductor current Il.

[0038] Therefore, the effects of switching frequency and phase shift angle on heating efficiency can be further confirmed.

[0039] In one possible implementation, the heating method includes: changing the switching frequency to minimize the total impedance in the high-frequency excitation circuit, thereby maximizing the battery current.

[0040] The principle needs to be explained here: the switching frequency affects impedance, mainly affecting capacitance and inductance. In the s-domain, the capacitance is... ,in ,and Therefore, the higher the frequency, the smaller the capacitance, while the inductance (sL) increases with higher frequency. Thus, the effect of switching frequency on total impedance is not linear; it changes with the values ​​of capacitance and inductance.

[0041] Impedance model establishment process: 1. Establish using KCL: 2. Sorted out: Therefore, by changing the switching frequency, the battery current Ibat can be maximized.

[0042] Please see Figure 6 , Figure 6 A schematic diagram illustrating the relationship between the phase shift angle and the battery current and inductor current in the heating method for the power battery provided in this application.

[0043] like Figure 6 As shown, in one possible implementation, the heating method further includes controlling the ratio of battery current to inductor current by changing the phase shift angle, so as to minimize the effective value of the inductor current.

[0044] The principle will also be explained: For example... Figure 6 As shown in the diagram, similarly, the phase shift angle φ affects Il. By adjusting the phase shift angle, the effective current value of Il can be changed. For example, as can be seen in the diagram, when the phase shift angle is 0, the sum of the two maximum positive values ​​yields the maximum effective current value. Simultaneously, the phase shift angle also affects the battery current Ibat and the capacitor current Ic. Therefore, by changing the phase angle φ, the ratio of the battery current Ibat to the inductor current Il can be controlled.

[0045] Please see Figure 7 , Figure 7 A schematic diagram illustrating the relationship between phase shift angle, switching frequency, and heating efficiency in the power battery heating method provided in this application.

[0046] In summary, by adjusting the above control parameters, a two-dimensional scan can be performed on the switching frequency and the phase shift angle between switches, yielding results including heating efficiency (i.e., the ratio of battery current to inductor current). Figure 7 .

[0047] In obtaining Figure 7 Furthermore, in one possible implementation, when controlling multiple switches, the switching frequency is set to ±1000Hz of the optimal combination of the switching frequency and the phase shift angle.

[0048] This can be understood as follows: during heating, it is not necessary to heat only at the point of highest heating efficiency. Instead, heating can be carried out over a range of areas with relatively high heating efficiency, thereby dispersing the switching frequency and avoiding high-frequency noise caused by frequency concentration.

[0049] In another possible implementation, it is also possible to utilize... Figure 7 The region with a phase shift angle of 140°-160° and a frequency of 3000Hz in the upper left corner. Figure 7 The two regions in the middle 6000Hz, with a phase shift angle of about 0°-140°, are heated to further disperse the switching frequency, which is not limited in this application.

[0050] Those skilled in the art will understand that the above describes a heating process within a complete cycle, but the circuit parameters differ under different temperatures, and the optimal combination of switching frequency and phase shift angle will also differ.

[0051] Therefore, in one possible implementation, the heating method further includes: monitoring the temperature of the power battery during the heating process, and repeatedly executing the step of confirming the optimal combination of switching frequency and phase shift angle based on temperature changes; and heating the power battery based on the new optimal combination of switching frequency and phase shift angle. This ensures efficient and quiet heating throughout the entire cycle.

[0052] A third aspect of this application also provides a vehicle including a heating system for a power battery according to any of the foregoing embodiments. This system can perform the heating methods described in any of the foregoing embodiments. This enables the vehicle to have low-cost, rapid self-heating capabilities, effectively improving the vehicle's low-temperature start-up performance and driving range.

[0053] It should be noted that the embodiments of the present invention have better implementability and are not intended to limit the present invention in any way. Any person skilled in the art may use the above-disclosed technical content to change or modify it into equivalent effective embodiments. However, any modifications or equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention shall still fall within the scope of the technical solution of the present invention.

Claims

1. A method for heating a power battery, characterized in that, The heating method includes: When the power battery needs to be heated, a two-dimensional scan is performed on the switching frequency of multiple switches in the high-frequency excitation circuit of the power battery and the phase shift angle between the switches. Based on the scanning results, with the goal of maximizing the ratio of the battery current of the power battery to the inductor current in the high-frequency excitation circuit, the optimal combination of the switching frequency and phase shift angle of the power battery is determined. Multiple switches in the high-frequency excitation circuit are controlled based on the optimal combination of the switching frequency and the phase shift angle to heat the power battery; the switching frequency is set to ±1000Hz of the optimal combination of the switching frequency and the phase shift angle.

2. The heating method for a power battery as described in claim 1, characterized in that, The heating method further includes: A Randle equivalent circuit model of the power battery is established, wherein the equivalent circuit model represents the power battery as a component consisting of a first resistor and a capacitor connected in parallel and then connected in series with a second resistor. The effect of the combination of the switching frequency and the phase shift angle on the heating efficiency is determined by using the equivalent circuit model.

3. The heating method for a power battery as described in claim 2, characterized in that, The heating method includes: changing the switching frequency to minimize the total impedance in the high-frequency excitation circuit, thereby maximizing the battery current.

4. The heating method for a power battery as described in claim 2, characterized in that, The heating method includes controlling the ratio of the battery current to the inductor current by changing the phase shift angle.

5. The method as described in claim 1, characterized in that, The heating method further includes: during the heating process, monitoring the temperature of the power battery, and repeatedly performing the step of confirming the optimal combination of switching frequency and phase shift angle according to the temperature change; and heating the power battery based on the new optimal combination of switching frequency and phase shift angle.

6. A heating system for a power battery, characterized in that, The power battery heating system operates the power battery heating method as described in any one of claims 1-5.

7. The heating system for a power battery as described in claim 6, characterized in that, The heating system includes a power battery, a BOOST module, and a motor connected in sequence; the BOOST module and the power battery form a high-frequency excitation circuit; all three phase arms of the motor are kept off.

8. A car, characterized in that, The vehicle includes a heating system for the power battery as described in any one of claims 6-7.

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