Lithium battery temperature estimation method and device based on harmonic characteristics and storage medium

Abstract

The invention relates to a lithium battery temperature estimation method and device based on harmonic characteristics and a storage medium, and the method comprises the steps: collecting a voltage signal and a current signal outputted to a lithium battery by a power conversion circuit in the charging process of the lithium battery; extracting the second harmonic quantity of the voltage signal and the current signal; determining target imaginary part impedance under the target frequency based on the second harmonic quantity; wherein the target frequency is the frequency of the second harmonic quantity. According to the method, in the charging process of the lithium battery, a voltage signal and a current signal output to the lithium battery by a power conversion circuit are collected, and target imaginary part impedance under target frequency is determined based on second harmonic quantity extracted from the voltage signal and the current signal; the target temperature of the lithium battery is estimated by combining the preset mapping relation between the imaginary part impedance and the internal temperature of the battery, disturbance signals do not need to be additionally introduced, impedance measurement and temperature calculation are carried out through harmonic waves generated by the power conversion circuit, and the internal temperature measurement of the battery is simpler and more convenient on the premise that the precision is guaranteed.

Description

Technical Field

[0001] The present application relates to the field of lithium battery technology, and in particular to a lithium battery temperature estimation method, device and storage medium based on harmonic characteristics. Background Art

[0002] As urban environmental and oil resource problems become increasingly serious, people are increasingly studying the technical fields related to electric vehicles. At present, power conversion circuits such as PWM rectifiers have been widely used in electric vehicle charging, and battery safety issues have also attracted more and more attention, especially complex safety issues such as battery thermal runaway. In response to the safety issues of battery thermal runaway, various new energy vehicle manufacturers and battery manufacturers have been constantly exploring and trying to continuously improve the accuracy of real-time temperature measurement methods for automotive power batteries through different technical routes and different products, while reducing their monitoring costs. However, the current battery temperature measurement is mostly based on temperature sensors, which have high hardware costs, and complex sensor power supply and signal transmission lines. Sensorless solutions based on lithium battery impedance estimation have attracted attention, but they all require the injection of additional disturbances, which will affect the normal operation of lithium batteries and increase costs. Summary of the invention

[0003] The present application provides a lithium battery temperature estimation method, device and storage medium based on harmonic characteristics to solve the problem of how to achieve lithium battery temperature measurement without adding disturbance signals.

[0004] In a first aspect, the present application provides a lithium battery temperature estimation method based on harmonic characteristics, the method comprising:

[0005] During the charging process of the lithium battery, the voltage signal and current signal outputted from the power conversion circuit to the lithium battery are collected;

[0006] Extracting the second harmonic amount of the voltage signal and the current signal;

[0007] Determining a target imaginary impedance at a target frequency based on the second harmonic amount; wherein the target frequency is the frequency of the second harmonic amount;

[0008] The target temperature of the lithium battery is determined according to a preset mapping relationship and the target imaginary impedance; wherein the mapping relationship is a mapping relationship between the imaginary impedance and the internal temperature of the battery.

[0009] Optionally, before determining the target temperature of the lithium battery according to the preset mapping relationship and the target imaginary impedance, the method further includes:

[0010] Offline fitting of the mapping relationship between the imaginary impedance and the internal temperature of the battery;

[0011] The offline fitting process of the mapping relationship includes:

[0012] Selecting a target temperature set point from a set of temperature set points;

[0013] Offline charging of the lithium battery at the target temperature set point condition, calculating the imaginary impedance of the lithium battery at the second harmonic current frequency, and measuring the internal temperature of the battery;

[0014] Selecting the next target temperature set point from the set of temperature set points, and performing the steps of offline charging the lithium battery under the target temperature set point condition, calculating the imaginary impedance of the lithium battery at the second harmonic current frequency, and measuring the internal temperature of the battery, until all target temperature set points are selected;

[0015] The mapping relationship is obtained by fitting the imaginary impedance at the second harmonic current frequency and the internal temperature of the battery.

[0016] Optionally, before selecting the target temperature set point from the temperature set point set, the method further comprises:

[0017] Select a target charging state from the charging state interval;

[0018] Accordingly, after all target temperature setting points under the target charging state are selected, the method further includes:

[0019] The steps of selecting the next target charging state from the charging state interval and selecting the target temperature setting point from the temperature setting point set are performed, and the steps of selecting the next target temperature setting point from the temperature setting point set, and charging the lithium battery offline under the target temperature setting point condition, calculating the imaginary impedance of the lithium battery at the second harmonic current frequency, and measuring the internal temperature of the battery are performed, until all the target temperature setting points are selected, and until all the target charging states are selected.

[0020] Optionally, extracting the second harmonic amount of the voltage signal and the current signal includes:

[0021] Sampling the voltage signal and the current signal using a sliding window iteration method to obtain sampling data;

[0022] Performing discrete Fourier transform on the sampled data to obtain frequency spectrum information of the sampled data;

[0023] The second harmonic amount is determined based on the frequency spectrum information.

[0024] Optionally, determining a target imaginary impedance at a target frequency based on the second harmonic amount includes:

[0025] The target imaginary impedance of the second harmonic at the target frequency is calculated by a dual-channel digital lock-in amplifier.

[0026] Optionally, the target frequency is 100 Hz.

[0027] Optionally, the power conversion circuit includes a PWM rectifier circuit and a Boost PFC circuit.

[0028] In a second aspect, the present application provides a lithium battery temperature estimation device based on harmonic characteristics, the device comprising:

[0029] The acquisition module is used to collect the voltage signal and current signal output from the power conversion circuit to the lithium battery during the charging process of the lithium battery;

[0030] An extraction module, used for extracting the second harmonic amount of the voltage signal and the current signal;

[0031] A determination module, configured to determine a target imaginary impedance at a target frequency based on the second harmonic amount; wherein the target frequency is the frequency of the second harmonic amount;

[0032] An estimation module is used to determine the target temperature of the lithium battery according to a preset mapping relationship and the target imaginary impedance; wherein the mapping relationship is a mapping relationship between the imaginary impedance and the internal temperature of the lithium battery.

[0033] In a third aspect, the present application provides an electronic device, including a processor, a communication interface, a memory, and a communication bus, wherein the processor, the communication interface, and the memory communicate with each other via the communication bus;

[0034] Memory, used to store computer programs;

[0035] The processor is used to implement the lithium battery temperature estimation method based on harmonic characteristics described in any embodiment of the first aspect when executing the program stored in the memory.

[0036] In a fourth aspect, the present application provides a computer-readable storage medium having a computer program stored thereon, and when the computer program is executed by a processor, the method for estimating the temperature of a lithium battery based on harmonic characteristics as described in any one of the embodiments of the first aspect is implemented.

[0037] The above technical solution provided by the embodiment of the present application has the following advantages over the prior art: the method provided by the embodiment of the present application, during the charging process of the lithium battery, collects the voltage signal and current signal output by the power conversion circuit to the lithium battery; extracts the second harmonic amount of the voltage signal and the current signal; determines the target imaginary impedance at the target frequency based on the second harmonic amount; wherein the target frequency is the frequency of the second harmonic amount; determines the target temperature of the lithium battery according to the preset mapping relationship and the target imaginary impedance; wherein the mapping relationship is the mapping relationship between the imaginary impedance and the internal temperature of the battery. During the charging process of the lithium battery, the method collects the voltage signal and current signal output by the power conversion circuit to the lithium battery, determines the target imaginary impedance at the target frequency based on the second harmonic amount extracted from the voltage signal and the current signal, and then estimates the target temperature of the lithium battery by combining the preset mapping relationship between the imaginary impedance and the internal temperature of the battery, without the need to introduce additional disturbance signals, and performs impedance measurement and temperature calculation through the harmonics generated by the power conversion circuit, so that the internal temperature measurement of the battery is simpler while ensuring accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present application and, together with the description, serve to explain the principles of the present application.

[0039] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0040] One or more embodiments are exemplarily described by pictures in the corresponding drawings, and these exemplified descriptions do not constitute limitations on the embodiments. Elements with the same reference numerals in the drawings represent similar elements, and unless otherwise stated, the figures in the drawings do not constitute proportional limitations.

[0041] Figure 1 A system architecture diagram of a lithium battery temperature estimation method based on harmonic characteristics provided in one embodiment of the present application;

[0042] Figure 2 A schematic diagram of a flow chart of a lithium battery temperature estimation method based on harmonic characteristics provided in one embodiment of the present application;

[0043] Figure 3 A schematic flow chart of a lithium battery temperature estimation method based on harmonic characteristics provided in another embodiment of the present application;

[0044] Figure 4A schematic diagram of collected SOC, voltage, and current waveforms provided for one embodiment of the present application;

[0045] Figure 5 A schematic diagram of Fourier decomposition after second harmonic suppression provided by an embodiment of the present application;

[0046] Figure 6 A block diagram of a battery temperature real-time estimation principle provided by an embodiment of the present application;

[0047] Figure 7 A schematic diagram of the structure of a lithium battery temperature estimation device based on harmonic characteristics provided by one embodiment of the present application;

[0048] Figure 8 A schematic diagram of the structure of an electronic device provided in accordance with an embodiment of the present application. DETAILED DESCRIPTION

[0049] In order to make the purpose, technical solution and advantages of the embodiments of the present application clearer, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0050] The disclosure below provides many different embodiments or examples to realize the different structures of the present application. In order to simplify the disclosure of the present application, the parts and settings of specific examples are described below. Of course, they are only examples, and the purpose is not to limit the present application. In addition, the present application can repeat reference numbers and / or letters in different examples. This repetition is for the purpose of simplification and clarity, and does not itself indicate the relationship between the various embodiments and / or settings discussed.

[0051] In order to realize the monitoring of internal temperature of batteries, many studies have been done at home and abroad. Common monitoring methods can be divided into direct sensor measurement method, model-based method, impedance-based method, data-driven method, etc.

[0052] The sensor direct measurement method uses a temperature sensor attached to the battery surface or embedded inside the battery to measure the temperature, such as thermocouples, magnetic nanoparticle thermometers, and optical fiber sensors. This method can directly measure the surface or internal temperature of the battery, but additional sensors, wires, sampling circuits, or excitation circuits may increase costs and cause safety issues.

[0053] Model-based methods build different forms of thermoelectric equivalent circuit models of batteries, and then estimate the surface or internal temperature of the battery based on voltage and current data and parameter identification algorithms (such as Kalman filter algorithms). Although these model-based schemes have good real-time performance, the estimation accuracy may be affected by the state of charge (SoC) and state of health (SoH) because the dynamic SoC and SoH are usually not considered in the model.

[0054] Data-driven methods, such as some advanced artificial intelligence and machine learning technologies, such as deep neural networks, artificial neural networks, transfer learning, and physical model integrated machine learning, have been used for battery temperature estimation. However, data-driven methods require complex training algorithms, large amounts of training data and labels, which invisibly add a lot of additional implementation costs and complexity.

[0055] At present, the main impedance-based battery temperature monitoring solutions are: using the impedance at the cutoff frequency to estimate the temperature; using the relationship between the phase angle and temperature to estimate the temperature; using the real and imaginary parts of the impedance to estimate the temperature, etc. However, the above solutions all require additional disturbance injection, that is, it is necessary to add an excitation circuit to generate a harmonic source. Since additional excitation injection is required, the normal operation of the battery is greatly affected and the cost is increased. In addition, the above methods are difficult to achieve practicality in terms of measurement accuracy (greatly affected by external circuits and ambient temperature, etc.), measurement cost (mostly using excitation source injection), and measurement speed.

[0056] For example, in terms of measurement accuracy, for example, the battery temperature is calculated using the relationship between phase angle and temperature. Since the phase angle φ will be affected to a certain extent by the peripheral circuit and will also change at different SOC levels, it is not a suitable thermally sensitive electrical parameter (TSEP) for temperature estimation, which may lead to low accuracy in estimated temperature. The real part of the battery impedance is greatly affected by the ambient temperature and battery status and is difficult to be used as an intermediate quantity for battery temperature calculation. In terms of measurement cost, existing methods for online measurement of battery impedance mostly use additional excitation sources to generate specific harmonic signals to excite the battery, thereby measuring the battery's response under excitation and calculating the impedance, which increases the cost of the excitation source.

[0057] In response to the above problems, in order to solve the technical problem of how to realize the temperature measurement of lithium batteries without adding disturbance signals in the prior art, the present application provides a lithium battery temperature estimation method, device and storage medium based on harmonic characteristics, which can realize impedance measurement and temperature calculation through the harmonics generated by the power conversion circuit without the need to introduce additional disturbance signals, making the internal temperature measurement of the battery simpler while ensuring accuracy.

[0058] The first embodiment of the present application provides a lithium battery temperature estimation method based on harmonic characteristics. The method can be applied to Figure 1 The system architecture shown in the figure includes at least an online temperature estimation module 101 and a lithium battery 102 . The online temperature estimation module 101 can perform online estimation on the temperature of the lithium battery 102 .

[0059] The method can be applied to the online temperature estimation module 101 in the system architecture. Next, based on the system architecture, the lithium battery temperature estimation method based on harmonic characteristics is described in detail. Figure 2 , the lithium battery temperature estimation method based on harmonic characteristics includes:

[0060] Step 201, during the charging process of the lithium battery, collecting the voltage signal and the current signal outputted from the power conversion circuit to the lithium battery.

[0061] In this embodiment, no additional harmonic excitation generator is required, and the voltage signal and current signal outputted from the power conversion circuit to the lithium battery can be collected during the charging process of the lithium battery. Specifically, the power conversion circuit can be a PWM rectifier circuit or a Boost PFC circuit.

[0062] In one embodiment, the mapping relationship between the imaginary impedance and the internal temperature of the battery may be fitted offline first.

[0063] Among them, the offline fitting process of the mapping relationship includes: selecting a target temperature set point from a temperature set point set; charging the lithium battery offline under the target temperature set point condition, calculating the imaginary impedance of the lithium battery at the second harmonic current frequency, and measuring the internal temperature of the battery; selecting the next target temperature set point from the temperature set point set, and executing the steps of charging the lithium battery offline under the target temperature set point condition, calculating the imaginary impedance of the lithium battery at the second harmonic current frequency, and measuring the internal temperature of the battery, until all target temperature set points are selected; and obtaining the mapping relationship according to the imaginary impedance at the second harmonic current frequency and the internal temperature of the battery.

[0064] In this embodiment, the temperature set point set can be a temperature interval, such as the operating temperature interval of a lithium battery, and the target temperature set point is the temperature in the temperature interval, such as all integer values ​​in the temperature interval. In order to make the mapping relationship of offline fitting more accurately covered, a temperature set point can be set at intervals of 0.1°C or smaller intervals without restriction. In the offline fitting process, all target temperature set points in the temperature set point set can be sequentially calculated for imaginary impedance and measured for the internal temperature of the battery, and finally a functional relationship fitting is performed based on all calculated imaginary impedances and measured internal temperature of the battery.

[0065] In one embodiment, before selecting the target temperature set point from the temperature set point set, the method further includes: selecting a target charging state from the charging state interval.

[0066] Accordingly, after all target temperature set points under the target charging state are selected, the method also includes: selecting the next target charging state from the charging state range, and selecting the target temperature set point from the temperature set point set, to selecting the next target temperature set point in the temperature set point set, and performing offline charging of the lithium battery under the target temperature set point conditions, calculating the imaginary impedance of the lithium battery at the second harmonic current frequency, and measuring the internal temperature of the battery, until all target temperature set points are selected, until all target charging states are selected.

[0067] In this embodiment, the mapping relationship can also be fitted in combination with the state of charge (SOC) parameters. For example, the above-mentioned offline fitting is performed in the SOC range of 20% to 80% in sequence. After fitting verification, the battery imaginary impedance is almost unaffected by the battery SOC and external temperature at 100Hz to 1kHz.

[0068] In this embodiment, the relationship between the temperature and the imaginary impedance of the lithium battery can be obtained through impedance testing. Taking the imaginary impedance of the battery under 100Hz harmonic disturbance as an example, the impedance test can be performed in a constant temperature box. For example, the constant temperature box can be set to an initial temperature of 25°C, and the constant current constant voltage charging (CC-CV) program can be used to charge and discharge the battery to between 20% and 80% (to prevent the battery from aging and attenuation, and because the battery SOC has no effect on the method of estimating the internal temperature of the battery, there is no strict requirement for the battery SOC), and then the temperature of the incubator is adjusted to the temperature setting point, and the battery charging program is started after standing for 1 hour, the imaginary impedance of the battery is estimated in real time, and the corresponding internal temperature of the battery is measured, and then the measured data is fitted with a function. The test process performs data collection work at different temperature setting points and different SOCs, and a large amount of data under different initial conditions are used to perform function fitting to ensure the accuracy of online battery internal temperature calculation and control the calculation error under different initial conditions.

[0069] Step 202: extract the second harmonic content of the voltage signal and the current signal.

[0070] In one embodiment, extracting the second harmonic amount of the voltage signal and the current signal includes: sampling the voltage signal and the current signal using a sliding window iteration method to obtain sampled data; performing a discrete Fourier transform on the sampled data to obtain spectrum information of the sampled data; and determining the second harmonic amount based on the spectrum information.

[0071] In this embodiment, the flow chart of the lithium battery temperature estimation method based on harmonic characteristics is as follows: Figure 3The power grid charges the lithium battery through a PWM rectifier circuit or a Boost PFC circuit. At this time, the ripple current (current signal) and ripple voltage (voltage signal) at both ends of the battery are collected, and the imaginary impedance at 100Hz is calculated. Combined with the mapping relationship between the temperature and the imaginary impedance obtained offline, the temperature of the lithium battery can be estimated. Taking the power conversion circuit as a PWM rectifier circuit as an example, the imaginary impedance of the battery can be calculated using the second harmonic current generated by the PWM rectifier circuit. Of course, the second harmonic current can be a suppressed second harmonic current. For example, set the initial SOC of the lithium battery to be tested to 40% and build a verification circuit simulation. The SOC, voltage, and current waveforms of the lithium battery are as follows: Figure 4 As shown in the figure, the horizontal axis represents time, and the vertical axis represents SOC value (%), voltage value (V) and current value (A). Since this method has an interval limit requirement for the amplitude of the second harmonic used, the battery current is subjected to harmonic suppression measurement, and then the battery current after harmonic suppression is subjected to fast Fourier transform (FFT) analysis. The schematic diagram of Fourier decomposition after second harmonic suppression is shown in the figure. Figure 5 It can be found that the battery current at this time is mainly composed of the fundamental frequency and the second harmonic of 100Hz. The second harmonic of the current is 100Hz, which has been effectively suppressed and can be used for the calculation of battery impedance.

[0072] Step 203, determining a target imaginary impedance at a target frequency based on the second harmonic amount; wherein the target frequency is the frequency of the second harmonic amount.

[0073] In one embodiment, determining a target imaginary impedance at a target frequency based on the second harmonic amount includes: calculating the target imaginary impedance of the second harmonic amount at the target frequency by a dual-channel digital lock-in amplifier.

[0074] In this embodiment, the principle block diagram of real-time battery temperature estimation is as follows: Figure 6As shown, Cell1...k represents lithium batteries, Vcell1, 2...k represents the voltage signal of each lithium battery collected, and Icell represents the collected current signal. First, the second harmonic current (SHC) injected into the battery pack needs to be suppressed to an appropriate level as a disturbance signal for online impedance measurement, and then the sliding window iteration method is used to extract the real-time second harmonic amount of the battery current, represented by V1f0, 2f0...kf0. The sliding window iteration DFT method is a signal processing method based on discrete Fourier transform. It samples the input signal and performs discrete Fourier transform on the sampled data to obtain the spectrum information of the signal. Then, a dual-channel digital lock-in amplifier (DLIA) is used to calculate the battery impedance Zcell1, 2...k of the second harmonic amount at the target frequency (Second Harmonic Frequency, referred to as SHF, also known as the second harmonic frequency). Specifically, the target frequency is 100Hz, and then combined with the functional relationship between the battery temperature and the imaginary impedance, the internal temperature Tcell1, 2...k of each lithium battery is obtained. The digital lock-in amplifier is an effective algorithm for detecting periodic components with low signal-to-noise ratio (SNR) in weak signals, which is based on the cross-correlation detection principle. At the same time, the Pisarenko harmonic decomposition algorithm can be used to estimate the actual SHF to ensure the accuracy of impedance calculation.

[0075] Step 204, determining the target temperature of the lithium battery according to a preset mapping relationship and the target imaginary impedance; wherein the mapping relationship is a mapping relationship between the imaginary impedance and the internal temperature of the battery.

[0076] During the charging process of the lithium battery, the method collects the voltage signal and the current signal output by the power conversion circuit to the lithium battery, determines the target imaginary impedance at the target frequency based on the second harmonic amount extracted from the voltage signal and the current signal, and then estimates the target temperature of the lithium battery in combination with the mapping relationship between the preset imaginary impedance and the internal temperature of the battery. No additional disturbance signal needs to be introduced, and the impedance measurement and temperature calculation are performed through the harmonics generated by the power conversion circuit, so that the internal temperature measurement of the battery is simpler while ensuring the accuracy.

[0077] In the above embodiments of the present application, the battery impedance is measured by harmonics generated by the power conversion circuit. According to the phenomenon that the real part, amplitude and phase angle of the impedance will be significantly affected by peripheral circuits including RC filtering circuits, balancing circuits and line resistance, while the imaginary impedance is almost unaffected by the peripheral circuits, and factors such as measurement cost control, the present application proposes to use the relationship between the imaginary impedance of the battery and the battery temperature to measure the battery temperature in real time, and the battery impedance measurement uses the proposed power conversion circuit such as PWM rectifier and other self-generated harmonic measurement scheme. This scheme can measure the battery temperature in real time and ensure that reliable estimation results can be obtained under different working conditions and different environmental conditions, while taking into account the cost and no additional excitation source is required to inject harmonics.

[0078] Based on the same technical concept, the second embodiment of the present application provides a lithium battery temperature estimation device based on harmonic characteristics, such as Figure 7 , the device comprises:

[0079] The acquisition module 701 is used to acquire the voltage signal and current signal outputted from the power conversion circuit to the lithium battery during the charging process of the lithium battery;

[0080] An extraction module 702, used to extract the second harmonic amount of the voltage signal and the current signal;

[0081] A determination module 703 is used to determine a target imaginary impedance at a target frequency based on the second harmonic amount; wherein the target frequency is the frequency of the second harmonic amount;

[0082] The estimation module 704 is used to determine the target temperature of the lithium battery according to a preset mapping relationship and the target imaginary impedance; wherein the mapping relationship is a mapping relationship between the imaginary impedance and the internal temperature of the lithium battery.

[0083] During the charging process of the lithium battery, the device collects the voltage signal and current signal output by the power conversion circuit to the lithium battery, determines the target imaginary impedance at the target frequency based on the second harmonic amount extracted from the voltage signal and the current signal, and then estimates the target temperature of the lithium battery in combination with the mapping relationship between the preset imaginary impedance and the internal temperature of the battery. There is no need to introduce additional disturbance signals. Impedance measurement and temperature calculation are performed through the harmonics generated by the power conversion circuit, making the measurement of the internal temperature of the battery simpler while ensuring accuracy.

[0084] like Figure 8 As shown, an embodiment of the present application provides an electronic device, including a processor 111, a communication interface 112, a memory 113 and a communication bus 114, wherein the processor 111, the communication interface 112, and the memory 113 communicate with each other through the communication bus 114.

[0085] Memory 113, used for storing computer programs;

[0086] In one embodiment of the present application, the processor 111 is used to execute the program stored in the memory 113 to implement the lithium battery temperature estimation method based on harmonic characteristics provided by any of the above method embodiments, including:

[0087] During the charging process of the lithium battery, the voltage signal and current signal outputted from the power conversion circuit to the lithium battery are collected;

[0088] Extracting the second harmonic amount of the voltage signal and the current signal;

[0089] Determining a target imaginary impedance at a target frequency based on the second harmonic amount; wherein the target frequency is the frequency of the second harmonic amount;

[0090] The target temperature of the lithium battery is determined according to a preset mapping relationship and the target imaginary impedance; wherein the mapping relationship is a mapping relationship between the imaginary impedance and the internal temperature of the battery.

[0091] The communication bus mentioned in the above terminal can be a Peripheral Component Interconnect (PCI) bus or an Extended Industry Standard Architecture (EISA) bus, etc. The communication bus can be divided into an address bus, a data bus, a control bus, etc. For ease of representation, only one thick line is used in the figure, but it does not mean that there is only one bus or one type of bus.

[0092] The communication interface is used for communication between the above terminal and other devices.

[0093] The memory may include a random access memory (RAM) or a non-volatile memory, such as at least one disk memory. Optionally, the memory may also be at least one storage device located away from the aforementioned processor.

[0094] The above-mentioned processor can be a general-purpose processor, including a central processing unit (CPU), a network processor (NP), etc.; it can also be a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA) or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components.

[0095] An embodiment of the present application further provides a computer-readable storage medium having a computer program stored thereon. When the computer program is executed by a processor, the method for estimating the temperature of a lithium battery based on harmonic characteristics as provided in any of the aforementioned method embodiments is implemented.

[0096] The device embodiments described above are only illustrative, wherein the units described as separate components may or may not be physically separated, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed on multiple network units. Some or all of the modules may be selected according to actual needs to achieve the purpose of the solution of this embodiment.

[0097] Through the description of the above implementation methods, those skilled in the art can clearly understand that each implementation method can be implemented by means of software plus a general hardware platform, and of course, by hardware. Based on this understanding, the above technical solution is essentially or the part that contributes to the relevant technology can be embodied in the form of a software product, and the computer software product can be stored in a computer-readable storage medium, such as ROM / RAM, a disk, an optical disk, etc., including a number of instructions for a computer device (which can be a personal computer, a server, or a network device, etc.) to execute the methods described in each embodiment or some parts of the embodiments.

[0098] It should be understood that the terms used herein are only for the purpose of describing specific example embodiments and are not intended to be limiting. Unless the context clearly indicates otherwise, the singular forms "one", "an" and "said" as used herein may also be meant to include plural forms. The terms "include", "comprise", "contain", and "have" are inclusive, and therefore specify the existence of stated features, steps, operations, elements and / or parts, but do not exclude the existence or addition of one or more other features, steps, operations, elements, parts, and / or combinations thereof. The method steps, processes, and operations described herein are not interpreted as necessarily requiring them to be performed in the specific order described or illustrated, unless the execution order is clearly indicated. It should also be understood that additional or alternative steps may be used.

[0099] It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application. In the description, the use of suffixes such as "module", "component" or "unit" used to represent elements is only for the purpose of facilitating the description of the present application and has no specific meaning in itself. Therefore, "module", "component" or "unit" can be used in a mixed manner.

[0100] The above description is only a specific implementation of the present application, so that those skilled in the art can understand or implement the present application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to the embodiments shown herein, but will conform to the widest range consistent with the principles and novel features applied for herein.

Claims

1. A lithium battery temperature estimation method based on harmonic characteristics, characterized in that: The method comprises: During the charging process of the lithium battery, the voltage signal and current signal outputted from the power conversion circuit to the lithium battery are collected; Extracting the second harmonic amount of the voltage signal and the current signal; Determining a target imaginary impedance at a target frequency based on the second harmonic amount; wherein the target frequency is the frequency of the second harmonic amount; The target temperature of the lithium battery is determined according to a preset mapping relationship and the target imaginary impedance; wherein the mapping relationship is a mapping relationship between the imaginary impedance and the internal temperature of the battery.

2. The method according to claim 1, characterized in that Before determining the target temperature of the lithium battery according to the preset mapping relationship and the target imaginary impedance, the method further includes: Offline fitting of the mapping relationship between the imaginary impedance and the internal temperature of the battery; The offline fitting process of the mapping relationship includes: Selecting a target temperature set point from a set of temperature set points; Offline charging of the lithium battery at the target temperature set point condition, calculating the imaginary impedance of the lithium battery at the second harmonic current frequency, and measuring the internal temperature of the battery; Selecting the next target temperature set point from the set of temperature set points, and performing the steps of offline charging the lithium battery under the target temperature set point condition, calculating the imaginary impedance of the lithium battery at the second harmonic current frequency, and measuring the internal temperature of the battery, until all target temperature set points are selected; The mapping relationship is obtained by fitting the imaginary impedance at the second harmonic current frequency and the internal temperature of the battery.

3. The method according to claim 2, characterized in that Before selecting the target temperature set point from the set of temperature set points, the method further includes: Select a target charging state from the charging state interval; Accordingly, after all target temperature setting points under the target charging state are selected, the method further includes: The steps of selecting the next target charging state from the charging state interval and selecting the target temperature setting point from the temperature setting point set are performed, and the steps of selecting the next target temperature setting point from the temperature setting point set, and charging the lithium battery offline under the target temperature setting point condition, calculating the imaginary impedance of the lithium battery at the second harmonic current frequency, and measuring the internal temperature of the battery are performed, until all the target temperature setting points are selected, and until all the target charging states are selected.

4. The method according to claim 1, characterized in that: Extracting the second harmonic amount of the voltage signal and the current signal includes: Sampling the voltage signal and the current signal using a sliding window iteration method to obtain sampling data; Performing discrete Fourier transform on the sampled data to obtain frequency spectrum information of the sampled data; The second harmonic amount is determined based on the frequency spectrum information.

5. The method according to claim 1, characterized in that Determining a target imaginary impedance at a target frequency based on the second harmonic amount includes: The target imaginary impedance of the second harmonic at the target frequency is calculated by a dual-channel digital lock-in amplifier.

6. The method according to claim 1, characterized in that The target frequency is 100 Hz.

7. The method according to claim 1, characterized in that The power conversion circuit includes a PWM rectifier circuit and a Boost PFC circuit.

8. A lithium battery temperature estimation device based on harmonic characteristics, characterized in that: The device comprises: The acquisition module is used to collect the voltage signal and current signal output from the power conversion circuit to the lithium battery during the charging process of the lithium battery; An extraction module, used for extracting the second harmonic amount of the voltage signal and the current signal; A determination module, configured to determine a target imaginary impedance at a target frequency based on the second harmonic amount; wherein the target frequency is the frequency of the second harmonic amount; An estimation module is used to determine the target temperature of the lithium battery according to a preset mapping relationship and the target imaginary impedance; wherein the mapping relationship is a mapping relationship between the imaginary impedance and the internal temperature of the lithium battery.

9. An electronic device, characterized in that: It includes a processor, a communication interface, a memory and a communication bus, wherein the processor, the communication interface and the memory communicate with each other through the communication bus; Memory, used to store computer programs; The processor is used to implement the lithium battery temperature estimation method based on harmonic characteristics as described in any one of claims 1 to 7 when executing the program stored in the memory.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the lithium battery temperature estimation method based on harmonic characteristics as described in any one of claims 1 to 7 is implemented.

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