Non-contact injection lithium battery high-frequency impedance online measurement method and system

Abstract

The invention discloses a non-contact injection lithium battery high-frequency impedance online measurement method and system. The method comprises the following operation steps: S1, setting the amplitude and frequency of a high-frequency characteristic signal vinj.f in a high-frequency sine power supply; s2, injecting a high-frequency characteristic signal vinj.f generated by the high-frequency sine power supply into the lithium battery through a non-contact injection unit in an electromagnetic coupling non-contact manner; s3, carrying out sampling and algorithm processing on the voltage vb at the two ends of the lithium battery and the current ib flowing through the lithium battery to obtain a characteristic voltage amplitude vb.f, a characteristic voltage phase angle thetav, a characteristic current amplitude ib.f and a characteristic current phase angle thetai of the lithium battery under the current specified high frequency f; s4, calculating to obtain a characteristic impedance amplitude zb.f and a characteristic impedance angle theta Z of the lithium battery under the specified high frequency f; under the condition that the original loop structure of the lithium battery is not changed, the high-frequency characteristic signal is injected into the lithium battery through the non-contact injection unit in an electromagnetic coupling non-contact mode, and effective online measurement of the high-frequency impedance of the lithium battery is achieved.

Description

Technical Field

[0001] The present invention relates to the field of lithium battery state monitoring, and particularly relates to a non-contact injection method and system for on-line measurement of high-frequency impedance of lithium batteries. Background Art

[0002] Due to advantages such as high energy density, long life, and no memory effect, lithium batteries have been widely used in various fields such as electronic devices, electric vehicles, electric ships, and energy storage power stations. In order to ensure the safe and reliable operation of the lithium battery system, it is necessary to monitor the state of the lithium battery. The most commonly used method is to reflect information such as its temperature, state of charge, and health state through the impedance of the lithium battery.

[0003] Currently, the measurement method of lithium battery impedance mainly calculates its impedance by using the alternating current voltage and current of the lithium battery. According to the different generation methods of the alternating current excitation, it can be divided into two categories: the injection method and the perturbation method.

[0004] The injection method uses an external injection source to inject an alternating current excitation signal with a specific frequency into the lithium battery. For example, the invention patent with the publication number CN119044801A discloses a method of injecting a parallel impedance excitation signal into a battery under test by using a current source to obtain its electrochemical impedance spectrum; the Chinese patent with the authorization announcement number CN109828218B discloses a battery dynamic electrochemical impedance spectrum test device, which directly injects a test current signal into the battery under test by using the alternating current generator in the device to calculate and obtain the dynamic electrochemical impedance spectrum of the battery under test.

[0005] The perturbation method generates a perturbation excitation signal by adjusting the system control method. For example, the Chinese patent with the authorization announcement number CN114895207B discloses a method for on-line measurement of the alternating current impedance of a lithium-ion battery based on a two-phase interleaved parallel bidirectional DC / DC circuit. This method generates the required perturbation excitation signal by changing the duty cycle of the converter, and then calculates its alternating current impedance according to the voltage and current sampling signals; the Chinese patent with the authorization announcement number CN115085549B discloses an impedance measurement device and its measurement method based on an interleaved parallel boost circuit. This method is based on the parallel interleaved boost main circuit, and a boost perturbation circuit is paralleled to generate a perturbation signal of an orthogonal pseudo-random binary sequence, and the battery impedance is measured accordingly.

[0006] Since the existing injection method usually needs to change the original structure of the circuit, which may affect the safe operation of the system and equipment; while the perturbation method, although it does not require an external injection source, changes the duty cycle of the converter or changes the original structure of the circuit, which may also interfere with the safe and stable operation of the lithium battery system, resulting in a relatively high measurement error rate.

[0007] For this reason, the applicant hopes to seek a technical solution to solve the above technical problems. Summary of the Invention

[0008] In view of this, the purpose of the present invention is to provide a non-contact injection method and system for on-line measurement of high-frequency impedance of lithium batteries. Without changing the original circuit structure of the lithium battery, a high-frequency characteristic signal is injected into the lithium battery in a non-contact manner by electromagnetic coupling through a non-contact injection unit, so as to realize effective on-line measurement of the high-frequency impedance of the lithium battery.

[0009] The technical solution adopted by the present invention is as follows: A non-contact injection method for on-line measurement of high-frequency impedance of lithium batteries includes the following operation steps: S1: System initialization: Set the amplitude and frequency of the high-frequency characteristic signal v inj.f in the high-frequency sine power supply; S2: High-frequency injection: Start the high-frequency sine power supply, and inject the high-frequency characteristic signal v inj.f generated by the high-frequency sine power supply into the lithium battery in a non-contact manner through electromagnetic coupling by the non-contact injection unit; S3: Signal sampling and processing: Sample and perform algorithm processing on the voltage v b across the lithium battery and the current i b flowing through the lithium battery to obtain the characteristic voltage amplitude v b.f , characteristic voltage phase angle θ v , characteristic current amplitude i b.f and characteristic current phase angle θ i of the lithium battery at the current specified high frequency f; S4: Impedance estimation: Based on the characteristic voltage amplitude v b.f , characteristic voltage phase angle θ v , characteristic current amplitude i b.f and characteristic current phase angle θ i of the lithium battery obtained in the above step S3 at the specified high frequency f, calculate the characteristic impedance amplitude z b.f and characteristic impedance angle θ Z of the lithium battery; The calculation formula adopted is as follows: ; .

[0010] Preferably, a converter input capacitor and a DC / DC converter are respectively connected in parallel between the positive and negative electrodes of the lithium battery, and are connected to the load through the DC / DC converter; wherein, the non-contact injection unit includes a magnetic ring and an injection-side coil, and the injection-side coil is electromagnetically coupled to the magnetic ring; The injection - side coil is connected to a high - frequency sine power supply for injecting the high - frequency characteristic signal; The magnetic ring is sleeved on the positive or negative cable between the lithium - battery and the input capacitor of the converter in a non - contact manner.

[0011] Preferably, the injection - side coil is wound around the magnetic ring, and the number of turns is N, where the value range of N is 5 ≤ N ≤ 100 and N is an integer; the equivalent number of turns of the positive or negative cable is 1.

[0012] Preferably, the magnetic ring is an open - type non - closed magnetic ring or a closed magnetic ring; an open - type non - closed magnetic ring is preferably used.

[0013] Preferably, in the step S1, the frequency of the high - frequency sine power supply can be arbitrarily set within the range of 1 kHz - 10 MHz.

[0014] Preferably, in the step S3, the voltage v across the lithium - battery is measured by a voltage measurement module b , and the current i flowing through the lithium - battery is measured by a current measurement module b ; wherein, the voltage measurement module is connected in parallel across the positive and negative electrodes of the lithium - battery; the current measurement module is sleeved on the core of the positive or negative cable in a non - contact manner; in the step S3, the voltage v across the lithium - battery b and the current i flowing through the lithium - battery b are sampled by an A / D sampling method.

[0015] Preferably, in the step S3, the algorithm processing includes: calculating and processing the sampled signal by the FFT (Fast Fourier Transform) algorithm to respectively extract the characteristic voltage amplitude v b.f , characteristic voltage phase angle θ v , characteristic current amplitude i b.f and characteristic current phase angle θ i of the lithium - battery at the currently specified high - frequency f; wherein, the FFT algorithm preferably includes the following algorithms: ; ; ; wherein, N is the length of x[n]; k is the index of the frequency - domain result; m is the index of the subsequence; X[k] is the k - th component in the frequency - domain sequence of the characteristic voltage or characteristic current; x even [m] and x odd [m] are respectively the even - time - domain signal and odd - time - domain signal of the characteristic voltage or characteristic current; two subsequences after x[n] is decomposed by parity index; WN k is a complex unit root; After processing the time-domain signal of the characteristic voltage or characteristic current through the above algorithm, the corresponding frequency-domain component is obtained. Let the index serial number of the currently specified high frequency f in the aforementioned frequency domain be k 1 , then the characteristic voltage component and characteristic current component of the currently specified high frequency f are respectively denoted as V[k 1 and I[k 1 , where both V[k 1 and I[k 1 are complex numbers; Based on V[k 1 , the characteristic voltage amplitude v b.f and characteristic voltage phase angle θ v of the lithium battery at the currently specified high frequency f are calculated; Based on I[k 1 , the characteristic current amplitude i b.f and characteristic current phase angle θ i of the lithium battery at the currently specified high frequency f are calculated.

[0016] Preferably, the impedance estimation in step S4 further includes the following calculation process: Based on the characteristic impedance amplitude z b.f of the lithium battery at the specified high frequency f and the characteristic impedance angle θ Z , the equivalent resistance R b.f of the lithium battery at the specified high frequency f and the equivalent inductance L b.f of the lithium battery at the specified high frequency f are respectively calculated. The adopted calculation formulas are as follows: ; .

[0017] Preferably, a non-contact injection type on-line measurement system for high-frequency impedance of a lithium battery. A converter input capacitor and a DC / DC converter are respectively connected in parallel between the positive and negative electrodes of the lithium battery and are connected to a load through the DC / DC converter; wherein, the on-line measurement system for high-frequency impedance of the lithium battery includes: High-frequency sine power supply: used to generate a high-frequency characteristic signal v inj.f to be injected; Non-contact injection unit: used to inject the high-frequency characteristic signal v inj.f into the lithium battery in a non-contact manner; wherein, the non-contact injection unit includes a magnetic ring and an injection-side coil, and the injection-side coil is electromagnetically coupled to the magnetic ring; the injection-side coil is connected to the high-frequency sine power supply and is used to inject the high-frequency characteristic signal; the magnetic ring is non-contactingly sleeved on the positive or negative electrode cable between the lithium battery and the converter input capacitor; Voltage measurement module: used to measure the voltage v across the lithium battery b ; Current measurement module: used to measure the current i flowing through the lithium battery b ; Signal sampling and processing module: used to sample and perform algorithm processing on the voltage v across the lithium battery b and the current i flowing through the lithium battery b to obtain the characteristic voltage amplitude v of the lithium battery at the currently specified high frequency f b.f and the characteristic current amplitude i b.f , Impedance estimation module: used to calculate the characteristic impedance amplitude z of the lithium battery at the currently specified high frequency f b.f .

[0018] Preferably, the high-frequency sine power supply uses a digital signal generator, whose output voltage range is 0 - 100Vpp, the frequency range is 0 - 50MHz, and the internal resistance is not higher than 1Ω; the sampling device of the signal sampling and processing module uses a high-speed data acquisition circuit, the sampling rate is not lower than 2MS / s, and the sampling window time is not lower than 1ms.

[0019] The applicant surprisingly discovers that, without changing the original circuit structure of the lithium battery, by injecting high-frequency characteristic signals into the lithium battery in a non-contact manner through electromagnetic coupling by a non-contact injection unit, a high-precision online measurement effect of the high-frequency impedance of the lithium battery can be achieved; compared with the prior art, the present invention has the following advantages: 1) Safe: The present invention is based on the electromagnetic coupling mechanism, injects high-frequency characteristic signals into the lithium battery in a non-contact manner, and maintains a safe electrical isolation from the original circuit structure of the lithium battery; 2) Simple: The system structure adopted by the present invention is simple, easy to install, the amplitude and frequency of the injected characteristic signals are controllable, and it is easy to realize the online measurement of the high-frequency impedance of the lithium battery at the target frequency; 3) Sensitive: In the high-frequency range involved in the method proposed by the present invention, the internal equivalent resistance and inductance of the lithium battery play a dominant role, and can more sensitively reflect the state information such as the core temperature of the lithium battery. Description of the Drawings

[0020] Figure 1 is the step block diagram of the non-contact injection method for online measurement of the high-frequency impedance of a lithium battery in the specific embodiment of the present application; Figure 2 is the system structure diagram of the non-contact injection method for online measurement of the high-frequency impedance of a lithium battery in the specific embodiment of the present application; Figure 3 is Figure 2 the corresponding equivalent circuit diagram; Figure 4aSchematic diagram of the non-contact injection unit proposed by the present invention; Figure 4b is Figure 4a corresponding equivalent circuit diagram; Figure 5 is the voltage v injected across the lithium battery at a frequency of 600 kHz in a specific embodiment of the present invention b and the current i flowing through the lithium battery b measured waveform diagram. Specific implementation manner

[0021] Please refer to Figure 1 , Figure 2 and Figure 3 as shown. This embodiment proposes a method for on-line measurement of the high-frequency impedance of a lithium battery by non-contact injection, including the following operating steps: S1: System initialization: Set the amplitude and frequency of the high-frequency characteristic signal v inj.f in the high-frequency sine power supply; preferably, in this step S1, the frequency of the high-frequency sine power supply can be arbitrarily set within the range of 1 kHz - 10 MHz; S2: High-frequency injection: Start the high-frequency sine power supply, and inject the high-frequency characteristic signal v inj.f generated by the high-frequency sine power supply into the lithium battery in a non-contact manner through electromagnetic coupling by the non-contact injection unit ( Figure 2 marked as "injection signal"); preferably, please further refer to Figure 4a and Figure 4b as shown. In this step S2), a converter input capacitor and a DC / DC converter are respectively connected in parallel between the positive and negative electrodes of the lithium battery, and the DC / DC converter is connected to the load; among them, the non-contact injection unit includes a magnetic ring 210 and an injection-side coil 220 (marked as "injection unit coil" in Figure 4b), and the injection-side coil 220 is electromagnetically coupled to the magnetic ring 210; the injection-side coil 220 is connected to the high-frequency sine power supply for injecting the high-frequency characteristic signal; the magnetic ring 210 is sleeved on the positive electrode cable 100 between the lithium battery and the converter input capacitor in a non-contact manner (in other embodiments, it can also be sleeved on the negative electrode cable between the lithium battery and the converter input capacitor); S3: Signal sampling and processing: Sample and perform algorithm processing on the voltage v b across the lithium battery and the current i b flowing through the lithium battery to obtain the characteristic voltage amplitude v b.f , characteristic voltage phase angle θ v , characteristic current amplitude i b.f and characteristic current phase angle θ i of the lithium battery at the current specified high frequency f; preferably, in this step S3, the voltage v b across the lithium battery is measured by a voltage measurement module (i.e.,Figure 2 (the marked "voltage measurement"), the current i flowing through the lithium battery is measured by the current measurement module b (i.e., Figure 2 (the marked "current measurement"); among them, the voltage measurement module is connected in parallel to the positive and negative electrodes of the lithium battery; the current measurement module is sleeved on the core of the positive or negative electrode cable in a non-contact manner (preferably at positions such as the output copper bar of the lithium battery, the connector between the lithium battery and the DC / DC converter, or the input copper bar of the DC / DC converter, etc., and this embodiment does not make a unique limitation on this); in step S3, the voltage v across the lithium battery is sampled by the A / D sampling method b and the current i flowing through the lithium battery b are sampled; the algorithm processing includes: calculating and processing the sampled signals by the FFT (Fast Fourier Transform) algorithm, and respectively extracting the characteristic voltage amplitude v of the lithium battery at the currently specified high frequency f b.f , the characteristic voltage phase angle θ v , the characteristic current amplitude i b.f and the characteristic current phase angle θ i ; preferably, in this embodiment, the FFT algorithm adopts the following algorithm: ; ; ; where N is the length of x[n]; k is the index of the frequency domain result; m is the index of the subsequence; X[k] is the k-th component in the frequency domain sequence of the characteristic voltage or characteristic current, that is to say, when it is the k-th component in the frequency domain sequence of the characteristic voltage, X[k] is represented as V[k]; when it is the k-th component in the frequency domain sequence of the characteristic current, X[k] is represented as I[k]; x even [m] and x odd [m] are respectively the even time domain signal and the odd time domain signal of the characteristic voltage or characteristic current; the two subsequences after x[n] is decomposed according to the parity index; W N k is the complex unit root; After processing the time domain signal of the characteristic voltage or characteristic current through the above algorithm, its corresponding frequency domain component is obtained. Let the index serial number of the currently specified high frequency f in the aforementioned frequency domain be k 1 , then the characteristic voltage component and the characteristic current component of the currently specified high frequency f are respectively denoted as V[k 1 and I[k 1 , where V[k 1 and I[k 1 are both complex numbers; Based on V[k1 Calculate the characteristic voltage amplitude v of the lithium battery at the currently specified high frequency f b.f and the characteristic voltage phase angle θ v , specifically, the calculation process is as follows: ; ; ; where Re(V[k 1 ) and Im(V[k 1 ) are the real part and the imaginary part of V[k 1 respectively; Based on I[k 1 , calculate the characteristic current amplitude i of the lithium battery at the currently specified high frequency f b.f and the characteristic current phase angle θ i ; it should be noted that the calculation processes of the characteristic current amplitude i b.f and the characteristic current phase angle θ i are the same as those of the characteristic voltage amplitude v b.f and the characteristic voltage phase angle θ v respectively above, only need to replace V[k 1 with I[k 1 . To save space for description, the calculation formulas are not elaborated in this embodiment; S4: Impedance estimation: Based on the characteristic voltage amplitude v b.f , characteristic voltage phase angle θ v , characteristic current amplitude i b.f and characteristic current phase angle θ i of the lithium battery obtained in the above step S3 at the currently specified high frequency f, calculate the characteristic impedance amplitude z b.f and characteristic impedance angle θ Z of the lithium battery at the specified high frequency f; the calculation formulas used are as follows: ; .

[0022] Preferably, in this step S4, the impedance estimation further includes the following calculation process: Based on the characteristic impedance amplitude z b.f and characteristic impedance angle θ Z of the lithium battery at the specified high frequency f, calculate the equivalent resistance R b.f and the equivalent inductance L b.f of the lithium battery at the specified high frequency f respectively. The calculation formulas used are as follows: ; .

[0023] This embodiment also proposes a non-contact injection lithium battery high-frequency impedance online measurement system for implementing the above-mentioned non-contact injection lithium battery high-frequency impedance online measurement method, wherein a converter input capacitor and a DC / DC converter are connected in parallel between the positive and negative electrodes of the lithium battery, respectively, and connected to the load through the DC / DC converter; the lithium battery high-frequency impedance online measurement system comprises: High-frequency sinusoidal power supply: used to generate the high-frequency characteristic signal v to be injected inj.f ; Non-contact injection unit: used to inject high-frequency characteristic signal v inj.f Injection into the lithium battery in a non-contact manner; wherein the non-contact injection unit includes a magnetic ring 210 and an injection side coil 220, and the injection side coil 220 is electromagnetically coupled to the magnetic ring 210; the injection side coil 220 is connected to a high-frequency sinusoidal power supply for injecting a high-frequency characteristic signal; the magnetic ring 210 is non-contactly mounted on the positive cable 100 between the lithium battery and the converter input capacitor (in other embodiments, it can also be mounted on the negative cable between the lithium battery and the converter input capacitor); in actual implementation, the magnetic ring 210 can be fixedly mounted by an external tooling piece, or a movable installation can be adopted. mode, and this embodiment does not make a unique limitation on it; preferably, in this embodiment, the injection side coil 220 is wound on the magnetic ring 210, and its number of turns is N. In order to improve the injection efficiency, the preferred value of the number of turns N is comprehensively determined based on the coupling turn ratio of the contactless injection unit and the impedance matching characteristics of the high-frequency sinusoidal power supply. Further preferably, in this embodiment, the value range of N is: 5≤N≤100, N is an integer; the number of equivalent coil turns of the positive or negative cable is 1; preferably, the magnetic ring 210 adopts a non-enclosed magnetic ring 210 with an opening or a closed magnetic ring 210; preferably, a non-enclosed magnetic ring 210 with an opening is adopted; Voltage measurement module: used to measure the voltage v at both ends of the lithium battery b ; Current measurement module: used to measure the current i flowing through the lithium battery b ; Signal sampling and processing module: used for the voltage v at both ends of the lithium battery b And the current i flowing through the lithium battery b Sampling and algorithm processing are performed to obtain the characteristic voltage amplitude v of the lithium battery at the current specified high frequency f. b.f and the characteristic current amplitude i b.f , Impedance estimation module: used to calculate the characteristic impedance amplitude z of the lithium battery at the current specified high frequency f b.f .

[0024] Preferably, in the present embodiment, the high-frequency sine power supply uses a digital signal generator, whose output voltage range is 0 - 100 Vpp, the frequency range is 0 - 50 MHz, and the internal resistance is not higher than 1 Ω; the sampling device of the signal sampling and processing module uses a high-speed data acquisition circuit, the sampling rate is not lower than 2 MS / s, and the sampling window time is not lower than 1 ms.

[0025] In order to enable those skilled in the art to better understand the technical solutions in the present invention, on the basis of the above embodiments, the following specific embodiments will be specifically proposed in combination with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts shall fall within the protection scope of the present invention.

[0026] In the following embodiments, the lithium battery is a lithium battery pack composed of 4 series-connected 18650GA ternary lithium batteries; the high-frequency sine power supply is a digital signal generator, and the measurement frequency range is 600 kHz - 1 MHz; The non-contact injection unit is composed of a magnetic ring 210 (specifically, a non-closed magnetic ring 210 with an opening) and an injection-side coil 220. The injection-side coil 220 is electromagnetically coupled to the magnetic ring 210; the injection-side coil 220 is connected to the high-frequency sine power supply; the magnetic ring 210 is sleeved on the positive cable between the lithium battery and the converter input capacitor in a non-contact manner; the injection-side coil 220 is wound around the magnetic ring 210, and the number of turns is 15; the equivalent number of turns of the positive cable is 1; The voltage measurement module is connected to the oscilloscope through a coaxial shielded wire via a BNC interface; The current measurement module uses a CYBERTEK CP8030B high-frequency AC / DC current probe, with a measurement range of 0 - 5 A and a bandwidth of DC - 30 MHz; The sampling device (specifically, an A / D sampling device) in the signal sampling and processing module is an oscilloscope, with a sampling rate of 250 MS / s and a window time of 10 ms; In order to further verify the technical effects achieved by the embodiments of the present application, the HIOKI impedance analyzer is particularly used in the present application to measure the impedance of the lithium battery pack offline to compare and verify the effectiveness of the method proposed in the embodiments of the present invention; among them, during the comparative implementation process, the high-frequency impedance of the lithium battery is measured by using the method proposed in the present embodiment under quasi-online and real-time online conditions respectively, and comparative measurements are respectively carried out by injecting signals of different frequencies. The results are shown in Table 1 below:

[0027] Among them, when the high-frequency characteristic signal v inj.fWhen the injection frequency is 600 kHz, the voltage v across the lithium battery b (i.e., Figure 5 "Lithium battery voltage v b " marked), and the measured waveform diagrams of the current i b flowing through the lithium battery (i.e., Figure 5 "Lithium battery current i b " marked) can be seen in Figure 5 shown below; Through the above comparison of the implementation results, it can be shown that the method provided in the embodiments of the present application, whether it is quasi-online measurement or real-time online measurement, maintains a high consistency with commercial instruments. The maximum errors in the two measurement modes are 3.96% and 3.86% respectively, verifying the effectiveness of the method provided in the embodiments of the present application.

[0028] For those skilled in the art, it is obvious that the present invention is not limited to the details of the above-described exemplary embodiments, and without departing from the spirit or basic characteristics of the present invention, the present invention can be implemented in other specific forms. Therefore, from any point of view, the embodiments should be regarded as exemplary and non-limiting. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be included in the present invention. Any reference signs in the claims should not be regarded as limiting the claimed rights.

[0029] In addition, it should be understood that although this specification is described according to embodiments, not every embodiment only contains an independent technical solution. This narrative way of the specification is only for clarity. Those skilled in the art should regard the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A non-contact injection lithium battery high-frequency impedance online measurement method, characterized in that: The steps are as follows: S1: System initialization: Set the high-frequency characteristic signal v in the high-frequency sinusoidal power supply inj.f The amplitude and frequency of S2: High frequency injection: Start the high frequency sinusoidal power supply and inject the high frequency characteristic signal v generated by the high frequency sinusoidal power supply into the inj.f Injecting lithium batteries into the battery in a non-contact manner by electromagnetic coupling through a non-contact injection unit; S3: Signal sampling and processing: voltage v at both ends of the lithium battery b And the current i flowing through the lithium battery b Sampling and algorithm processing are performed to obtain the characteristic voltage amplitude v of the lithium battery at the current specified high frequency f b.f 、Characteristic voltage phase angle θ v , characteristic current amplitude i b.f And the characteristic current phase angle θ i ; S4: Impedance estimation: Based on the characteristic voltage amplitude v of the lithium battery at the current specified high frequency f obtained in step S3 above b.f 、Characteristic voltage phase angle θ v , characteristic current amplitude i b.f And the characteristic current phase angle θ i Calculate the characteristic impedance amplitude z of the lithium battery at a specified high frequency f b.f And the characteristic impedance angle θ Z ; The calculation formula used is as follows: ； 。 2. The method for online measurement of high-frequency impedance of lithium batteries by non-contact injection according to claim 1, characterized in that: The positive and negative electrodes of the lithium battery are connected in parallel with the converter input capacitor and the DC / DC converter, respectively, and connected to the load through the DC / DC converter; wherein, The non-contact injection unit comprises a magnetic ring and an injection side coil, and the injection side coil is electromagnetically coupled to the magnetic ring; The injection side coil is connected to a high-frequency sinusoidal power supply and is used to inject the high-frequency characteristic signal; The magnetic ring is sheathed on the positive or negative cable between the lithium battery and the converter input capacitor in a non-contact manner.

3. The method for online measurement of high-frequency impedance of lithium batteries by non-contact injection according to claim 2, characterized in that: The injection side coil is wound on the magnetic ring, and the number of turns is N. The value range of N is: 5≤N≤100, and N is an integer; the number of turns of the equivalent coil of the positive or negative cable is 1.

4. The method for online measurement of high-frequency impedance of lithium batteries by non-contact injection according to claim 2, characterized in that: The magnetic ring is a non-closed magnetic ring with an opening or a closed magnetic ring; preferably, a non-closed magnetic ring with an opening is used.

5. The method for online measurement of high-frequency impedance of lithium batteries by non-contact injection according to claim 1, characterized in that: In the step S1, the frequency of the high-frequency sinusoidal power supply can be arbitrarily set within the frequency range of 1 kHz-10 MHz.

6. The method for online measurement of high-frequency impedance of lithium batteries by non-contact injection according to claim 1, characterized in that: In step S3, the voltage v at both ends of the lithium battery is measured by the voltage measurement module. b , the current i flowing through the lithium battery is measured by the current measurement module b ; wherein the voltage measurement module is connected in parallel to the positive and negative electrodes of the lithium battery; the current measurement module is mounted on the core of the positive or negative cable in a non-contact manner; in the step S3, the voltage v at both ends of the lithium battery is measured by A / D sampling. b And the current i flowing through the lithium battery b Take samples.

7. The method for online measurement of high-frequency impedance of lithium batteries by non-contact injection according to claim 1 or 6, characterized in that: In step S3, the algorithm processing includes: performing calculation processing on the sampled signal by using the FFT (Fast Fourier Transform) algorithm to extract the characteristic voltage amplitude v of the lithium battery at the current specified high frequency f. b.f 、Characteristic voltage phase angle θ v , characteristic current amplitude i b.f And the characteristic current phase angle θ i ; Wherein, the FFT algorithm preferably includes the following algorithm: ； ； ； Where N is the length of x[n]; k is the index of the frequency domain result; m is the index of the subsequence; X[k] is the kth component in the frequency domain sequence of the characteristic voltage or characteristic current; x even [m] and x odd [m] are the even time domain signal and odd time domain signal of characteristic voltage or characteristic current respectively; x[n] are two subsequences after decomposition according to odd and even indexes; W N k is a complex root of unity; The time domain signal of the characteristic voltage or characteristic current is processed by the above algorithm to obtain its corresponding frequency domain component. Assuming that the index sequence number of the current specified high frequency f in the aforementioned frequency domain is k1, the characteristic voltage component and characteristic current component of the current specified high frequency f are recorded as V[k1] and I[k1] respectively, where V[k1] and I[k1] are both complex numbers; Based on V[k1], the characteristic voltage amplitude v of the lithium battery at the current specified high frequency f is calculated b.f and characteristic voltage phase angle θ v ; Based on I[k1], the characteristic current amplitude i of the lithium battery at the current specified high frequency f is calculated b.f and characteristic current phase angle θ i .

8. The method for online measurement of high-frequency impedance of lithium batteries by non-contact injection according to claim 1, characterized in that: The impedance estimation in step S4 also includes the following calculation process: Based on the characteristic impedance amplitude z of lithium batteries at a specified high frequency f b.f And the characteristic impedance angle θ Z Calculate the equivalent resistance R of the lithium battery at a specified high frequency f b.f And the equivalent inductance L of the lithium battery at a specified high frequency f b.f , the calculation formula used is as follows: ； 。 9. A non-contact injection lithium battery high-frequency impedance online measurement system, wherein a converter input capacitor and a DC / DC converter are connected in parallel between the positive and negative electrodes of the lithium battery, and connected to a load through a DC / DC converter; characterized in that: The lithium battery high frequency impedance online measurement system comprises: High-frequency sinusoidal power supply: used to generate the high-frequency characteristic signal v to be injected inj.f ; Non-contact injection unit: used to inject high-frequency characteristic signal v inj.f Injecting the lithium battery in a non-contact manner; wherein the non-contact injection unit comprises a magnetic ring and an injection side coil, the injection side coil is electromagnetically coupled to the magnetic ring; the injection side coil is connected to a high-frequency sinusoidal power supply for injecting the high-frequency characteristic signal; the magnetic ring is non-contactly mounted on the positive or negative cable between the lithium battery and the converter input capacitor; Voltage measurement module: used to measure the voltage v at both ends of the lithium battery b ; Current measurement module: used to measure the current i flowing through the lithium battery b ; Signal sampling and processing module: used for the voltage v at both ends of the lithium battery b And the current i flowing through the lithium battery b Sampling and algorithm processing are performed to obtain the characteristic voltage amplitude v of the lithium battery at the current specified high frequency f b.f and the characteristic current amplitude i b.f , Impedance estimation module: used to calculate the characteristic impedance amplitude z of the lithium battery at the current specified high frequency f b.f .

10. The non-contact injection lithium battery high frequency impedance online measurement system according to claim 9, characterized in that: The high-frequency sinusoidal power supply adopts a digital signal generator, whose output voltage range is 0-100Vpp, frequency range is 0-50MHz, and internal resistance is not higher than 1Ω; the sampling device of the signal sampling and processing module adopts a high-speed data acquisition circuit, the sampling rate is not less than 2MS / s, and the sampling window time is not less than 1ms.

Images