A non-contact injection method and system for online high-frequency impedance measurement of lithium batteries

Abstract

This invention discloses a non-contact injection lithium battery high-frequency impedance online measurement method and system, including the following operation steps: S1: setting a high-frequency characteristic signal v in a high-frequency sinusoidal power supply. inj.f S2: The amplitude and frequency of the high-frequency characteristic signal v generated by the high-frequency sinusoidal power supply; inj.f Lithium batteries are injected into the lithium battery via a non-contact injection unit using electromagnetic coupling; S3: The voltage v across 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 characteristic current phase angle θ i S4: Calculate the characteristic impedance amplitude z of the lithium battery at a specified high frequency f. b.f and characteristic impedance angle i Z This invention achieves effective online measurement of the high-frequency impedance of lithium batteries by injecting high-frequency characteristic signals into them through a non-contact injection unit using electromagnetic coupling, without altering the original circuit structure of the lithium battery.

Description

Technical Field

[0001] This invention relates to the field of lithium battery state monitoring, and specifically to a non-contact injection lithium battery high-frequency impedance online measurement method and system. Background Technology

[0002] Lithium-ion batteries, due to their advantages such as high energy density, long lifespan, and lack of memory effect, have been widely used in various electronic devices, electric vehicles, electric ships, and energy storage power stations. To ensure the safe and reliable operation of lithium-ion battery systems, it is necessary to monitor the state of the lithium-ion batteries. The most common method is to use the impedance of the lithium-ion battery to reflect information such as its temperature, state of charge, and health status.

[0003] Currently, the main methods for measuring the impedance of lithium batteries are to calculate the impedance using the AC voltage and current of the lithium battery. Based on the different ways of generating AC excitation, these methods can be divided into two main categories: injection method and perturbation method.

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

[0005] The perturbation method generates a perturbation excitation signal by adjusting the system control mode. For example, Chinese Patent No. CN114895207B discloses an online measurement method for the AC 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 AC impedance based on the voltage and current sampling signals. Chinese Patent No. CN115085549B discloses an impedance measurement device and its measurement method based on an interleaved parallel boost circuit. This method adds a boost perturbation circuit in parallel to the parallel interleaved boost main circuit to generate a perturbation signal of orthogonal pseudo-random binary sequence, and measures the battery impedance accordingly.

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

[0007] Therefore, the applicant hopes to find a technical solution to address 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 online 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, thereby realizing the effective online measurement of the high-frequency impedance of the lithium battery.

[0009] The technical solution adopted in this invention is as follows:

[0010] A non-contact injection method for online high-frequency impedance measurement of lithium batteries includes the following steps:

[0011] S1: System Initialization: Set the high-frequency characteristic signal v in the high-frequency sinusoidal power supply. inj.f Amplitude and frequency;

[0012] 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. inj.f Lithium batteries are injected into the batteries via a non-contact injection unit using electromagnetic coupling.

[0013] S3: Signal Sampling and Processing: Sampling the voltage v across the lithium battery terminals. 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 characteristic current phase angle θ i ;

[0014] 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 characteristic current phase angle θ i The characteristic impedance amplitude z of the lithium battery at a specified high frequency f is calculated. b.f and characteristic impedance angle θ Z The calculation formula used is as follows:

[0015] ;

[0016] .

[0017] Preferably, a converter input capacitor and a DC / DC converter are connected in parallel between the positive and negative terminals of the lithium battery, respectively, and the DC / DC converter is connected to the load; wherein,

[0018] The non-contact injection unit includes a magnetic ring and an injection-side coil, wherein the injection-side coil is electromagnetically coupled to the magnetic ring.

[0019] The injection-side coil is connected to a high-frequency sinusoidal power supply and is used to inject the high-frequency characteristic signal;

[0020] The magnetic ring is fitted onto the positive or negative cable between the lithium battery and the converter input capacitor in a non-contact manner.

[0021] Preferably, the injection-side coil is wound on the magnetic ring, and its number of turns is N, where N is in the range of 5 ≤ N ≤ 100, and N is an integer; the equivalent number of turns of the positive or negative cable is 1.

[0022] Preferably, the magnetic ring is an open, non-closed magnetic ring or a closed magnetic ring; more preferably, it is an open, non-closed magnetic ring.

[0023] Preferably, in step S1, the frequency of the high-frequency sinusoidal power supply can be arbitrarily set within the 1kHz-10MHz frequency band.

[0024] Preferably, in step S3, the voltage v across the lithium battery is measured by a voltage measurement module. b The current i flowing through the lithium battery is measured by the current measurement module. b The voltage measurement module is connected in parallel to the positive and negative terminals of the lithium battery; the current measurement module is non-contactly mounted on the core of the positive or negative cable; in step S3, the voltage v across the lithium battery is measured using an A / D sampling method. b and the current i flowing through the lithium battery b Perform sampling.

[0025] Preferably, in step S3, the algorithm processing includes: performing calculations on the sampled signal 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 characteristic current phase angle θ i The FFT algorithm preferably includes the following algorithms:

[0026] ;

[0027] ;

[0028] ;

[0029] 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; x even [m] and x odd [m] represents the even-time domain signal and the odd-time domain signal of the characteristic voltage or characteristic current, respectively; x[n] represents the two subsequences decomposed according to the even / odd index; W N k It is the root of unity of a complex number;

[0030] After processing the time-domain signal of the characteristic voltage or characteristic current using the above algorithm, the corresponding frequency-domain component is obtained. Let the index sequence number of the current specified high frequency f in the aforementioned frequency domain be k1. Then the characteristic voltage component and characteristic current component of the current specified high frequency f are denoted as V[k1] and I[k1], respectively, where V[k1] and I[k1] are both complex numbers.

[0031] The characteristic voltage amplitude v of the lithium battery at the specified high frequency f is calculated based on V[k1]. b.f and characteristic voltage phase angle θ v ;

[0032] 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 .

[0033] Preferably, the impedance estimation in step S4 further includes the following calculation process:

[0034] Based on the characteristic impedance amplitude z of the lithium battery at a specified high frequency f b.f and characteristic impedance angle θ Z The equivalent resistance R of the lithium battery at a specified high frequency f was calculated respectively. 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:

[0035] ;

[0036] .

[0037] Preferably, a non-contact injection lithium battery high-frequency impedance online measurement system comprises a converter input capacitor and a DC / DC converter connected in parallel between the positive and negative terminals of the lithium battery, respectively, and connected to a load through the DC / DC converter; wherein, the lithium battery high-frequency impedance online measurement system includes:

[0038] High-frequency sinusoidal power supply: used to generate the high-frequency characteristic signal v to be injected. inj.f ;

[0039] Non-contact injection unit: used to inject high-frequency characteristic signals v inj.f A lithium battery is injected in a non-contact manner; wherein, the non-contact injection unit includes a magnetic ring and an injection-side coil, the injection-side coil being 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;

[0040] Voltage measurement module: used to measure the voltage V across the lithium battery terminals. b ;

[0041] Current measurement module: used to measure the current i flowing through the lithium battery. b ;

[0042] Signal sampling and processing module: used for voltage V across 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 characteristic current amplitude i b.f ,

[0043] Impedance estimation module: used to calculate the characteristic impedance amplitude z of the lithium battery at a specified high frequency f. b.f .

[0044] Preferably, the high-frequency sinusoidal power supply adopts a digital signal generator with an output voltage range of 0-100Vpp, a frequency range of 0-50MHz, and an internal resistance of no more than 1Ω; the sampling device of the signal sampling and processing module adopts a high-speed data acquisition circuit with a sampling rate of no less than 2MS / s and a sampling window time of no less than 1ms.

[0045] The applicant has made a surprising discovery: without altering the original circuit structure of the lithium battery, a high-precision online measurement of the high-frequency impedance of the lithium battery can be achieved by injecting high-frequency characteristic signals into the lithium battery through a non-contact injection unit using electromagnetic coupling. Compared with the prior art, this invention has the following advantages:

[0046] 1) Safety: Based on the electromagnetic coupling mechanism, this invention injects high-frequency characteristic signals into the lithium battery in a non-contact manner, maintaining safe electrical isolation from the original circuit structure of the lithium battery;

[0047] 2) Simplicity: The system structure adopted in this invention is simple and easy to install. The amplitude and frequency of the injected characteristic signal are controllable, making it easy to realize online measurement of high-frequency impedance of lithium battery at the target frequency.

[0048] 3) Sensitivity: Within the high-frequency range covered by the method proposed in this invention, the equivalent resistance and inductance inside the lithium battery play a dominant role, which can more sensitively reflect the state information such as the temperature of the lithium battery core. Attached Figure Description

[0049] Figure 1 This is a flowchart illustrating the steps of the non-contact injection lithium battery high-frequency impedance online measurement method according to a specific embodiment of this application;

[0050] Figure 2 This is a structural diagram of a non-contact injection lithium battery high-frequency impedance online measurement system according to a specific embodiment of this application;

[0051] Figure 3 for Figure 2 The corresponding equivalent circuit diagram;

[0052] Figure 4a This is a schematic diagram of the non-contact injection unit proposed in this invention; Figure 4b for Figure 4a The corresponding equivalent circuit diagram;

[0053] Figure 5 In a specific embodiment of the present invention, the voltage v injected into the two ends of the lithium battery at a frequency of 600kHz is... b and the current i flowing through the lithium battery b The measured waveform diagram. Detailed Implementation

[0054] Please refer to the above. Figure 1 , Figure 2 and Figure 3 As shown in the figure, this embodiment proposes a non-contact injection method for online high-frequency impedance measurement of lithium batteries, including the following operation steps:

[0055] S1: System Initialization: Set the high-frequency characteristic signal v in the high-frequency sinusoidal power supply. inj.f The amplitude and frequency; preferably, in this step S1, the frequency of the high-frequency sinusoidal power supply can be arbitrarily set within the 1kHz-10MHz frequency band;

[0056] 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. inj.f Lithium batteries are injected into the non-contact battery via electromagnetic coupling through a non-contact injection unit. Figure 2 (marked as "injected signal"); preferably, please refer to further details. Figure 4a and Figure 4bAs shown, in step S2), the converter input capacitor and the DC / DC converter are connected in parallel between the positive and negative terminals of the lithium battery, respectively, and the load is connected through the DC / DC converter. The non-contact injection unit includes a magnetic ring 210 and an injection-side coil 220 (labeled "injection unit coil" in Figure 4b). The injection-side coil 220 and the magnetic ring 210 are electromagnetically coupled. The injection-side coil 220 is connected to a high-frequency sinusoidal power supply for injecting high-frequency characteristic signals. 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).

[0057] S3: Signal Sampling and Processing: Sampling the voltage v across the lithium battery terminals. 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 characteristic current phase angle θ i Preferably, in step S3, the voltage v across the lithium battery is measured by a voltage measurement module. b (that is) Figure 2 The "voltage measurement" marked on the label obtains the current i flowing through the lithium battery via the current measurement module. b (that is) Figure 2 The “current measurement” is marked as such. The voltage measurement module is connected in parallel to the positive and negative terminals of the lithium battery. The current measurement module is non-contactly mounted on the core of the positive or negative cable (preferably at the lithium battery output copper busbar, the connector between the lithium battery and the DC / DC converter, or the input copper busbar of the DC / DC converter, etc.; this embodiment does not limit this to a single location). In step S3, the A / D sampling method measures the voltage v across the lithium battery. b and the current i flowing through the lithium battery b Sampling is performed; algorithm processing includes: calculating and processing the sampled signal 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 characteristic current phase angle θ i Preferably, in this embodiment, the FFT algorithm uses the following algorithm:

[0058] ;

[0059] ;

[0060] ;

[0061] 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, 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] represents the even-time domain signal and the odd-time domain signal of the characteristic voltage or characteristic current, respectively; x[n] represents the two subsequences decomposed according to the even / odd index; W N k It is the root of unity of a complex number;

[0062] After processing the time-domain signal of the characteristic voltage or characteristic current using the above algorithm, the corresponding frequency-domain component is obtained. Let the index sequence number of the current specified high frequency f in the aforementioned frequency domain be k1. Then the characteristic voltage component and characteristic current component of the current specified high frequency f are denoted as V[k1] and I[k1], respectively, where V[k1] and I[k1] are both complex numbers.

[0063] The characteristic voltage amplitude v of the lithium battery at the specified high frequency f is calculated based on V[k1]. b.f and characteristic voltage phase angle θ v Specifically, the calculation process is as follows:

[0064] ;

[0065] ;

[0066] ;

[0067] Where Re(V[k1]) and Im(V[k1]) are the real and imaginary parts of V[k1], respectively;

[0068] 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 It should be noted that the characteristic current amplitude i b.f and characteristic current phase angle θ i The calculation process is the same as that for the characteristic voltage amplitude v. b.f and characteristic voltage phase angle θ v The above calculation process only requires replacing V[k1] with I[k1]. To save space, this embodiment will not elaborate on the calculation formula.

[0069] 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 characteristic current phase angle θ i The characteristic impedance amplitude z of the lithium battery at a specified high frequency f is calculated. b.f and characteristic impedance angle θ Z The calculation formula used is as follows:

[0070] ;

[0071] .

[0072] Preferably, in step S4, the impedance estimation further includes the following calculation process:

[0073] Based on the characteristic impedance amplitude z of the lithium battery at a specified high frequency f b.f and characteristic impedance angle θ Z The equivalent resistance R of the lithium battery at a specified high frequency f was calculated respectively. 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:

[0074] ;

[0075] .

[0076] This embodiment also proposes a non-contact injection lithium battery high-frequency impedance online measurement system for implementing the non-contact injection lithium battery high-frequency impedance online measurement method as described above. A converter input capacitor and a DC / DC converter are connected in parallel between the positive and negative terminals of the lithium battery, respectively, and the load is connected through the DC / DC converter. The lithium battery high-frequency impedance online measurement system includes:

[0077] High-frequency sinusoidal power supply: used to generate the high-frequency characteristic signal v to be injected. inj.f ;

[0078] Non-contact injection unit: used to inject high-frequency characteristic signals v inj.fA non-contact injection method is used to inject lithium batteries. The non-contact injection unit includes a magnetic ring 210 and an injection-side coil 220, which are electromagnetically coupled together. The injection-side coil 220 is connected to a high-frequency sinusoidal power supply for injecting high-frequency characteristic signals. 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 practice, the magnetic ring 210 can be fixedly mounted using external tooling or can be installed in a movable manner. The method is not limited to a single one in this embodiment; 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 determined based on the coupling turns ratio of the non-contact injection unit and the impedance matching characteristics of the high-frequency sinusoidal power supply. More preferably, in this embodiment, the value range of N is: 5≤N≤100, where N is an integer; the equivalent coil turns of the positive or negative cable is 1; preferably, the magnetic ring 210 is a non-closed magnetic ring 210 with an opening or a closed magnetic ring 210; preferably, a non-closed magnetic ring 210 with an opening is used.

[0079] Voltage measurement module: used to measure the voltage V across the lithium battery terminals. b ;

[0080] Current measurement module: used to measure the current i flowing through the lithium battery. b ;

[0081] Signal sampling and processing module: used for voltage V across 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 characteristic current amplitude i b.f ,

[0082] Impedance estimation module: used to calculate the characteristic impedance amplitude z of the lithium battery at a specified high frequency f. b.f .

[0083] Preferably, in this embodiment, the high-frequency sinusoidal power supply adopts a digital signal generator with an output voltage range of 0-100Vpp, a frequency range of 0-50MHz, and an internal resistance of no more than 1Ω; the sampling device of the signal sampling and processing module adopts a high-speed data acquisition circuit with a sampling rate of no less than 2MS / s and a sampling window time of no less than 1ms.

[0084] To enable those skilled in the art to better understand the technical solutions of this invention, based on the above embodiments, the following specific embodiments will be proposed in conjunction with the accompanying drawings. Obviously, the described embodiments are merely some embodiments of this invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort should fall within the scope of protection of this invention.

[0085] In the following embodiment, the lithium battery is a lithium battery pack consisting of four 18650GA ternary lithium batteries connected in series; the high-frequency sinusoidal power supply is a digital signal generator with a measurement frequency range of 600kHz-1MHz.

[0086] The non-contact injection unit consists 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 a high-frequency sinusoidal power supply. The magnetic ring 210 is non-contactly mounted on the positive cable between the lithium battery and the converter input capacitor. The injection-side coil 220 is wound on the magnetic ring 210 with 15 turns. The equivalent number of turns of the positive cable is 1.

[0087] The voltage measurement module is connected to the oscilloscope via a coaxial shielded cable and a BNC interface.

[0088] The current measurement module uses a CYBERTEK CP8030B high-frequency AC / DC current probe with a range of 0~5A and a bandwidth of DC~30MHz;

[0089] The sampling device (specifically the A / D sampling device) in the signal sampling and processing module is an oscilloscope with a sampling rate of 250MS / s and a window time of 10ms.

[0090] To further verify the technical effects achieved by the embodiments of this application, this application specifically used a HIOKI impedance analyzer to measure the impedance of the lithium battery pack offline, in order to compare and verify the effectiveness of the method proposed in the embodiments of this invention. During the comparison process, the high-frequency impedance of the lithium battery was measured using the method proposed in this embodiment under quasi-online and real-time online conditions, and comparative measurements were performed by injecting signals of different frequencies. The results are shown in Table 1 below:

[0091]

[0092] Among them, when the high-frequency characteristic signal v inj.f When the injection frequency is 600kHz, the voltage v across the lithium battery is... b (that is) Figure 5 The marked "lithium battery voltage v" b") and the current i flowing through the lithium battery b (that is) Figure 5 The marked "lithium battery current i" b Please refer to the measured waveform diagram for ). Figure 5 As shown;

[0093] The above comparative results show that the method provided in this application embodiment maintains a high degree of consistency with commercial instruments, whether it is quasi-online measurement or real-time online measurement. The maximum errors in the two measurement modes are 3.96% and 3.86%, respectively, which verifies the effectiveness of the method provided in this application embodiment.

[0094] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

[0095] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider 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 method for online high-frequency impedance measurement of lithium batteries, characterized in that, The following steps are included: S1: System Initialization: Set the high-frequency characteristic signal v in the high-frequency sinusoidal power supply. inj.f Amplitude and frequency; 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. inj.f Lithium batteries are injected into the batteries via a non-contact injection unit using electromagnetic coupling. S3: Signal Sampling and Processing: Sampling the voltage v across the lithium battery terminals. 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 characteristic current phase angle θ i ; In step S3, the algorithm processing includes: performing calculations on the sampled signal 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 characteristic current phase angle θ i The FFT algorithm includes the following algorithms: ； ； 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; x even [m] and x odd [m] represents the even-time domain signal and the odd-time domain signal of the characteristic voltage or characteristic current, respectively; x[n] represents the two subsequences decomposed according to the even / odd index; W N k It is the root of unity of a complex number; After processing the time-domain signal of the characteristic voltage or characteristic current using the above algorithm, the corresponding frequency-domain component is obtained. Let the index sequence number of the current specified high frequency f in the aforementioned frequency domain be k1. Then the characteristic voltage component and characteristic current component of the current specified high frequency f are denoted as V[k1] and I[k1], respectively, where V[k1] and I[k1] are both complex numbers. The characteristic voltage amplitude v of the lithium battery at the specified high frequency f is calculated based on V[k1]. 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 ; 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 characteristic current phase angle θ i The characteristic impedance amplitude z of the lithium battery at a specified high frequency f is calculated. b.f and characteristic impedance angle θ Z The calculation formula used is as follows: ； 。 2. The non-contact injection lithium battery high-frequency impedance online measurement method according to claim 1, characterized in that, The input capacitor of the converter and the DC / DC converter are connected in parallel between the positive and negative terminals of the lithium battery, respectively, and the load is connected through the DC / DC converter; wherein, The non-contact injection unit includes a magnetic ring and an injection-side coil, wherein 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 fitted onto the positive or negative cable between the lithium battery and the converter input capacitor in a non-contact manner.

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

4. The non-contact injection lithium battery high-frequency impedance online measurement method according to claim 2, characterized in that, The magnetic ring can be a non-closed magnetic ring with an opening or a closed magnetic ring.

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

6. The non-contact injection lithium battery high-frequency impedance online measurement method according to claim 2, characterized in that, In step S3, the voltage v across 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 The voltage measurement module is connected in parallel to the positive and negative terminals of the lithium battery; the current measurement module is non-contactly mounted on the core of the positive or negative cable; in step S3, the voltage v across the lithium battery is measured using an A / D sampling method. b and the current i flowing through the lithium battery b Perform sampling.

7. The non-contact injection lithium battery high-frequency impedance online measurement method 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 the lithium battery at a specified high frequency f b.f and characteristic impedance angle θ Z The equivalent resistance R of the lithium battery at a specified high frequency f was calculated respectively. 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: ； 。 8. A non-contact injection lithium battery high-frequency impedance online measurement system used in the non-contact injection lithium battery high-frequency impedance online measurement method according to any one of claims 1-7, wherein a converter input capacitor and a DC / DC converter are connected in parallel between the positive and negative terminals of the lithium battery, and the load is connected through the DC / DC converter; characterized in that, The lithium battery high-frequency impedance online measurement system includes: 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 signals v inj.f A lithium battery is injected in a non-contact manner; wherein, the non-contact injection unit includes a magnetic ring and an injection-side coil, the injection-side coil being 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 across the lithium battery terminals. b ; Current measurement module: used to measure the current i flowing through the lithium battery. b ; Signal sampling and processing module: used for voltage V across 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 characteristic current amplitude i b.f , Impedance estimation module: used to calculate the characteristic impedance amplitude z of the lithium battery at a specified high frequency f. b.f .

9. The non-contact injection lithium battery high-frequency impedance online measurement system according to claim 8, characterized in that, The high-frequency sinusoidal power supply uses a digital signal generator with an output voltage range of 0-100Vpp, a frequency range of 0-50MHz, and an internal resistance of no more than 1Ω; the sampling device of the signal sampling and processing module uses a high-speed data acquisition circuit with a sampling rate of no less than 2MS / s and a sampling window time of no less than 1ms.

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