A differential battery high-frequency impedance online detection system

Abstract

The application discloses a kind of difference type battery high-frequency impedance online detection system, respectively constructs first oscillation loop and second oscillation loop, first oscillation loop is measured battery, first switch S1, resonant inductance L r And resonant capacitor C r Series composition;Second oscillation loop is second switch S2, resonant inductance L r And resonant capacitor C r Series composition;The positive and negative pole of measured battery is connected with the series first switch S1 and second switch S2;By first switch S1 and second switch S2 alternately conducting action, so that the oscillation loop of corresponding switch when conducting respectively excite high-frequency oscillation;First oscillation loop and second oscillation loop respectively generated high-frequency oscillation current i r , based on difference mode online estimation battery high-frequency impedance parameter;The application is measured by difference type measurement framework, effectively offset the influence of detection circuit internal parameter fluctuation, realizes the high-precision online detection of battery high-frequency impedance absolute value.

Description

Technical Field

[0001] This invention relates to the field of online high-frequency impedance detection for batteries, and specifically to a differential online high-frequency impedance detection system for batteries. Background Technology

[0002] To improve the performance of online battery state sensing, online detection technology of battery high-frequency impedance (e.g., in the 10kHz-1MHz frequency band) is gradually becoming a research hotspot both domestically and internationally. Taking lithium batteries as an example, under the influence of high-frequency ion effects, the battery's high-frequency impedance can directly characterize the temperature state of the current collector metal and the electrochemical state of the electrolyte, significantly improving the sensitivity of battery state sensing. Existing online battery high-frequency impedance detection systems mainly fall into two categories: magnetic coupling injection method and switching oscillation method.

[0003] The magnetic coupling injection method can accurately measure the magnitude of the high-frequency impedance of a battery. However, under high-frequency conditions, the battery impedance is mainly inductive (impedance angle is close to 90°). Small phase errors in the measurement of voltage and current signals may lead to inaccurate measurement of the real part of the battery's high-frequency impedance (i.e., high-frequency resistance).

[0004] The switching oscillation method generates high-frequency switching oscillations in the battery through switching, and uses the high-frequency switching oscillation current or voltage signal to estimate the battery's high-frequency impedance online. This method does not have the phase error problem of multi-signal measurement and can simultaneously and accurately measure the slight changes in the battery's high-frequency resistance and high-frequency inductance.

[0005] For example, Chinese invention patent application CN116184240A discloses a method and system for online continuous monitoring of lithium battery impedance based on self-excited switching oscillation of a DC-DC converter. This scheme treats the lithium battery pack (or module) as an equivalent high-voltage, high-capacity lithium battery. It utilizes the high-frequency oscillation generated by the self-excitation of the DC-DC converter's PWM switching transient process in the battery, and achieves online continuous monitoring of the battery's high-frequency impedance by extracting the frequency and damping characteristics of the oscillation current signal. On this basis, a resonant capacitor is connected in parallel across each cell connected in series in the lithium battery pack. By collecting the switching oscillation signal on the resonant capacitor of each cell generated by the self-excitation of the DC-DC converter, the high-frequency impedance of each individual cell in the lithium battery pack is detected online. However, this method relies on the high-frequency oscillation generated by the DC-DC converter's PWM switching transient in the battery system. In actual systems, the self-excited switching oscillation signal is often weak, which may affect the accuracy of the online detection of the battery's high-frequency impedance.

[0006] The paper "Operando Li metal plating diagnostics via MHz band electromagnetics, Nature Communications, 20(2)3,14:7275" proposes an online high-frequency resistance detection circuit for lithium batteries based on LC switching oscillation for online monitoring of lithium plating status. This method uses a dedicated battery switching oscillation circuit, which has the advantage of strong signal and is beneficial to improving the detection accuracy of high-frequency impedance of batteries. However, the proposed method still has the following two problems:

[0007] Firstly, the accuracy of high-frequency impedance detection is affected by the components of the detection circuit: To detect changes in the high-frequency resistance of the battery, the method proposed in this paper assumes that the parameters of each component within the detection circuit remain constant. However, in actual systems, the switching time and on-state resistance of the electronic switch SW may fluctuate with voltage and temperature, the capacitance value of the resonant capacitor may fluctuate with voltage and temperature, and the inductance parameter of the resonant inductor may also drift during long-term operation, thus affecting the estimation accuracy of the battery's high-frequency resistance parameters. Especially for large-capacity lithium batteries (e.g., with a capacity greater than several hundred Ah), the high-frequency impedance change caused by changes in battery state is very small (e.g., several hundred μΩ), making it difficult for this method to meet the accuracy requirements.

[0008] Secondly, it is difficult to obtain the absolute value of the high-frequency impedance of the battery under test: the high-frequency inductance and high-frequency resistance parameters estimated by using the high-frequency oscillating voltage signal are the sum parameters of the resonant circuit of the battery under test and the detection circuit. To obtain the absolute value of the impedance of the battery under test, the high-frequency impedance parameters of the detection circuit must be subtracted. However, in actual systems, the high-frequency parameters of the detection circuit are difficult to obtain directly and fluctuate within a certain range. Therefore, this method is difficult to directly detect the absolute value of the high-frequency impedance of the battery under test. Summary of the Invention

[0009] In view of this, the purpose of this invention is to provide a differential battery high-frequency impedance online detection system. Through the differential measurement architecture, the influence of fluctuations in the internal parameters of the detection system circuit is effectively offset, and high-precision online detection of the absolute value of the battery high-frequency impedance is achieved.

[0010] The technical solution adopted in this invention is as follows:

[0011] A differential battery high-frequency impedance online detection system is provided, comprising a first oscillation circuit and a second oscillation circuit. The first oscillation circuit consists of the battery under test, a first switch S1, and a resonant inductor L. r and resonant capacitor C r The second oscillation circuit is composed of a series connection; the second oscillation circuit consists of a second switch S2 and a resonant inductor L. r and resonant capacitor C r Composed of series connections.

[0012] A first switch S1 and a second switch S2 are connected in series between the positive and negative terminals of the battery under test; by alternately turning on the first switch S1 and the second switch S2, the oscillation circuit in which the corresponding switch is turned on is excited with high frequency oscillation.

[0013] The high-frequency oscillation current i generated by the first oscillation circuit and the second oscillation circuit are measured respectively. r Online estimation of battery high-frequency resistance R, a high-frequency impedance parameter of the battery, based on differential estimation method. B With battery high-frequency inductor L B .

[0014] Preferably, the resonant inductance L of the first oscillation circuit r The resonant inductance L of the second oscillation circuit r The same resonant inductor; the resonant capacitance C of the first oscillation circuit r The resonant capacitor C of the second oscillation circuit r They are the same resonant capacitor.

[0015] Preferably, the resonant inductor is a hollow inductor to avoid nonlinear errors introduced by magnetic core saturation; the resonant capacitor is a high-precision, low-temperature-drift capacitor.

[0016] Preferably, the resonant capacitor is an adjustable resonant capacitor, which consists of multiple switches and capacitor elements with different capacitance parameters, and is used to realize multi-frequency measurement of the battery's high-frequency impedance parameters.

[0017] Preferably, the line impedance of the first oscillation circuit and the line impedance of the second oscillation circuit are equal or at least nearly equal.

[0018] Preferably, the high-frequency current sensor is mounted on the resonant inductor L. r Or the resonant capacitor C r On the branch line where it is located, it is used for non-contact measurement of the high-frequency oscillating current. The signal output terminal of the high-frequency current sensor is connected to the controller, which performs online estimation of the received signal based on a differential method.

[0019] Preferably, the online estimation based on the differential method includes at least the following calculation process:

[0020] When the first switch S1 is turned on (the second switch S2 is turned off), the first oscillation circuit generates a high-frequency oscillation current i. r The first resonant frequency f of the signal 0(1) Based on the first resonant frequency f 0(1) The first equivalent inductance L1 and the first equivalent resistance R1 of the first oscillation circuit are calculated respectively.

[0021] When the second switch S2 is turned on (the first switch S1 is turned off), the second oscillation circuit generates a high-frequency oscillation current i. r The second resonant frequency f of the signal 0(2) Based on the second resonant frequency f 0(2) The second equivalent inductance L2 and the second equivalent resistance R2 of the second oscillation circuit are calculated.

[0022] The high-frequency inductance L of the battery is obtained by subtracting the first equivalent inductance L1 and the second equivalent inductance L2. B :L B =L1-L2;

[0023] The high-frequency resistance R of the battery is obtained by subtracting the first equivalent resistance R1 and the second equivalent resistance R2. B :R B =R1-R2.

[0024] Preferably, the equivalent resonant angular frequency ω1 of the first oscillation circuit is calculated using the following formula:

[0025] In the formula, L loop The total stray inductance of the first oscillation circuit;

[0026] The equivalent resonant angular frequency ω2 of the second oscillation circuit is calculated using the following formula:

[0027] In the formula, L loop This represents the total stray inductance of the second oscillating circuit;

[0028] The first equivalent inductance L1 is calculated using the following formula:

[0029] L1= ;

[0030] The second equivalent inductance L2 is calculated using the following formula:

[0031] L2= ;

[0032] Battery high-frequency inductor L B The calculation formula is as follows:

[0033] .

[0034] Preferably, the first equivalent resistance R1 is calculated using the following formula:

[0035] In the formula, ζ1 is the first damping ratio of the first oscillation circuit, which is calculated using the half-power bandwidth method.

[0036] The second equivalent resistance R2 is calculated using the following formula:

[0037] In the formula, ζ2 is the second damping ratio of the second oscillation circuit, which is calculated using the half-power bandwidth method.

[0038] The first damping ratio ζ1 is calculated using the following formula:

[0039] In the formula, This is the lower limit frequency of the half-power bandwidth of the first oscillation circuit. The frequency point at the upper limit of the half-power bandwidth of the first oscillation circuit. This represents the half-power bandwidth of the first oscillation circuit.

[0040] The second damping ratio ζ2 is calculated using the following formula:

[0041] ζ2 In the formula, This is the lower limit frequency of the half-power bandwidth of the second oscillation circuit. This is the upper limit frequency of the half-power bandwidth of the second oscillation circuit. This is the half-power bandwidth of the second oscillation circuit.

[0042] Preferably, its circuit structure includes:

[0043] The first oscillation circuit;

[0044] The second oscillation circuit;

[0045] A high-frequency current sensor is non-contactly fitted onto the resonant inductor L r Or the resonant capacitor C r On the branch where it is located, the high-frequency oscillating current i will be collected. r The signal is converted into an analog voltage signal;

[0046] A controller communicatively connected to a high-frequency current sensor, wherein the controller includes:

[0047] Switch control unit: Outputs two complementary PWM control signals to drive the first switch S1 and the second switch S2 to alternately conduct.

[0048] AD sampling unit: Receives analog voltage signals from a high-frequency current sensor and converts them into digital voltage values. The signal is then sent to the high-frequency impedance estimation unit.

[0049] Frequency modulation control unit: By controlling the switching of the switch to adjust the capacitance parameter of the adjustable resonant capacitor, the oscillation frequency can be segmented within the range of 10kHz-10MHz to meet the requirements of high-frequency impedance detection of the battery in different frequency bands;

[0050] High-frequency impedance estimation unit: This unit processes the digital voltage output from the AD sampling unit. Perform the online estimation based on the difference method.

[0051] The main working mechanism of this invention application:

[0052] 1) Differential measurement architecture: This invention creatively constructs two oscillation circuits, one containing the battery under test and the other not. By calculating the difference between the measurement results of the two oscillation circuits, the influence of internal parameters of the detection circuit (including line impedance, parasitic inductance of the switching transistor, and on-state resistance) on the measurement accuracy is fundamentally eliminated, realizing high-precision online detection of the absolute value of the battery's high-frequency impedance and overcoming the defect of the traditional switching oscillation method in obtaining the absolute value of the battery's high-frequency impedance.

[0053] 2) Battery self-excitation technology: This invention directly uses the DC voltage of the battery under test as the excitation source, without the need for an external high-frequency excitation source or the PWM switching transient process of the DC-DC converter, and can generate a high-frequency oscillation signal with sufficient amplitude in the battery under test, which significantly improves the signal-to-noise ratio and detection accuracy.

[0054] 3) Dual-loop common-mode suppression mechanism: Drawing on the idea of ​​differential signal processing, by constructing two oscillating loops with symmetrical parameters (specifically, sharing the same resonant inductor and the same resonant capacitor) and extracting the difference features, the interference of detection circuit component parameter drift (such as temperature fluctuation of the on-state resistance of the switching transistor, aging drift of the resonant inductor parameters, etc.) on the detection accuracy is effectively eliminated.

[0055] The present invention application has the following main advantages:

[0056] 1) High precision: Through the differential measurement architecture, the influence of fluctuations in the internal parameters of the detection system circuit is effectively offset, realizing high-precision online detection of the absolute value of the high-frequency impedance of the battery.

[0057] 2) No external excitation source required: The high-frequency oscillation signal is generated directly by the DC voltage of the battery under test, eliminating the need for an expensive high-frequency signal generator and reducing system cost and complexity.

[0058] 3) Single signal detection: Only the high-frequency oscillating current signal needs to be measured to simultaneously obtain the battery's high-frequency resistance and high-frequency inductance parameters. There is no phase error problem in the dual signal measurement of voltage and current in the magnetic coupling injection method, and it is easy to implement. Attached Figure Description

[0059] Figure 1 This is a circuit diagram of the differential battery high-frequency impedance online detection system according to a specific embodiment of this application;

[0060] Figure 2 This is a circuit diagram illustrating the working principle of the differential battery high-frequency impedance online detection system according to a specific embodiment of this application.

[0061] Figure 3 This is a schematic diagram illustrating the calculation principle of the half-power bandwidth method used in the specific implementation of this application.

[0062] Figure 4 This is a schematic diagram of the PCB circuit board used in the differential battery high-frequency impedance detection system in a specific embodiment of this application;

[0063] Figure 5 The high-frequency oscillation current i output by the differential battery high-frequency impedance detection circuit in the specific embodiment of this application is... r Signal waveform diagram;

[0064] Figure 6 This is a graph showing the measured data of the battery's high-frequency resistance, high-frequency inductance, and temperature under dynamic conditions of high-rate charging and discharging in a specific embodiment of this application. Detailed Implementation

[0065] Please refer to the above. Figure 1 and Figure 2 As shown, this embodiment proposes a differential battery high-frequency impedance online detection system, which constructs a first oscillation circuit and a second oscillation circuit respectively. The first oscillation circuit consists of the battery under test, a first switch S1 (specifically a switching transistor in this embodiment), and a resonant inductor L. r and resonant capacitor C r The second oscillation circuit consists of a series connection; the second oscillation circuit is composed of a second switch S2 (specifically a switching transistor in this embodiment) and a resonant inductor L. r and resonant capacitor C r Composed of series connections.

[0066] A first switch S1 and a second switch S2 are connected in series between the positive and negative terminals of the battery under test. By alternately turning on the first switch S1 and the second switch S2, the oscillation circuits in which the corresponding switches are turned on are excited with high-frequency oscillations.

[0067] Measure the high-frequency oscillation current i generated by the first oscillation circuit and the second oscillation circuit respectively. r Online estimation of battery high-frequency resistance R, a high-frequency impedance parameter of the battery, based on differential estimation method. B With battery high-frequency inductor L B .

[0068] Preferably, in this embodiment, the circuit structure of the differential battery high-frequency impedance online detection system includes:

[0069] First oscillation circuit;

[0070] Second oscillation circuit;

[0071] A high-frequency current sensor is non-contactly mounted on the resonant inductor L. r Or resonant capacitor C r On the branch where it is located, the high-frequency oscillating current i will be collected. r The signal is converted into an analog voltage signal;

[0072] A controller that is communicatively connected to a high-frequency current sensor, wherein the controller includes:

[0073] Switch control unit: Outputs two complementary PWM control signals to drive the first switch S1 and the second switch S2 to alternately conduct. Specifically, in this embodiment, the specific operating sequence is as follows: First, the first switch S1 is driven to conduct, enabling the first oscillation circuit to establish high-frequency oscillation. After the oscillation signal stabilizes, the oscillation current waveform under the conducting state of the first switch S1 is acquired. At this time, the second switch S2 is in the off state. This operating state corresponds to... Figure 2 The marked "Mode 1"; then the first switch S1 is turned off, and after a short dead time delay, the second switch S2 is driven to turn on, enabling the second oscillation circuit to establish high-frequency oscillation. The oscillation current waveform under the condition that the second switch S2 is turned on is collected. This working state corresponds to Figure 2 The marked "Mode 2"; the two switching transistors work alternately to ensure that the two measurements are as close as possible in time to eliminate the influence of slow changes in battery state on the differential measurement results; it should be noted that in practical applications, based on the principle of ensuring that the two measurements are as close as possible in time, the alternating conduction time should ensure that no oscillation or aliasing occurs during the alternating conduction of the two switching transistors (i.e., the first switch S1 and the second switch S2). Preferably, the recommended time interval between the alternating conduction of the two switching transistors should be greater than 100 microseconds.

[0074] AD sampling unit: Receives analog voltage signals from a high-frequency current sensor and converts them into digital voltage values. The signal is then sent to the high-frequency impedance estimation unit.

[0075] Frequency modulation control unit: By controlling the switching of the switch to adjust the capacitance parameter of the adjustable resonant capacitor, the oscillation frequency (i.e., the resonant frequency) can be segmented and adjusted within the range of 10kHz-10MHz to meet the requirements of high-frequency impedance detection of the battery in different frequency bands.

[0076] High-frequency impedance estimation unit: This unit processes the digital voltage output from the AD sampling unit. The online estimation based on the differential method is performed. Since the present invention only needs to measure the spectral characteristics (resonant frequency and half-power bandwidth) of the oscillating current during implementation, it does not require high-speed real-time sampling of high-frequency signals. Therefore, ADC chips with conventional sampling rates can be used, reducing hardware costs.

[0077] Preferably, in this embodiment, the resonant inductance L of the first oscillation circuit r The resonant inductor L of the second oscillating circuit r The same resonant inductor; the resonant capacitance C of the first oscillation circuit r The resonant capacitance C of the second oscillation circuit r They are the same resonant capacitor.

[0078] Preferably, in this embodiment, the resonant inductor is an air-core inductor to avoid nonlinear errors introduced by magnetic core saturation; the resonant capacitor is a high-precision, low-temperature-drift capacitor, such as a ±30ppm / ℃ ceramic capacitor, to ensure that the capacitor parameters remain stable under different temperature conditions, thereby ensuring the accuracy of frequency measurement.

[0079] Preferably, in this embodiment, the resonant capacitor is an adjustable resonant capacitor, which consists of multiple switches and capacitor elements with different capacitance parameters, and is used to realize multi-frequency measurement of the battery's high-frequency impedance parameters.

[0080] Preferably, in this embodiment, the line impedance of the first oscillation circuit and the line impedance of the second oscillation circuit are equal, or are set to be at least close to equal as much as possible.

[0081] Preferably, in this embodiment, the high-frequency current sensor is mounted on the resonant inductor L. r Or resonant capacitor C r On the branch line where it is located, it is used for non-contact measurement of high-frequency oscillating current. The signal output terminal of the high-frequency current sensor is connected to the controller, which performs online estimation of the received signal based on differential measurement. The non-contact measurement method avoids introducing additional impedance interference into the oscillation circuit, ensuring measurement accuracy.

[0082] Preferably, in this embodiment, the online estimation based on the differential method includes at least the following calculation process:

[0083] When the first switch S1 is turned on (the second switch S2 is turned off), the high-frequency oscillating current i generated by the first oscillation circuit is extracted by FFT spectrum analysis (which is common knowledge in the field). r The first resonant frequency f of the signal 0(1) Based on the first resonant frequency f 0(1)The first equivalent inductance L1 and the first equivalent resistance R1 of the first oscillation circuit are calculated respectively; when the switch control unit controls the first switch S1 to turn on, the DC voltage of the battery under test is applied to L1. r -C r The series branch excites a high-frequency oscillating current i in the battery under test. r The first equivalent resonant angular frequency ω1 of this circuit is determined by the high-frequency inductance L of the battery under test. B All stray inductance L loop and resonant inductor L r Together, they determine the resonant capacitance C. r It is a known fixed value.

[0084] When the second switch S2 is turned on (the first switch S1 is turned off), the high-frequency oscillating current i generated by the second oscillation circuit is extracted by FFT spectrum analysis (which is common knowledge in the field). r The second resonant frequency f of the signal 0(2) Based on the second resonant frequency f 0(2) The second equivalent inductance L2 and the second equivalent resistance R2 of the second oscillation circuit are calculated; when the second switch S2 is turned on, the same applies to L... r -C r A high-frequency oscillating current is generated in the series branch; the second equivalent resonant angular frequency ω2 of this circuit is determined solely by the total stray inductance L. loop With resonant inductor L r Decide.

[0085] The high-frequency inductance L of the battery is obtained by subtracting the first equivalent inductance L1 and the second equivalent inductance L2. B :L B =L1-L2;

[0086] The high-frequency resistance R of the battery is obtained by subtracting the first equivalent resistance R1 and the second equivalent resistance R2. B :R B =R1-R2.

[0087] Preferably, in this embodiment, the equivalent resonant angular frequency ω1 of the first oscillation circuit is calculated using the following formula:

[0088] In the formula, L loop The total stray inductance of the first oscillating circuit includes:

[0089] All stray inductances in the first oscillation circuit, including those from the circuitry and the parasitic inductance of the switching transistor;

[0090] The equivalent resonant angular frequency ω2 of the second oscillation circuit is calculated using the following formula:

[0091] In the formula, L loop The total stray inductance of the second oscillating circuit includes:

[0092] All stray inductances in the second oscillation circuit, including those from the circuitry and the parasitic inductance of the switching transistor;

[0093] The first equivalent inductance L1 is calculated using the following formula:

[0094] L1= ;

[0095] The second equivalent inductance L2 is calculated using the following formula:

[0096] L2= ;

[0097] Battery high-frequency inductor L B The calculation formula is as follows:

[0098] .

[0099] Preferably, in this embodiment, the first equivalent resistance R1 is calculated using the following formula:

[0100] In the formula, ζ1 is the first damping ratio of the first oscillation circuit, which is calculated using the half-power bandwidth method.

[0101] The second equivalent resistance R2 is calculated using the following formula:

[0102] In the formula, ζ2 is the second damping ratio of the second oscillation circuit, which is calculated using the half-power bandwidth method.

[0103] The first damping ratio ζ1 is calculated using the following formula:

[0104] In the formula, This is the lower limit frequency of the half-power bandwidth of the first oscillation circuit. The frequency point at the upper limit of the half-power bandwidth of the first oscillation circuit. This represents the half-power bandwidth of the first oscillation circuit.

[0105] The second damping ratio ζ2 is calculated using the following formula:

[0106] ζ2 In the formula, This is the lower limit frequency of the half-power bandwidth of the second oscillation circuit. This is the upper limit frequency of the half-power bandwidth of the second oscillation circuit. This is the half-power bandwidth of the second oscillation circuit.

[0107] Through the differential-based online estimation provided in this embodiment, the total stray inductance of the two oscillating circuits is calculated. Common-mode components such as the parasitic parameters of the switching transistor are effectively canceled, thereby achieving high-precision extraction of the absolute value of the high-frequency impedance of the battery under test.

[0108] 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.

[0109] Based on the above implementation plan, the feasibility and effectiveness of the present invention will be verified below by combining an example of online high-frequency impedance detection of a large-capacity lithium iron phosphate single cell.

[0110] Please refer to the above for further details. Figure 4 As shown in Table 1 below, please refer to the model selection:

[0111] Table 1:

[0112]

[0113] In this specific embodiment, the high-frequency oscillation current i generated by the differential battery high-frequency impedance detection system is self-excited. r Please refer to the signal waveform diagram. Figure 5 As shown; through this Figure 5 It can be seen that when the first switch S1 and the second switch S2 are turned on, the oscillation frequencies are 250 kHz (corresponding to the first switch S1 being turned on) and 260 kHz (corresponding to the second switch S2 being turned on), respectively; the maximum amplitude of the oscillation current is 4.56A, and the excitation current intensity is less than 0.02C.

[0114] To further illustrate the implementation and application effects of the specific embodiments of this application, this embodiment also conducted a high-rate charge-discharge dynamic test on a large-capacity lithium battery. In this high-rate charge-discharge test, the battery was first subjected to a 150A constant current discharge for one hour, then left to stand for 10 minutes without power, and finally charged again with a 150A constant current for one hour. For the measured results of the battery's high-frequency resistance, high-frequency inductance, and temperature under this high-rate charge-discharge dynamic condition, please refer to [link to relevant documentation]. Figure 6 As shown; Figure 6 The equivalent resistance and equivalent inductance in the figure are the battery high-frequency resistance and high-frequency inductance measured online using the differential battery high-frequency impedance detection system provided in this embodiment, and the temperature is the battery center temperature measured by a thermocouple.

[0115] pass Figure 6 It can be seen that under the self-heating effect of high-rate charging and discharging, the battery temperature gradually rises, and the changes in the battery's high-frequency resistance and high-frequency inductance are positively correlated with the temperature. This further confirms that the differential battery high-frequency impedance detection system proposed in this embodiment can sensitively detect the slight changes in high-frequency impedance caused by changes in the state of a large-capacity battery (such as temperature, state of charge, etc.) online.

[0116] 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.

[0117] 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 differential battery high-frequency impedance online detection system, characterized in that, A first oscillation circuit and a second oscillation circuit are constructed respectively. The first oscillation circuit consists of the battery under test, a first switch S1, and a resonant inductor L. r and resonant capacitor C r The second oscillation circuit is composed of a series connection; the second oscillation circuit consists of a second switch S2 and a resonant inductor L. r and resonant capacitor C r Composed of series; among which, A first switch S1 and a second switch S2 are connected in series between the positive and negative terminals of the battery under test; by alternately turning on the first switch S1 and the second switch S2, the oscillation circuit in which the corresponding switch is turned on is excited with high frequency oscillation. The high-frequency oscillation current i generated by the first oscillation circuit and the second oscillation circuit are measured respectively. r Online estimation of battery high-frequency resistance R, a high-frequency impedance parameter of the battery, based on differential estimation method. B With battery high-frequency inductor L B .

2. The differential battery high-frequency impedance online detection system according to claim 1, characterized in that, The resonant inductance L of the first oscillation circuit r The resonant inductance L of the second oscillation circuit r The same resonant inductor device; the resonant capacitance C of the first oscillation circuit r The resonant capacitor C of the second oscillation circuit r They are the same resonant capacitor.

3. The differential battery high-frequency impedance online detection system according to claim 2, characterized in that, The resonant inductor is a hollow inductor to avoid nonlinear errors introduced by magnetic core saturation; the resonant capacitor is a high-precision, low-temperature drift capacitor.

4. The differential battery high-frequency impedance online detection system according to claim 2, characterized in that, The resonant capacitor device is an adjustable resonant capacitor, which consists of multiple switches and capacitor elements with different capacitance parameters, and is used to realize multi-frequency measurement of the battery's high-frequency impedance parameters.

5. The differential battery high-frequency impedance online detection system according to claim 1, characterized in that, The line impedance of the first oscillating circuit and the line impedance of the second oscillating circuit are equal or at least nearly equal.

6. The differential battery high-frequency impedance online detection system according to claim 1, characterized in that, The high-frequency current sensor is mounted on the resonant inductor L. r Or the resonant capacitor C r On the branch line where it is located, it is used for non-contact measurement of the high-frequency oscillating current. The signal output terminal of the high-frequency current sensor is connected to the controller, which performs online estimation of the received signal based on a differential method.

7. The differential battery high-frequency impedance online detection system according to claim 1, characterized in that, The online estimation based on the differential method includes at least the following calculation process: When the first switch S1 is turned on (the second switch S2 is turned off), the first oscillation circuit generates a high-frequency oscillation current i. r The first resonant frequency f of the signal 0(1) Based on the first resonant frequency f 0(1) The first equivalent inductance L1 and the first equivalent resistance R1 of the first oscillation circuit are calculated respectively. When the second switch S2 is turned on (the first switch S1 is turned off), the second oscillation circuit generates a high-frequency oscillation current i. r The second resonant frequency f of the signal 0(2) Based on the second resonant frequency f 0(2) The second equivalent inductance L2 and the second equivalent resistance R2 of the second oscillation circuit are calculated. The high-frequency inductance L of the battery is obtained by subtracting the first equivalent inductance L1 and the second equivalent inductance L2. B :L B =L1-L2; The high-frequency resistance R of the battery is obtained by subtracting the first equivalent resistance R1 and the second equivalent resistance R2. B :R B =R1-R2.

8. The differential battery high-frequency impedance online detection system according to claim 7, characterized in that, The equivalent resonant angular frequency ω1 of the first oscillation circuit is calculated using the following formula: In the formula, L loop The total stray inductance of the first oscillation circuit; The equivalent resonant angular frequency ω2 of the second oscillation circuit is calculated using the following formula: In the formula, L loop This represents the total stray inductance of the second oscillating circuit; The first equivalent inductance L1 is calculated using the following formula: L1= ； The second equivalent inductance L2 is calculated using the following formula: L2= ； Battery high-frequency inductor L B The calculation formula is as follows: 。 9. The differential battery high-frequency impedance online detection system according to claim 8, characterized in that, The first equivalent resistance R1 is calculated using the following formula: In the formula, ζ1 is the first damping ratio of the first oscillation circuit, which is calculated using the half-power bandwidth method. The second equivalent resistance R2 is calculated using the following formula: In the formula, ζ2 is the second damping ratio of the second oscillation circuit, which is calculated using the half-power bandwidth method. The first damping ratio ζ1 is calculated using the following formula: In the formula, This is the lower limit frequency of the half-power bandwidth of the first oscillation circuit. The frequency point at the upper limit of the half-power bandwidth of the first oscillation circuit. This represents the half-power bandwidth of the first oscillation circuit. The second damping ratio ζ2 is calculated using the following formula: ζ2 In the formula, This is the lower limit frequency of the half-power bandwidth of the second oscillation circuit. This is the upper limit frequency of the half-power bandwidth of the second oscillation circuit. This is the half-power bandwidth of the second oscillation circuit.

10. The differential battery high-frequency impedance online detection system according to claim 1, characterized in that, Its circuit structure includes: The first oscillation circuit; The second oscillation circuit; A high-frequency current sensor is non-contactly fitted onto the resonant inductor L r Or the resonant capacitor C r On the branch where it is located, the high-frequency oscillating current i will be collected. r The signal is converted into an analog voltage signal; A controller communicatively connected to a high-frequency current sensor, wherein the controller includes: Switch control unit: Outputs two complementary PWM control signals to drive the first switch S1 and the second switch S2 to alternately conduct. AD sampling unit: Receives analog voltage signals from a high-frequency current sensor and converts them into digital voltage values. The signal is then sent to the high-frequency impedance estimation unit. Frequency modulation control unit: By controlling the switching of the switch to adjust the capacitance parameter of the adjustable resonant capacitor, the oscillation frequency can be segmented within the range of 10kHz-10MHz to meet the requirements of high-frequency impedance detection of the battery in different frequency bands; High-frequency impedance estimation unit: This unit processes the digital voltage output from the AD sampling unit. Perform the online estimation based on the difference method.

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