Method, system and circuit for testing battery ac impedance

Abstract

The application discloses a battery AC impedance test method, a test system and a test circuit, which can electrically connect a power supply to be tested and a resonant circuit to form a test loop, wherein the power supply is an offline single battery or an offline battery pack, and the resonant circuit is a passive circuit; AC response characteristic data of the power supply is collected, wherein the AC response characteristic data comprises output voltage data and output current data of the power supply; and impedance of an equivalent circuit of the power supply is determined according to the AC response characteristic data. It can be seen that the application can externally connect a passive resonant circuit, collect AC response characteristic data of the power supply generated under the action of the resonant circuit, and then determine the impedance of the equivalent circuit of the power supply according to the AC response characteristic data, without applying external power supply to disturb the power supply to be tested, so that the application is convenient, fast, easy to realize and low in cost.

Description

Technical Field

[0001] This invention relates to the field of testing technology, and in particular to a method, system and circuit for testing the AC impedance of a battery. Background Technology

[0002] Electrochemical impedance spectroscopy (EIS), also known as AC impedance spectroscopy, is a powerful tool for detecting battery material properties and exploring their operating kinetics. The basic principle of this testing method is as follows: (1) By providing the battery with an AC excitation of current (or voltage) at a certain frequency, the terminal voltage (or current) response of the battery under that frequency condition is detected; (2) By changing the excitation frequency, impedance spectrum testing from low-frequency to ultra-high-frequency ranges is achieved; (3) The battery state is then determined by the characteristics of the impedance spectrum. Based on the characteristics of the excitation waveform, this method can be divided into sinusoidal excitation, quasi-sinusoidal excitation, square wave excitation, and stepped wave excitation. Based on the different excitation forms, it can be divided into voltage excitation and current excitation. Based on the battery's operating state during the test, it can also be divided into static offline testing and dynamic online testing.

[0003] Static offline testing of standard sinusoidal AC voltage (or current) is an effective testing method for individual battery cells during use and for battery packs after assembly. Currently, whether for individual battery cells or battery packs, the common approach is to apply an AC disturbance signal from an external power source to test the equivalent circuit parameters of the battery pack. This method is significantly affected by factors such as the accuracy of the DC voltage of the disturbance source, the frequency and accuracy of the AC disturbance, and the applied current, making it difficult and costly to implement. Therefore, how to efficiently and quickly perform AC impedance testing on batteries and battery packs remains a pressing technical problem for researchers in this field. Summary of the Invention

[0004] In view of the above problems, the present invention provides a method, system and circuit for testing the AC impedance of a battery, so as to solve the technical problems existing in the background art.

[0005] Firstly, a method for testing the AC impedance of a battery, comprising:

[0006] The power supply to be tested is electrically connected to the resonant circuit to form a test loop, wherein the power supply is an offline single cell or an offline battery pack, and the resonant circuit is a passive circuit.

[0007] Collect AC response characteristic data of the power supply, wherein the AC response characteristic data includes the output voltage data and output current data of the power supply;

[0008] Based on the AC response characteristic data, the impedance of the equivalent circuit of the power supply is determined.

[0009] Optionally, in some alternative embodiments, after acquiring the AC response characteristic data of the power supply, the method further includes:

[0010] Disconnect the power supply from the resonant circuit;

[0011] Change the circuit parameters of the resonant circuit;

[0012] The power supply to be tested is then electrically connected to the resonant circuit to form a test loop.

[0013] The AC response characteristic data of the power supply is collected again, and this process is repeated multiple times to obtain multiple AC response characteristic data of the power supply under different resonant circuit parameters.

[0014] Optionally, in some alternative embodiments, changing the circuit parameters of the resonant circuit includes:

[0015] Change at least one of the total resistance, total inductance, and total capacitance of the resonant circuit.

[0016] Optionally, in some alternative embodiments, changing at least one of the total resistance, total inductance, and total capacitance of the resonant circuit includes:

[0017] By performing at least one of methods one, two, and three, at least one of the total resistance, total inductance, and total capacitance of the resonant circuit can be changed;

[0018] One of the methods is to change the total resistance of the resonant circuit by changing the switching state of multiple resistors in the resonant circuit.

[0019] Method 2: Change the total inductance of the resonant circuit by changing the switching states of multiple inductors in the resonant circuit;

[0020] Method 3: Change the total capacitance of the resonant circuit by changing the switching states of multiple capacitors in the resonant circuit.

[0021] Optionally, in some alternative implementations, the acquisition of the AC response characteristic data of the power supply includes:

[0022] The AC response characteristic data of the power supply are collected according to the sampling frequency, wherein the sampling frequency is higher than the frequency of the resonant circuit.

[0023] Optionally, in some alternative embodiments, the output voltage data is a graph of the output voltage of the power supply, and the output current data is a graph of the output current of the power supply, wherein the graph is a Nyquist plot or a Bode plot.

[0024] Optionally, in some alternative embodiments, determining the impedance of the equivalent circuit of the power supply based on the AC response characteristic data includes:

[0025] From the output voltage curve, determine the corresponding first effective value;

[0026] From the output current curve, determine the corresponding second effective value;

[0027] The impedance of the equivalent circuit of the power supply is determined based on the first effective value and the second effective value.

[0028] Optionally, in some alternative embodiments, determining the impedance of the equivalent circuit of the power supply based on the AC response characteristic data includes:

[0029] From the output voltage curve, determine the corresponding first minimum value data and first maximum value data;

[0030] From the output current curve, determine the corresponding second minimum value data and second maximum value data;

[0031] The impedance of the equivalent circuit of the power supply is determined based on the first minimum value data, the first maximum value data, the second minimum value data, and the second maximum value data.

[0032] Secondly, a test circuit includes: a power supply to be tested, a first switch, a resonant circuit, a current acquisition element, and a voltage acquisition terminal;

[0033] The power supply, the first switch, the current acquisition element, and the resonant circuit are connected together to form a series circuit.

[0034] The power source is used to provide voltage and current to the resonant circuit;

[0035] The first switch is used to control the connection state of the series circuit, wherein the connection state includes open and closed;

[0036] The resonant circuit is used to make the output voltage and output current of the power supply generate sinusoidal oscillations;

[0037] The current acquisition element is used to acquire the output current data of the power supply;

[0038] The voltage acquisition terminal is used to provide a connection point to an external voltage acquisition device, so that the voltage acquisition device can acquire the output voltage data of the power supply through the voltage acquisition terminal.

[0039] Optionally, in some alternative embodiments, the power supply, the first switch, the current acquisition element, and the resonant circuit are connected together to form a series circuit, including:

[0040] The positive terminal of the power supply is connected to one end of the first switch;

[0041] The other end of the first switch is connected to the positive terminal of the resonant circuit;

[0042] The negative terminal of the resonant circuit is connected to one end of the current acquisition element;

[0043] The other end of the current acquisition element is connected to the negative terminal of the power supply.

[0044] Optionally, in some alternative embodiments, the resonant circuit includes: a first inductor, a first capacitor, and a first resistor;

[0045] The first inductor, the first capacitor, and the first resistor are connected in series in any order.

[0046] Optionally, in some alternative embodiments, the first inductor, the first capacitor, and the first resistor are connected in series in any order, including:

[0047] One end of the first inductor serves as the positive terminal of the resonant circuit;

[0048] The other end of the first inductor is connected to one end of the first capacitor;

[0049] The other end of the first capacitor is connected to one end of the first resistor;

[0050] The other end of the first resistor serves as the negative terminal of the resonant circuit.

[0051] Optionally, in some alternative embodiments, the resonant circuit further includes: a parallel inductor circuit;

[0052] The parallel inductor circuit includes multiple parallel branches, each of which includes an inductor and an inductor switch. The inductor and the inductor switch of the same parallel branch are connected in series. The total inductance of the resonant circuit is controlled by controlling the connection state of the inductor switch.

[0053] The parallel inductor circuit is connected in parallel with the first inductor.

[0054] Optionally, in some alternative embodiments, the resonant circuit further includes a parallel capacitor circuit;

[0055] The parallel capacitor circuit includes multiple parallel branches, each of which includes a capacitor and a capacitor switch. The capacitor and the capacitor switch of the same parallel branch are connected in series. The total capacitance of the resonant circuit is controlled by controlling the connection state of the capacitor switch.

[0056] The parallel capacitor circuit is connected in parallel with the first capacitor.

[0057] Optionally, in some alternative embodiments, the resonant circuit further includes a parallel resistor circuit;

[0058] The parallel resistor circuit includes multiple parallel branches, each of which includes a resistor and a resistor switch. The resistor and the resistor switch of the same parallel branch are connected in series. The total resistance of the resonant circuit is controlled by controlling the connection state of the resistor switch.

[0059] The parallel resistor circuit is connected in parallel with the first resistor.

[0060] Optionally, in some alternative embodiments, the current acquisition element is a current sensor or a sampling resistor.

[0061] Optionally, in some alternative implementations, the power source is an offline battery or battery pack.

[0062] Thirdly, a battery AC impedance testing system includes: a voltage acquisition device, a central control unit, and the aforementioned testing circuit;

[0063] The voltage acquisition device is connected in parallel with the power supply terminals in the test circuit to acquire the output voltage data of the power supply.

[0064] Both the voltage acquisition device and the test circuit are connected to the central control unit to transmit data to the central control unit;

[0065] The central control unit is used to execute any of the test methods described above.

[0066] By employing the above technical solution, the present invention provides a method, system, and circuit for testing the AC impedance of a battery. This method connects the power supply to be tested to a resonant circuit to form a test loop. The power supply is an offline single cell or an offline battery pack, and the resonant circuit is a passive circuit. The method collects AC response characteristic data of the power supply, including output voltage and output current data. Based on the AC response characteristic data, the impedance of the equivalent circuit of the power supply is determined. Therefore, the present invention can use an external passive resonant circuit to collect AC response characteristic data generated by the power supply under the action of the resonant circuit, and then determine the impedance of the equivalent circuit of the power supply based on the AC response characteristic data. This eliminates the need to apply an external power source to disturb the power supply under test, making it convenient, quick, easy to implement, and low-cost.

[0067] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it in accordance with the contents of the specification, and in order to make the above and other objects, features and advantages of the present invention more apparent and understandable, specific embodiments of the present invention are described below. Attached Figure Description

[0068] Various other advantages and benefits will become apparent to those skilled in the art upon reading the following detailed description of preferred embodiments. The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings:

[0069] Figure 1 A flowchart of a battery AC impedance testing method provided by the present invention is shown;

[0070] Figure 2 (a) and Figure 2 (b) shows the equivalent circuit diagram of the power supply provided by the present invention;

[0071] Figure 3 A schematic diagram of the voltage and current waveforms provided by the present invention is shown;

[0072] Figure 4 This invention provides a test circuit diagram.

[0073] Figure 5 A flowchart of another method for testing the AC impedance of a battery provided by the present invention is shown;

[0074] Figure 6-11 Six other test circuit diagrams provided by this invention are shown;

[0075] Figure 12A schematic diagram of the structure of a testing system provided by the present invention is shown;

[0076] Figure 13 A schematic diagram of the structure of an electronic device provided by the present invention is shown. Detailed Implementation

[0077] Exemplary embodiments of the invention will now be described in more detail with reference to the accompanying drawings. While exemplary embodiments of the invention are shown in the drawings, it should be understood that the invention may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this invention will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.

[0078] like Figure 1 As shown, the present invention provides a method for testing the AC impedance of a battery, including: S100, S200 and S300;

[0079] S100. Connect the power supply to be tested to the resonant circuit to form a test loop, wherein the power supply is an offline single cell or an offline battery pack, and the resonant circuit is a passive circuit.

[0080] Optionally, the resonant circuit of the present invention can be an LCR resonant circuit composed of resistors, inductors and capacitors.

[0081] The resonant circuit can be connected to the power supply under test via a switch. The connection state between the power supply and the resonant circuit (including connection and disconnection) can be controlled by the switch. This invention does not limit this.

[0082] Optionally, the power supply of the present invention can be equivalent to a corresponding equivalent circuit, please refer to the following for details. Figure 2 (a) and Figure 2 The equivalent circuit diagram is shown in (b) above. Figure 2 In the diagram, (a) is the conventional equivalent circuit. Figure 2 (b) is the equivalent circuit diagram under high-frequency disturbance conditions.

[0083] It should be noted that: Figure 2 (a) and Figure 2 V in (b) oc The open-circuit voltage of the power supply, R s R is the ohmic impedance of the power supply. ct The charge transfer resistance of the power supply, Q is the double-layer capacitance, W is the Warburg impedance, and L is the voltage drop across the power supply. s The equivalent inductance of the battery. Under high-frequency disturbance conditions, W inside the power supply can be ignored, and Q can be equivalent to a complete capacitor C. p .therefore, Figure 2In the above, (a) can be simplified to the following under high-frequency disturbance conditions: Figure 2 The equivalent circuit shown in (b) is shown in the diagram.

[0084] Optionally, the difference between this invention and the prior art is that the prior art generally requires an external test power supply to excite the power supply under test, while this invention only requires connecting the power supply under test to the resonant circuit, without the need for an external test power supply. That is, after the switch is closed, the passive resonant circuit can be understood as the test power supply for the power supply under test, causing the voltage and current output by the power supply under test to exhibit the following characteristics: Figure 3 The sine wave shown.

[0085] It should be noted that: Figure 3 A sine wave with a medium to large amplitude represents the output current waveform of the power supply under test, while a sine wave with a smaller amplitude represents the output current waveform of the power supply under test. This invention only uses... Figure 3 Briefly describe the sinusoidal fluctuations exhibited by the resonant circuit after the power supply is connected and energized, without limitation to... Figure 3 The specific voltage and current values ​​are shown.

[0086] To further illustrate that the output voltage and output current of the resonant circuit after power is applied exhibit sinusoidal fluctuations, let V... oc ' is the equivalent open-circuit voltage of the power supply, which can be considered a constant; R s ' is the equivalent series internal resistance of the power supply; C p ' is the equivalent double-layer capacitance of the power supply; R ct ' is the equivalent charge transfer resistance of the power supply; L' is the equivalent inductance of the power supply (the series inductance of a single cell or the overall equivalent inductance of the battery pack); V out I is the equivalent output voltage of the battery pack. out The value is the equivalent output current. L is the inductance of the passive resonant circuit, C is the capacitance of the passive resonant circuit, and R is the resistance of the passive resonant circuit.

[0087] Let the overall equivalent series inductance of the test circuit be L0, the equivalent series capacitance be C0, and the equivalent series damping resistance be R0. For example... Figure 4 As shown, due to the instant switch S is closed, R ct 'and C p The impact is minimal. ct 'and C p The influence of the imaginary part can be neglected in the parallel circuit of '. Therefore, in the following analysis, let L in the resonant circuit be... s Let L'+L be the equivalent series inductance of the power output conductor. s +L=L0, and L0≈L; R+R s =R0, since R s 'much smaller than R, therefore R0≈R; C and Cp ' / / R ct The sum of the imaginary parts is C0, therefore C0≈C. When switch S is not closed, the power supply is in a steady state, and the equivalent output voltage V... out For V oc ', I out The value is 0; at the instant that switch S is closed, based on Kirchhoff's voltage law (also known as KVL law) and Kirchhoff's first law (also known as KCL law), the state of the resonant circuit is:

[0088]

[0089] Differentiating equation (1) reveals that:

[0090]

[0091] Equation (2) is a non-homogeneous second-order differential equation. Solving it, we can find that the output current Iout of the power supply is:

[0092]

[0093] At this time, the battery's output voltage V out It can be approximately determined by L, C, and R. According to the KVL law, V out for:

[0094]

[0095] I s =-I out That is, the output current of the power supply under test by the LCR excitation source:

[0096]

[0097] Combination Figure 3 The waveforms shown indicate that the peaks and troughs of the output voltage and current waveforms at the power supply terminal exhibit a decreasing trend in fluctuation exponentially. This is due to β in equations (3) and (4). When β is much smaller than ω, the output current approximates a standard sine wave, and the output voltage is a sine wave with a bias of Voc'. This is because during the test, the V of the power supply... oc 'It is constant and can be considered as a constant voltage value.' From formula (5), it can be seen that after switch S is closed, the current in the circuit is a nearsighted sine wave. Therefore, the power supply is composed of R s '、C p '、R ct The voltage of the equivalent circuit (approximately a resonant cavity) formed by ' and L' is biased to 0. Therefore, using KVL's law, the output voltage of the power supply at this time is biased to V. oc An approximate sine wave.

[0098] Theoretically, after removing the open-circuit voltage, the response caused by the battery's equivalent circuit parameters is V. cs =V out -V oc The waveform is approximately a standard zero-bias sine wave. Based on this, the present invention can obtain important information about voltage and current, such as the corresponding effective value, maximum value, minimum value, period, frequency, phase difference, real part, and imaginary part.

[0099] S200. Collect AC response characteristic data of the power supply, wherein the AC response characteristic data includes the output voltage data and output current data of the power supply;

[0100] Optionally, as mentioned above, the resonant circuit, originally intended as a load, can be considered an external test power source after being connected to a power supply, thus enabling the application of current and voltage disturbances to the power source under test. Therefore, this invention can replace the function of traditional electrochemical workstations and other testing equipment as an external test power source.

[0101] Therefore, this invention can collect AC response characteristic data at both ends of the power supply, including output voltage and output current data, even when the power supply is disturbed by the resonant circuit. It should be noted that this invention can collect AC response characteristic data at a certain sampling frequency, the specific sampling frequency of which can be selected based on the frequency of the resonant circuit.

[0102] For example, in some alternative implementations, S200 includes: step 4.1;

[0103] Step 4.1: Collect AC response characteristic data of the power supply according to the sampling frequency, wherein the sampling frequency is higher than the frequency of the resonant circuit.

[0104] Therefore, when selecting the sampling frequency, the frequency of the resonant circuit can be referenced (or vice versa, i.e., the sampling frequency can be referenced when selecting the frequency of the resonant circuit), and the frequency of the resonant circuit is related to the inductance, capacitance, and resistance in the resonant circuit. Therefore, this invention requires selecting appropriate inductance, capacitance, and resistance when constructing the resonant circuit, or setting variable inductance, capacitance, and resistance, so that the frequency of the resonant circuit can be changed at any time when needed. For the selection of the inductance, capacitance, and resistance of the resonant circuit, the maximum discharge current of the power supply and the safe operating voltage of the power supply can be referenced, specifically as shown in equations (4) and (5) above. In addition, this invention can also comprehensively consider dimensions such as the sampling frequency and accuracy of the sampling system to select a suitable frequency for the resonant circuit.

[0105] Generally, it is sufficient to ensure that the decay rate of voltage and current is slow. During the stage of acquiring AC response characteristic data, the total number of oscillation cycles of the acquired output voltage and current data can be greater than 20 cycles. This facilitates subsequent operations such as RMS value statistics and phase difference calculation, thereby improving the testing accuracy of this invention. Of course, this invention is not limited to a maximum of 20 cycles; any feasible method falls within the scope of protection of this invention. That is, the sampling frequency is generally more than 20 times higher than the frequency of the resonant circuit.

[0106] Optionally, to improve the testing accuracy of this invention, in addition to having a sampling frequency much higher than the frequency of the resonant circuit, the accuracy of the sampling system can also be set to the μV level. Specifically, the sampling system can achieve high-precision sampling of the output current through a current sensor or a sampling resistor to obtain highly accurate current output data. Simultaneously, the sampling system can use a high-precision voltage sensor to acquire highly accurate current output data.

[0107] Optionally, in some alternative embodiments, the output voltage data is a graph of the output voltage of the power supply, and the output current data is a graph of the output current of the power supply, wherein the graph is a Nyquist plot or a Bode plot.

[0108] For example, the present invention can obtain equivalent circuit parameters by changing the frequency of the resonant circuit multiple times, and then construct a Nyquist plot or a Bode plot.

[0109] It should be noted that Nyquist plots and Bode plots are well-known concepts in the art, and will not be described in detail in this invention. Please refer to the relevant descriptions in the art for details.

[0110] Of course, the output voltage data and output current data mentioned in this invention can also be data sequences with a certain order. Specifically, the collected data can be converted into other forms of data display according to actual needs. This invention does not limit this.

[0111] In actual testing, the influence of power supply on circuit parameters varies depending on the frequency of the resonant circuit: at high frequencies, L' and R... s 'Has a significant impact; in the mid-frequency band, all parameters take effect; in the ultra-low frequency band, R...' ct '、C p 'and R s The impact is significant. Therefore, this invention can directly obtain Bode plots or Nyquist plots obtained from tests at different frequency points, which facilitates the subsequent calculation of battery equivalent circuit parameters.

[0112] Specifically, after obtaining the output voltage and output current data at a specific frequency of the resonant circuit, it can be disconnected first. Figure 4 Switch S as shown, then adjust the frequency of the resonant circuit. After the power supply stabilizes again, test other frequency points (the frequency of the resonant circuit) to obtain the output voltage and output current data at different frequencies of the resonant circuit.

[0113] For example, combining Figure 1 In some optional embodiments, after S200, the method further includes steps 1.1, 1.2, 1.3, and 1.4.

[0114] Step 1.1: Disconnect the power supply from the resonant circuit;

[0115] Optional, with Figure 4 For example, it can be disconnected. Figure 4 The switch S in the circuit is used to disconnect the power supply from the resonant circuit.

[0116] Step 1.2: Change the circuit parameters of the resonant circuit;

[0117] Optionally, the present invention can change the circuit parameters of the resonant circuit by altering one or more of the resistance, inductance, and capacitance of the resonant circuit. It should be noted that the circuit parameters referred to here can be understood as any one or more of the resistance, inductance, capacitance, and frequency of the resonant circuit, and the present invention does not impose any limitation on this.

[0118] That is, combining Figure 1 In some optional embodiments of the implementation shown, step 1.2 includes: step 2.1;

[0119] Step 2.1: Change at least one of the total resistance, total inductance, and total capacitance of the resonant circuit.

[0120] Alternatively, the methods for changing the total resistance, total inductance, and total capacitance of a resonant circuit are basically the same. Taking changing the total resistance as an example, there are generally three ways: 1. Remove the original resistor and replace it with a resistor of a different value. 2. The resistors in the resonant circuit are variable resistors; their resistance values ​​are directly changed based on the characteristics of variable resistors. 3. Multiple resistors are connected in parallel in the resonant circuit. Each parallel resistor can be controlled by an independent switch. By closing and opening the switch, the corresponding resistor is controlled to be connected to the circuit, thus changing the total resistance in sequence.

[0121] For example, in some alternative implementations, step 2.1 includes: step 3.1;

[0122] Step 3.1: By executing at least one of Method 1, Method 2, and Method 3, change at least one of the total resistance, total inductance, and total capacitance of the resonant circuit;

[0123] One of the methods is to change the total resistance of the resonant circuit by changing the switching state of multiple resistors in the resonant circuit.

[0124] Method 2: Change the total inductance of the resonant circuit by changing the switching states of multiple inductors in the resonant circuit;

[0125] Method 3: Change the total capacitance of the resonant circuit by changing the switching states of multiple capacitors in the resonant circuit.

[0126] Step 1.3: Connect the power supply to be tested to the resonant circuit again to form a test circuit;

[0127] Optional, with Figure 4 For example, it can be done again Figure 4 Switch S in the circuit is used to connect the power supply and the resonant circuit to form a test loop.

[0128] Step 1.4: Collect the AC response characteristic data of the power supply again, and repeat this process multiple times to obtain multiple AC response characteristic data of the power supply under different resonant circuit parameters.

[0129] Optionally, after each change of the circuit parameters of the resonant circuit and the formation of a test loop, the present invention can collect the corresponding AC response characteristic data, including the corresponding output voltage data and output current data, so that the impedance of the equivalent circuit of the power supply can be accurately calculated based on the AC response characteristic data under different circuit parameters of the resonant circuit.

[0130] To clearly describe the process of repeatedly changing circuit parameters and repeatedly collecting AC response characteristic data in this invention, please refer to [link to relevant documentation]. Figure 5 The example shown.

[0131] It should be noted that this invention allows for setting specific conditions under which the process of repeatedly changing circuit parameters and repeatedly collecting AC response characteristic data will cease. That is, Figure 5 The round1 in the middle can be set with corresponding compliance conditions according to actual needs.

[0132] S300. Based on the AC response characteristic data, determine the impedance of the equivalent circuit of the power supply.

[0133] Optionally, in some alternative implementations, S300 includes: steps 5.1, 5.2, and 5.3;

[0134] Step 5.1: Determine the corresponding first effective value from the output voltage curve;

[0135] Optionally, taking a Bode plot as an example, the Bode plot of the output voltage records voltage changes over various oscillation periods. By analyzing each peak value of the output voltage's Bode plot, the corresponding effective value can be calculated (generally speaking: That is, from the output voltage curve, multiple first effective values ​​can be determined, and each first effective value corresponds to a peak.

[0136] Optionally, due to the differences in the frequency of the resonant circuit used in the test and the influence of the equivalent parameters of the power supply, this invention selects the waveforms of voltage and current after the third oscillation cycle for effective values ​​and subsequent calculations.

[0137] Step 5.2: Determine the corresponding second effective value from the output current curve;

[0138] Optionally, step 5.2 can be understood in the same way as the explanation in step 5.1, and the present invention will not elaborate on it further.

[0139] Step 5.3: Determine the impedance of the equivalent circuit of the power supply based on the first effective value and the second effective value.

[0140] Optionally, determining the impedance of the equivalent circuit based on the effective values ​​of the voltage and current is a well-known technique in the art, and this invention will not describe it in detail. Please refer to the relevant descriptions in the art for details.

[0141] Optionally, in some alternative implementations, step S300 includes: steps 6.1, 6.2, and 6.3;

[0142] Step 6.1: Determine the corresponding first minimum value data and first maximum value data from the output voltage curve;

[0143] Optionally, due to the differences in the frequency of the resonant circuit used in the test and the influence of the equivalent parameters of the power supply, this invention selects the waveforms after the third oscillation cycle of voltage and current to calculate the maximum and minimum values ​​and the corresponding time points.

[0144] Step 6.2: Determine the corresponding second minimum value data and second maximum value data from the output current curve;

[0145] Optionally, step 6.2 can be understood in the same way as the explanation in step 6.1, and the present invention will not elaborate on it further.

[0146] Step 6.3: Determine the impedance of the equivalent circuit of the power supply based on the first minimum value data, the first maximum value data, the second minimum value data, and the second maximum value data.

[0147] It should be noted that the first minimum value data, the first maximum value data, the second minimum value data, and the second maximum value data mentioned in this invention all include the corresponding extreme value data and time point data.

[0148] Optionally, the present invention can obtain parameters such as the period, frequency, phase difference, and effective value of voltage and current through the waveforms of the voltage and current. Specifically, these parameters can be calculated using the zero-crossing points, maximum value time points, and minimum value time points in the waveforms.

[0149] Optionally, determining the impedance of the equivalent circuit based on the minimum and maximum values ​​of the voltage, the minimum and maximum values ​​of the current, and the corresponding time points is a well-known technique in the art, and this invention will not describe it in detail. Please refer to the relevant descriptions in the art for details.

[0150] For example, the impedance and other parameters of the equivalent circuit of a power source can be obtained by solving a system of multivariate equations.

[0151] In other words, it should be noted that during the single-point frequency test of the equivalent circuit, the power supply's output voltage is its switching voltage V. out The oscillating waveform is approximately sinusoidal on a biased basis, while the current is an approximately sinusoidal waveform without bias. The AC voltage waveform caused by the equivalent parameters is: V cs =V out -V oc The difference. Simultaneously, the input current I of the power supply. s This represents the negative value of the output current. After sampling and calculating the voltage and current waveforms, in addition to determining the impedance of the equivalent circuit, other parameters of the equivalent circuit can also be determined. For example, determining the frequency and phase difference: using the voltage V... cs and current I s By determining the zero-crossing time or the time corresponding to the peak and trough, the oscillation period, frequency, time difference, and phase difference of the voltage and current waveforms can be established. Since the current waveform is closer to a sine wave, it is recommended that the frequency parameter be based on the current waveform.

[0152] As can be seen, this invention can be connected to an external passive resonant circuit to collect AC response characteristic data generated by the power supply under the action of the resonant circuit, and then determine the impedance of the equivalent circuit of the power supply based on the AC response characteristic data. It does not require applying an external power supply to disturb the power supply under test, which is convenient, quick and easy to implement, and has a low cost.

[0153] like Figure 6 As shown, the present invention provides a test circuit, including: a power supply DC to be tested, a first switch S, a resonant circuit RCL, a current acquisition element CA, and a voltage acquisition terminal VA;

[0154] The power supply DC, the first switch S, the current acquisition element CA and the resonant circuit RCL are connected together to form a series circuit.

[0155] The DC power supply is used to provide voltage and current to the resonant circuit RCL;

[0156] The first switch S is used to control the connection state of the series circuit, wherein the connection state includes open and closed;

[0157] The resonant circuit RCL is used to make the output voltage and output current of the power supply DC generate sinusoidal oscillations.

[0158] The current acquisition element CA is used to acquire the output current data of the power supply DC.

[0159] The voltage acquisition terminal VA is used to provide a connection point to an external voltage acquisition device, so that the voltage acquisition device can acquire the output voltage data of the power supply DC through the voltage acquisition terminal VA.

[0160] It should be noted that in some optional embodiments, the power source DC is an offline battery or battery pack.

[0161] Optionally, in some alternative embodiments, the current acquisition element CA is a current sensor or a sampling resistor.

[0162] Optionally, the power supply DC, the first switch S, the current acquisition element CA, and the resonant circuit RCL are connected together to form a series circuit, including:

[0163] The positive terminal of the power supply DC is connected to one end of the first switch S;

[0164] The other end of the first switch S is connected to the positive terminal of the resonant circuit RCL;

[0165] The negative terminal of the resonant circuit RCL is connected to one end of the current acquisition element CA.

[0166] The other end of the current acquisition element CA is connected to the negative terminal of the power supply DC.

[0167] like Figure 7 As shown, in some optional embodiments, the resonant circuit RCL includes: a first inductor L, a first capacitor C, and a first resistor R;

[0168] The first inductor L, the first capacitor C, and the first resistor R are connected in series in any order.

[0169] Optionally, the first inductor L, the first capacitor C, and the first resistor R are connected in series in any order, including:

[0170] One end of the first inductor L serves as the positive terminal of the resonant circuit RCL;

[0171] The other end of the first inductor L is connected to one end of the first capacitor C;

[0172] The other end of the first capacitor C is connected to one end of the first resistor R;

[0173] The other end of the first resistor R serves as the negative terminal of the resonant circuit RCL.

[0174] It should be noted that the first inductance L of the resonant circuit RCL can be much larger than L' in the equivalent circuit; the first capacitance C can be much larger than C in the equivalent circuit. p 'and R ct The first resistor R can be much larger than R in the equivalent circuit. s '.

[0175] like Figure 8 As shown, in some optional embodiments, the resonant circuit RCL further includes: a parallel inductor circuit PL;

[0176] The parallel inductor circuit PL includes multiple parallel branches. Each parallel branch includes an inductor Lp and an inductor switch Kl. The inductor Lp and the inductor switch Kl of the same parallel branch are connected in series. By controlling the connection state of the inductor switch Kl, the total inductance of the resonant circuit RCL is controlled.

[0177] The parallel inductor circuit PL is connected in parallel with the first inductor L.

[0178] like Figure 9 As shown, in some optional embodiments, the resonant circuit RCL further includes a parallel capacitor circuit PC;

[0179] The parallel capacitor circuit PC includes multiple parallel branches. Each parallel branch includes a capacitor Cc and a capacitor switch Kc. The capacitor Cc and the capacitor switch Kc of the same parallel branch are connected in series. By controlling the connection state of the capacitor switch Kc, the total capacitance of the resonant circuit RCL is controlled.

[0180] The parallel capacitor circuit PC is connected in parallel with the first capacitor C.

[0181] like Figure 10 As shown, in some optional embodiments, the resonant circuit RCL further includes a parallel resistor circuit PR;

[0182] The parallel resistor circuit PR includes multiple parallel branches. Each parallel branch includes a resistor Rp and a resistor switch Kr. The resistor Rp and the resistor switch Kr of the same parallel branch are connected in series. By controlling the connection state of the resistor switch Kr, the total resistance of the resonant circuit RCL can be controlled.

[0183] The parallel resistor circuit PR is connected in parallel with the first resistor R.

[0184] It should be noted that: the present invention can also... Figure 8 and Figure 9 Combine, or Figure 8 and Figure 10 Combine, or Figure 9 and Figure 10 Combine, or Figure 8 , Figure 9 and Figure 10 By combining these methods, new embodiments are obtained, which will not be described in detail in this invention.

[0185] Optionally, the above Figures 8 to 10 All of these employ a parallel connection method to allow for arbitrary changes to the total inductance, total capacitance, and total resistance in the resonant circuit RCL. In addition, this invention can also employ methods such as... Figure 11 The series connection shown allows for arbitrary changes to the total resistance in the resonant circuit RCL. Specifically, when Kone is closed and Ktwo is open, the total resistance of the resonant circuit is R; when Kone is open and Ktwo is closed, the total resistance of the resonant circuit is R+R. For the total capacitance and total inductance, corresponding embodiments can be derived by referring to the series connection of the total resistance, which will not be elaborated upon further in this invention.

[0186] As can be seen, the present invention can be connected to an external passive resonant circuit RCL to collect AC response characteristic data generated by the power supply DC under the action of the resonant circuit RCL, and then determine the impedance of the equivalent circuit of the power supply DC based on the AC response characteristic data. It does not require applying an external power supply to disturb the power supply DC under test, which is convenient, quick and easy to implement, and has a low cost.

[0187] like Figure 12 As shown, the present invention provides a battery AC impedance testing system, comprising: a voltage acquisition device 100, a central control unit 200, and a test circuit 300 as described in any one of the above.

[0188] The voltage acquisition device 100 is connected in parallel with the DC power supply terminals in the test circuit 300 to acquire the output voltage data of the DC power supply.

[0189] The voltage acquisition device 100 and the test circuit 300 are both connected to the central control unit 200 to transmit data to the central control unit 200;

[0190] The central control unit 200 is used to execute any of the test methods described above.

[0191] As can be seen, the present invention can be connected to an external passive resonant circuit RCL to collect AC response characteristic data generated by the power supply DC under the action of the resonant circuit RCL, and then determine the impedance of the equivalent circuit of the power supply DC based on the AC response characteristic data. It does not require applying an external power supply to disturb the power supply DC under test, which is convenient, quick and easy to implement, and has a low cost.

[0192] The present invention provides a computer-readable storage medium having a program stored thereon, which, when executed by a processor, implements the method for testing the AC impedance of a battery as described above.

[0193] like Figure 13 As shown, the present invention provides an electronic device 70, which includes at least one processor 701, at least one memory 702 and a bus 703 connected to the processor 701; wherein the processor 701 and the memory 702 communicate with each other through the bus 703; the processor 701 is used to call program instructions in the memory 702 to execute the battery AC impedance test method described above.

[0194] In this invention, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, without necessarily requiring or implying any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0195] The various embodiments in this specification are described in a related manner. Similar or identical parts between embodiments can be referred to mutually. Each embodiment focuses on describing the differences from other embodiments. In particular, the system embodiments are basically similar to the method embodiments, so the description is relatively simple; relevant parts can be referred to the descriptions of the method embodiments.

[0196] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined in this invention may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

[0197] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention are included within the scope of protection of the present invention.

Claims

1. A method for testing the AC impedance of a battery, characterized in that, include: The power supply to be tested is electrically connected to the resonant circuit to form a test loop, wherein the power supply is an offline single cell or an offline battery pack, and the resonant circuit is a passive circuit. The AC response characteristic data of the power supply is collected, wherein the AC response characteristic data includes the output voltage data and output current data of the power supply; the output voltage data includes the output voltage of the power supply. The output voltage Open circuit voltage for use with the power supply Calculated AC voltage The AC voltage The impedance of the equivalent circuit of the power supply is used to determine the impedance of the power supply.

2. The method according to claim 1, characterized in that, After acquiring the AC response characteristic data of the power supply, the method further includes: Disconnect the power supply from the resonant circuit; Change the circuit parameters of the resonant circuit; The power supply to be tested is then electrically connected to the resonant circuit to form a test loop. The AC response characteristic data of the power supply is collected again, and this process is repeated multiple times to obtain multiple AC response characteristic data of the power supply under different resonant circuit parameters.

3. The method according to claim 2, characterized in that, Changing the circuit parameters of the resonant circuit includes: Change at least one of the total resistance, total inductance, and total capacitance of the resonant circuit.

4. The method according to claim 3, characterized in that, Changing at least one of the total resistance, total inductance, and total capacitance of the resonant circuit includes: By performing at least one of methods one, two, and three, at least one of the total resistance, total inductance, and total capacitance of the resonant circuit can be changed; One of the methods is to change the total resistance of the resonant circuit by changing the switching state of multiple resistors in the resonant circuit. Method 2: Change the total inductance of the resonant circuit by changing the switching states of multiple inductors in the resonant circuit; Method 3: Change the total capacitance of the resonant circuit by changing the switching states of multiple capacitors in the resonant circuit.

5. The method according to any one of claims 1-4, characterized in that, The acquisition of AC response characteristic data of the power supply includes: The AC response characteristic data of the power supply are collected according to the sampling frequency, wherein the sampling frequency is higher than the frequency of the resonant circuit.

6. A test circuit, characterized in that, include: The power supply to be tested, the first switch, the resonant circuit, the current acquisition element, and the voltage acquisition terminal; The power supply, the first switch, the current acquisition element, and the resonant circuit are connected together to form a series circuit. The power source is used to provide voltage and current to the resonant circuit; The first switch is used to control the connection state of the series circuit, wherein the connection state includes open and closed; The resonant circuit is used to make the output voltage and output current of the power supply generate sinusoidal oscillations; The current acquisition element is used to acquire the output current data of the power supply; The voltage acquisition terminal is used to provide a connection point to an external voltage acquisition device, so that the voltage acquisition device can acquire the output voltage data of the power supply through the voltage acquisition terminal.

7. The test circuit according to claim 6, characterized in that, The power supply, the first switch, the current acquisition element, and the resonant circuit are connected together to form a series circuit, including: The positive terminal of the power supply is connected to one end of the first switch; The other end of the first switch is connected to the positive terminal of the resonant circuit; The negative terminal of the resonant circuit is connected to one end of the current acquisition element; The other end of the current acquisition element is connected to the negative terminal of the power supply.

8. The test circuit according to claim 6, characterized in that, The resonant circuit includes: a first inductor, a first capacitor, and a first resistor; The first inductor, the first capacitor, and the first resistor are connected in series in any order.

9. The test circuit according to claim 8, characterized in that, The first inductor, the first capacitor, and the first resistor are connected in series in any order, including: One end of the first inductor serves as the positive terminal of the resonant circuit; The other end of the first inductor is connected to one end of the first capacitor; The other end of the first capacitor is connected to one end of the first resistor; The other end of the first resistor serves as the negative terminal of the resonant circuit.

10. The test circuit according to claim 9, characterized in that, The resonant circuit further includes: a parallel inductor circuit; The parallel inductor circuit includes multiple parallel branches, each of which includes an inductor and an inductor switch. The inductor and the inductor switch of the same parallel branch are connected in series. The total inductance of the resonant circuit is controlled by controlling the connection state of the inductor switch. The parallel inductor circuit is connected in parallel with the first inductor.

11. The test circuit according to any one of claims 9-10, characterized in that, The resonant circuit also includes: a parallel capacitor circuit; The parallel capacitor circuit includes multiple parallel branches, each of which includes a capacitor and a capacitor switch. The capacitor and the capacitor switch of the same parallel branch are connected in series. The total capacitance of the resonant circuit is controlled by controlling the connection state of the capacitor switch. The parallel capacitor circuit is connected in parallel with the first capacitor.

12. The test circuit according to any one of claims 9-10, characterized in that, The resonant circuit further includes: a parallel resistor circuit; The parallel resistor circuit includes multiple parallel branches, each of which includes a resistor and a resistor switch. The resistor and the resistor switch of the same parallel branch are connected in series. The total resistance of the resonant circuit is controlled by controlling the connection state of the resistor switch. The parallel resistor circuit is connected in parallel with the first resistor.

13. The test circuit according to claim 6, characterized in that, The current acquisition element is a current sensor or a sampling resistor.

14. The test circuit according to claim 6, characterized in that, The power source is an offline battery or battery pack.

15. A battery AC impedance testing system, characterized in that, include: Voltage acquisition equipment, central control unit, and test circuit according to any one of claims 6-14; The voltage acquisition device is connected in parallel with the power supply terminals in the test circuit to acquire the output voltage data of the power supply. Both the voltage acquisition device and the test circuit are connected to the central control unit to transmit data to the central control unit; The central control unit is used to execute the test method according to any one of claims 1-5.

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